Merge pull request 'Bound a consumer's identity by the provision it requires (hq issue 263, ADR 0225)' (#76) from fix/263-identity-bound-per-provision into main

The one global 20-character bound made every consumer pay an object
store's key length, even for provisions that keep no name, and a single
overflow refused the provider's whole declaration. An offer now states
its own bound (identity: {max, in} or false); unsaid, a provider told its
consumers keeps 20 and one told nothing keeps none. module check judges
every identity on the longest machine name before merge, and a provider
leaves an overflowing consumer out of its grants and composes, with the
consumer named by push, plan and status (ADR 0225).

cmd/mesh-controller/build.go

@@ -679,6 +679,10 @@ type answers struct {
 	// failing is every consumer a provider says it keeps failing (novox/hq ADR 0224): a provider's
 	// journal was the only place that said so for a day (04-ISSUES/179).
 	failing []inventory.ProviderStanding
+	// overflowing is every module whose identity overflows the bound of a provision it requires
+	// (novox/hq ADR 0225): its provider leaves it out of the grants and composes everything else, so
+	// this is the one place it is said across the mesh. Not well while there is any.
+	overflowing []catalogue.Overflow
 }
 
 // heldBy is every artifact this mesh has built, for a build that may need one as its base.

cmd/mesh-controller/check.go

@@ -25,7 +25,17 @@ import (
 // mesh seat is judged fully only at registration. A seat another module declares is unknown unless
 // that module's manifest is passed too. Both are printed as a note, not as a problem — a check that
 // refused what it could not see would teach people to ignore it.
+//
+// **And every identity against every bound it meets** (novox/hq ADR 0225, issue 263): each module's
+// identity, on a machine whose name is `longestMachine` characters, against the bound of every
+// provision it wants that a manifest given here offers. An overflow is refused in the pull request
+// that introduces it — a new requirement, a lowered bound, a longer slug — instead of on the
+// provider's machine when a real machine's name first meets the module's.
 func moduleCheck(paths []string, out io.Writer) error {
+	return moduleCheckFor(paths, catalogue.DefaultLongestMachine, out)
+}
+
+func moduleCheckFor(paths []string, longestMachine int, out io.Writer) error {
 	if len(paths) == 0 {
 		return errors.New("module check <manifest.json>... — one file per module; pass every " +
 			"manifest of a repository together so the rules between them are checked too")
@@ -74,6 +84,15 @@ func moduleCheck(paths []string, out io.Writer) error {
 	}
 	failed += len(problems)
 
+	// Between the manifests too: an identity against the bounds of the provisions it wants, which
+	// only the provider's manifest states.
+	identities := catalogue.IdentityProblems(shelf, longestMachine)
+	sort.Strings(identities)
+	for _, p := range identities {
+		fmt.Fprintln(out, p)
+	}
+	failed += len(identities)
+
 	var names []string
 	for name := range shelf {
 		names = append(names, name)
@@ -109,7 +128,8 @@ func moduleCheck(paths []string, out io.Writer) error {
 	}
 	fmt.Fprintf(out, "%d manifest(s) checked. Judged against the seats this binary carries; a claim on "+
 		"one of the mesh's own seats is judged fully at registration, and a seat declared by a "+
-		"module not given here reads as unknown\n", len(paths))
+		"module not given here reads as unknown. Identities judged on a %d-character machine name, "+
+		"against the bounds of the providers given here\n", len(paths), longestMachine)
 	return nil
 }
 

cmd/mesh-controller/identity_bound_test.go

@@ -0,0 +1,150 @@
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/novox/mesh-controller/internal/catalogue"
+)
+
+// novox/hq ADR 0225, issue 263: a consumer's identity is bounded by the provision it requires, an
+// overflow is refused before merge by `module check`, and a provider's machine is never refused for
+// one consumer's identity.
+
+// `module check` refuses the pull request that introduces an overflow, naming the module.
+func TestModuleCheckRefusesAnIdentityThatOverflowsWhatItRequires(t *testing.T) {
+	dir := t.TempDir()
+	write := func(name, body string) string {
+		p := filepath.Join(dir, name+".json")
+		if err := os.WriteFile(p, []byte(body), 0o600); err != nil {
+			t.Fatal(err)
+		}
+		return p
+	}
+	objects := write("objects", `{"module":"objects","version":"1",
+		"provides":[{"name":"s3-bucket","scope":"mesh","identity":{"max":20,"in":"an S3 access key"}}],
+		"receives":{"s3-bucket":"/var/lib/mesh/objects/mesh.json"}}`)
+	resolver := write("resolver", `{"module":"resolver","version":"1",
+		"provides":[{"name":"wildcard-resolution","scope":"mesh","identity":false}]}`)
+	album := write("photoalbum", `{"module":"photoalbum","version":"1","requires":["s3-bucket"]}`)
+	nm := write("networkmanager", `{"module":"networkmanager","version":"1","requires":["wildcard-resolution"]}`)
+
+	var out bytes.Buffer
+	if err := moduleCheckFor([]string{resolver, nm}, 6, &out); err != nil {
+		t.Fatalf("a long name requiring a keyless provision was refused (issue 263): %v\n%s", err, out.String())
+	}
+	out.Reset()
+	err := moduleCheckFor([]string{objects, album, resolver, nm}, 6, &out)
+	if err == nil {
+		t.Fatalf("an identity overflowing an S3 access key passed:\n%s", out.String())
+	}
+	if !strings.Contains(out.String(), "photoalbum wants s3-bucket") ||
+		!strings.Contains(out.String(), "`slug` of at most 8 characters") ||
+		strings.Contains(out.String(), "networkmanager wants") {
+		t.Fatalf("the refusal does not name the one overflowing module and its remedy:\n%s", out.String())
+	}
+}
+
+// Tonight's case, through the commands: networkmanager on a six-character machine requires the
+// resolver provision, and a second consumer there overflows an object store's access key. The
+// provider's machine still composes; the overflowing consumer is left out of its grants and named,
+// by push and by `status`, and the keyless consumer is granted with its long name.
+func TestAnOverflowingConsumerNeverRefusesItsProvidersMachine(t *testing.T) {
+	open := aMesh(t)
+	ctx := t.Context()
+	register(t, open, catalogue.Manifest{Module: "objects", Version: "1",
+		Provides: []catalogue.Offer{{Name: "s3-bucket", Scope: catalogue.ScopeMesh,
+			Identity: &catalogue.OfferIdentity{Max: 20, In: "an S3 access key"}}},
+		Receives: map[string]string{"s3-bucket": "/var/lib/mesh/objects/mesh.json"}})
+	register(t, open, catalogue.Manifest{Module: "resolver", Version: "1",
+		Provides: []catalogue.Offer{{Name: "wildcard-resolution", Scope: catalogue.ScopeMesh}}})
+	register(t, open, catalogue.Manifest{Module: "networkmanager", Version: "1",
+		Requires: []string{"wildcard-resolution"}})
+	register(t, open, catalogue.Manifest{Module: "photoalbum", Version: "1", Requires: []string{"s3-bucket"}})
+	register(t, open, catalogue.Manifest{Module: "files", Version: "1", Requires: []string{"s3-bucket"}})
+	for _, a := range [][2]string{{"anchor", "objects"}, {"anchor", "resolver"},
+		{"laptop", "networkmanager"}, {"laptop", "photoalbum"}, {"laptop", "files"}} {
+		if _, err := assign(ctx, open, a[0], a[1]); err != nil {
+			t.Fatalf("assign %s %s: %v", a[0], a[1], err)
+		}
+	}
+
+	// The consumer's machine resolves, and says which of its modules no provider will grant.
+	consumer, _, err := planFor(ctx, open, "laptop")
+	if err != nil {
+		t.Fatal(err)
+	}
+	over := consumer.Overflowing()
+	if len(over) != 1 || over[0].Module != "photoalbum" || over[0].Provision != "s3-bucket" {
+		t.Fatalf("the consumer's side does not name exactly photoalbum: %+v", over)
+	}
+
+	// The provider's machine composes. Under ADR 0049's one bound this was a refusal naming
+	// networkmanager, and no push to the provider could go through.
+	plan, settings, err := planFor(ctx, open, "anchor")
+	if err != nil {
+		t.Fatal(err)
+	}
+	declared, err := declarationFor(ctx, open, "anchor", plan, settings)
+	if err != nil {
+		t.Fatalf("one consumer's identity refused its provider's whole machine: %v", err)
+	}
+	if len(declared.withheld) != 1 || declared.withheld[0].Identity != "mesh_laptop_photoalbum" {
+		t.Fatalf("the overflowing consumer is not the one withheld: %+v", declared.withheld)
+	}
+	grants, _, err := grantsFor(ctx, open, "anchor")
+	if err != nil {
+		t.Fatal(err)
+	}
+	var keyless bool
+	for _, g := range grants {
+		keyless = keyless || g.Provision == "wildcard-resolution" && g.From == "networkmanager"
+	}
+	if !keyless {
+		t.Fatalf("networkmanager, 26 characters, is not granted the keyless resolver provision: %+v", grants)
+	}
+	var granted []string
+	for _, c := range declared.Received["objects"]["s3-bucket"] {
+		granted = append(granted, c.From)
+	}
+	if strings.Join(granted, ",") != "files" {
+		t.Fatalf("the object store grants %v; files and only files fit", granted)
+	}
+	said := printed(t, func() error { reportLeftOut("anchor", declared); return nil })
+	if !strings.Contains(said, `photoalbum on laptop requires s3-bucket from anchor`) ||
+		!strings.Contains(said, "left out of anchor's grants") {
+		t.Fatalf("the push does not say whom it leaves out:\n%s", said)
+	}
+
+	// And `status` names it, and does not call the mesh well while it stands.
+	asked, err := theThreeQuestions(ctx, open)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(asked.overflowing) != 1 || asked.overflowing[0].Module != "photoalbum" {
+		t.Fatalf("status does not carry the overflow: %+v", asked.overflowing)
+	}
+	if asked.well() {
+		t.Fatal("a mesh with a consumer left out of its grants reads as well")
+	}
+	shown := printed(t, func() error { return printStatus(asked) })
+	if !strings.Contains(shown, "identified too long for a provision they require") ||
+		!strings.Contains(shown, "mesh_laptop_photoalbum") {
+		t.Fatalf("status does not say it:\n%s", shown)
+	}
+	body, err := statusAsJSON(asked)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var doc struct {
+		Overflowing []catalogue.Overflow `json:"overflowing"`
+	}
+	if err := json.Unmarshal(body, &doc); err != nil || len(doc.Overflowing) != 1 ||
+		doc.Overflowing[0].Bound.Max != 20 {
+		t.Fatalf("the document does not carry it: %v\n%s", err, body)
+	}
+}

cmd/mesh-controller/main.go

@@ -232,7 +232,7 @@ func usage() {
   licence add|list|use|key       model access, under the name a person calls it
   licence manager <name> <node>  the node that holds a refreshable licence's refresh token
   licence refresh <name>         mint a new access token and seal it to every holder
-  rotate <provision> [--consumer <n>]  a new credential for every holder, both ends at once
+  rotate <provision> [--consumer <n>] [--module <m>]  a new credential for every holder, both ends at once
   ask <module> <tool> [json]           call one of a module's tools over the broker, and print its answer
   pin <node> <provision> <from-node> <module>
                                  which provider this one gets a provision from: the module, and its node

cmd/mesh-controller/modules.go

@@ -59,8 +59,19 @@ func moduleCommand(ctx context.Context, args []string) error {
 	// `check` needs no mesh, and must not: it is what somebody runs in their own repository before
 	// there is a mesh in reach (novox/hq issue 148). A directory expands to every manifest under it.
 	if args[0] == "check" {
+		set := flag.NewFlagSet("module check", flag.ContinueOnError)
+		// The longest machine name an identity must fit on (novox/hq ADR 0225): a mesh passes its own.
+		longest := set.Int("longest-machine-name", catalogue.DefaultLongestMachine,
+			"judge each module's identity on a machine name this many characters long")
+		given, err := parseAround(set, args[1:])
+		if err != nil {
+			return err
+		}
+		if *longest < 1 {
+			return errors.New("--longest-machine-name is a length, at least 1")
+		}
 		var paths []string
-		for _, a := range args[1:] {
+		for _, a := range given {
 			if info, err := os.Stat(a); err == nil && info.IsDir() {
 				under, err := manifestsUnder(a)
 				if err != nil {
@@ -71,7 +82,7 @@ func moduleCommand(ctx context.Context, args []string) error {
 			}
 			paths = append(paths, a)
 		}
-		return moduleCheck(paths, os.Stdout)
+		return moduleCheckFor(paths, *longest, os.Stdout)
 	}
 	open, err := openStores(ctx)
 	if err != nil {

cmd/mesh-controller/plan.go

@@ -399,7 +399,7 @@ func declarationWith(ctx context.Context, open *stores, node string,
 	}
 	out := sendable{Resources: composed.Resources, Adoption: adoption,
 		Received: composed.Received, Mesh: with.Mesh, BusUsers: with.BusUsers,
-		LeftOut: sortedKeysOf(composed.LeftOut), leftOutWhy: composed.LeftOut}
+		LeftOut: sortedKeysOf(composed.LeftOut), leftOutWhy: composed.LeftOut, withheld: with.Withheld}
 	// And which build of each module it carries, for the send to record (novox/hq issue 259, ADR
 	// 0221). Read only on the send path: a question about what would be sent records nothing.
 	if choosing == Allocating {
@@ -464,6 +464,11 @@ func reportLeftOut(node string, declared sendable) {
 			"what the machine holds for it is kept and its containers are untouched. %s\n",
 			node, m, declared.leftOutWhy[m])
 	}
+	// And whom it serves nothing, because their identity overflows what the provision keeps (ADR
+	// 0225): the machine is sent everything else, and the consumer is named.
+	for _, o := range declared.withheld {
+		fmt.Printf("%s: %s\n", node, o)
+	}
 }
 
 // renderingFor is everything a node's declaration is composed with, and the node's record.
@@ -471,7 +476,7 @@ func renderingFor(ctx context.Context, open *stores, node string,
 	plan catalogue.Resolution, settings catalogue.SettingsBy,
 	gens map[string]catalogue.Generator, choosing Choosing) (catalogue.Rendering, inventory.Node, error) {
 	inv := open.inventory
-	grants, err := grantsFor(ctx, open, node)
+	grants, withheld, err := grantsFor(ctx, open, node)
 	if err != nil {
 		return catalogue.Rendering{}, inventory.Node{}, err
 	}
@@ -794,7 +799,7 @@ func renderingFor(ctx context.Context, open *stores, node string,
 		Suffix: overlay.Suffix(), MeshRange: meshRange, TunnelInterface: overlay.Interface, Accounts: accounts, Foundation: foundation,
 		Kept: kept, Adopted: record.Adopted, OutwardLinks: outwardLinks,
 		Given: given, Taken: taken, Seats: seats, ArtifactStore: artifactStore, SeatReach: reach, Built: built,
-		BusUsers: busUsers,
+		BusUsers: busUsers, Withheld: withheld,
 	}, record, nil
 }
 
@@ -930,28 +935,34 @@ func certificateFor(ctx context.Context, open *stores, node string) (string, str
 // The mirror of what a consumer is given, and the half that makes the credential real: a password
 // nothing was told to create is a password that authenticates nowhere. Sealed to this node, so
 // the mesh hands over something it cannot itself use.
-func grantsFor(ctx context.Context, open *stores, node string) ([]catalogue.Grant, error) {
+//
+// **One consumer's identity never refuses the provider's machine** (novox/hq ADR 0225, issue 263).
+// A consumer whose identity overflows the provision's bound is left out of the grants and returned
+// beside them, for push, plan and `status` to say; every other consumer is granted and the provider's
+// declaration composes. Refusing here once made a whole machine unpushable for one module elsewhere.
+func grantsFor(ctx context.Context, open *stores, node string) ([]catalogue.Grant, []catalogue.Overflow, error) {
 	inv := open.inventory
 	issued, err := inv.SecretsFrom(ctx, node)
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 
 	// Where each consumer is, so a provider that must reach back to one does not have to know how
 	// the mesh names machines.
 	shelf, err := inv.Catalogue(ctx)
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	onNetwork, err := whereEveryoneIs(ctx, inv, shelf)
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 
 	// What each consumer actually asked for, taken from that machine's own resolution rather than
 	// from a record beside it. A provider told to create a password and not what to create it for
 	// can do nothing with it, and the name a consumer wants is the consumer's to say.
 	out := make([]catalogue.Grant, 0, len(issued))
+	var withheld []catalogue.Overflow
 	for _, s := range issued {
 		plan, settings, err := planFor(ctx, open, s.Consumer)
 		switch {
@@ -964,11 +975,11 @@ func grantsFor(ctx context.Context, open *stores, node string) ([]catalogue.Gran
 			// The mesh could not be asked what they wanted, which is not the same as their wanting
 			// nothing — and withholding a grant on that reading takes a consumer's access away
 			// (novox/hq 04-ISSUES/152).
-			return nil, fmt.Errorf("what %s asked of %s cannot be read: %w", s.Consumer, s.Name, err)
+			return nil, nil, fmt.Errorf("what %s asked of %s cannot be read: %w", s.Consumer, s.Name, err)
 		}
 		values, asks, err := plan.ContributionsFrom(s.Name, s.ConsumerModule, settings)
 		if err != nil {
-			return nil, err
+			return nil, nil, err
 		}
 		// A port in there is the consumer's software port until this. The consumer is on another
 		// machine, so the assignment that moved it is that machine's — fetched here rather than
@@ -976,7 +987,7 @@ func grantsFor(ctx context.Context, open *stores, node string) ([]catalogue.Gran
 		// this case (novox/hq 04-ISSUES/038, the cross-node half).
 		published, err := portsOn(ctx, inv, s.Consumer, s.ConsumerModule)
 		if err != nil {
-			return nil, err
+			return nil, nil, err
 		}
 		values = catalogue.AtPublishedPort(values, s.ConsumerModule, published)
 		from := s.ConsumerModule
@@ -987,9 +998,10 @@ func grantsFor(ctx context.Context, open *stores, node string) ([]catalogue.Gran
 			from = ""
 		}
 		// The consumer's identity slug, from its own manifest, carried on the grant so the provider
-		// derives the same login the consumer does (novox/hq ADR 0049). Refused here if it still would
+		// derives the same login the consumer does (novox/hq ADR 0049). Judged against the bound of
-		// not fit the tightest backend — the mesh chose the name, so the mesh refuses it, with the
+		// this provision, as the consumer's resolution states it from the provider's offer (ADR
-		// remedy a short slug rather than a login a provider silently shortened.
+		// 0225): a consumer it would not fit is left out of the grants and said, rather than a login a
+		// provider silently shortened — and rather than this whole machine refused for it.
 		slug := ""
 		for _, mm := range plan.Modules {
 			if mm.Module == s.ConsumerModule {
@@ -998,15 +1010,32 @@ func grantsFor(ctx context.Context, open *stores, node string) ([]catalogue.Gran
 			}
 		}
 		if from != "" {
-			if err := catalogue.CheckIdentity(s.Consumer, catalogue.IdentitySource(slug, s.ConsumerModule)); err != nil {
+			bound := boundOfGrant(plan, s, node)
-				return nil, err
+			source := catalogue.IdentitySource(slug, s.ConsumerModule)
+			if catalogue.CheckIdentityWithin(s.Consumer, source, bound) != nil {
+				withheld = append(withheld, catalogue.Overflow{Provision: s.Name, Provider: node,
+					Consumer: s.Consumer, Module: s.ConsumerModule,
+					Identity: catalogue.ConsumerIdentity(s.Consumer, source), Bound: bound})
+				continue
 			}
 		}
 		out = append(out, catalogue.Grant{
 			Provision: s.Name, Consumer: s.Consumer, At: onNetwork[s.Consumer],
 			From: from, Values: values, Slug: slug, Sealed: s.ForProvider, Local: s.Local})
 	}
-	return out, nil
+	return out, withheld, nil
+}
+
+// boundOfGrant is the identity bound the consumer's own resolution states for the requirement this
+// grant answers. A requirement not found there is held to the tightest bound the mesh knows rather
+// than to none: what the provider keeps of it is not known here.
+func boundOfGrant(consumer catalogue.Resolution, s inventory.Secret, provider string) catalogue.IdentityBound {
+	for _, n := range consumer.Needs {
+		if n.Name == s.Name && n.For == s.ConsumerModule && n.From == provider {
+			return n.Identity
+		}
+	}
+	return catalogue.DefaultIdentityBound
 }
 
 // listensLines is what a person is told about what this module would open, and why — the same
@@ -1082,6 +1111,11 @@ func planCommand(ctx context.Context, args []string) error {
 		left := plan.LeftOut(settings, record.Adopted)
 		reportLeftOut(args[0], sendable{LeftOut: sortedKeysOf(left), leftOutWhy: left})
 	}
+	// And which of its modules no provider will grant, because the identity overflows the bound of
+	// what it requires (novox/hq ADR 0225) — said on the machine the remedy is for.
+	for _, o := range plan.Overflowing() {
+		fmt.Printf("%s: %s\n", args[0], o)
+	}
 	// And a setting that reaches nothing — refused where it is stored, and said here for one
 	// stored before its definition moved from under it.
 	for _, m := range plan.Modules {

cmd/mesh-controller/readable.go

@@ -83,6 +83,9 @@ type meshStatus struct {
 	// document without this called the mesh well while the identity provider refused every consumer
 	// for a day (04-ISSUES/179).
 	Failing []inventory.ProviderStanding `json:"failing,omitempty"`
+	// Overflowing is every module whose identity overflows the bound of a provision it requires, and
+	// so is left out of its provider's grants (novox/hq ADR 0225). Absent when every identity fits.
+	Overflowing []catalogue.Overflow `json:"overflowing,omitempty"`
 }
 
 // machineFiltered is one rule set on a converged machine that the mesh did not write and that
@@ -216,6 +219,7 @@ func statusAsJSON(asked answers) ([]byte, error) {
 	}
 	out.Unheld = asked.unheld
 	out.Failing = asked.failing
+	out.Overflowing = asked.overflowing
 	for name := range asked.refused {
 		out.Unresolved = append(out.Unresolved, machineUnresolved{
 			Node: name, Problem: asked.refused[name]})

cmd/mesh-controller/rotate.go

@@ -6,6 +6,8 @@ import (
 	"flag"
 	"fmt"
 	"sort"
+
+	"github.com/novox/mesh-controller/internal/inventory"
 )
 
 // rotateCommand replaces a credential and moves both ends together.
@@ -33,12 +35,16 @@ func rotateCommand(ctx context.Context, args []string) error {
 	// One consumer rather than all of them. Ordinary: a credential is suspected on one machine,
 	// and rotating the other nine would be a great deal of disruption for one suspicion.
 	only := set.String("consumer", "", "only this machine's credential, rather than every holder's")
+	// One consuming module rather than every module on the machine. A machine runs many consumers
+	// of one provision, each with its own credential; one module that leaked its credential (novox/hq
+	// issue 268) is no reason to restart every other one on the machine.
+	module := set.String("module", "", "only this consuming module's credential")
 	positionals, err := parseAround(set, args)
 	if err != nil {
 		return err
 	}
 	if len(positionals) != 1 {
-		return errors.New("rotate <provision> [--consumer <machine>]")
+		return errors.New("rotate <provision> [--consumer <machine>] [--module <module>]")
 	}
 	provision := positionals[0]
 
@@ -53,6 +59,12 @@ func rotateCommand(ctx context.Context, args []string) error {
 	if err != nil {
 		return err
 	}
+	holders = ofModule(holders, *module)
+	if len(holders) == 0 && *module != "" {
+		return fmt.Errorf(
+			"no module %s%s holds a credential for %q, so there is nothing to rotate. `plan <machine>` "+
+				"says what a machine holds", *module, onMachine(*only), provision)
+	}
 	if len(holders) == 0 {
 		// Said, not silent. "Nobody holds this" and "this did not run" must never look the same —
 		// and a rotation somebody believes happened is worse than one they know did not.
@@ -116,6 +128,27 @@ func rotateCommand(ctx context.Context, args []string) error {
 	return nil
 }
 
+// ofModule is the holders whose consuming module is this one; all of them when none is named.
+func ofModule(holders []inventory.Holder, module string) []inventory.Holder {
+	if module == "" {
+		return holders
+	}
+	var out []inventory.Holder
+	for _, h := range holders {
+		if h.ConsumerModule == module {
+			out = append(out, h)
+		}
+	}
+	return out
+}
+
+func onMachine(machine string) string {
+	if machine == "" {
+		return ""
+	}
+	return " on " + machine
+}
+
 // asLocal names the credential inside the consumer where it holds several (ADR 0094).
 func asLocal(local string) string {
 	if local == "" {

cmd/mesh-controller/rotate_test.go

@@ -0,0 +1,27 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/novox/mesh-controller/internal/inventory"
+)
+
+// One consuming module's credential, and not its neighbours' on the same machine (novox/hq issue
+// 268): a module that leaked its database password is no reason to restart every other consumer.
+func TestARotationNarrowedToAModuleTouchesOnlyThatModulesCredential(t *testing.T) {
+	holders := []inventory.Holder{
+		{Provision: "postgres-database", Consumer: "ace", ConsumerModule: "letta", Provider: "ace"},
+		{Provision: "postgres-database", Consumer: "ace", ConsumerModule: "n8n", Provider: "ace"},
+		{Provision: "postgres-database", Consumer: "ace", ConsumerModule: "letta", Local: "reader", Provider: "ace"},
+	}
+	got := ofModule(holders, "letta")
+	if len(got) != 2 || got[0].ConsumerModule != "letta" || got[1].Local != "reader" {
+		t.Fatalf("narrowed to letta: %+v", got)
+	}
+	if len(ofModule(holders, "")) != 3 {
+		t.Fatal("no module named narrowed anyway")
+	}
+	if len(ofModule(holders, "absent")) != 0 {
+		t.Fatal("a module holding nothing matched")
+	}
+}

cmd/mesh-controller/seatverbs.go

@@ -371,6 +371,11 @@ func (a *verbArguments) commandLine() ([]string, error) {
 			if c := str("consumer"); c != "" {
 				argv = append(argv, "--consumer", c)
 			}
+			// With a provision, module narrows to one consuming module (novox/hq issue 268); node
+			// and secret stay the other shape's, and are refused as passed over.
+			if m := str("module"); m != "" {
+				argv = append(argv, "--module", m)
+			}
 			return argv, nil
 		}
 		_, node := a.given["node"]

cmd/mesh-controller/seatverbs_test.go

@@ -43,6 +43,10 @@ func TestRotateTakesAProvisionOrAnOwnSecret(t *testing.T) {
 	if strings.Join(argv, " ") != "rotate postgres-database --consumer ace" {
 		t.Fatalf("a pair credential: %v", argv)
 	}
+	argv, _ = argvFor("rotate", map[string]any{"provision": "postgres-database", "consumer": "ace", "module": "letta"})
+	if strings.Join(argv, " ") != "rotate postgres-database --consumer ace --module letta" {
+		t.Fatalf("one consuming module's pair credential: %v", argv)
+	}
 	argv, _ = argvFor("rotate", map[string]any{"node": "ace", "module": "nodered", "secret": "api-token"})
 	if strings.Join(argv, " ") != "secret rotate ace nodered api-token" {
 		t.Fatalf("an own secret: %v", argv)

cmd/mesh-controller/sendable.go

@@ -43,6 +43,9 @@ type sendable struct {
 	LeftOut []string
 	// leftOutWhy is why each was, for push and plan to say; never on the wire.
 	leftOutWhy map[string]string
+	// withheld is every consumer this machine's grants leave out, because its identity overflows the
+	// provision's bound (novox/hq ADR 0225); for push and plan to say, never on the wire.
+	withheld []catalogue.Overflow
 	// Builds is the build of each module this declaration carries — module to the commit its build
 	// was made from — recorded with the send and never on the wire (novox/hq issue 259, ADR 0221).
 	// Composed only on the send path; nil records that it is not known.

cmd/mesh-controller/status.go

@@ -302,6 +302,19 @@ func printStatus(asked answers) error {
 		fmt.Printf("\n  `assign <node> <holder>` meets it; reported until every machine has its holders, then refused\n\n")
 	}
 
+	if len(asked.overflowing) > 0 {
+		// **Reported, and the provider still pushed** (novox/hq ADR 0225, issue 263). Each is left
+		// out of its provider's grants, so the module holds a login nothing created; the provider's
+		// machine is sent everything else rather than refused for one consumer elsewhere.
+		fmt.Printf("%d module(s) identified too long for a provision they require, and not granted it:\n",
+			len(asked.overflowing))
+		for _, o := range asked.overflowing {
+			fmt.Printf("  %-12s %-20s %-22s %q is %d, %s keeps %d\n", o.Consumer, o.Module, o.Provision,
+				o.Identity, len(o.Identity), o.Bound.In, o.Bound.Max)
+		}
+		fmt.Printf("\n  a shorter `slug` in the module's definition fits it; `module check` refuses one before merge\n\n")
+	}
+
 	if adopted := adoptedNodes(nodes); len(adopted) > 0 {
 		// Said, because nothing forces the flip: a node left adopted is visible here rather than
 		// read as converged (novox/hq ADR 0100). Not a fault, so it does not break "all well".
@@ -419,6 +432,10 @@ func theThreeQuestions(ctx context.Context, open *stores) (answers, error) {
 			return answers{}, err
 		}
 		out.unheld = append(out.unheld, plan.Unheld...)
+		// And which of its modules a provider leaves out of its grants, for an identity too long
+		// for what the provision keeps (novox/hq ADR 0225) — judged from the consumer's own
+		// resolution, as the provider's composition judges it.
+		out.overflowing = append(out.overflowing, plan.Overflowing()...)
 	}
 	// And every consumer a provider says it keeps failing (novox/hq ADR 0224). Read from what the
 	// providers announced: nothing else in the mesh knows whether a provision is being made.
@@ -538,7 +555,7 @@ func untakenModules(ctx context.Context, inv *inventory.Inventory, nodes []inven
 func (a answers) well() bool {
 	return len(a.wrong) == 0 && len(a.quiet) == 0 && len(a.behind) == 0 &&
 		len(a.waiting) == 0 && len(a.refused) == 0 && a.network == "" && len(a.untaken) == 0 &&
-		len(a.filtered) == 0 && len(a.unheld) == 0 && len(a.failing) == 0
+		len(a.filtered) == 0 && len(a.unheld) == 0 && len(a.failing) == 0 && len(a.overflowing) == 0
 }
 
 // hostSplit is which machines report which host version, for every version more than one machine

internal/catalogue/catalogue_check_test.go

@@ -119,3 +119,41 @@ func TestEveryCatalogueStoreSaysHowItIsBackedUp(t *testing.T) {
 		t.Fatal("no module in the catalogue provides a store, so this proved nothing")
 	}
 }
+
+// TestEveryCatalogueIdentityFitsWhatItRequires is ADR 0225's check over the real catalogue: every
+// module's identity, on the longest machine name, fits the bound of every provision it wants. An
+// overflow fails here, in the pull request that introduces it, rather than on the provider's machine
+// the first time a real machine's name meets the module's (issue 263).
+func TestEveryCatalogueIdentityFitsWhatItRequires(t *testing.T) {
+	root := catalogueRoot(t)
+	found, err := filepath.Glob(filepath.Join(root, "modules", "*", "module.json"))
+	if err != nil || len(found) == 0 {
+		t.Fatalf("no manifests under %s: %v", root, err)
+	}
+	shelf := Shelf{}
+	for _, p := range found {
+		raw, err := os.ReadFile(p)
+		if err != nil {
+			t.Fatalf("%s: %v", p, err)
+		}
+		m, err := ParseManifest(raw)
+		if err != nil {
+			t.Fatalf("%s: %v", p, err)
+		}
+		shelf[m.Module] = m
+	}
+	for _, p := range IdentityProblems(shelf, DefaultLongestMachine) {
+		t.Error(p)
+	}
+	// The night it was found: the resolver provision bounds nothing, and the object store still 20.
+	if dns, ok := shelf["dnsmasq"]; ok {
+		if b := dns.IdentityBoundOf("wildcard-resolution"); b.Bounded() {
+			t.Errorf("the resolver provision bounds its consumers' identities: %+v", b)
+		}
+	}
+	if store, ok := shelf["minio"]; ok {
+		if b := store.IdentityBoundOf("s3-bucket"); b.Max != 20 {
+			t.Errorf("the object store's access key is not bounded at 20: %+v", b)
+		}
+	}
+}

internal/catalogue/consumer_into_serves.go

@@ -114,7 +114,9 @@ func consumerInto(value, as string) (string, error) {
 // asDNSLabel writes a minted identity as a DNS label.
 //
 // The mesh's identities are already lower-case letters, digits and `_` (ConsumerIdentity), and
-// already short enough for the tightest backend they reach (CheckIdentity, twenty characters). So
+// already inside the bound of the provision serving them: a provider that serves one as a DNS label
+// bounds it at 63 or less (CheckServes, novox/hq ADR 0225), and one that serves it at all without
+// saying is held to twenty (IdentityBoundOf). So
 // this is the separator and nothing else — no lower-casing of what is already lower case, no
 // truncation to a limit the identity is already inside, no padding of a name that is already long
 // enough. Each of those would be the mesh guessing at a rule it has not been given.
@@ -141,11 +143,31 @@ func CheckServes(m Manifest) []string {
 				problems = append(problems, fmt.Sprintf(
 					"%s serves %s, and the value it serves as %q %s", m.Module, provision, key, err))
 			}
+			// A label longer than DNS keeps is not truncated here (asDNSLabel), so the offer's own
+			// bound has to keep the identity inside one (ADR 0225).
+			if strings.Contains(text, "${consumer:as:dns}") {
+				if b := m.IdentityBoundOf(provision); !b.Bounded() || b.Max > dnsLabelLimit {
+					problems = append(problems, fmt.Sprintf(
+						"%s serves %s's consumers their identity as a DNS label in %q, and bounds "+
+							"that identity at %s: a label keeps %d — state an `identity` of at most %d",
+						m.Module, provision, key, boundWords(b), dnsLabelLimit, dnsLabelLimit))
+				}
+			}
 		}
 	}
 	return problems
 }
 
+// dnsLabelLimit is the longest DNS label (RFC 1035 §2.3.4).
+const dnsLabelLimit = 63
+
+func boundWords(b IdentityBound) string {
+	if !b.Bounded() {
+		return "nothing"
+	}
+	return fmt.Sprintf("%d", b.Max)
+}
+
 func sortedServes(serves map[string]map[string]any) []string {
 	out := make([]string, 0, len(serves))
 	for k := range serves {

internal/catalogue/declaration.go

@@ -170,6 +170,10 @@ type Rendering struct {
 	// rather than resolved, because who consumes a node is a fact about the rest of the mesh and
 	// resolution answers questions about one machine.
 	Grants []Grant
+	// Withheld is every consumer left out of Grants because its identity overflows the provision's
+	// bound (novox/hq ADR 0225). Composed into nothing; carried so the machine's declaration can say
+	// whom it does not serve, and why, beside what it does.
+	Withheld []Overflow
 
 	// Ports is where this machine puts what each module needs reachable, by module and by the
 	// port the software itself uses (novox/hq ADR 0038).

internal/catalogue/identity.go

@@ -3,6 +3,7 @@ package catalogue
 import (
 	"fmt"
 	"regexp"
+	"sort"
 	"strings"
 )
 
@@ -56,13 +57,36 @@ func ConsumerIdentity(node, module string) string {
 	return IdentityPrefix + clean(node) + "_" + clean(module)
 }
 
-// identityLimit is the shortest identifier limit among the systems these names reach: an S3 access
+// IdentityBound is the longest consumer identity one provision's backend keeps, and what keeps it
-// key's 20 (novox/hq 04-ISSUES/010). PostgreSQL keeps 63 and MinIO 20, so 20 is the one that binds —
+// (novox/hq ADR 0049, refined by ADR 0225). Max zero means no bound: the provision keeps no name
-// the comment used to name PostgreSQL and was wrong. A name over it is refused, with the remedy a
+// derived from its consumer, or keeps one in something with no limit the mesh need respect.
-// short slug (ADR 0049), not silently cut to fit.
+type IdentityBound struct {
-const identityLimit = 20
+	// Max is the longest identity that backend keeps, in characters; zero for none.
+	Max int `json:"max,omitempty"`
+	// In is what keeps it, in words a refusal can quote: "an S3 access key", "a PostgreSQL role".
+	In string `json:"in,omitempty"`
+}
 
-// CheckIdentity refuses an identity that would not fit the tightest backend a consumer reaches.
+// Bounded is whether this bound refuses anything.
+func (b IdentityBound) Bounded() bool { return b.Max > 0 }
+
+// DefaultIdentityLimit is the bound on a provision whose provider receives its consumers and does
+// not say how long a name it keeps: an S3 access key's 20 (novox/hq 04-ISSUES/010, 034), the
+// tightest backend the mesh has met. It was the bound on every provision until ADR 0225; it stays
+// the bound on any that has not said otherwise, because a provider that is told each consumer's
+// identity may create a name from it in a backend nobody has measured.
+const DefaultIdentityLimit = 20
+
+// DefaultIdentityBound is DefaultIdentityLimit, said as a bound.
+var DefaultIdentityBound = IdentityBound{Max: DefaultIdentityLimit,
+	In: "a backend that has not said its limit (the tightest known, an S3 access key's)"}
+
+// identityLimit is the bound CheckIdentity applies, for a caller that does not know which provision
+// the identity is for.
+const identityLimit = DefaultIdentityLimit
+
+// CheckIdentity refuses an identity that would not fit the tightest backend the mesh knows. A caller
+// that knows the provision uses CheckIdentityWithin and that provision's own bound (ADR 0225).
 //
 // **Truncation is not an error in most of these systems** — a name past the limit is cut to fit and
 // the statement succeeds, so two consumers agreeing for the first N bytes would become one login
@@ -70,12 +94,127 @@ const identityLimit = 20
 // name and is the only thing that can choose another. The remedy is a first-class one: give the
 // module a short `slug` (ADR 0049), or shorten the machine's name.
 func CheckIdentity(node, module string) error {
+	return CheckIdentityWithin(node, module, IdentityBound{Max: identityLimit, In: "a backend (an S3 access key)"})
+}
+
+// CheckIdentityWithin refuses an identity that would not fit one provision's bound, and accepts any
+// identity for a provision with none (novox/hq ADR 0225).
+func CheckIdentityWithin(node, module string, bound IdentityBound) error {
+	if !bound.Bounded() {
+		return nil
+	}
 	got := ConsumerIdentity(node, module)
-	if len(got) <= identityLimit {
+	if len(got) <= bound.Max {
 		return nil
 	}
 	return fmt.Errorf(
-		"%s on %s is identified as %q, %d characters where a backend (an S3 access key) keeps %d — "+
+		"%s on %s is identified as %q, %d characters where %s keeps %d — "+
 			"give the module a shorter `slug` or shorten the machine's name",
-		module, node, got, len(got), identityLimit)
+		module, node, got, len(got), bound.In, bound.Max)
+}
+
+// Overflow is one consumer whose identity does not fit the provision it requires: left out of its
+// provider's grants and reported, never a reason to refuse the provider's machine (ADR 0225).
+type Overflow struct {
+	// Provision is what was required, Provider the machine answering it.
+	Provision string `json:"provision"`
+	Provider  string `json:"provider"`
+	// Consumer is the machine, Module the module on it that required it.
+	Consumer string `json:"consumer"`
+	Module   string `json:"module"`
+	// Identity is the name the mesh derived, and Bound what it overflows.
+	Identity string        `json:"identity"`
+	Bound    IdentityBound `json:"bound"`
+}
+
+func (o Overflow) String() string {
+	return fmt.Sprintf("%s on %s requires %s from %s and is identified as %q, %d characters where %s "+
+		"keeps %d — left out of %s's grants until the module's `slug` is shorter",
+		o.Module, o.Consumer, o.Provision, o.Provider, o.Identity, len(o.Identity), o.Bound.In,
+		o.Bound.Max, o.Provider)
+}
+
+// Overflowing is every requirement of this machine's modules whose identity overflows the bound of
+// the provision answering it. The same judgement the provider's composition makes before it grants
+// (grantsFor), made from the consumer's side so `status` can say it about every machine.
+func (r Resolution) Overflowing() []Overflow {
+	slugs := map[string]string{}
+	for _, m := range r.Modules {
+		slugs[m.Module] = m.Slug
+	}
+	var out []Overflow
+	seen := map[string]bool{}
+	for _, n := range r.Needs {
+		if n.ByRecord || !n.Identity.Bounded() {
+			continue
+		}
+		source := IdentitySource(slugs[n.For], n.For)
+		if CheckIdentityWithin(r.Node, source, n.Identity) == nil {
+			continue
+		}
+		key := n.Name + "\x00" + n.From + "\x00" + n.For
+		if seen[key] {
+			continue // one line per requirement, however many local names it has
+		}
+		seen[key] = true
+		out = append(out, Overflow{Provision: n.Name, Provider: n.From, Consumer: r.Node, Module: n.For,
+			Identity: ConsumerIdentity(r.Node, source), Bound: n.Identity})
+	}
+	sort.Slice(out, func(i, j int) bool {
+		if out[i].Module != out[j].Module {
+			return out[i].Module < out[j].Module
+		}
+		return out[i].Provision < out[j].Provision
+	})
+	return out
+}
+
+// DefaultLongestMachine is the machine name the catalogue check judges identities on when it is not
+// told one: the longest name of the mesh this catalogue is written for, so a catalogue that passes
+// passes on every machine that mesh has. `module check --longest-machine-name` says another mesh's;
+// a mesh that names a longer machine raises this in the same change (ADR 0225).
+const DefaultLongestMachine = 6
+
+// IdentityProblems is every module whose identity would overflow a provision it wants, on a machine
+// whose name is `longestMachine` characters — judged before merge, over the catalogue alone, so the
+// pull request that introduces an overflow is the one refused (novox/hq ADR 0225, issue 263). A
+// provision no module in the shelf offers is not judged: its bound is not known here.
+func IdentityProblems(shelf Shelf, longestMachine int) []string {
+	offeredBy := map[string][]string{}
+	for _, name := range shelfOrder(shelf) {
+		for _, o := range shelf[name].Offers() {
+			offeredBy[o] = append(offeredBy[o], name)
+		}
+	}
+	machine := strings.Repeat("n", longestMachine)
+	var problems []string
+	for _, name := range shelfOrder(shelf) {
+		m := shelf[name]
+		source := IdentitySource(m.Slug, m.Module)
+		for _, want := range m.Wants() {
+			// The tightest bound among the modules offering it: whichever one answers on a given
+			// machine, the identity has to fit it.
+			tightest, by := IdentityBound{}, ""
+			for _, provider := range offeredBy[want] {
+				if provider == name {
+					continue // a module answering its own requirement is not its own consumer
+				}
+				b := shelf[provider].IdentityBoundOf(want)
+				if b.Bounded() && (!tightest.Bounded() || b.Max < tightest.Max) {
+					tightest, by = b, provider
+				}
+			}
+			if CheckIdentityWithin(machine, source, tightest) == nil {
+				continue
+			}
+			got := ConsumerIdentity(machine, source)
+			problems = append(problems, fmt.Sprintf(
+				"%s wants %s, and %s keeps its consumers' identities in %s of at most %d characters: "+
+					"on a machine with a %d-character name it is identified as %q, %d — give %s a "+
+					"`slug` of at most %d characters",
+				name, want, by, tightest.In, tightest.Max, longestMachine, got, len(got), name,
+				tightest.Max-len(IdentityPrefix)-longestMachine-1))
+		}
+	}
+	return problems
 }

internal/catalogue/identity_bound_test.go

@@ -0,0 +1,190 @@
+package catalogue
+
+import (
+	"encoding/json"
+	"strings"
+	"testing"
+)
+
+// Each test names the decision it defends: novox/hq ADR 0225, which refines ADR 0049 after issue 263.
+
+// The provision a module requires sets the bound on its identity, not the tightest backend anywhere.
+func TestABoundIsTheProvisionsOwn(t *testing.T) {
+	store := Manifest{Module: "objects", Provides: []Offer{{Name: "s3-bucket", Scope: ScopeMesh,
+		Identity: &OfferIdentity{Max: 20, In: "an S3 access key"}}},
+		Receives: map[string]string{"s3-bucket": "/var/lib/mesh/objects/mesh.json"}}
+	database := Manifest{Module: "db", Provides: []Offer{{Name: "postgres-database", Scope: ScopeMesh,
+		Identity: &OfferIdentity{Max: 63, In: "a PostgreSQL role"}}},
+		Receives: map[string]string{"postgres-database": "/var/lib/mesh/db/mesh.json"}}
+	if b := store.IdentityBoundOf("s3-bucket"); b.Max != 20 || b.In != "an S3 access key" {
+		t.Errorf("an object store's stated bound was not taken: %+v", b)
+	}
+	if b := database.IdentityBoundOf("postgres-database"); b.Max != 63 {
+		t.Errorf("a database's stated bound was not taken: %+v", b)
+	}
+	// mesh_workstation_keycloak is 25: refused by the object store, accepted by the database.
+	if CheckIdentityWithin("workstation", "keycloak", store.IdentityBoundOf("s3-bucket")) == nil {
+		t.Error("a 25-character identity fit a 20-character access key")
+	}
+	if err := CheckIdentityWithin("workstation", "keycloak", database.IdentityBoundOf("postgres-database")); err != nil {
+		t.Errorf("a database consumer paid the object store's limit: %v", err)
+	}
+}
+
+// What an offer leaves unsaid follows from whether its provider can keep a name at all.
+func TestAnUnstatedBoundFollowsWhatTheProviderIsTold(t *testing.T) {
+	// Told nothing about its consumers — no receives, nothing served from their identity: no bound.
+	// The resolver provision is exactly this, and its consumers paid an object store's limit (263).
+	resolver := Manifest{Module: "resolver", Provides: []Offer{{Name: "wildcard-resolution", Scope: ScopeMesh}}}
+	if b := resolver.IdentityBoundOf("wildcard-resolution"); b.Bounded() {
+		t.Errorf("a provision that is told nothing of its consumers bounds them: %+v", b)
+	}
+	// Told each consumer and silent about its backend: the old global bound, not none.
+	told := Manifest{Module: "told", Provides: []Offer{{Name: "thing", Scope: ScopeMesh}},
+		Receives: map[string]string{"thing": "/var/lib/mesh/told/mesh.json"}}
+	if b := told.IdentityBoundOf("thing"); b.Max != DefaultIdentityLimit {
+		t.Errorf("a provider told its consumers and silent about its backend is not held to %d: %+v",
+			DefaultIdentityLimit, b)
+	}
+	// Serving a value built from the identity is being told it, too.
+	serving := Manifest{Module: "serving", Provides: []Offer{{Name: "bucket", Scope: ScopeMesh}},
+		Serves: map[string]map[string]any{"bucket": {"name": "b-${consumer:as:dns}"}}}
+	if b := serving.IdentityBoundOf("bucket"); b.Max != DefaultIdentityLimit {
+		t.Errorf("a provider deriving a name from its consumers is not bounded: %+v", b)
+	}
+	// And `false` says it outright, even for a provider that receives.
+	routes := Manifest{Module: "routes", Provides: []Offer{{Name: "route", Scope: ScopeMesh,
+		Identity: &OfferIdentity{None: true}}},
+		Receives: map[string]string{"route": "/var/lib/mesh/routes/mesh.json"}}
+	if b := routes.IdentityBoundOf("route"); b.Bounded() {
+		t.Errorf("`identity: false` still bounds: %+v", b)
+	}
+}
+
+// The field reads as written and writes back the same, and refuses what says nothing.
+func TestAnOffersIdentityIsParsedStrictly(t *testing.T) {
+	for _, raw := range []string{
+		`{"name":"s3-bucket","scope":"mesh","identity":{"max":20,"in":"an S3 access key"}}`,
+		`{"name":"wildcard-resolution","scope":"mesh","identity":false}`,
+		`{"name":"redis-cache","scope":"mesh","identity":{"in":"a Redis ACL user"}}`,
+	} {
+		var o Offer
+		if err := json.Unmarshal([]byte(raw), &o); err != nil {
+			t.Fatalf("%s: %v", raw, err)
+		}
+		back, err := json.Marshal(o)
+		if err != nil || string(back) != raw {
+			t.Errorf("did not round-trip:\n%s\n%s (%v)", raw, back, err)
+		}
+	}
+	for _, raw := range []string{
+		`{"name":"x","identity":true}`,
+		`{"name":"x","identity":{"max":20,"in":"y","most":3}}`,
+	} {
+		var o Offer
+		if err := json.Unmarshal([]byte(raw), &o); err == nil {
+			t.Errorf("accepted %s", raw)
+		}
+	}
+	bad := Manifest{Module: "bad", Version: "1", Provides: []Offer{
+		{Name: "unsaid", Scope: ScopeMesh, Identity: &OfferIdentity{Max: 20}},
+		{Name: "tiny", Scope: ScopeMesh, Identity: &OfferIdentity{Max: 4, In: "nothing usable"}},
+	}}
+	raw, err := json.Marshal(bad)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = ParseManifest(raw)
+	if err == nil || !strings.Contains(err.Error(), "without saying what keeps them") ||
+		!strings.Contains(err.Error(), "the shortest the mesh makes") {
+		t.Fatalf("a bound with no `in`, or too short for any identity, was accepted: %v", err)
+	}
+}
+
+// Refused before merge: the catalogue check judges each module's identity, on the longest machine
+// name, against the bound of every provision it wants — and names the module and the slug to set.
+func TestTheCatalogueCheckRefusesAnIdentityThatOverflowsWhatItRequires(t *testing.T) {
+	shelf := Shelf{
+		"objects": {Module: "objects", Provides: []Offer{{Name: "s3-bucket", Scope: ScopeMesh,
+			Identity: &OfferIdentity{Max: 20, In: "an S3 access key"}}},
+			Receives: map[string]string{"s3-bucket": "/var/lib/mesh/objects/mesh.json"}},
+		"photoalbum": {Module: "photoalbum", Requires: []string{"s3-bucket"}},
+		"files":      {Module: "files", Requires: []string{"s3-bucket"}},
+	}
+	problems := IdentityProblems(shelf, 6)
+	if len(problems) != 1 || !strings.Contains(problems[0], "photoalbum wants s3-bucket") ||
+		!strings.Contains(problems[0], `"mesh_nnnnnn_photoalbum", 22`) ||
+		!strings.Contains(problems[0], "`slug` of at most 8 characters") {
+		t.Fatalf("one overflow, named with its remedy, was expected: %q", problems)
+	}
+	// A longer machine name refuses more: the check is about the mesh's machines, not one.
+	if got := IdentityProblems(shelf, 10); len(got) != 2 {
+		t.Fatalf("on a 10-character name both overflow (mesh_nnnnnnnnnn_files is 21): %q", got)
+	}
+	// And a slug is the remedy it names.
+	album := shelf["photoalbum"]
+	album.Slug = "album"
+	shelf["photoalbum"] = album
+	if got := IdentityProblems(shelf, 6); len(got) != 0 {
+		t.Fatalf("a slug that fits is still refused: %q", got)
+	}
+}
+
+// Tonight's case (issue 263): networkmanager, no slug, requiring the mesh's resolver provision on a
+// machine with a six-character name. Under ADR 0049's one bound it was refused, and its provider's
+// whole machine with it; the resolver keeps no name, so it is not refused at all.
+func TestARequirementOnAKeylessProvisionComposesWithALongName(t *testing.T) {
+	shelf := Shelf{
+		"resolver":       {Module: "resolver", Provides: []Offer{{Name: "wildcard-resolution", Scope: ScopeMesh}}},
+		"networkmanager": {Module: "networkmanager", Requires: []string{"wildcard-resolution"}},
+	}
+	if CheckIdentity("laptop", "networkmanager") == nil {
+		t.Fatal("the regression is not reproduced: mesh_laptop_networkmanager fits the old global bound")
+	}
+	if got := IdentityProblems(shelf, 6); len(got) != 0 {
+		t.Fatalf("a requirement on a keyless provision was refused for its length: %q", got)
+	}
+	r := Resolution{Node: "laptop", Modules: []Manifest{shelf["networkmanager"]},
+		Needs: []Needed{{Name: "wildcard-resolution", From: "anchor", For: "networkmanager",
+			Identity: shelf["resolver"].IdentityBoundOf("wildcard-resolution")}}}
+	if got := r.Overflowing(); len(got) != 0 {
+		t.Fatalf("a keyless requirement is reported as overflowing: %+v", got)
+	}
+}
+
+// The consumer's side of the same judgement the provider's composition makes: what `status` says.
+func TestAnOverflowingRequirementIsNamedFromTheConsumersSide(t *testing.T) {
+	bound := IdentityBound{Max: 20, In: "an S3 access key"}
+	r := Resolution{Node: "laptop",
+		Modules: []Manifest{{Module: "photoalbum"}, {Module: "files"}, {Module: "gallery", Slug: "gal"}},
+		Needs: []Needed{
+			{Name: "s3-bucket", From: "anchor", For: "photoalbum", Identity: bound},
+			{Name: "s3-bucket", From: "anchor", For: "photoalbum", Local: "second", Identity: bound},
+			{Name: "s3-bucket", From: "anchor", For: "files", Identity: bound},
+			{Name: "s3-bucket", From: "anchor", For: "gallery", Identity: bound},
+			{Name: "licence", From: "records", For: "photoalbum", ByRecord: true, Identity: bound},
+		}}
+	got := r.Overflowing()
+	if len(got) != 1 || got[0].Module != "photoalbum" || got[0].Identity != "mesh_laptop_photoalbum" ||
+		got[0].Provider != "anchor" {
+		t.Fatalf("one overflow, once, was expected: %+v", got)
+	}
+	if said := got[0].String(); !strings.Contains(said, "an S3 access key keeps 20") ||
+		!strings.Contains(said, "slug") {
+		t.Fatalf("the overflow does not say what keeps it or the remedy: %s", said)
+	}
+}
+
+// An identity served as a DNS label is never truncated, so the offer's bound must keep it in one.
+func TestAnIdentityServedAsADNSLabelIsBoundedToOne(t *testing.T) {
+	serves := map[string]map[string]any{"bucket": {"name": "${consumer:as:dns}"}}
+	wide := Manifest{Module: "wide", Serves: serves, Provides: []Offer{{Name: "bucket", Scope: ScopeMesh,
+		Identity: &OfferIdentity{Max: 255, In: "a client id"}}}}
+	if got := CheckServes(wide); len(got) != 1 || !strings.Contains(got[0], "a label keeps 63") {
+		t.Fatalf("a 255-character bound on a DNS label passed: %q", got)
+	}
+	unsaid := Manifest{Module: "unsaid", Serves: serves, Provides: []Offer{{Name: "bucket", Scope: ScopeMesh}}}
+	if got := CheckServes(unsaid); len(got) != 0 {
+		t.Fatalf("the default bound (20) on a DNS label was refused: %q", got)
+	}
+}

internal/catalogue/manifest.go

@@ -8,6 +8,7 @@ package catalogue
 import (
 	"bytes"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"regexp"
 	"sort"
@@ -153,6 +154,84 @@ type Offer struct {
 	// a seat's holder gated by the machine's graphical session, and pulling one in for whatever asked
 	// is the misassignment research 026 found. Unmet, the requirement is refused naming who could.
 	Reach string `json:"reach,omitempty"`
+	// Identity is the longest consumer identity this provision's backend keeps (novox/hq ADR 0225):
+	// `{"max": 63, "in": "a PostgreSQL role"}`, or `false` for a provision that keeps no name derived
+	// from its consumer. Unsaid, the mesh assumes the tightest backend it knows when the provider is
+	// told its consumers, and no bound when it is not — see IdentityBoundOf.
+	Identity *OfferIdentity `json:"identity,omitempty"`
+}
+
+// OfferIdentity is what an offer says about the names its backend keeps for its consumers.
+type OfferIdentity struct {
+	// None is set by `"identity": false`: the provision keeps no name derived from its consumer.
+	None bool
+	// Max is the longest identity kept, in characters; zero with In set means no limit worth stating.
+	Max int
+	// In is what keeps it, for a refusal to quote.
+	In string
+}
+
+// UnmarshalJSON accepts `false` or `{"max": N, "in": "..."}`.
+func (i *OfferIdentity) UnmarshalJSON(raw []byte) error {
+	var flag bool
+	if err := json.Unmarshal(raw, &flag); err == nil {
+		if flag {
+			return errors.New("an offer's identity is false (it keeps no name) or {max, in}; true says nothing")
+		}
+		*i = OfferIdentity{None: true}
+		return nil
+	}
+	var full struct {
+		Max int    `json:"max,omitempty"`
+		In  string `json:"in"`
+	}
+	dec := json.NewDecoder(bytes.NewReader(raw))
+	dec.DisallowUnknownFields()
+	if err := dec.Decode(&full); err != nil {
+		return fmt.Errorf("an offer's identity is false or {max, in}: %w", err)
+	}
+	*i = OfferIdentity{Max: full.Max, In: full.In}
+	return nil
+}
+
+// MarshalJSON writes it back in the form it was written.
+func (i OfferIdentity) MarshalJSON() ([]byte, error) {
+	if i.None {
+		return []byte("false"), nil
+	}
+	return json.Marshal(struct {
+		Max int    `json:"max,omitempty"`
+		In  string `json:"in"`
+	}{i.Max, i.In})
+}
+
+// IdentityBoundOf is the bound this module's offer of a provision puts on its consumers' identities
+// (novox/hq ADR 0225).
+//
+// **What an offer says, it gets.** Where it says nothing, the bound follows from whether the
+// provider can keep a name at all: a provider that receives the provision, or serves its consumers
+// a value built from their identity, is told who each consumer is and may create a name from it in
+// a backend nobody measured — so it keeps the old global bound, DefaultIdentityBound. One that does
+// neither is told nothing about its consumers and keeps nothing of them: no bound. The resolver
+// provision is that case, and its consumers paid an object store's limit until this (issue 263).
+func (m Manifest) IdentityBoundOf(provision string) IdentityBound {
+	for _, o := range m.Provides {
+		if o.Name != provision || o.Identity == nil {
+			continue
+		}
+		if o.Identity.None {
+			return IdentityBound{}
+		}
+		return IdentityBound{Max: o.Identity.Max, In: o.Identity.In}
+	}
+	if _, receives := m.Receives[provision]; receives {
+		return DefaultIdentityBound
+	}
+	if served, err := json.Marshal(m.Serves[provision]); err == nil &&
+		bytes.Contains(served, []byte("${consumer:as")) {
+		return DefaultIdentityBound
+	}
+	return IdentityBound{}
 }
 
 // MachineReach is whether a provision is usable only on its provider's own machine.
@@ -206,20 +285,21 @@ func (o *Offer) UnmarshalJSON(raw []byte) error {
 		Scope      string           `json:"scope,omitempty"`
 		Credential *OfferCredential `json:"credential,omitempty"`
 		Reach      string           `json:"reach,omitempty"`
+		Identity   *OfferIdentity   `json:"identity,omitempty"`
 	}
 	dec := json.NewDecoder(bytes.NewReader(raw))
 	dec.DisallowUnknownFields()
 	if err := dec.Decode(&full); err != nil {
-		return fmt.Errorf("a provided name is either a string or {name, scope, credential, reach}: %w", err)
+		return fmt.Errorf("a provided name is either a string or {name, scope, credential, reach, identity}: %w", err)
 	}
-	o.Name, o.Scope, o.Credential, o.Reach = full.Name, full.Scope, full.Credential, full.Reach
+	o.Name, o.Scope, o.Credential, o.Reach, o.Identity = full.Name, full.Scope, full.Credential, full.Reach, full.Identity
 	return nil
 }
 
 // MarshalJSON writes back the short form when there is nothing else to say, so a manifest that
 // went through the mesh comes out looking like the one that went in.
 func (o Offer) MarshalJSON() ([]byte, error) {
-	if o.Scope == "" && o.Credential == nil && o.Reach == "" {
+	if o.Scope == "" && o.Credential == nil && o.Reach == "" && o.Identity == nil {
 		return json.Marshal(o.Name)
 	}
 	return json.Marshal(struct {
@@ -227,7 +307,8 @@ func (o Offer) MarshalJSON() ([]byte, error) {
 		Scope      string           `json:"scope,omitempty"`
 		Credential *OfferCredential `json:"credential,omitempty"`
 		Reach      string           `json:"reach,omitempty"`
-	}{o.Name, o.Scope, o.Credential, o.Reach})
+		Identity   *OfferIdentity   `json:"identity,omitempty"`
+	}{o.Name, o.Scope, o.Credential, o.Reach, o.Identity})
 }
 
 // Manifest is everything a module says about itself.
@@ -237,9 +318,10 @@ type Manifest struct {
 
 	// Slug is a short identifier the mesh uses in place of the module name when it derives a
 	// consumer's login (novox/hq ADR 0049). Optional: a module with a short name needs none. It
-	// exists because `mesh_<node>_<module>` must fit the tightest backend a consumer reaches — an S3
+	// exists because `mesh_<node>_<module>` must fit the bound of every provision the module
-	// access key is 20 characters — and a long module name would overflow it. A person choosing
+	// requires — an S3 access key's 20 characters is the tightest — and a long module name would
-	// `kc` for keycloak keeps the identity legible where a hash would not.
+	// overflow it (ADR 0225: the bound is the provision's own, and a keyless one has none). A person
+	// choosing `kc` for keycloak keeps the identity legible where a hash would not.
 	Slug string `json:"slug,omitempty"`
 
 	// Provides are the names other modules may require. A module always provides its own name;
@@ -1265,8 +1347,10 @@ func ParseManifest(raw []byte) (Manifest, error) {
 			"%q is not a usable module name: lower-case letters, digits, dashes and dots", m.Module))
 	}
 	// A slug is a short identifier the mesh derives a login from (novox/hq ADR 0049). The same
-	// charset as a name; its length is checked against a backend's limit at assignment, where the
+	// charset as a name; its length is judged against the bound of each provision it wants on the
-	// node it joins is known — a slug that is fine on one machine's short name can overflow another's.
+	// longest machine name by the catalogue check (IdentityProblems, ADR 0225), and against the
+	// machine it is on when its provider grants it — a slug that is fine on one machine's short name
+	// can overflow another's.
 	if m.Slug != "" && !name.MatchString(m.Slug) {
 		problems = append(problems, fmt.Sprintf(
 			"%q is not a usable slug: lower-case letters, digits, dashes and dots", m.Slug))
@@ -1303,6 +1387,20 @@ func ParseManifest(raw []byte) (Manifest, error) {
 		if !name.MatchString(p) {
 			problems = append(problems, fmt.Sprintf("%q is not a usable name to provide", p))
 		}
+		// A bound says what keeps the name, so the refusal it causes can say it (ADR 0225); and it
+		// leaves room for the shortest identity the mesh makes, or it would refuse every consumer.
+		if id := offer.Identity; id != nil && !id.None {
+			if strings.TrimSpace(id.In) == "" {
+				problems = append(problems, fmt.Sprintf(
+					"%s bounds the identities of %s's consumers without saying what keeps them: `in`",
+					m.Module, p))
+			}
+			if shortest := len(IdentityPrefix) + 3; id.Max < 0 || id.Max > 0 && id.Max < shortest {
+				problems = append(problems, fmt.Sprintf(
+					"%s bounds %s's consumers' identities at %d characters, and the shortest the mesh "+
+						"makes is %d", m.Module, p, id.Max, shortest))
+			}
+		}
 		if offer.Credential != nil {
 			own, declared := m.OwnSecrets[offer.Credential.Own]
 			switch {

internal/catalogue/resolve.go

@@ -194,6 +194,11 @@ type Needed struct {
 	// state, not a consumer missing its key. Set by the plan, which is the only layer that knows a
 	// licence's manager; empty for every consumer.
 	Manager bool
+	// Identity is the longest consumer identity the answering provision keeps (novox/hq ADR 0225),
+	// from the provider's own offer: what the mesh judges this consumer's identity against, on the
+	// consumer's side for `status` and on the provider's before it grants. No bound for a provision
+	// answered by a record, which keeps no name of anybody's.
+	Identity IdentityBound
 }
 
 // Refusal is why a set of assignments cannot become a declaration.
@@ -403,7 +408,7 @@ func Resolve(catalogue map[string]Manifest, assigned []string, node Node, world
 				needs = append(needs, Needed{
 					Name: want, From: node.Name, At: at,
 					Serves: servedByOne(by, want), For: because[want],
-					SharedOwn: sharedByOne(by, want)})
+					SharedOwn: sharedByOne(by, want), Identity: by.IdentityBoundOf(want)})
 			} else if served := servedByOne(by, want); len(served) > 0 {
 				// Answered here with no credential to mint, but the provider serves facts the
 				// consumer cannot guess — a port, a model name — and so still needs a binding.
@@ -447,11 +452,15 @@ func Resolve(catalogue map[string]Manifest, assigned []string, node Node, world
 					return
 				}
 				shared := ""
+				// A provider whose definition is not in hand is held to the tightest bound the
+				// mesh knows, not to none: what it keeps is not known here (ADR 0225).
+				bound := DefaultIdentityBound
 				if pm, known := catalogue[p.Module]; known {
 					shared, _ = pm.SharedCredentialOf(want)
+					bound = pm.IdentityBoundOf(want)
 				}
 				needs = append(needs, Needed{Name: want, From: p.Node, At: p.At,
-					Serves: p.Serves, For: because[want], SharedOwn: shared})
+					Serves: p.Serves, For: because[want], SharedOwn: shared, Identity: bound})
 			}
 			switch {
 			case world.Unchecked:

internal/catalogue/verbs.go

@@ -142,7 +142,7 @@ var ControllerVerbs = []Verb{
 			"node":   "the machine's name; without it, every machine that is behind",
 			"behind": "\"true\": every machine that is behind, the whole mesh — the same as naming none, said outright; not with node",
 		}, nil, "behind")},
-	{Name: "rotate", Description: "Replace a credential. A pair credential, by provision (and a consuming machine, " +
+	{Name: "rotate", Description: "Replace a credential. A pair credential, by provision (and a consuming machine and module, " +
 		"else every holder): both ends are re-sent together. Or a module's own secret, by machine, module and " +
 		"name: made anew and the machine sent, so the module starts again on it — only for a secret its " +
 		"definition says it reads at start; a value given to the mesh, or one the module applies to a backend, is refused with the reason.",
@@ -150,7 +150,7 @@ var ControllerVerbs = []Verb{
 			"provision": "a pair credential: the provision whose credential to replace",
 			"consumer":  "with provision: only the holder on this machine (optional)",
 			"node":      "an own secret: the machine",
-			"module":    "an own secret: the module",
+			"module":    "an own secret: the module; with provision: only this consuming module's credential (optional)",
 			"secret":    "an own secret: its name in the module's definition",
 		}, nil)},
 	{Name: "issue", Description: "Give a module on a machine its account on the bus: minted, and sealed to the " +