mesh-cli: give a terminal line the standard input mesh-cli carried, refuse it to any other, keep it nowhere

A secret given at the controller's terminal through mesh-cli (secret accept … --from -) never reached the
line: every line ran with no standard input. A line that runs as the terminal now reads what mesh-cli
carried (at most 64 KiB); an ordinary call carrying any is refused and nothing runs; the calls record keeps
only that some was given, the journal and the answer nothing of it.

cmd/mesh-controller/meshcli.go

@@ -141,6 +141,12 @@ func runForMeshCLI(ctx context.Context, node string, asked link.CLIAsked, v cliV
 	if v.refused != "" {
 		return link.CLIRefusal(v.refused)
 	}
+	// Standard input is the terminal's alone: a secret given at the terminal reaches `secret accept`, and no ordinary
+	// call is handed what the asker's standard input held (novox/hq ADR 0259 §10, ADR 0272).
+	if len(asked.Stdin) > 0 && !v.terminal {
+		return link.CLIAnswer{Exit: 1, Why: v.why, Refused: "standard input is given to a line that runs as the " +
+			"controller's terminal alone, and this one does not. Nothing ran"}
+	}
 	if cliServers[asked.Line[0]] {
 		return link.CLIAnswer{Exit: 1, Why: v.why, Refused: fmt.Sprintf("%s serves until stopped, and is not a "+
 			"command line mesh-cli runs. Nothing ran", asked.Line[0])}
@@ -155,8 +161,12 @@ func runForMeshCLI(ctx context.Context, node string, asked link.CLIAsked, v cliV
 	}
 	cmd := selfCommand(ctx, line)
 	cmd.Env = commandEnvironment(fmt.Sprintf("%s through mesh-cli on %s", asked.Account, node), verb, v.terminal)
-	// No standard input: a command that reads one gets nothing, and fails saying so (ADR 0272 §5).
+	// No standard input unless mesh-cli carried one for a terminal line: a command that reads one gets nothing, and
+	// fails saying so (ADR 0272 §5).
 	cmd.Stdin = nil
+	if len(asked.Stdin) > 0 {
+		cmd.Stdin = bytes.NewReader(asked.Stdin)
+	}
 	var stdout, stderr bytes.Buffer
 	cmd.Stdout, cmd.Stderr = &stdout, &stderr
 	err := cmd.Run()

cmd/mesh-controller/meshcli_stdin_test.go

@@ -0,0 +1,99 @@
+package main
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"strings"
+	"sync"
+	"testing"
+)
+
+// secretAcceptWants makes the test binary, run as a command line, read a secret as `secret accept` reads it and
+// say whether it is the value whose SHA-256 the variable names (TestMain).
+const secretAcceptWants = "MESH_TEST_SECRET_ACCEPT_WANTS"
+
+// readAsSecretAccept is that process: `secret accept <node> <module> <name> [--from -]`, the value read by
+// valueFor, compared by digest, and only the verdict printed.
+func readAsSecretAccept(want string, argv []string) int {
+	if len(argv) < 5 || argv[0] != "secret" || argv[1] != "accept" {
+		fmt.Printf("not a secret accept line: %q\n", argv)
+		return 2
+	}
+	from := ""
+	if len(argv) == 7 && argv[5] == "--from" {
+		from = argv[6]
+	}
+	value, err := valueFor(argv[2], argv[3], argv[4], from)
+	if err != nil {
+		fmt.Printf("secret accept read nothing: %v\n", err)
+		return 1
+	}
+	sum := sha256.Sum256([]byte(asSupplied(value)))
+	if hex.EncodeToString(sum[:]) != want {
+		fmt.Printf("secret accept read something else (%d bytes)\n", len(value))
+		return 1
+	}
+	fmt.Println("secret accept read the value it was given")
+	return 0
+}
+
+// novox/hq ADR 0259 §10, ADR 0272: what mesh-cli's standard input held reaches `secret accept` on a line that runs
+// as the controller's terminal, and appears nowhere else — not in the answer, not in the journal, not in the calls
+// record; an ordinary line carrying it is refused and nothing runs.
+func TestStandardInputReachesSecretAcceptAtTheTerminalAndNowhereElse(t *testing.T) {
+	token := "123456789:AAEhBOweik6ad9r_QxGivenAtTheTerminal"
+	sum := sha256.Sum256([]byte(token))
+	t.Setenv(secretAcceptWants, hex.EncodeToString(sum[:]))
+	var journal []string
+	var mu sync.Mutex
+	was := cliJournal
+	cliJournal = func(line string) { mu.Lock(); journal = append(journal, line); mu.Unlock() }
+	t.Cleanup(func() { cliJournal = was })
+	ctx := context.Background()
+
+	for _, line := range [][]string{
+		{"secret", "accept", "anchor", "telegram", "telegram-token", "--from", "-"},
+		{"secret", "accept", "anchor", "telegram", "telegram-token"}, // the prompt's path, a line on standard input
+	} {
+		asked := cliAsked("operator", 1000, line...)
+		asked.Stdin = []byte(token + "\n")
+		a := runForMeshCLI(ctx, "control", asked, cliVerdict{terminal: true, why: "the terminal"})
+		if a.Exit != 0 || !strings.Contains(string(a.Stdout), "read the value it was given") {
+			t.Fatalf("%q: secret accept did not read what mesh-cli carried: %+v (%s)", line, a, a.Stdout)
+		}
+		if body, _ := json.Marshal(a); strings.Contains(string(body), "AAEh") || strings.Contains(string(body), base64.StdEncoding.EncodeToString([]byte(token))) {
+			t.Fatalf("the answer carries the secret: %s", body)
+		}
+	}
+
+	// Without standard input, the line reads nothing, as before.
+	a := runForMeshCLI(ctx, "control", cliAsked("operator", 1000, "secret", "accept", "anchor", "telegram",
+		"telegram-token", "--from", "-"), cliVerdict{terminal: true, why: "the terminal"})
+	if a.Exit == 0 {
+		t.Fatalf("a line with no standard input read a value: %+v", a)
+	}
+
+	// An ordinary call is never handed it: refused, and nothing ran.
+	asked := cliAsked("operator", 1000, "status")
+	asked.Stdin = []byte(token)
+	a = runForMeshCLI(ctx, "laptop", asked, cliVerdict{why: "not the terminal"})
+	if a.Exit == 0 || !strings.Contains(a.Refused, "terminal alone") || len(a.Stdout) != 0 {
+		t.Fatalf("an ordinary line was given standard input: %+v", a)
+	}
+
+	mu.Lock()
+	defer mu.Unlock()
+	for _, l := range journal {
+		if strings.Contains(l, "AAEh") {
+			t.Fatalf("the journal says the secret: %s", l)
+		}
+	}
+	if len(journal) == 0 {
+		t.Fatal("the lines were not said in the journal at all")
+	}
+
+}

cmd/mesh-controller/sayable_test.go

@@ -28,6 +28,11 @@ import (
 func TestMain(m *testing.M) {
 	// The process a mesh-cli test runs as a command line: it says the verb and the caller it was given, and
 	// ends (meshcli_test.go).
+	// The process a mesh-cli test runs as `secret accept`: it reads its value exactly as `secret accept` does
+	// (valueFor) and says whether it is the one the test gave, never the value (meshcli_stdin_test.go).
+	if want := os.Getenv(secretAcceptWants); want != "" {
+		os.Exit(readAsSecretAccept(want, os.Args[1:]))
+	}
 	if os.Getenv(echoEnvironment) != "" {
 		fmt.Printf("verb=%q caller=%q terminal=%v\n", os.Getenv("MESH_VERB"), os.Getenv("MESH_CALLER"), startedAtTheTerminal())
 		os.Exit(0)

internal/link/calls.go

@@ -461,7 +461,7 @@ func kept(args json.RawMessage) json.RawMessage {
 	for k, v := range given {
 		s, isString := v.(string)
 		switch {
-		case k == "values" || k == "secret":
+		case k == "values" || k == "secret" || k == "stdin":
 			out[k] = "(given, not kept)"
 		case k == "line":
 			// A mesh-cli line (ADR 0272): its command word, never the rest, which may carry settings.

internal/link/meshcli.go

@@ -41,6 +41,30 @@ type CLIAsked struct {
 	// (`session-<id>.scope` under the account's own slice), or empty: a service, a user unit. Only a login session is
 	// the terminal (novox/hq ADR 0272).
 	Session string `json:"session,omitempty"`
+	// Stdin is what mesh-cli's standard input held, at most CLIMaxStdin: given to a line that runs as the terminal,
+	// as its standard input, and refused with any other (novox/hq ADR 0259 §10, ADR 0272). It is kept nowhere: not in
+	// the calls record (cliRecorded), not in the journal, not in the answer.
+	Stdin []byte `json:"stdin,omitempty"`
+}
+
+// CLIMaxStdin bounds the standard input a mesh-cli line carries (mesh-sdk go/cli MaxStdin).
+const CLIMaxStdin = 64 << 10
+
+// cliRecorded is the request as the calls record keeps it: everything but the standard input, which the record
+// never holds in any form. The line itself is cut to its command word by the record's own rule (kept).
+func cliRecorded(raw json.RawMessage) json.RawMessage {
+	var m map[string]json.RawMessage
+	if json.Unmarshal(raw, &m) != nil {
+		return json.RawMessage(`{}`)
+	}
+	if _, given := m["stdin"]; given {
+		// Said as given, under a key of its own: the record still reads as the request it was (followCLI decodes
+		// it), and holds nothing of the input.
+		delete(m, "stdin")
+		m["stdin-given"] = json.RawMessage(`true`)
+	}
+	body, _ := json.Marshal(m)
+	return body
 }
 
 // CLIAnswer is what the controller answers, as the `result` of a call's answer: what the command printed, how it
@@ -135,6 +159,10 @@ func (b OverNATS) answerCLI(msg *nats.Msg, calls *CallLog, slots chan struct{},
 	case len(asked.Line) == 0:
 		respond(cliEnvelope(CLIRefusal("the request names no command, so nothing ran")))
 		return
+	case len(asked.Stdin) > CLIMaxStdin:
+		respond(cliEnvelope(CLIRefusal(fmt.Sprintf("standard input of more than %d bytes is not taken, so nothing ran",
+			CLIMaxStdin))))
+		return
 	}
 	select {
 	case slots <- struct{}{}:
@@ -145,7 +173,7 @@ func (b OverNATS) answerCLI(msg *nats.Msg, calls *CallLog, slots chan struct{},
 		return
 	}
 	limit := b.Conn.MaxPayload()
-	calls.serveCallWithin(CLISeat, node, msg.Data, msg.Reply, func(ctx context.Context, _ json.RawMessage) (any, error) {
+	calls.serveCallWithin(CLISeat, node, cliRecorded(msg.Data), msg.Reply, func(ctx context.Context, _ json.RawMessage) (any, error) {
 		return fitCLI(handle(ctx, node, asked), limit-4096), nil
 	}, msg.Respond, limit, logger)
 }

internal/link/meshcli_test.go

@@ -30,6 +30,10 @@ func TestTheMeshCLIRequestAndAnswerKeepTheirFieldNames(t *testing.T) {
 	if got := keysIn(t, body); got != "cut exit refused stderr stdout terminal why" {
 		t.Fatalf("the answer's fields are %q", got)
 	}
+	body, _ = json.Marshal(CLIAsked{Line: []string{"secret"}, Account: "a", UID: 1, Stdin: []byte("x")})
+	if got := keysIn(t, body); got != "account line stdin uid" {
+		t.Fatalf("a request with standard input has the fields %q", got)
+	}
 	body, _ = json.Marshal(CLIAsked{Follow: "call-1", Account: "a", UID: 1})
 	if got := keysIn(t, body); got != "account follow uid" {
 		t.Fatalf("a follow's fields are %q", got)
@@ -267,3 +271,26 @@ func TestTheWithholdingTestsHoldSomething(t *testing.T) {
 		t.Fatalf("a record carrying the answer is not found carrying it: %s", body)
 	}
 }
+
+// novox/hq ADR 0259 §10: mesh-cli's standard input — a secret given at the terminal — is never in the calls record,
+// in any form, whichever way the request reaches it.
+func TestAMeshCLIRecordNeverKeepsItsStandardInput(t *testing.T) {
+	secret := "123456789:AAEhBOweik6ad9r_QxGivenAtTheTerminal"
+	raw, _ := json.Marshal(CLIAsked{Line: []string{"secret", "accept", "anchor", "telegram", "telegram-token", "--from", "-"},
+		Account: "operator", UID: 1000, Stdin: []byte(secret)})
+	for name, got := range map[string]json.RawMessage{"as answerCLI records it": kept(cliRecorded(raw)),
+		"as the record alone would keep it": kept(raw)} {
+		if carries(got, secret) || strings.Contains(string(got), base64.StdEncoding.EncodeToString([]byte(secret))[:20]) {
+			t.Fatalf("%s, the record keeps %s", name, got)
+		}
+		if !strings.Contains(string(got), "secret") || !strings.Contains(string(got), "given, not kept") &&
+			!strings.Contains(string(got), "stdin-given") {
+			t.Fatalf("%s, the record does not say a line was asked with standard input: %s", name, got)
+		}
+	}
+	// The record still reads as the request, so the asker can follow its call.
+	var asked CLIAsked
+	if err := json.Unmarshal(kept(cliRecorded(raw)), &asked); err != nil || asked.Account != "operator" || len(asked.Stdin) > 0 {
+		t.Fatalf("the recorded request reads as %+v (%v)", asked, err)
+	}
+}