Move ssh-client's tests and dependencies onto the SDK's forgekey (issue 1480), part 3 of 17

modules/ssh-client/cmd/ssh-client-tools/helpers_test.go

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"encoding/base64"
+	"encoding/binary"
+)
+
+// ed25519Line is a public key line with a well-formed ed25519 blob.
+func ed25519Line(seed byte, comment string) string {
+	blob := []byte{}
+	for _, part := range [][]byte{[]byte("ssh-ed25519"), make([]byte, 32)} {
+		part2 := append([]byte(nil), part...)
+		if len(part2) == 32 {
+			part2[0] = seed
+		}
+		l := make([]byte, 4)
+		binary.BigEndian.PutUint32(l, uint32(len(part2)))
+		blob = append(append(blob, l...), part2...)
+	}
+	return "ssh-ed25519 " + base64.StdEncoding.EncodeToString(blob) + " " + comment
+}