refactor(db): migrate all ids to a uniform canonical 128-bit base62 encoding (#5824)

* refactor(model): extract canonical 128-bit base62 id codec

* feat(model): generate random ids as canonical 128-bit base62 values

* feat(scanner): emit legacy PIDs in canonical base62 encoding

* feat(db): add id canonicalization transform for the uniform-ids migration

* feat(db): migrate all ids to canonical 128-bit base62 encoding

* fix(db): canonicalize ids in junction tables and JSON columns

* chore(jellyfin): update id-family notes for uniform canonical ids

* test(ids): harden codec input contract and migration edge coverage

* refactor(model): use log.Fatal for Encode128 contract guard per project convention

* fix(db): force full rescan after id migration for legacy PID configs

* test(db): guard id-column inventory against schema drift

* refactor(ids): compile-time Encode128 contract and unified column rewrite helper

* refactor(db): apply review feedback to id migration

Filter empty strings in collectColumn's SQL, reuse a prepared statement
for rewriteColumn updates, and clarify the legacy ID functions' comment
now that they emit the canonical encoding.

* feat(auth): split session and public-link JWT secrets, rotating sessions on id migration

* test(subsonic): initialize public token secret in helpers suite

The suite sets auth.TokenAuth directly instead of calling auth.Init, so the
new PublicTokenAuth was nil whenever Ginkgo's spec order ran a helpers spec
before any spec that calls auth.Init, panicking in publicurl.ImageURL.

* refactor(db): inline canonicalID into its only consumer, the uniform-ids migration

* refactor(model): rename Encode128/Decode128 to Encode/Decode

With every id now exactly 128 bits, the width suffix is redundant; the
package-qualified id.Encode/id.Decode carries the same information.

* test(db): make the id-columns guard classify JSON columns too

The guard only inspected columns named id/pid/*_id, so it could not see ids
embedded in JSON. Widen it to *_ids and to every JSON column, and drive the
"covered" set from a new embeddedIDColumns list instead of the inline calls
in the migration.

Every JSON column the schema has now carries a verdict. The four denormalized
caches -- media_file/album.participants, media_file/album.tags,
album.folder_ids and artist.similar_artists -- hold only artist, tag and
folder ids. Those all come from id.NewHash, whose 22-char base62 encoding of
a 128-bit MD5 is already in canonical range, so canonicalID is the identity
on them and the migration correctly leaves them alone. A new codec test pins
that invariant, since the exemptions depend on it.

Verified on a copy of a 727MB/96k-track production database: canonicalizing
those four columns changed zero rows, and artist, tag and folder ids were
themselves unchanged by the migration (only media_file ids moved, 95108 of
96666).

core/auth/auth.go

@@ -19,35 +19,41 @@ import (
 )
 
 var (
-	once      sync.Once
+	once sync.Once
+	// TokenAuth signs UI/API session tokens. Rotated by the id migration so stale sessions die.
 	TokenAuth *jwtauth.JWTAuth
+	// PublicTokenAuth signs public-link tokens (artwork, share streams), on a separate secret that survives the rotation.
+	PublicTokenAuth *jwtauth.JWTAuth
 )
 
-// Init creates a JWTAuth object from the secret stored in the DB.
-// If the secret is not found, it will create a new one and store it in the DB.
+// Init creates the JWTAuth objects from the secrets stored in the DB.
+// Missing or undecryptable secrets are regenerated and stored.
 func Init(ds model.DataStore) {
 	once.Do(func() {
 		ctx := context.TODO()
 		log.Info("Setting Session Timeout", "value", conf.Server.SessionTimeout)
 
-		secret, err := ds.Property(ctx).Get(consts.JWTSecretKey)
-		if err != nil || secret == "" {
-			log.Info(ctx, "Creating new JWT secret, used for encrypting UI sessions")
-			secret = createNewSecret(ctx, ds)
-		} else {
-			if secret, err = utils.Decrypt(ctx, getEncKey(), secret); err != nil {
-				log.Error(ctx, "Could not decrypt JWT secret, creating a new one", err)
-				secret = createNewSecret(ctx, ds)
-			}
-		}
-
-		TokenAuth = jwtauth.New("HS256", []byte(secret), nil)
+		TokenAuth = jwtauth.New("HS256", []byte(loadOrCreateSecret(ctx, ds, consts.JWTSecretKey)), nil)
+		PublicTokenAuth = jwtauth.New("HS256", []byte(loadOrCreateSecret(ctx, ds, consts.JWTPublicSecretKey)), nil)
 	})
 }
 
+func loadOrCreateSecret(ctx context.Context, ds model.DataStore, key string) string {
+	secret, err := ds.Property(ctx).Get(key)
+	if err != nil || secret == "" {
+		log.Info(ctx, "Creating new JWT secret", "key", key)
+		return createNewSecret(ctx, ds, key)
+	}
+	if secret, err = utils.Decrypt(ctx, getEncKey(), secret); err != nil {
+		log.Error(ctx, "Could not decrypt JWT secret, creating a new one", "key", key, err)
+		return createNewSecret(ctx, ds, key)
+	}
+	return secret
+}
+
 func CreatePublicToken(claims Claims) (string, error) {
 	claims.Issuer = consts.JWTIssuer
-	_, token, err := TokenAuth.Encode(claims.ToMap())
+	_, token, err := PublicTokenAuth.Encode(claims.ToMap())
 	return token, err
 }
 
@@ -56,7 +62,7 @@ func CreateExpiringPublicToken(exp time.Time, claims Claims) (string, error) {
 	if !exp.IsZero() {
 		claims.ExpiresAt = exp
 	}
-	_, token, err := TokenAuth.Encode(claims.ToMap())
+	_, token, err := PublicTokenAuth.Encode(claims.ToMap())
 	return token, err
 }
 
@@ -91,6 +97,15 @@ func Validate(tokenStr string) (Claims, error) {
 	return ClaimsFromToken(token), nil
 }
 
+// ValidatePublic verifies a public-link token against the public secret.
+func ValidatePublic(tokenStr string) (Claims, error) {
+	token, err := jwtauth.VerifyToken(PublicTokenAuth, tokenStr)
+	if err != nil {
+		return Claims{}, err
+	}
+	return ClaimsFromToken(token), nil
+}
+
 func WithAdminUser(ctx context.Context, ds model.DataStore) context.Context {
 	u, err := ds.User(ctx).FindFirstAdmin()
 	if err != nil {
@@ -107,14 +122,14 @@ func WithAdminUser(ctx context.Context, ds model.DataStore) context.Context {
 	return request.WithUser(ctx, *u)
 }
 
-func createNewSecret(ctx context.Context, ds model.DataStore) string {
+func createNewSecret(ctx context.Context, ds model.DataStore, key string) string {
 	secret := id.NewRandom()
 	encSecret, err := utils.Encrypt(ctx, getEncKey(), secret)
 	if err != nil {
 		log.Error(ctx, "Could not encrypt JWT secret", err)
 		return secret
 	}
-	if err := ds.Property(ctx).Put(consts.JWTSecretKey, encSecret); err != nil {
+	if err := ds.Property(ctx).Put(key, encSecret); err != nil {
 		log.Error(ctx, "Could not save JWT secret in DB", err)
 	}
 	return secret

core/auth/auth_test.go

@@ -89,6 +89,51 @@ var _ = Describe("Auth", func() {
 		})
 	})
 
+	Describe("Session/Public secret split", func() {
+		claims := func() map[string]any {
+			return map[string]any{"iss": "issuer", "exp": time.Now().Add(1 * time.Minute).Unix()}
+		}
+
+		It("verifies a session token via Validate but not ValidatePublic", func() {
+			_, tokenStr, err := auth.TokenAuth.Encode(claims())
+			Expect(err).NotTo(HaveOccurred())
+			_, err = auth.Validate(tokenStr)
+			Expect(err).NotTo(HaveOccurred())
+			_, err = auth.ValidatePublic(tokenStr)
+			Expect(err).To(HaveOccurred())
+		})
+
+		It("verifies a public token via ValidatePublic but not Validate", func() {
+			_, tokenStr, err := auth.PublicTokenAuth.Encode(claims())
+			Expect(err).NotTo(HaveOccurred())
+			_, err = auth.ValidatePublic(tokenStr)
+			Expect(err).NotTo(HaveOccurred())
+			_, err = auth.Validate(tokenStr)
+			Expect(err).To(HaveOccurred())
+		})
+
+		It("decodes public tokens minted by CreatePublicToken via PublicTokenAuth", func() {
+			tokenStr, err := auth.CreatePublicToken(auth.Claims{ID: "art-1"})
+			Expect(err).NotTo(HaveOccurred())
+			claims, err := auth.ValidatePublic(tokenStr)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(claims.ID).To(Equal("art-1"))
+			_, err = auth.Validate(tokenStr)
+			Expect(err).To(HaveOccurred())
+		})
+
+		It("decodes expiring public tokens minted by CreateExpiringPublicToken via PublicTokenAuth", func() {
+			exp := time.Now().Add(1 * time.Hour)
+			tokenStr, err := auth.CreateExpiringPublicToken(exp, auth.Claims{ID: "art-2"})
+			Expect(err).NotTo(HaveOccurred())
+			claims, err := auth.ValidatePublic(tokenStr)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(claims.ID).To(Equal("art-2"))
+			_, err = auth.Validate(tokenStr)
+			Expect(err).To(HaveOccurred())
+		})
+	})
+
 	Describe("TouchToken", func() {
 		It("updates the expiration time", func() {
 			yesterday := time.Now().Add(-oneDay)