refactor: move vendor app credentials and signing keys into config

The provider apps' own identifiers and protocol keys were scattered as
constants across six packages. They are not user secrets and stay baked in so
the tool still works out of the box, but they are now mirrored into the config
so that when a provider rotates one, a user can fix their install with a config
edit instead of waiting for a release.

Moved, each with the current value as the default in internal/config:
  qobuz     mobile_app_id, mobile_app_secret
  tidal     app_client_id, app_client_secret
  deezer    api_key, gateway_key, blowfish_secret
  yandex    sign_key, legacy_mp3_sign_salt
  beatport  app_client_id

applyVendorDefaults backfills any empty value, so configs written before these
keys existed keep working and the clients never have to nil-check them. Each
client reads through a small accessor; the package-level signing helpers
(mobileSignRequest, yandexDownloadSign, legacyDirectURL, deriveGatewayAuthToken
and friends, deriveDeezerBlowfishKey) now take the key as a parameter instead
of closing over a constant. The blowfish secret reaches internal/download
through a field on Downloader set by app.New.

The blowfish key derivation XORs 16 bytes of the secret, so a mistyped override
would have panicked; a wrong-length value is now rejected with a warning and
the built-in value is used. Tests pin the length and that the qobuz mobile
secret is valid hex, since the HKDF step requires it.

Also drops soundcloud.client_id and soundcloud.app_version: soundcloud goes
through yt-dlp, which supplies its own, so nothing read them.

config.toml.example documents each new key as "leave empty unless the vendor
rotates theirs".

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

internal/app/app.go

@@ -129,6 +129,9 @@ func New(cfg *config.Config) (*Main, error) {
 		Pending:   []media.Pending{},
 		Media:     []media.Media{},
 	}
+	// The downloader does the Deezer decryption, so it needs the protocol
+	// secret from config rather than a constant of its own.
+	m.DL.DeezerBlowfishSecret = cfg.Session.Deezer.BlowfishSecret
 	verbose.SetSink(func(msg string) { m.DL.Logf("%s", msg) })
 	return m, nil
 }

internal/config/config.go

@@ -66,6 +66,11 @@ type QobuzConfig struct {
 	PasswordOrToken string   `toml:"password_or_token"`
 	AppID           string   `toml:"app_id"`
 	Secrets         []string `toml:"secrets"`
+
+	// Vendor app credentials for the mobile API fallback. Defaulted in code;
+	// override here when Qobuz rotates them, instead of waiting for a release.
+	MobileAppID     string `toml:"mobile_app_id"`
+	MobileAppSecret string `toml:"mobile_app_secret"`
 }
 
 type TidalConfig struct {
@@ -77,6 +82,10 @@ type TidalConfig struct {
 	AccessToken    string `toml:"access_token"`
 	RefreshToken   string `toml:"refresh_token"`
 	TokenExpiry    int64  `toml:"token_expiry"`
+
+	// Vendor OAuth app credentials. Defaulted in code; override on rotation.
+	AppClientID     string `toml:"app_client_id"`
+	AppClientSecret string `toml:"app_client_secret"`
 }
 
 type DeezerConfig struct {
@@ -86,12 +95,21 @@ type DeezerConfig struct {
 	Email                      string `toml:"email"`
 	Password                   string `toml:"password"`
 	RefreshToken               string `toml:"refresh_token"`
+
+	// Vendor protocol keys. Defaulted in code; override on rotation.
+	APIKey         string `toml:"api_key"`
+	GatewayKey     string `toml:"gateway_key"`
+	BlowfishSecret string `toml:"blowfish_secret"`
 }
 
 type YandexConfig struct {
 	Quality     int    `toml:"quality"`
 	AccessToken string `toml:"access_token"`
 	UserID      string `toml:"user_id"`
+
+	// Vendor request-signing keys. Defaulted in code; override on rotation.
+	SignKey           string `toml:"sign_key"`
+	LegacyMP3SignSalt string `toml:"legacy_mp3_sign_salt"`
 }
 
 type BeatportConfig struct {
@@ -102,12 +120,15 @@ type BeatportConfig struct {
 	AccessToken             string `toml:"access_token"`
 	RefreshToken            string `toml:"refresh_token"`
 	TokenExpiry             int64  `toml:"token_expiry"`
+
+	// Vendor OAuth app credential. Defaulted in code; override on rotation.
+	AppClientID string `toml:"app_client_id"`
 }
 
+// SoundcloudConfig has no client_id/app_version: soundcloud is handled via
+// yt-dlp, which supplies its own, so those keys were read by no code.
 type SoundcloudConfig struct {
-	Quality    int    `toml:"quality"`
-	ClientID   string `toml:"client_id"`
-	AppVersion string `toml:"app_version"`
+	Quality int `toml:"quality"`
 }
 
 type DatabaseConfig struct {
@@ -211,6 +232,60 @@ func Load(path string) (*Config, error) {
 	return &Config{Path: resolvedPath, File: data, Session: cloneConfigData(data)}, nil
 }
 
+// Vendor app credentials and protocol keys.
+//
+// These are the provider apps' own identifiers and signing keys, not user
+// secrets, and they are baked in so the tool works out of the box. They are
+// mirrored into the config so that when a provider rotates one, a user can fix
+// their install with a config edit instead of waiting for a new release.
+const (
+	DefaultQobuzMobileAppID     = "312369995"
+	DefaultQobuzMobileAppSecret = "e79f8b9be485692b0e5f9dd895826368"
+	DefaultTidalAppClientID     = "fX2JxdmntZWK0ixT"
+	DefaultTidalAppClientSecret = "1Nm5AfDAjxrgJFJbKNWLeAyKGVGmINuXPPLHVXAvxAg="
+	DefaultDeezerAPIKey         = "4VCYIJUCDLOUELGD1V8WBVYBNVDYOXEWSLLZDONGBBDFVXTZJRXPR29JRLQFO6ZE"
+	DefaultDeezerGatewayKey     = "VBK1FSUEXHTSDBJJ"
+	DefaultDeezerBlowfishSecret = "g4el58wc0zvf9na1"
+	DefaultYandexSignKey        = "kzqU4XhfCaY6B6JTHODeq5"
+	DefaultYandexLegacyMP3Salt  = "XGRlBW9FXlekgbPrRHuSiA"
+	DefaultBeatportAppClientID  = "ryZ8LuyQVPqbK2mBX2Hwt4qSMtnWuTYSqBPO92yQ"
+)
+
+// applyVendorDefaults fills in any vendor credential the user has not set, so
+// the provider clients never have to nil-check them.
+func applyVendorDefaults(data *ConfigData) {
+	if data.Qobuz.MobileAppID == "" {
+		data.Qobuz.MobileAppID = DefaultQobuzMobileAppID
+	}
+	if data.Qobuz.MobileAppSecret == "" {
+		data.Qobuz.MobileAppSecret = DefaultQobuzMobileAppSecret
+	}
+	if data.Tidal.AppClientID == "" {
+		data.Tidal.AppClientID = DefaultTidalAppClientID
+	}
+	if data.Tidal.AppClientSecret == "" {
+		data.Tidal.AppClientSecret = DefaultTidalAppClientSecret
+	}
+	if data.Deezer.APIKey == "" {
+		data.Deezer.APIKey = DefaultDeezerAPIKey
+	}
+	if data.Deezer.GatewayKey == "" {
+		data.Deezer.GatewayKey = DefaultDeezerGatewayKey
+	}
+	if data.Deezer.BlowfishSecret == "" {
+		data.Deezer.BlowfishSecret = DefaultDeezerBlowfishSecret
+	}
+	if data.Yandex.SignKey == "" {
+		data.Yandex.SignKey = DefaultYandexSignKey
+	}
+	if data.Yandex.LegacyMP3SignSalt == "" {
+		data.Yandex.LegacyMP3SignSalt = DefaultYandexLegacyMP3Salt
+	}
+	if data.Beatport.AppClientID == "" {
+		data.Beatport.AppClientID = DefaultBeatportAppClientID
+	}
+}
+
 // qualityRange is the accepted quality id range per source. Qobuz and Beatport
 // have no "lowest" tier, so their floor is 1.
 var qualityRange = map[string][2]int{
@@ -426,6 +501,7 @@ func DefaultConfigData() ConfigData {
 		},
 	}
 
+	applyVendorDefaults(&data)
 	return data
 }
 
@@ -471,6 +547,7 @@ func saveConfigData(path string, data ConfigData) error {
 }
 
 func applyRuntimeDefaults(data *ConfigData) {
+	applyVendorDefaults(data)
 	home, _ := os.UserHomeDir()
 	appDir := defaultAppDir()
 	if data.Downloads.Folder == "" {

internal/config/config_test.go

@@ -1,6 +1,7 @@
 package config
 
 import (
+	"encoding/hex"
 	"errors"
 	"fmt"
 	"os"
@@ -326,3 +327,67 @@ func TestUpdateTokensPersistsAndIsConcurrencySafe(t *testing.T) {
 		t.Error("no token persisted")
 	}
 }
+
+// TestVendorDefaultsAreApplied guards the Phase-3 move of vendor credentials
+// into config: an empty value must resolve to the built-in constant, or the
+// providers silently authenticate and sign with empty keys.
+func TestVendorDefaultsAreApplied(t *testing.T) {
+	d := DefaultConfigData()
+	checks := map[string]string{
+		"qobuz.mobile_app_id":     d.Qobuz.MobileAppID,
+		"qobuz.mobile_app_secret": d.Qobuz.MobileAppSecret,
+		"tidal.app_client_id":     d.Tidal.AppClientID,
+		"tidal.app_client_secret": d.Tidal.AppClientSecret,
+		"deezer.api_key":          d.Deezer.APIKey,
+		"deezer.gateway_key":      d.Deezer.GatewayKey,
+		"deezer.blowfish_secret":  d.Deezer.BlowfishSecret,
+		"yandex.sign_key":         d.Yandex.SignKey,
+		"yandex.legacy_sign_salt": d.Yandex.LegacyMP3SignSalt,
+		"beatport.app_client_id":  d.Beatport.AppClientID,
+	}
+	for name, got := range checks {
+		if got == "" {
+			t.Errorf("%s is empty in DefaultConfigData()", name)
+		}
+	}
+
+	// An explicitly empty config must be backfilled too, since that is what a
+	// user config written before these keys existed looks like.
+	var blank ConfigData
+	applyVendorDefaults(&blank)
+	if blank.Qobuz.MobileAppSecret != DefaultQobuzMobileAppSecret {
+		t.Error("applyVendorDefaults did not backfill qobuz.mobile_app_secret")
+	}
+	if blank.Deezer.BlowfishSecret != DefaultDeezerBlowfishSecret {
+		t.Error("applyVendorDefaults did not backfill deezer.blowfish_secret")
+	}
+}
+
+func TestVendorDefaultsAreNotOverriddenWhenSet(t *testing.T) {
+	d := ConfigData{}
+	d.Tidal.AppClientID = "mine"
+	d.Deezer.BlowfishSecret = "0123456789abcdef"
+	applyVendorDefaults(&d)
+	if d.Tidal.AppClientID != "mine" {
+		t.Errorf("user value overwritten: %q", d.Tidal.AppClientID)
+	}
+	if d.Deezer.BlowfishSecret != "0123456789abcdef" {
+		t.Errorf("user value overwritten: %q", d.Deezer.BlowfishSecret)
+	}
+}
+
+// TestDeezerBlowfishSecretLength pins the length the key derivation depends
+// on: it XORs 16 bytes, so a different length would panic or silently derive a
+// wrong key.
+func TestDeezerBlowfishSecretLength(t *testing.T) {
+	if got := len(DefaultDeezerBlowfishSecret); got != 16 {
+		t.Fatalf("DefaultDeezerBlowfishSecret is %d bytes, want 16", got)
+	}
+}
+
+// TestQobuzMobileAppSecretIsHex pins the format the HKDF step requires.
+func TestQobuzMobileAppSecretIsHex(t *testing.T) {
+	if _, err := hex.DecodeString(DefaultQobuzMobileAppSecret); err != nil {
+		t.Fatalf("DefaultQobuzMobileAppSecret is not hex: %v", err)
+	}
+}

internal/download/downloader.go

@@ -21,6 +21,7 @@ import (
 	"github.com/vbauerster/mpb/v8/decor"
 	"golang.org/x/term"
 
+	"streamrip-go/internal/config"
 	"streamrip-go/internal/netutil"
 	"streamrip-go/internal/verbose"
 
@@ -32,6 +33,10 @@ type Downloader struct {
 	showProgress bool
 	progress     *mpb.Progress
 	barStarted   atomic.Int32
+
+	// DeezerBlowfishSecret overrides the built-in Deezer protocol secret.
+	// Set from config by app.New; empty means use the default.
+	DeezerBlowfishSecret string
 }
 
 // downloadBufferSize sizes HTTP-to-disk copies. 1 MiB cuts read/write syscalls
@@ -136,7 +141,7 @@ func (d *Downloader) FileDeezerEncrypted(ctx context.Context, sourceURL, outputP
 		}()
 	}
 
-	block, err := blowfish.NewCipher(deriveDeezerBlowfishKey(trackID))
+	block, err := blowfish.NewCipher(deriveDeezerBlowfishKey(d.blowfishSecret(), trackID))
 	if err != nil {
 		return err
 	}
@@ -831,10 +836,28 @@ const deezerBFChunkSize = 2048
 
 var deezerBFIV = []byte{0, 1, 2, 3, 4, 5, 6, 7}
 
-func deriveDeezerBlowfishKey(trackID string) []byte {
+// defaultDeezerBlowfishSecret aliases the single definition in internal/config
+// so the literal is not duplicated here.
+const defaultDeezerBlowfishSecret = config.DefaultDeezerBlowfishSecret
+
+// blowfishSecret returns the configured Deezer blowfish secret.
+//
+// The key derivation XORs 16 bytes of it, so a secret of any other length
+// would panic; fall back to the built-in value rather than crash on a
+// mistyped config entry.
+func (d *Downloader) blowfishSecret() string {
+	if len(d.DeezerBlowfishSecret) == 16 {
+		return d.DeezerBlowfishSecret
+	}
+	if d.DeezerBlowfishSecret != "" {
+		verbose.Printf(verbose.V, "ignoring deezer.blowfish_secret: got %d bytes, want 16\n", len(d.DeezerBlowfishSecret))
+	}
+	return defaultDeezerBlowfishSecret
+}
+
+func deriveDeezerBlowfishKey(secret, trackID string) []byte {
 	sum := md5.Sum([]byte(trackID))
 	md5Hex := fmt.Sprintf("%x", sum)
-	secret := "g4el58wc0zvf9na1"
 	key := make([]byte, 16)
 	for i := 0; i < 16; i++ {
 		key[i] = md5Hex[i] ^ md5Hex[i+16] ^ secret[i]

internal/download/downloader_test.go

@@ -70,7 +70,7 @@ func TestManifestDetection(t *testing.T) {
 
 func TestDeezerBlowfishKeyDerivation(t *testing.T) {
 	trackID := "3135556"
-	key := deriveDeezerBlowfishKey(trackID)
+	key := deriveDeezerBlowfishKey(defaultDeezerBlowfishSecret, trackID)
 	if len(key) != 16 {
 		t.Fatalf("blowfish key len = %d, want 16", len(key))
 	}
@@ -85,7 +85,7 @@ func TestFileDeezerEncrypted(t *testing.T) {
 	enc := make([]byte, len(plain))
 	copy(enc, plain)
 
-	block, err := blowfish.NewCipher(deriveDeezerBlowfishKey(trackID))
+	block, err := blowfish.NewCipher(deriveDeezerBlowfishKey(defaultDeezerBlowfishSecret, trackID))
 	if err != nil {
 		t.Fatalf("cipher error: %v", err)
 	}

internal/provider/beatport/client.go

@@ -24,7 +24,6 @@ import (
 
 const (
 	baseURL       = "https://api.beatport.com/v4"
-	clientID      = "ryZ8LuyQVPqbK2mBX2Hwt4qSMtnWuTYSqBPO92yQ"
 	tokenEndpoint = "/auth/o/token/"
 	authEndpoint  = "/auth/o/authorize/"
 	loginEndpoint = "/auth/login/"
@@ -376,11 +375,11 @@ func (c *Client) loginPasswordFlow(ctx context.Context) error {
 	if err != nil {
 		return err
 	}
-	return c.issueToken(ctx, map[string]string{"client_id": clientID, "grant_type": "authorization_code", "code": code})
+	return c.issueToken(ctx, map[string]string{"client_id": c.appClientID(), "grant_type": "authorization_code", "code": code})
 }
 
 func (c *Client) authorize(ctx context.Context) (string, error) {
-	params := url.Values{"client_id": []string{clientID}, "response_type": []string{"code"}}
+	params := url.Values{"client_id": []string{c.appClientID()}, "response_type": []string{"code"}}
 	resp, status, err := c.rawRequest(ctx, http.MethodGet, authEndpoint, params, nil, "", false)
 	if err != nil {
 		return "", err
@@ -397,7 +396,7 @@ func (c *Client) authorize(ctx context.Context) (string, error) {
 
 func (c *Client) refresh(ctx context.Context) error {
 	b := &c.cfg.Session.Beatport
-	return c.issueToken(ctx, map[string]string{"client_id": clientID, "grant_type": "refresh_token", "refresh_token": b.RefreshToken})
+	return c.issueToken(ctx, map[string]string{"client_id": c.appClientID(), "grant_type": "refresh_token", "refresh_token": b.RefreshToken})
 }
 
 func (c *Client) issueToken(ctx context.Context, payload map[string]string) error {
@@ -846,3 +845,12 @@ func cloneValues(in url.Values) url.Values {
 	}
 	return out
 }
+
+// appClientID reads the vendor OAuth app credential from config, falling back
+// to the built-in default.
+func (c *Client) appClientID() string {
+	if v := strings.TrimSpace(c.cfg.Session.Beatport.AppClientID); v != "" {
+		return v
+	}
+	return config.DefaultBeatportAppClientID
+}

internal/provider/deezer/client.go

@@ -33,8 +33,6 @@ var (
 	mediaURL     = "https://media.deezer.com/v1/get_url"
 	pipeURL      = "https://pipe.deezer.com/api"
 	authURL      = "https://auth.deezer.com/login/renew"
-	apiKey       = "4VCYIJUCDLOUELGD1V8WBVYBNVDYOXEWSLLZDONGBBDFVXTZJRXPR29JRLQFO6ZE"
-	gatewayDec   = "VBK1FSUEXHTSDBJJ"
 	deezerUAPool = []string{
 		"Deezer/9.0.11.4 (Android; 14; Mobile; us) Xiaomi Redmi Note 7",
 		"Deezer/9.0.11.4 (Android; 14; Mobile; us) Samsung SM-G991B",
@@ -499,7 +497,7 @@ func (c *Client) loginWithCredentials(ctx context.Context, email, password strin
 	if err != nil {
 		return err
 	}
-	authToken, err := deriveGatewayAuthToken(mobileToken)
+	authToken, err := deriveGatewayAuthToken(c.gatewayKey(), mobileToken)
 	if err != nil {
 		return err
 	}
@@ -509,7 +507,7 @@ func (c *Client) loginWithCredentials(ctx context.Context, email, password strin
 	}
 	c.sid = jsonutil.FirstNonEmpty(c.sid, sid)
 
-	encryptedPassword, err := encryptPassword(mobileToken, password)
+	encryptedPassword, err := encryptPassword(c.gatewayKey(), mobileToken, password)
 	if err != nil {
 		return err
 	}
@@ -528,7 +526,7 @@ func (c *Client) loginWithCredentials(ctx context.Context, email, password strin
 		"password":                          encryptedPassword,
 	}
 	params := url.Values{}
-	params.Set("api_key", apiKey)
+	params.Set("api_key", c.apiKey())
 	params.Set("sid", c.sid)
 	params.Set("method", "mobile_userAuth")
 	params.Set("output", "3")
@@ -737,7 +735,7 @@ func (c *Client) bootstrapSID(ctx context.Context) (string, error) {
 	if err != nil {
 		return "", err
 	}
-	authToken, err := deriveGatewayAuthToken(mobileToken)
+	authToken, err := deriveGatewayAuthToken(c.gatewayKey(), mobileToken)
 	if err != nil {
 		return "", err
 	}
@@ -749,7 +747,7 @@ func (c *Client) mobileAuth(ctx context.Context) (string, error) {
 		return "", err
 	}
 	params := url.Values{}
-	params.Set("api_key", apiKey)
+	params.Set("api_key", c.apiKey())
 	params.Set("output", "3")
 	params.Set("method", "mobile_auth")
 	params.Set("network", randomHexN(32))
@@ -802,7 +800,7 @@ func (c *Client) apiCheckToken(ctx context.Context, authToken string) (string, e
 		return "", err
 	}
 	params := url.Values{}
-	params.Set("api_key", apiKey)
+	params.Set("api_key", c.apiKey())
 	params.Set("method", "api_checkToken")
 	params.Set("auth_token", authToken)
 	params.Set("output", "3")
@@ -865,7 +863,7 @@ func (c *Client) mobileUserAutolog(ctx context.Context) error {
 		payload["refresh_token"] = strings.TrimSpace(c.refresh)
 	}
 	params := url.Values{}
-	params.Set("api_key", apiKey)
+	params.Set("api_key", c.apiKey())
 	params.Set("sid", c.sid)
 	params.Set("output", "3")
 	params.Set("input", "3")
@@ -1075,8 +1073,10 @@ func (c *Client) refreshLicenseFromPipe(ctx context.Context) error {
 	return nil
 }
 
-func deriveGatewayAuthToken(mobileToken string) (string, error) {
-	dec, err := decryptMobileToken(mobileToken)
+// deriveGatewayAuthToken and friends take gatewayKey explicitly so the key
+// comes from config rather than a package constant.
+func deriveGatewayAuthToken(gatewayKey, mobileToken string) (string, error) {
+	dec, err := decryptMobileToken(gatewayKey, mobileToken)
 	if err != nil {
 		return "", err
 	}
@@ -1092,19 +1092,19 @@ func deriveGatewayAuthToken(mobileToken string) (string, error) {
 	return hex.EncodeToString(enc), nil
 }
 
-func decryptMobileToken(mobileToken string) ([]byte, error) {
+func decryptMobileToken(gatewayKey, mobileToken string) ([]byte, error) {
 	b, err := hex.DecodeString(strings.TrimSpace(mobileToken))
 	if err != nil {
 		return nil, err
 	}
-	return aesECBDecrypt([]byte(gatewayDec), b)
+	return aesECBDecrypt([]byte(gatewayKey), b)
 }
 
-func encryptPassword(mobileToken, password string) (string, error) {
+func encryptPassword(gatewayKey, mobileToken, password string) (string, error) {
 	if strings.TrimSpace(password) == "" {
 		return "", errors.New("missing deezer password")
 	}
-	dec, err := decryptMobileToken(mobileToken)
+	dec, err := decryptMobileToken(gatewayKey, mobileToken)
 	if err != nil {
 		return "", err
 	}
@@ -1513,3 +1513,19 @@ func enrichAlbumImage(meta map[string]any) {
 		"original":   cover,
 	}
 }
+
+// apiKey and gatewayKey read the vendor protocol keys from config, falling
+// back to the built-in defaults.
+func (c *Client) apiKey() string {
+	if v := strings.TrimSpace(c.cfg.Session.Deezer.APIKey); v != "" {
+		return v
+	}
+	return config.DefaultDeezerAPIKey
+}
+
+func (c *Client) gatewayKey() string {
+	if v := strings.TrimSpace(c.cfg.Session.Deezer.GatewayKey); v != "" {
+		return v
+	}
+	return config.DefaultDeezerGatewayKey
+}

internal/provider/deezer/client_test.go

@@ -728,7 +728,7 @@ func TestMobileUserAutologIncludesRefreshToken(t *testing.T) {
 func testMobileToken(t *testing.T) string {
 	t.Helper()
 	plain := []byte(strings.Repeat("A", 64) + strings.Repeat("B", 16) + strings.Repeat("C", 16))
-	enc, err := aesECBEncrypt([]byte(gatewayDec), plain)
+	enc, err := aesECBEncrypt([]byte(config.DefaultDeezerGatewayKey), plain)
 	if err != nil {
 		t.Fatalf("aesECBEncrypt() error = %v", err)
 	}

internal/provider/qobuz/client.go

@@ -40,8 +40,6 @@ import (
 const baseURL = "https://www.qobuz.com/api.json/0.2"
 
 const (
-	mobileAppID        = "312369995"
-	mobileAppSecret    = "e79f8b9be485692b0e5f9dd895826368"
 	mobileUserAgent    = "Dalvik/2.1.0 (Linux; U; Android 9; Nexus 6P Build/PQ3A.190801.002) QobuzMobileAndroid/9.7.0.3-b26022717"
 	mobileAppVersion   = "9.7.0.3"
 	mobileSessionProf  = "qbz-1"
@@ -1046,11 +1044,11 @@ func (c *Client) ensureMobileSession(ctx context.Context) error {
 func (c *Client) mobileLogin(ctx context.Context, username, password string) error {
 	ts := time.Now().Unix()
 	params := url.Values{}
-	params.Set("app_id", mobileAppID)
+	params.Set("app_id", c.mobileAppID())
 	params.Set("username", username)
 	params.Set("password", password)
 	params.Set("request_ts", strconv.FormatInt(ts, 10))
-	params.Set("request_sig", mobileSignRequest("oauth2/login", []kv{{"password", password}, {"username", username}}, ts))
+	params.Set("request_sig", mobileSignRequest(c.mobileAppSecret(), "oauth2/login", []kv{{"password", password}, {"username", username}}, ts))
 
 	reqURL := baseURL + "/oauth2/login?" + params.Encode()
 	req, err := http.NewRequestWithContext(ctx, http.MethodGet, reqURL, nil)
@@ -1088,9 +1086,9 @@ func (c *Client) mobileLogin(ctx context.Context, username, password string) err
 func (c *Client) mobileStartSession(ctx context.Context) error {
 	ts := time.Now().Unix()
 	params := url.Values{}
-	params.Set("app_id", mobileAppID)
+	params.Set("app_id", c.mobileAppID())
 	params.Set("request_ts", strconv.FormatInt(ts, 10))
-	params.Set("request_sig", mobileSignRequest("session/start", []kv{{"profile", mobileSessionProf}}, ts))
+	params.Set("request_sig", mobileSignRequest(c.mobileAppSecret(), "session/start", []kv{{"profile", mobileSessionProf}}, ts))
 
 	reqURL := baseURL + "/session/start?" + params.Encode()
 	form := url.Values{}
@@ -1132,12 +1130,12 @@ func (c *Client) mobileStartSession(ctx context.Context) error {
 func (c *Client) mobileGetFileURL(ctx context.Context, trackID string, formatID int) (*mobileFileURL, error) {
 	ts := time.Now().Unix()
 	params := url.Values{}
-	params.Set("app_id", mobileAppID)
+	params.Set("app_id", c.mobileAppID())
 	params.Set("track_id", trackID)
 	params.Set("format_id", strconv.Itoa(formatID))
 	params.Set("intent", "stream")
 	params.Set("request_ts", strconv.FormatInt(ts, 10))
-	params.Set("request_sig", mobileSignRequest("file/url", []kv{{"format_id", strconv.Itoa(formatID)}, {"intent", "stream"}, {"track_id", trackID}}, ts))
+	params.Set("request_sig", mobileSignRequest(c.mobileAppSecret(), "file/url", []kv{{"format_id", strconv.Itoa(formatID)}, {"intent", "stream"}, {"track_id", trackID}}, ts))
 	reqURL := baseURL + "/file/url?" + params.Encode()
 	req, err := http.NewRequestWithContext(ctx, http.MethodGet, reqURL, nil)
 	if err != nil {
@@ -1259,7 +1257,7 @@ func (c *Client) mobileDownloadSegment(ctx context.Context, sourceURL string) ([
 
 func (c *Client) setMobileHeaders(req *http.Request) {
 	req.Header.Set("User-Agent", mobileUserAgent)
-	req.Header.Set("X-App-Id", mobileAppID)
+	req.Header.Set("X-App-Id", c.mobileAppID())
 	req.Header.Set("X-App-Version", mobileAppVersion)
 	req.Header.Set("X-Device-Platform", "android")
 	req.Header.Set("X-Device-Model", "Nexus 6P")
@@ -1272,7 +1270,9 @@ func (c *Client) setMobileHeaders(req *http.Request) {
 	}
 }
 
-func mobileSignRequest(endpoint string, params []kv, ts int64) string {
+// mobileSignRequest signs a mobile API request. appSecret comes from config
+// (Client.mobileAppSecret) so a rotation can be fixed without a rebuild.
+func mobileSignRequest(appSecret, endpoint string, params []kv, ts int64) string {
 	method := strings.ReplaceAll(endpoint, "/", "")
 	sortKVs(params)
 	var sb strings.Builder
@@ -1282,7 +1282,7 @@ func mobileSignRequest(endpoint string, params []kv, ts int64) string {
 		sb.WriteString(p.Value)
 	}
 	sb.WriteString(strconv.FormatInt(ts, 10))
-	sb.WriteString(mobileAppSecret)
+	sb.WriteString(appSecret)
 	h := md5.Sum([]byte(sb.String()))
 	return hex.EncodeToString(h[:])
 }
@@ -1321,7 +1321,7 @@ func (c *Client) mobileDeriveTrackKey(encryptedKey string) ([]byte, error) {
 	// A non-hex secret used to be swallowed and HKDF keyed on nil, which
 	// derives a wrong KEK and yields silently corrupt audio rather than an
 	// error.
-	secretKey, err := hex.DecodeString(mobileAppSecret)
+	secretKey, err := hex.DecodeString(c.mobileAppSecret())
 	if err != nil {
 		return nil, fmt.Errorf("decode mobile app secret: %w", err)
 	}
@@ -1491,3 +1491,19 @@ func readU24BE(data []byte, off int) uint32 {
 	}
 	return uint32(data[off])<<16 | uint32(data[off+1])<<8 | uint32(data[off+2])
 }
+
+// mobileAppID and mobileAppSecret read the vendor mobile app credentials from
+// config, falling back to the built-in defaults.
+func (c *Client) mobileAppID() string {
+	if v := strings.TrimSpace(c.cfg.Session.Qobuz.MobileAppID); v != "" {
+		return v
+	}
+	return config.DefaultQobuzMobileAppID
+}
+
+func (c *Client) mobileAppSecret() string {
+	if v := strings.TrimSpace(c.cfg.Session.Qobuz.MobileAppSecret); v != "" {
+		return v
+	}
+	return config.DefaultQobuzMobileAppSecret
+}

internal/provider/tidal/client.go

@@ -28,8 +28,6 @@ const (
 	lyricsAPIv1          = "https://api.tidal.com/v1"
 	openAPIV2            = "https://openapi.tidal.com/v2"
 	authURL              = "https://auth.tidal.com/v1/oauth2"
-	clientID             = "fX2JxdmntZWK0ixT"
-	clientSec            = "1Nm5AfDAjxrgJFJbKNWLeAyKGVGmINuXPPLHVXAvxAg="
 	tidalRequestAttempts = 3
 )
 
@@ -146,7 +144,7 @@ func (c *Client) refreshAccessToken(ctx context.Context) error {
 	}
 
 	form := url.Values{}
-	form.Set("client_id", clientID)
+	form.Set("client_id", c.appClientID())
 	form.Set("refresh_token", refresh)
 	form.Set("grant_type", "refresh_token")
 	form.Set("scope", "r_usr+w_usr+w_sub")
@@ -972,7 +970,7 @@ func (c *Client) apiPost(ctx context.Context, endpoint string, form url.Values,
 		req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
 		req.Header.Set("User-Agent", "streamrip-go/0.1")
 		if basicAuth {
-			auth := base64.StdEncoding.EncodeToString([]byte(clientID + ":" + clientSec))
+			auth := base64.StdEncoding.EncodeToString([]byte(c.appClientID() + ":" + c.appClientSecret()))
 			req.Header.Set("Authorization", "Basic "+auth)
 		}
 		return req, nil
@@ -1004,3 +1002,20 @@ func tidalImageMap(cover string) map[string]any {
 		"original":   base + "/1280x1280.jpg",
 	}
 }
+
+// appClientID and appClientSecret read the vendor OAuth app credentials from
+// config, falling back to the built-in defaults. Config is the source of truth
+// so a rotation can be fixed without a rebuild.
+func (c *Client) appClientID() string {
+	if v := strings.TrimSpace(c.cfg.Session.Tidal.AppClientID); v != "" {
+		return v
+	}
+	return config.DefaultTidalAppClientID
+}
+
+func (c *Client) appClientSecret() string {
+	if v := strings.TrimSpace(c.cfg.Session.Tidal.AppClientSecret); v != "" {
+		return v
+	}
+	return config.DefaultTidalAppClientSecret
+}

internal/provider/yandex/client.go

@@ -30,12 +30,10 @@ import (
 )
 
 const (
-	baseURL               = "https://api.music.yandex.net"
-	desktopClientHeader   = "YandexMusicDesktopAppWindows/5.13.2"
-	desktopOrigin         = "music-application://desktop"
-	requestAttempts       = 3
-	desktopWindowsSignKey = "kzqU4XhfCaY6B6JTHODeq5"
-	legacyMP3SignSalt     = "XGRlBW9FXlekgbPrRHuSiA"
+	baseURL             = "https://api.music.yandex.net"
+	desktopClientHeader = "YandexMusicDesktopAppWindows/5.13.2"
+	desktopOrigin       = "music-application://desktop"
+	requestAttempts     = 3
 )
 
 var ErrMissingYandexToken = errors.New("missing yandex access_token")
@@ -345,7 +343,7 @@ func (c *Client) getLegacyDownloadable(ctx context.Context, trackID string) (*pr
 	if err != nil {
 		return nil, err
 	}
-	directURL, err := legacyDirectURL(xmlInfo)
+	directURL, err := legacyDirectURL(c.legacyMP3Salt(), xmlInfo)
 	if err != nil {
 		return nil, err
 	}
@@ -366,7 +364,7 @@ func (c *Client) getLegacyDownloadable(ctx context.Context, trackID string) (*pr
 
 func (c *Client) getDesktopDownloadable(ctx context.Context, trackID string, quality int, transport string) (*provider.Downloadable, error) {
 	qualityParam, codecs := downloadRequestProfile(quality)
-	sign, ts := yandexDownloadSign(trackID, qualityParam, codecs, transport)
+	sign, ts := yandexDownloadSign(c.signKey(), trackID, qualityParam, codecs, transport)
 	params := url.Values{}
 	params.Set("trackId", trackID)
 	params.Set("codecs", strings.Join(codecs, ","))
@@ -432,11 +430,11 @@ func (c *Client) fetchLegacyXML(ctx context.Context, xmlURL string) (*legacyDown
 	return &out, nil
 }
 
-func legacyDirectURL(info *legacyDownloadInfoXML) (string, error) {
+func legacyDirectURL(salt string, info *legacyDownloadInfoXML) (string, error) {
 	if info == nil || info.Host == "" || info.Path == "" || info.TS == "" || info.S == "" {
 		return "", errors.New("invalid yandex legacy xml payload")
 	}
-	sum := md5.Sum([]byte(legacyMP3SignSalt + strings.TrimPrefix(info.Path, "/") + info.S))
+	sum := md5.Sum([]byte(salt + strings.TrimPrefix(info.Path, "/") + info.S))
 	return "https://" + info.Host + "/get-mp3/" + hex.EncodeToString(sum[:]) + "/" + info.TS + info.Path, nil
 }
 
@@ -944,9 +942,11 @@ func isExplicit(raw map[string]any) bool {
 	return jsonutil.BoolFromAny(raw["explicit"])
 }
 
-func yandexDownloadSign(trackID, quality string, codecs []string, transport string) (string, int64) {
+// yandexDownloadSign signs a download request. signKey comes from config
+// (Client.signKey) so a rotation can be fixed without a rebuild.
+func yandexDownloadSign(signKey, trackID, quality string, codecs []string, transport string) (string, int64) {
 	ts := time.Now().Unix()
-	mac := hmac.New(sha256.New, []byte(desktopWindowsSignKey))
+	mac := hmac.New(sha256.New, []byte(signKey))
 	_, _ = mac.Write([]byte(strconv.FormatInt(ts, 10) + trackID + quality + strings.Join(codecs, "") + transport))
 	return strings.TrimRight(base64.StdEncoding.EncodeToString(mac.Sum(nil)), "="), ts
 }
@@ -1027,3 +1027,19 @@ func firstPositiveInt(vals ...int) int {
 	}
 	return 0
 }
+
+// signKey and legacyMP3Salt read the vendor request-signing keys from config,
+// falling back to the built-in defaults.
+func (c *Client) signKey() string {
+	if v := strings.TrimSpace(c.cfg.Session.Yandex.SignKey); v != "" {
+		return v
+	}
+	return config.DefaultYandexSignKey
+}
+
+func (c *Client) legacyMP3Salt() string {
+	if v := strings.TrimSpace(c.cfg.Session.Yandex.LegacyMP3SignSalt); v != "" {
+		return v
+	}
+	return config.DefaultYandexLegacyMP3Salt
+}

internal/provider/yandex/client_test.go

@@ -15,7 +15,7 @@ import (
 )
 
 func TestYandexDownloadSignMatchesCapturedFormat(t *testing.T) {
-	sign, ts := yandexDownloadSign("32038184", "lossless", []string{"flac", "aac", "he-aac", "mp3", "flac-mp4", "aac-mp4", "he-aac-mp4"}, "raw")
+	sign, ts := yandexDownloadSign(config.DefaultYandexSignKey, "32038184", "lossless", []string{"flac", "aac", "he-aac", "mp3", "flac-mp4", "aac-mp4", "he-aac-mp4"}, "raw")
 	if ts <= 0 {
 		t.Fatalf("timestamp = %d", ts)
 	}
@@ -168,7 +168,7 @@ func TestGetMetadataTrackUsesModernTracksEndpoint(t *testing.T) {
 }
 
 func TestLegacyDirectURLBuildsPlayableMP3URL(t *testing.T) {
-	url, err := legacyDirectURL(&legacyDownloadInfoXML{
+	url, err := legacyDirectURL(config.DefaultYandexLegacyMP3Salt, &legacyDownloadInfoXML{
 		Host: "example.test",
 		Path: "/abc123",
 		TS:   "1234567890",