Add asymmetric JWT signing (#16010)

* Added asymmetric token signing.

* Load signing key from settings.

* Added optional kid parameter.

* Updated documentation.

* Add "kid" to token header.

Author: KN4CK3R

cmd/generate.go

@@ -71,7 +71,7 @@ func runGenerateInternalToken(c *cli.Context) error {
 }
 
 func runGenerateLfsJwtSecret(c *cli.Context) error {
-	JWTSecretBase64, err := generate.NewJwtSecret()
+	JWTSecretBase64, err := generate.NewJwtSecretBase64()
 	if err != nil {
 		return err
 	}

docs/content/doc/advanced/config-cheat-sheet.en-us.md

@@ -858,7 +858,9 @@ NB: You must have `DISABLE_ROUTER_LOG` set to `false` for this option to take ef
 - `ACCESS_TOKEN_EXPIRATION_TIME`: **3600**: Lifetime of an OAuth2 access token in seconds
 - `REFRESH_TOKEN_EXPIRATION_TIME`: **730**: Lifetime of an OAuth2 refresh token in hours
 - `INVALIDATE_REFRESH_TOKENS`: **false**: Check if refresh token has already been used
-- `JWT_SECRET`: **\<empty\>**: OAuth2 authentication secret for access and refresh tokens, change this a unique string.
+- `JWT_SIGNING_ALGORITHM`: **RS256**: Algorithm used to sign OAuth2 tokens. Valid values: \[`HS256`, `HS384`, `HS512`, `RS256`, `RS384`, `RS512`, `ES256`, `ES384`, `ES512`\]
+- `JWT_SECRET`: **\<empty\>**: OAuth2 authentication secret for access and refresh tokens, change this to a unique string. This setting is only needed if `JWT_SIGNING_ALGORITHM` is set to `HS256`, `HS384` or `HS512`.
+- `JWT_SIGNING_PRIVATE_KEY_FILE`: **jwt/private.pem**: Private key file path used to sign OAuth2 tokens. The path is relative to `CUSTOM_PATH`. This setting is only needed if `JWT_SIGNING_ALGORITHM` is set to `RS256`, `RS384`, `RS512`, `ES256`, `ES384` or `ES512`. The file must contain a RSA or ECDSA private key in the PKCS8 format.
 - `MAX_TOKEN_LENGTH`: **32767**: Maximum length of token/cookie to accept from OAuth2 provider
 
 ## i18n (`i18n`)

docs/content/doc/developers/oauth2-provider.md

@@ -23,10 +23,13 @@ Gitea supports acting as an OAuth2 provider to allow third party applications to
 
 ## Endpoints
 
-| Endpoint               | URL                         |
-| ---------------------- | --------------------------- |
-| Authorization Endpoint | `/login/oauth/authorize`    |
-| Access Token Endpoint  | `/login/oauth/access_token` |
+| Endpoint                 | URL                                 |
+| ------------------------ | ----------------------------------- |
+| OpenID Connect Discovery | `/.well-known/openid-configuration` |
+| Authorization Endpoint   | `/login/oauth/authorize`            |
+| Access Token Endpoint    | `/login/oauth/access_token`         |
+| OpenID Connect UserInfo  | `/login/oauth/userinfo`             |
+| JSON Web Key Set         | `/login/oauth/keys`                 |
 
 ## Supported OAuth2 Grants
 

models/oauth2.go

@@ -132,6 +132,9 @@ func GetActiveOAuth2Providers() ([]string, map[string]OAuth2Provider, error) {
 
 // InitOAuth2 initialize the OAuth2 lib and register all active OAuth2 providers in the library
 func InitOAuth2() error {
+	if err := oauth2.InitSigningKey(); err != nil {
+		return err
+	}
 	if err := oauth2.Init(x); err != nil {
 		return err
 	}

models/oauth2_application.go

@@ -12,8 +12,8 @@ import (
 	"strings"
 	"time"
 
+	"code.gitea.io/gitea/modules/auth/oauth2"
 	"code.gitea.io/gitea/modules/secret"
-	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/timeutil"
 	"code.gitea.io/gitea/modules/util"
 
@@ -540,10 +540,10 @@ type OAuth2Token struct {
 // ParseOAuth2Token parses a singed jwt string
 func ParseOAuth2Token(jwtToken string) (*OAuth2Token, error) {
 	parsedToken, err := jwt.ParseWithClaims(jwtToken, &OAuth2Token{}, func(token *jwt.Token) (interface{}, error) {
-		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
+		if token.Method == nil || token.Method.Alg() != oauth2.DefaultSigningKey.SigningMethod().Alg() {
 			return nil, fmt.Errorf("unexpected signing algo: %v", token.Header["alg"])
 		}
-		return setting.OAuth2.JWTSecretBytes, nil
+		return oauth2.DefaultSigningKey.VerifyKey(), nil
 	})
 	if err != nil {
 		return nil, err
@@ -559,8 +559,9 @@ func ParseOAuth2Token(jwtToken string) (*OAuth2Token, error) {
 // SignToken signs the token with the JWT secret
 func (token *OAuth2Token) SignToken() (string, error) {
 	token.IssuedAt = time.Now().Unix()
-	jwtToken := jwt.NewWithClaims(jwt.SigningMethodHS512, token)
-	return jwtToken.SignedString(setting.OAuth2.JWTSecretBytes)
+	jwtToken := jwt.NewWithClaims(oauth2.DefaultSigningKey.SigningMethod(), token)
+	oauth2.DefaultSigningKey.PreProcessToken(jwtToken)
+	return jwtToken.SignedString(oauth2.DefaultSigningKey.SignKey())
 }
 
 // OIDCToken represents an OpenID Connect id_token
@@ -583,8 +584,9 @@ type OIDCToken struct {
 }
 
 // SignToken signs an id_token with the (symmetric) client secret key
-func (token *OIDCToken) SignToken(clientSecret string) (string, error) {
+func (token *OIDCToken) SignToken(signingKey oauth2.JWTSigningKey) (string, error) {
 	token.IssuedAt = time.Now().Unix()
-	jwtToken := jwt.NewWithClaims(jwt.SigningMethodHS256, token)
-	return jwtToken.SignedString([]byte(clientSecret))
+	jwtToken := jwt.NewWithClaims(signingKey.SigningMethod(), token)
+	signingKey.PreProcessToken(jwtToken)
+	return jwtToken.SignedString(signingKey.SignKey())
 }