Prefer native parser for SSH public key parsing

custom/conf/app.example.ini

@@ -186,8 +186,8 @@ RUN_MODE = ; prod
 ;; default is the system temporary directory.
 ;SSH_KEY_TEST_PATH =
 ;;
-;; Path to ssh-keygen, default is 'ssh-keygen' which means the shell is responsible for finding out which one to call.
-;SSH_KEYGEN_PATH = ssh-keygen
+;; Use `ssh-keygen` to parse public SSH keys. The value is passed to the shell. By default, Gitea does the parsing itself.
+;SSH_KEYGEN_PATH =
 ;;
 ;; Enable SSH Authorized Key Backup when rewriting all keys, default is true
 ;SSH_AUTHORIZED_KEYS_BACKUP = true

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

@@ -345,7 +345,7 @@ The following configuration set `Content-Type: application/vnd.android.package-a
 - `SSH_SERVER_MACS`: **[email protected], hmac-sha2-256, hmac-sha1**: For the built-in SSH server, choose the MACs to support for SSH connections, for system SSH this setting has no effect
 - `SSH_SERVER_HOST_KEYS`: **ssh/gitea.rsa, ssh/gogs.rsa**: For the built-in SSH server, choose the keypairs to offer as the host key. The private key should be at `SSH_SERVER_HOST_KEY` and the public `SSH_SERVER_HOST_KEY.pub`. Relative paths are made absolute relative to the `APP_DATA_PATH`. If no key exists a 4096 bit RSA key will be created for you.
 - `SSH_KEY_TEST_PATH`: **/tmp**: Directory to create temporary files in when testing public keys using ssh-keygen, default is the system temporary directory.
-- `SSH_KEYGEN_PATH`: **ssh-keygen**: Path to ssh-keygen, default is 'ssh-keygen' which means the shell is responsible for finding out which one to call.
+- `SSH_KEYGEN_PATH`: **\<empty\>**: Use `ssh-keygen` to parse public SSH keys. The value is passed to the shell. By default, Gitea does the parsing itself.
 - `SSH_EXPOSE_ANONYMOUS`: **false**: Enable exposure of SSH clone URL to anonymous visitors, default is false.
 - `SSH_PER_WRITE_TIMEOUT`: **30s**: Timeout for any write to the SSH connections. (Set to
   -1 to disable all timeouts.)

models/asymkey/ssh_key_parse.go

@@ -179,7 +179,7 @@ func CheckPublicKeyString(content string) (_ string, err error) {
 		keyType string
 		length  int
 	)
-	if setting.SSH.StartBuiltinServer {
+	if len(setting.SSH.KeygenPath) == 0 {
 		fnName = "SSHNativeParsePublicKey"
 		keyType, length, err = SSHNativeParsePublicKey(content)
 	} else {
@@ -285,7 +285,12 @@ func SSHKeyGenParsePublicKey(key string) (string, int, error) {
 		}
 	}()
 
-	stdout, stderr, err := process.GetManager().Exec("SSHKeyGenParsePublicKey", setting.SSH.KeygenPath, "-lf", tmpName)
+	keygenPath := setting.SSH.KeygenPath
+	if len(keygenPath) == 0 {
+		keygenPath = "ssh-keygen"
+	}
+
+	stdout, stderr, err := process.GetManager().Exec("SSHKeyGenParsePublicKey", keygenPath, "-lf", tmpName)
 	if err != nil {
 		return "", 0, fmt.Errorf("fail to parse public key: %s - %s", err, stderr)
 	}

models/asymkey/ssh_key_test.go

@@ -57,6 +57,14 @@ func Test_SSHParsePublicKey(t *testing.T) {
 				assert.Equal(t, tc.keyType, keyTypeK)
 				assert.EqualValues(t, tc.length, lengthK)
 			})
+			t.Run("SSHParseKeyNative", func(t *testing.T) {
+				keyTypeK, lengthK, err := SSHNativeParsePublicKey(tc.content)
+				if err != nil {
+					assert.Fail(t, "%v", err)
+				}
+				assert.Equal(t, tc.keyType, keyTypeK)
+				assert.EqualValues(t, tc.length, lengthK)
+			})
 		})
 	}
 }

modules/setting/ssh.go

@@ -58,7 +58,7 @@ var SSH = struct {
 	ServerCiphers:                 []string{"[email protected]", "aes128-ctr", "aes192-ctr", "aes256-ctr", "[email protected]", "[email protected]"},
 	ServerKeyExchanges:            []string{"curve25519-sha256", "ecdh-sha2-nistp256", "ecdh-sha2-nistp384", "ecdh-sha2-nistp521", "diffie-hellman-group14-sha256", "diffie-hellman-group14-sha1"},
 	ServerMACs:                    []string{"[email protected]", "hmac-sha2-256", "hmac-sha1"},
-	KeygenPath:                    "ssh-keygen",
+	KeygenPath:                    "",
 	MinimumKeySizeCheck:           true,
 	MinimumKeySizes:               map[string]int{"ed25519": 256, "ed25519-sk": 256, "ecdsa": 256, "ecdsa-sk": 256, "rsa": 2047},
 	ServerHostKeys:                []string{"ssh/gitea.rsa", "ssh/gogs.rsa"},
@@ -134,7 +134,7 @@ func loadSSHFrom(rootCfg ConfigProvider) {
 		}
 	}
 
-	SSH.KeygenPath = sec.Key("SSH_KEYGEN_PATH").MustString("ssh-keygen")
+	SSH.KeygenPath = sec.Key("SSH_KEYGEN_PATH").String()
 	SSH.Port = sec.Key("SSH_PORT").MustInt(22)
 	SSH.ListenPort = sec.Key("SSH_LISTEN_PORT").MustInt(SSH.Port)
 	SSH.UseProxyProtocol = sec.Key("SSH_SERVER_USE_PROXY_PROTOCOL").MustBool(false)