Handle misencoding of login_source cfg in mssql (go-gitea#16268)

Backport go-gitea#16268

Unfortunately due a bug in xorm (see https://gitea.com/xorm/xorm/pulls/1957) updating
loginsources on MSSQL causes them to become corrupted. (go-gitea#16252)

Whilst waiting for the referenced PR to be merged and to handle the corrupted
loginsources correctly we need to add a wrapper to the `FromDB()` methods to look
for and ignore the misplaced BOMs that have been added.

Fix go-gitea#16252

Signed-off-by: Andrew Thornton <art27@cantab.net>

Author: zeripath

models/login_source.go

@@ -69,15 +69,25 @@ var (
 	_ convert.Conversion = &SSPIConfig{}
 )
 
+// jsonUnmarshalIgnoreErroneousBOM - due to a bug in xorm (see https://gitea.com/xorm/xorm/pulls/1957) - it's
+// possible that a Blob may gain an unwanted prefix of 0xff 0xfe.
+func jsonUnmarshalIgnoreErroneousBOM(bs []byte, v interface{}) error {
+	json := jsoniter.ConfigCompatibleWithStandardLibrary
+	err := json.Unmarshal(bs, &v)
+	if err != nil && len(bs) > 2 && bs[0] == 0xff && bs[1] == 0xfe {
+		err = json.Unmarshal(bs[2:], &v)
+	}
+	return err
+}
+
 // LDAPConfig holds configuration for LDAP login source.
 type LDAPConfig struct {
 	*ldap.Source
 }
 
 // FromDB fills up a LDAPConfig from serialized format.
 func (cfg *LDAPConfig) FromDB(bs []byte) error {
-	json := jsoniter.ConfigCompatibleWithStandardLibrary
-	return json.Unmarshal(bs, &cfg)
+	return jsonUnmarshalIgnoreErroneousBOM(bs, &cfg)
 }
 
 // ToDB exports a LDAPConfig to a serialized format.
@@ -104,8 +114,7 @@ type SMTPConfig struct {
 
 // FromDB fills up an SMTPConfig from serialized format.
 func (cfg *SMTPConfig) FromDB(bs []byte) error {
-	json := jsoniter.ConfigCompatibleWithStandardLibrary
-	return json.Unmarshal(bs, cfg)
+	return jsonUnmarshalIgnoreErroneousBOM(bs, cfg)
 }
 
 // ToDB exports an SMTPConfig to a serialized format.
@@ -122,8 +131,7 @@ type PAMConfig struct {
 
 // FromDB fills up a PAMConfig from serialized format.
 func (cfg *PAMConfig) FromDB(bs []byte) error {
-	json := jsoniter.ConfigCompatibleWithStandardLibrary
-	return json.Unmarshal(bs, &cfg)
+	return jsonUnmarshalIgnoreErroneousBOM(bs, cfg)
 }
 
 // ToDB exports a PAMConfig to a serialized format.
@@ -144,8 +152,7 @@ type OAuth2Config struct {
 
 // FromDB fills up an OAuth2Config from serialized format.
 func (cfg *OAuth2Config) FromDB(bs []byte) error {
-	json := jsoniter.ConfigCompatibleWithStandardLibrary
-	return json.Unmarshal(bs, cfg)
+	return jsonUnmarshalIgnoreErroneousBOM(bs, cfg)
 }
 
 // ToDB exports an SMTPConfig to a serialized format.
@@ -165,8 +172,7 @@ type SSPIConfig struct {
 
 // FromDB fills up an SSPIConfig from serialized format.
 func (cfg *SSPIConfig) FromDB(bs []byte) error {
-	json := jsoniter.ConfigCompatibleWithStandardLibrary
-	return json.Unmarshal(bs, cfg)
+	return jsonUnmarshalIgnoreErroneousBOM(bs, cfg)
 }
 
 // ToDB exports an SSPIConfig to a serialized format.

models/repo_unit.go

@@ -28,8 +28,7 @@ type UnitConfig struct{}
 
 // FromDB fills up a UnitConfig from serialized format.
 func (cfg *UnitConfig) FromDB(bs []byte) error {
-	json := jsoniter.ConfigCompatibleWithStandardLibrary
-	return json.Unmarshal(bs, &cfg)
+	return jsonUnmarshalIgnoreErroneousBOM(bs, &cfg)
 }
 
 // ToDB exports a UnitConfig to a serialized format.
@@ -45,8 +44,7 @@ type ExternalWikiConfig struct {
 
 // FromDB fills up a ExternalWikiConfig from serialized format.
 func (cfg *ExternalWikiConfig) FromDB(bs []byte) error {
-	json := jsoniter.ConfigCompatibleWithStandardLibrary
-	return json.Unmarshal(bs, &cfg)
+	return jsonUnmarshalIgnoreErroneousBOM(bs, &cfg)
 }
 
 // ToDB exports a ExternalWikiConfig to a serialized format.
@@ -64,8 +62,7 @@ type ExternalTrackerConfig struct {
 
 // FromDB fills up a ExternalTrackerConfig from serialized format.
 func (cfg *ExternalTrackerConfig) FromDB(bs []byte) error {
-	json := jsoniter.ConfigCompatibleWithStandardLibrary
-	return json.Unmarshal(bs, &cfg)
+	return jsonUnmarshalIgnoreErroneousBOM(bs, &cfg)
 }
 
 // ToDB exports a ExternalTrackerConfig to a serialized format.
@@ -83,8 +80,7 @@ type IssuesConfig struct {
 
 // FromDB fills up a IssuesConfig from serialized format.
 func (cfg *IssuesConfig) FromDB(bs []byte) error {
-	json := jsoniter.ConfigCompatibleWithStandardLibrary
-	return json.Unmarshal(bs, &cfg)
+	return jsonUnmarshalIgnoreErroneousBOM(bs, &cfg)
 }
 
 // ToDB exports a IssuesConfig to a serialized format.
@@ -106,8 +102,7 @@ type PullRequestsConfig struct {
 
 // FromDB fills up a PullRequestsConfig from serialized format.
 func (cfg *PullRequestsConfig) FromDB(bs []byte) error {
-	json := jsoniter.ConfigCompatibleWithStandardLibrary
-	return json.Unmarshal(bs, &cfg)
+	return jsonUnmarshalIgnoreErroneousBOM(bs, &cfg)
 }
 
 // ToDB exports a PullRequestsConfig to a serialized format.