Expanded minimum RSA Keylength to 3072 (#26604)

German Federal Office for Information Security requests in its technical
guideline BSI TR-02102-1 RSA Keylength not shorter than 3000bits
starting 2024, in the year 2023 3000bits as a recommendation. Gitea
should request longer RSA Keys by default in favor of security and drop
old clients which do not support longer keys.


https://www.bsi.bund.de/SharedDocs/Downloads/DE/BSI/Publikationen/TechnischeRichtlinien/TR02102/BSI-TR-02102.pdf?__blob=publicationFile&v=9
- Page 19, Table 1.2

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/activitypub/user_settings.go

@@ -8,7 +8,7 @@ import (
 	"code.gitea.io/gitea/modules/util"
 )
 
-const rsaBits = 2048
+const rsaBits = 3072
 
 // GetKeyPair function returns a user's private and public keys
 func GetKeyPair(user *user_model.User) (pub, priv string, err error) {

modules/setting/ssh.go

@@ -60,7 +60,7 @@ var SSH = struct {
 	ServerMACs:                    []string{"hmac-sha2-256-etm@openssh.com", "hmac-sha2-256", "hmac-sha1"},
 	KeygenPath:                    "",
 	MinimumKeySizeCheck:           true,
-	MinimumKeySizes:               map[string]int{"ed25519": 256, "ed25519-sk": 256, "ecdsa": 256, "ecdsa-sk": 256, "rsa": 2047},
+	MinimumKeySizes:               map[string]int{"ed25519": 256, "ed25519-sk": 256, "ecdsa": 256, "ecdsa-sk": 256, "rsa": 3071},
 	ServerHostKeys:                []string{"ssh/gitea.rsa", "ssh/gogs.rsa"},
 	AuthorizedKeysCommandTemplate: "{{.AppPath}} --config={{.CustomConf}} serv key-{{.Key.ID}}",
 	PerWriteTimeout:               PerWriteTimeout,