Add ssh certificate support (#12281)

* Add ssh certificate support

* Add ssh certificate support to builtin ssh

* Write trusted-user-ca-keys.pem based on configuration

* Update app.example.ini

* Update templates/user/settings/keys_principal.tmpl

Co-authored-by: silverwind <[email protected]>

* Remove unused locale string

* Update options/locale/locale_en-US.ini

Co-authored-by: silverwind <[email protected]>

* Update options/locale/locale_en-US.ini

Co-authored-by: silverwind <[email protected]>

* Update models/ssh_key.go

Co-authored-by: silverwind <[email protected]>

* Add missing creation of SSH.Rootpath

* Update cheatsheet, example and locale strings

* Update models/ssh_key.go

Co-authored-by: zeripath <[email protected]>

* Update models/ssh_key.go

Co-authored-by: zeripath <[email protected]>

* Update models/ssh_key.go

Co-authored-by: zeripath <[email protected]>

* Update models/ssh_key.go

Co-authored-by: zeripath <[email protected]>

* Update models/ssh_key.go

* Optimizations based on feedback

* Validate CA keys for external sshd

* Add filename option and change default filename

Add a SSH_TRUSTED_USER_CA_KEYS_FILENAME option which default is
RUN_USER/.ssh/gitea-trusted-user-ca-keys.pem

Do not write a file when SSH_TRUSTED_USER_CA_KEYS is empty.

Add some more documentation.

* Remove unneeded principalkey functions

* Add blank line

* Apply suggestions from code review

Co-authored-by: zeripath <[email protected]>

* Add SSH_AUTHORIZED_PRINCIPALS_ALLOW option

This adds a SSH_AUTHORIZED_PRINCIPALS_ALLOW which is default
email,username this means that users only can add the principals
that match their email or username.

To allow anything the admin need to set the option anything.

This allows for a safe default in gitea which protects against malicious
users using other user's prinicipals. (before that user could set it).

This commit also has some small other fixes from the last code review.

* Rewrite principal keys file on user deletion

* Use correct rewrite method

* Set correct AuthorizedPrincipalsBackup default setting

* Rewrite principalsfile when adding principals

* Add update authorized_principals option to admin dashboard

* Handle non-primary emails

Signed-off-by: Andrew Thornton <[email protected]>

* Add the command actually to the dashboard template

* Update models/ssh_key.go

Co-authored-by: silverwind <[email protected]>

* By default do not show principal options unless there are CA keys set or they are explicitly set

Signed-off-by: Andrew Thornton <[email protected]>

* allow settings when enabled

* Fix typos in TrustedUserCAKeys path

* Allow every CASignatureAlgorithms algorithm

As this depends on the content of TrustedUserCAKeys we should allow all
signature algorithms as admins can choose the specific algorithm on their
signing CA

* Update models/ssh_key.go

Co-authored-by: Lauris BH <[email protected]>

* Fix linting issue

Co-authored-by: silverwind <[email protected]>
Co-authored-by: zeripath <[email protected]>
Co-authored-by: Lauris BH <[email protected]>
Co-authored-by: techknowlogick <[email protected]>
Co-authored-by: techknowlogick <[email protected]>

Author: 5 people

cmd/serv.go

@@ -113,9 +113,12 @@ func runServ(c *cli.Context) error {
 		if err != nil {
 			fail("Internal error", "Failed to check provided key: %v", err)
 		}
-		if key.Type == models.KeyTypeDeploy {
+		switch key.Type {
+		case models.KeyTypeDeploy:
 			println("Hi there! You've successfully authenticated with the deploy key named " + key.Name + ", but Gitea does not provide shell access.")
-		} else {
+		case models.KeyTypePrincipal:
+			println("Hi there! You've successfully authenticated with the principal " + key.Content + ", but Gitea does not provide shell access.")
+		default:
 			println("Hi there, " + user.Name + "! You've successfully authenticated with the key named " + key.Name + ", but Gitea does not provide shell access.")
 		}
 		println("If this is unexpected, please log in with password and setup Gitea under another user.")

custom/conf/app.example.ini

@@ -297,6 +297,9 @@ SSH_ROOT_PATH =
 ; Gitea will create a authorized_keys file by default when it is not using the internal ssh server
 ; If you intend to use the AuthorizedKeysCommand functionality then you should turn this off.
 SSH_CREATE_AUTHORIZED_KEYS_FILE = true
+; Gitea will create a authorized_principals file by default when it is not using the internal ssh server
+; If you intend to use the AuthorizedPrincipalsCommand functionality then you should turn this off.
+SSH_CREATE_AUTHORIZED_PRINCIPALS_FILE = true
 ; For the built-in SSH server, choose the ciphers to support for SSH connections,
 ; for system SSH this setting has no effect
 SSH_SERVER_CIPHERS = aes128-ctr, aes192-ctr, aes256-ctr, [email protected], arcfour256, arcfour128
@@ -312,7 +315,26 @@ 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
 ; Enable SSH Authorized Key Backup when rewriting all keys, default is true
-SSH_BACKUP_AUTHORIZED_KEYS = true
+SSH_AUTHORIZED_KEYS_BACKUP = true
+; Determines which principals to allow
+; - empty: if SSH_TRUSTED_USER_CA_KEYS is empty this will default to off, otherwise will default to email, username.
+; - off: Do not allow authorized principals
+; - email: the principal must match the user's email
+; - username: the principal must match the user's username
+; - anything: there will be no checking on the content of the principal
+SSH_AUTHORIZED_PRINCIPALS_ALLOW = email, username
+; Enable SSH Authorized Principals Backup when rewriting all keys, default is true
+SSH_AUTHORIZED_PRINCIPALS_BACKUP = true
+; Specifies the public keys of certificate authorities that are trusted to sign user certificates for authentication.
+; Multiple keys should be comma separated.
+; E.g."ssh-<algorithm> <key>". or "ssh-<algorithm> <key1>, ssh-<algorithm> <key2>".
+; For more information see "TrustedUserCAKeys" in the sshd config manpages.
+SSH_TRUSTED_USER_CA_KEYS =
+; Absolute path of the `TrustedUserCaKeys` file gitea will manage.
+; Default this `RUN_USER`/.ssh/gitea-trusted-user-ca-keys.pem
+; If you're running your own ssh server and you want to use the gitea managed file you'll also need to modify your
+; sshd_config to point to this file. The official docker image will automatically work without further configuration.
+SSH_TRUSTED_USER_CA_KEYS_FILENAME =
 ; Enable exposure of SSH clone URL to anonymous visitors, default is false
 SSH_EXPOSE_ANONYMOUS = false
 ; Indicate whether to check minimum key size with corresponding type

docker/root/etc/templates/sshd_config

@@ -13,6 +13,9 @@ HostKey /data/ssh/ssh_host_ecdsa_key
 HostKey /data/ssh/ssh_host_dsa_key
 
 AuthorizedKeysFile .ssh/authorized_keys
+AuthorizedPrincipalsFile .ssh/authorized_principals
+TrustedUserCAKeys /data/git/.ssh/gitea-trusted-user-ca-keys.pem
+CASignatureAlgorithms ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],ssh-ed25519,[email protected],rsa-sha2-512,rsa-sha2-256,ssh-rsa
 
 UseDNS no
 AllowAgentForwarding no

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

@@ -251,6 +251,11 @@ Values containing `#` or `;` must be quoted using `` ` `` or `"""`.
 - `SSH_LISTEN_PORT`: **%(SSH\_PORT)s**: Port for the built-in SSH server.
 - `SSH_ROOT_PATH`: **~/.ssh**: Root path of SSH directory. 
 - `SSH_CREATE_AUTHORIZED_KEYS_FILE`: **true**: Gitea will create a authorized_keys file by default when it is not using the internal ssh server. If you intend to use the AuthorizedKeysCommand functionality then you should turn this off.
+- `SSH_TRUSTED_USER_CA_KEYS`: **\<empty\>**: Specifies the public keys of certificate authorities that are trusted to sign user certificates for authentication. Multiple keys should be comma separated. E.g.`ssh-<algorithm> <key>` or `ssh-<algorithm> <key1>, ssh-<algorithm> <key2>`. For more information see `TrustedUserCAKeys` in the sshd config man pages. When empty no file will be created and `SSH_AUTHORIZED_PRINCIPALS_ALLOW` will default to `off`.
+- `SSH_TRUSTED_USER_CA_KEYS_FILENAME`: **`RUN_USER`/.ssh/gitea-trusted-user-ca-keys.pem**: Absolute path of the `TrustedUserCaKeys` file gitea will manage. If you're running your own ssh server and you want to use the gitea managed file you'll also need to modify your sshd_config to point to this file. The official docker image will automatically work without further configuration.
+- `SSH_AUTHORIZED_PRINCIPALS_ALLOW`: **off** or **username, email**: \[off, username, email, anything\]: Specify the principals values that users are allowed to use as principal. When set to `anything` no checks are done on the principal string. When set to `off` authorized principal are not allowed to be set.
+- `SSH_CREATE_AUTHORIZED_PRINCIPALS_FILE`: **false/true**: Gitea will create a authorized_principals file by default when it is not using the internal ssh server and `SSH_AUTHORIZED_PRINCIPALS_ALLOW` is not `off`.
+- `SSH_AUTHORIZED_PRINCIPALS_BACKUP`: **false/true**: Enable SSH Authorized Principals Backup when rewriting all keys, default is true if `SSH_AUTHORIZED_PRINCIPALS_ALLOW` is not `off`.
 - `SSH_SERVER_CIPHERS`: **aes128-ctr, aes192-ctr, aes256-ctr, [email protected], arcfour256, arcfour128**: For the built-in SSH server, choose the ciphers to support for SSH connections, for system SSH this setting has no effect.
 - `SSH_SERVER_KEY_EXCHANGES`: **diffie-hellman-group1-sha1, diffie-hellman-group14-sha1, ecdh-sha2-nistp256, ecdh-sha2-nistp384, ecdh-sha2-nistp521, [email protected]**: For the built-in SSH server, choose the key exchange algorithms to support for SSH connections, for system SSH this setting has no effect.
 - `SSH_SERVER_MACS`: **[email protected], hmac-sha2-256, hmac-sha1, hmac-sha1-96**: For the built-in SSH server, choose the MACs to support for SSH connections, for system SSH this setting has no effect

models/ssh_key.go

@@ -40,6 +40,8 @@ const (
 	tplCommentPrefix = `# gitea public key`
 	tplCommand       = "%s --config=%s serv key-%d"
 	tplPublicKey     = tplCommentPrefix + "\n" + `command=%s,no-port-forwarding,no-X11-forwarding,no-agent-forwarding,no-pty %s` + "\n"
+
+	authorizedPrincipalsFile = "authorized_principals"
 )
 
 var sshOpLocker sync.Mutex
@@ -52,6 +54,8 @@ const (
 	KeyTypeUser = iota + 1
 	// KeyTypeDeploy specifies the deploy key
 	KeyTypeDeploy
+	// KeyTypePrincipal specifies the authorized principal key
+	KeyTypePrincipal
 )
 
 // PublicKey represents a user or deploy SSH public key.
@@ -401,6 +405,9 @@ func appendAuthorizedKeysToFile(keys ...*PublicKey) error {
 	}
 
 	for _, key := range keys {
+		if key.Type == KeyTypePrincipal {
+			continue
+		}
 		if _, err = f.WriteString(key.AuthorizedString()); err != nil {
 			return err
 		}
@@ -571,6 +578,25 @@ func SearchPublicKeyByContent(content string) (*PublicKey, error) {
 	return searchPublicKeyByContentWithEngine(x, content)
 }
 
+func searchPublicKeyByContentExactWithEngine(e Engine, content string) (*PublicKey, error) {
+	key := new(PublicKey)
+	has, err := e.
+		Where("content = ?", content).
+		Get(key)
+	if err != nil {
+		return nil, err
+	} else if !has {
+		return nil, ErrKeyNotExist{}
+	}
+	return key, nil
+}
+
+// SearchPublicKeyByContentExact searches content
+// and returns public key found.
+func SearchPublicKeyByContentExact(content string) (*PublicKey, error) {
+	return searchPublicKeyByContentExactWithEngine(x, content)
+}
+
 // SearchPublicKey returns a list of public keys matching the provided arguments.
 func SearchPublicKey(uid int64, fingerprint string) ([]*PublicKey, error) {
 	keys := make([]*PublicKey, 0, 5)
@@ -586,7 +612,7 @@ func SearchPublicKey(uid int64, fingerprint string) ([]*PublicKey, error) {
 
 // ListPublicKeys returns a list of public keys belongs to given user.
 func ListPublicKeys(uid int64, listOptions ListOptions) ([]*PublicKey, error) {
-	sess := x.Where("owner_id = ?", uid)
+	sess := x.Where("owner_id = ? AND type != ?", uid, KeyTypePrincipal)
 	if listOptions.Page != 0 {
 		sess = listOptions.setSessionPagination(sess)
 
@@ -662,6 +688,10 @@ func DeletePublicKey(doer *User, id int64) (err error) {
 	}
 	sess.Close()
 
+	if key.Type == KeyTypePrincipal {
+		return RewriteAllPrincipalKeys()
+	}
+
 	return RewriteAllPublicKeys()
 }
 
@@ -727,11 +757,10 @@ func RegeneratePublicKeys(t io.StringWriter) error {
 }
 
 func regeneratePublicKeys(e Engine, t io.StringWriter) error {
-	err := e.Iterate(new(PublicKey), func(idx int, bean interface{}) (err error) {
+	if err := e.Where("type != ?", KeyTypePrincipal).Iterate(new(PublicKey), func(idx int, bean interface{}) (err error) {
 		_, err = t.WriteString((bean.(*PublicKey)).AuthorizedString())
 		return err
-	})
-	if err != nil {
+	}); err != nil {
 		return err
 	}
 
@@ -1041,3 +1070,204 @@ func SearchDeployKeys(repoID int64, keyID int64, fingerprint string) ([]*DeployK
 	}
 	return keys, x.Where(cond).Find(&keys)
 }
+
+// __________       .__              .__             .__
+// \______   _______|__| ____   ____ |_____________  |  |   ______
+//  |     ___\_  __ |  |/    \_/ ___\|  \____ \__  \ |  |  /  ___/
+//  |    |    |  | \|  |   |  \  \___|  |  |_> / __ \|  |__\___ \
+//  |____|    |__|  |__|___|  /\___  |__|   __(____  |____/____  >
+//                          \/     \/   |__|       \/          \/
+
+// AddPrincipalKey adds new principal to database and authorized_principals file.
+func AddPrincipalKey(ownerID int64, content string, loginSourceID int64) (*PublicKey, error) {
+	sess := x.NewSession()
+	defer sess.Close()
+	if err := sess.Begin(); err != nil {
+		return nil, err
+	}
+
+	// Principals cannot be duplicated.
+	has, err := sess.
+		Where("content = ? AND type = ?", content, KeyTypePrincipal).
+		Get(new(PublicKey))
+	if err != nil {
+		return nil, err
+	} else if has {
+		return nil, ErrKeyAlreadyExist{0, "", content}
+	}
+
+	key := &PublicKey{
+		OwnerID:       ownerID,
+		Name:          content,
+		Content:       content,
+		Mode:          AccessModeWrite,
+		Type:          KeyTypePrincipal,
+		LoginSourceID: loginSourceID,
+	}
+	if err = addPrincipalKey(sess, key); err != nil {
+		return nil, fmt.Errorf("addKey: %v", err)
+	}
+
+	if err = sess.Commit(); err != nil {
+		return nil, err
+	}
+
+	sess.Close()
+
+	return key, RewriteAllPrincipalKeys()
+}
+
+func addPrincipalKey(e Engine, key *PublicKey) (err error) {
+	// Save Key representing a principal.
+	if _, err = e.Insert(key); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// CheckPrincipalKeyString strips spaces and returns an error if the given principal contains newlines
+func CheckPrincipalKeyString(user *User, content string) (_ string, err error) {
+	if setting.SSH.Disabled {
+		return "", ErrSSHDisabled{}
+	}
+
+	content = strings.TrimSpace(content)
+	if strings.ContainsAny(content, "\r\n") {
+		return "", errors.New("only a single line with a single principal please")
+	}
+
+	// check all the allowed principals, email, username or anything
+	// if any matches, return ok
+	for _, v := range setting.SSH.AuthorizedPrincipalsAllow {
+		switch v {
+		case "anything":
+			return content, nil
+		case "email":
+			emails, err := GetEmailAddresses(user.ID)
+			if err != nil {
+				return "", err
+			}
+			for _, email := range emails {
+				if !email.IsActivated {
+					continue
+				}
+				if content == email.Email {
+					return content, nil
+				}
+			}
+
+		case "username":
+			if content == user.Name {
+				return content, nil
+			}
+		}
+	}
+
+	return "", fmt.Errorf("didn't match allowed principals: %s", setting.SSH.AuthorizedPrincipalsAllow)
+}
+
+// RewriteAllPrincipalKeys removes any authorized principal and rewrite all keys from database again.
+// Note: x.Iterate does not get latest data after insert/delete, so we have to call this function
+// outside any session scope independently.
+func RewriteAllPrincipalKeys() error {
+	return rewriteAllPrincipalKeys(x)
+}
+
+func rewriteAllPrincipalKeys(e Engine) error {
+	// Don't rewrite key if internal server
+	if setting.SSH.StartBuiltinServer || !setting.SSH.CreateAuthorizedPrincipalsFile {
+		return nil
+	}
+
+	sshOpLocker.Lock()
+	defer sshOpLocker.Unlock()
+
+	if setting.SSH.RootPath != "" {
+		// First of ensure that the RootPath is present, and if not make it with 0700 permissions
+		// This of course doesn't guarantee that this is the right directory for authorized_keys
+		// but at least if it's supposed to be this directory and it doesn't exist and we're the
+		// right user it will at least be created properly.
+		err := os.MkdirAll(setting.SSH.RootPath, 0700)
+		if err != nil {
+			log.Error("Unable to MkdirAll(%s): %v", setting.SSH.RootPath, err)
+			return err
+		}
+	}
+
+	fPath := filepath.Join(setting.SSH.RootPath, authorizedPrincipalsFile)
+	tmpPath := fPath + ".tmp"
+	t, err := os.OpenFile(tmpPath, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0600)
+	if err != nil {
+		return err
+	}
+	defer func() {
+		t.Close()
+		os.Remove(tmpPath)
+	}()
+
+	if setting.SSH.AuthorizedPrincipalsBackup && com.IsExist(fPath) {
+		bakPath := fmt.Sprintf("%s_%d.gitea_bak", fPath, time.Now().Unix())
+		if err = com.Copy(fPath, bakPath); err != nil {
+			return err
+		}
+	}
+
+	if err := regeneratePrincipalKeys(e, t); err != nil {
+		return err
+	}
+
+	t.Close()
+	return os.Rename(tmpPath, fPath)
+}
+
+// ListPrincipalKeys returns a list of principals belongs to given user.
+func ListPrincipalKeys(uid int64, listOptions ListOptions) ([]*PublicKey, error) {
+	sess := x.Where("owner_id = ? AND type = ?", uid, KeyTypePrincipal)
+	if listOptions.Page != 0 {
+		sess = listOptions.setSessionPagination(sess)
+
+		keys := make([]*PublicKey, 0, listOptions.PageSize)
+		return keys, sess.Find(&keys)
+	}
+
+	keys := make([]*PublicKey, 0, 5)
+	return keys, sess.Find(&keys)
+}
+
+// RegeneratePrincipalKeys regenerates the authorized_principals file
+func RegeneratePrincipalKeys(t io.StringWriter) error {
+	return regeneratePrincipalKeys(x, t)
+}
+
+func regeneratePrincipalKeys(e Engine, t io.StringWriter) error {
+	if err := e.Where("type = ?", KeyTypePrincipal).Iterate(new(PublicKey), func(idx int, bean interface{}) (err error) {
+		_, err = t.WriteString((bean.(*PublicKey)).AuthorizedString())
+		return err
+	}); err != nil {
+		return err
+	}
+
+	fPath := filepath.Join(setting.SSH.RootPath, authorizedPrincipalsFile)
+	if com.IsExist(fPath) {
+		f, err := os.Open(fPath)
+		if err != nil {
+			return err
+		}
+		scanner := bufio.NewScanner(f)
+		for scanner.Scan() {
+			line := scanner.Text()
+			if strings.HasPrefix(line, tplCommentPrefix) {
+				scanner.Scan()
+				continue
+			}
+			_, err = t.WriteString(line + "\n")
+			if err != nil {
+				f.Close()
+				return err
+			}
+		}
+		f.Close()
+	}
+	return nil
+}

models/user.go

@@ -1254,6 +1254,10 @@ func deleteUser(e *xorm.Session, u *User) error {
 	if err != nil {
 		return err
 	}
+	err = rewriteAllPrincipalKeys(e)
+	if err != nil {
+		return err
+	}
 	// ***** END: PublicKey *****
 
 	// ***** START: GPGPublicKey *****