Merge pull request #2637 from Gibheer/ssh-publickeys
allow native and ssh-keygen public key check
This commit is contained in:
Unknwon
commit
83c74878df
16
conf/app.ini
16
conf/app.ini
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@ -71,6 +71,13 @@ SSH_PORT = 22
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SSH_LISTEN_PORT = %(SSH_PORT)s
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; Root path of SSH directory, default is '~/.ssh', but you have to use '/home/git/.ssh'.
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SSH_ROOT_PATH =
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; override engine choice to check public keys (default: 'ssh-keygen' when
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; DISABLE_SSH is set to false else 'native')
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SSH_PUBLICKEY_CHECK =
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; directory to create temporary files when using ssh-keygen (default: /tmp)
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SSH_WORK_PATH =
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; path to ssh-keygen (default: result of `which ssh-keygen`)
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SSH_KEYGEN_PATH =
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; Disable CDN even in "prod" mode
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OFFLINE_MODE = false
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DISABLE_ROUTER_LOG = false
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@ -132,6 +139,15 @@ ENABLE_REVERSE_PROXY_AUTHENTICATION = false
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ENABLE_REVERSE_PROXY_AUTO_REGISTRATION = false
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; Enable captcha validation for registration
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ENABLE_CAPTCHA = true
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; Do not check minimum key size with corresponding type
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ENABLE_MINIMUM_KEY_SIZE_CHECK = false
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; define allowed algorithms and their minimum key length (use -1 to disable a type)
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[service.minimum_key_sizes]
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ED25519 = 256
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ECDSA = 256
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RSA = 2048
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DSA = 1024
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[webhook]
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; Hook task queue length
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@ -12,9 +12,11 @@ import (
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"fmt"
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"io"
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"io/ioutil"
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"math/big"
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"os"
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"path"
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"path/filepath"
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"strconv"
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"strings"
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"sync"
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"time"
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@ -33,7 +35,10 @@ const (
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_TPL_PUBLICK_KEY = `command="%s serv key-%d --config='%s'",no-port-forwarding,no-X11-forwarding,no-agent-forwarding,no-pty %s` + "\n"
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)
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var sshOpLocker = sync.Mutex{}
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var (
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sshOpLocker = sync.Mutex{}
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SSHUnknownKeyType = fmt.Errorf("unknown key type")
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)
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type KeyType int
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@ -153,7 +158,110 @@ func parseKeyString(content string) (string, error) {
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return keyType + " " + keyContent + " " + keyComment, nil
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}
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// extract key type and length using ssh-keygen
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func SSHKeyGenParsePublicKey(key string) (string, int, error) {
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// The ssh-keygen in Windows does not print key type, so no need go further.
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if setting.IsWindows {
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return "", 0, nil
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}
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tmpFile, err := ioutil.TempFile(setting.SSHWorkPath, "gogs_keytest")
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if err != nil {
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return "", 0, err
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}
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tmpName := tmpFile.Name()
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defer os.Remove(tmpName)
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if ln, err := tmpFile.WriteString(key); err != nil {
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tmpFile.Close()
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return "", 0, err
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} else if ln != len(key) {
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tmpFile.Close()
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return "", 0, fmt.Errorf("could not write complete public key (written: %d, should be: %d): %s", ln, len(key), key)
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}
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tmpFile.Close()
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stdout, stderr, err := process.Exec("CheckPublicKeyString", setting.SSHKeyGenPath, "-lf", tmpName)
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if err != nil {
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return "", 0, fmt.Errorf("public key check failed with error '%s': %s", err, stderr)
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}
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if strings.HasSuffix(stdout, "is not a public key file.") {
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return "", 0, SSHUnknownKeyType
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}
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fields := strings.Split(stdout, " ")
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if len(fields) < 4 {
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return "", 0, fmt.Errorf("invalid public key line: %s", stdout)
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}
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length, err := strconv.Atoi(fields[0])
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if err != nil {
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return "", 0, err
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}
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keyType := strings.Trim(fields[len(fields)-1], "()\r\n")
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return strings.ToLower(keyType), length, nil
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}
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// extract the key type and length using the golang ssh library
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func SSHNativeParsePublicKey(keyLine string) (string, int, error) {
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fields := strings.Fields(keyLine)
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if len(fields) < 2 {
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return "", 0, fmt.Errorf("not enough fields in public key line: %s", string(keyLine))
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}
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raw, err := base64.StdEncoding.DecodeString(fields[1])
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if err != nil {
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return "", 0, err
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}
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pkey, err := ssh.ParsePublicKey(raw)
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if err != nil {
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if strings.HasPrefix(err.Error(), "ssh: unknown key algorithm") {
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return "", 0, SSHUnknownKeyType
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}
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return "", 0, err
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}
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// The ssh library can parse the key, so next we find out what key exactly we
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// have.
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switch pkey.Type() {
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case ssh.KeyAlgoDSA:
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rawPub := struct {
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Name string
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P, Q, G, Y *big.Int
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}{}
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if err := ssh.Unmarshal(pkey.Marshal(), &rawPub); err != nil {
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return "", 0, err
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}
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// as per https://bugzilla.mindrot.org/show_bug.cgi?id=1647 we should never
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// see dsa keys != 1024 bit, but as it seems to work, we will not check here
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return "dsa", rawPub.P.BitLen(), nil // use P as per crypto/dsa/dsa.go (is L)
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case ssh.KeyAlgoRSA:
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rawPub := struct {
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Name string
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E *big.Int
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N *big.Int
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}{}
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if err := ssh.Unmarshal(pkey.Marshal(), &rawPub); err != nil {
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return "", 0, err
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}
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return "rsa", rawPub.N.BitLen(), nil // use N as per crypto/rsa/rsa.go (is bits)
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case ssh.KeyAlgoECDSA256:
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return "ecdsa", 256, nil
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case ssh.KeyAlgoECDSA384:
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return "ecdsa", 384, nil
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case ssh.KeyAlgoECDSA521:
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return "ecdsa", 521, nil
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case "ssh-ed25519": // TODO replace with ssh constant when available
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return "ed25519", 256, nil
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default:
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return "", 0, fmt.Errorf("no support for key length detection for type %s", pkey.Type())
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}
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return "", 0, fmt.Errorf("SSHNativeParsePublicKey failed horribly, please investigate why")
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}
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// CheckPublicKeyString checks if the given public key string is recognized by SSH.
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//
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// The function returns the actual public key line on success.
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func CheckPublicKeyString(content string) (_ string, err error) {
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content, err = parseKeyString(content)
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if err != nil {
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@ -168,22 +276,34 @@ func CheckPublicKeyString(content string) (_ string, err error) {
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// remove any unnecessary whitespace now
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content = strings.TrimSpace(content)
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fields := strings.Fields(content)
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if len(fields) < 2 {
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return "", errors.New("too less fields")
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var (
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keyType string
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length int
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)
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if setting.SSHPublicKeyCheck == setting.SSH_PUBLICKEY_CHECK_NATIVE {
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keyType, length, err = SSHNativeParsePublicKey(content)
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} else if setting.SSHPublicKeyCheck == setting.SSH_PUBLICKEY_CHECK_KEYGEN {
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keyType, length, err = SSHKeyGenParsePublicKey(content)
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} else {
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log.Error(4, "invalid public key check type: %s", setting.SSHPublicKeyCheck)
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return "", fmt.Errorf("invalid public key check type")
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}
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key, err := base64.StdEncoding.DecodeString(fields[1])
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if err != nil {
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return "", fmt.Errorf("StdEncoding.DecodeString: %v", err)
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}
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pkey, err := ssh.ParsePublicKey([]byte(key))
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if err != nil {
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log.Trace("invalid public key of type '%s' with length %d: %s", keyType, length, err)
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return "", fmt.Errorf("ParsePublicKey: %v", err)
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}
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log.Trace("Key type: %s", pkey.Type())
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log.Trace("Key type: %s", keyType)
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if !setting.Service.EnableMinimumKeySizeCheck {
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return content, nil
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}
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if minLen, found := setting.Service.MinimumKeySizes[keyType]; found && length >= minLen {
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return content, nil
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} else if found && length < minLen {
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return "", fmt.Errorf("key not large enough - got %d, needs %d", length, minLen)
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}
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return "", fmt.Errorf("key type '%s' is not allowed", keyType)
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}
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// saveAuthorizedKeyFile writes SSH key content to authorized_keys file.
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@ -247,7 +367,7 @@ func addKey(e Engine, key *PublicKey) (err error) {
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}
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stdout, stderr, err := process.Exec("AddPublicKey", "ssh-keygen", "-lf", tmpPath)
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if err != nil {
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return errors.New("ssh-keygen -lf: " + stderr)
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return fmt.Errorf("'ssh-keygen -lf %s' failed with error '%s': %s", tmpPath, err, stderr)
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} else if len(stdout) < 2 {
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return errors.New("not enough output for calculating fingerprint: " + stdout)
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}
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@ -267,6 +387,7 @@ func addKey(e Engine, key *PublicKey) (err error) {
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// AddPublicKey adds new public key to database and authorized_keys file.
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func AddPublicKey(ownerID int64, name, content string) (*PublicKey, error) {
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log.Trace(content)
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if err := checkKeyContent(content); err != nil {
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return nil, err
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}
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39
models/ssh_key_test.go
Normal file
39
models/ssh_key_test.go
Normal file
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@ -0,0 +1,39 @@
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package models
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import (
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"github.com/gogits/gogs/modules/setting"
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"testing"
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)
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func TestSSHKeyVerification(t *testing.T) {
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setting.SSHWorkPath = "/tmp"
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setting.SSHKeyGenPath = "/usr/bin/ssh-keygen"
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keys := map[string]string{
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"dsa-1024": string("ssh-dss 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 nocomment"),
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"rsa-1024": string("ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAAAgQDAu7tvIvX6ZHrRXuZNfkR3XLHSsuCK9Zn3X58lxBcQzuo5xZgB6vRwwm/QtJuF+zZPtY5hsQILBLmF+BZ5WpKZp1jBeSjH2G7lxet9kbcH+kIVj0tPFEoyKI9wvWqIwC4prx/WVk2wLTJjzBAhyNxfEq7C9CeiX9pQEbEqJfkKCQ== nocomment\n"),
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"rsa-2048": string("ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDMZXh+1OBUwSH9D45wTaxErQIN9IoC9xl7MKJkqvTvv6O5RR9YW/IK9FbfjXgXsppYGhsCZo1hFOOsXHMnfOORqu/xMDx4yPuyvKpw4LePEcg4TDipaDFuxbWOqc/BUZRZcXu41QAWfDLrInwsltWZHSeG7hjhpacl4FrVv9V1pS6Oc5Q1NxxEzTzuNLS/8diZrTm/YAQQ/+B+mzWI3zEtF4miZjjAljWd1LTBPvU23d29DcBmmFahcZ441XZsTeAwGxG/Q6j8NgNXj9WxMeWwxXV2jeAX/EBSpZrCVlCQ1yJswT6xCp8TuBnTiGWYMBNTbOZvPC4e0WI2/yZW/s5F nocomment"),
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"ecdsa-256": string("ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBFQacN3PrOll7PXmN5B/ZNVahiUIqI05nbBlZk1KXsO3d06ktAWqbNflv2vEmA38bTFTfJ2sbn2B5ksT52cDDbA= nocomment"),
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"ecdsa-384": string("ecdsa-sha2-nistp384 AAAAE2VjZHNhLXNoYTItbmlzdHAzODQAAAAIbmlzdHAzODQAAABhBINmioV+XRX1Fm9Qk2ehHXJ2tfVxW30ypUWZw670Zyq5GQfBAH6xjygRsJ5wWsHXBsGYgFUXIHvMKVAG1tpw7s6ax9oA+dJOJ7tj+vhn8joFqT+sg3LYHgZkHrfqryRasQ== nocomment"),
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"ecdsa-512": string("ecdsa-sha2-nistp521 AAAAE2VjZHNhLXNoYTItbmlzdHA1MjEAAAAIbmlzdHA1MjEAAACFBACGt3UG3EzRwNOI17QR84l6PgiAcvCE7v6aXPj/SC6UWKg4EL8vW9ZBcdYL9wzs4FZXh4MOV8jAzu3KRWNTwb4k2wFNUpGOt7l28MztFFEtH5BDDrtAJSPENPy8pvPLMfnPg5NhvWycqIBzNcHipem5wSJFN5PdpNOC2xMrPWKNqj+ZjQ== nocomment"),
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}
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for name, pubkey := range keys {
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keyTypeN, lengthN, errN := SSHNativeParsePublicKey(pubkey)
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if errN != nil {
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if errN != SSHUnknownKeyType {
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t.Errorf("error parsing public key '%s': %s", name, errN)
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continue
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}
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}
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keyTypeK, lengthK, errK := SSHKeyGenParsePublicKey(pubkey)
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if errK != nil {
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t.Errorf("error parsing public key '%s': %s", name, errK)
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continue
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}
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// we know that ed25519 is currently not supported by native and returns SSHUnknownKeyType
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if (keyTypeN != keyTypeK || lengthN != lengthK) && errN != SSHUnknownKeyType {
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t.Errorf("key mismatch for '%s': native: %s(%d), ssh-keygen: %s(%d)", name, keyTypeN, lengthN, keyTypeK, lengthK)
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}
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}
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}
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@ -27,6 +27,11 @@ import (
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"github.com/gogits/gogs/modules/user"
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)
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const (
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SSH_PUBLICKEY_CHECK_NATIVE = "native"
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SSH_PUBLICKEY_CHECK_KEYGEN = "ssh-keygen"
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)
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type Scheme string
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const (
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@ -67,6 +72,9 @@ var (
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SSHPort int
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SSHListenPort int
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SSHRootPath string
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SSHPublicKeyCheck string
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SSHWorkPath string
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SSHKeyGenPath string
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OfflineMode bool
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DisableRouterLog bool
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CertFile, KeyFile string
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@ -330,6 +338,29 @@ func NewContext() {
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if err := os.MkdirAll(SSHRootPath, 0700); err != nil {
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log.Fatal(4, "Fail to create '%s': %v", SSHRootPath, err)
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}
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checkDefault := SSH_PUBLICKEY_CHECK_KEYGEN
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if StartSSHServer {
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checkDefault = SSH_PUBLICKEY_CHECK_NATIVE
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}
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SSHPublicKeyCheck = sec.Key("SSH_PUBLICKEY_CHECK").MustString(checkDefault)
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if SSHPublicKeyCheck != SSH_PUBLICKEY_CHECK_NATIVE &&
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SSHPublicKeyCheck != SSH_PUBLICKEY_CHECK_KEYGEN {
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log.Fatal(4, "SSH_PUBLICKEY_CHECK must be ssh-keygen or native")
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}
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SSHWorkPath = sec.Key("SSH_WORK_PATH").MustString(os.TempDir())
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if !DisableSSH && (!StartSSHServer || SSHPublicKeyCheck == SSH_PUBLICKEY_CHECK_KEYGEN) {
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if tmpDirStat, err := os.Stat(SSHWorkPath); err != nil || !tmpDirStat.IsDir() {
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log.Fatal(4, "directory '%s' set in SSHWorkPath is not a directory: %s", SSHWorkPath, err)
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}
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}
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SSHKeyGenPath = sec.Key("SSH_KEYGEN_PATH").MustString("")
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if !DisableSSH && !StartSSHServer &&
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SSHKeyGenPath == "" && SSHPublicKeyCheck == SSH_PUBLICKEY_CHECK_KEYGEN {
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SSHKeyGenPath, err = exec.LookPath("ssh-keygen")
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if err != nil {
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log.Fatal(4, "could not find ssh-keygen, maybe set DISABLE_SSH to use the internal ssh server")
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}
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}
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OfflineMode = sec.Key("OFFLINE_MODE").MustBool()
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DisableRouterLog = sec.Key("DISABLE_ROUTER_LOG").MustBool()
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StaticRootPath = sec.Key("STATIC_ROOT_PATH").MustString(workDir)
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@ -461,6 +492,8 @@ var Service struct {
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EnableReverseProxyAuth bool
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EnableReverseProxyAutoRegister bool
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EnableCaptcha bool
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EnableMinimumKeySizeCheck bool
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MinimumKeySizes map[string]int
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}
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func newService() {
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@ -473,6 +506,15 @@ func newService() {
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Service.EnableReverseProxyAuth = sec.Key("ENABLE_REVERSE_PROXY_AUTHENTICATION").MustBool()
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Service.EnableReverseProxyAutoRegister = sec.Key("ENABLE_REVERSE_PROXY_AUTO_REGISTRATION").MustBool()
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Service.EnableCaptcha = sec.Key("ENABLE_CAPTCHA").MustBool()
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Service.EnableMinimumKeySizeCheck = sec.Key("ENABLE_MINIMUM_KEY_SIZE_CHECK").MustBool()
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Service.MinimumKeySizes = map[string]int{}
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minimumKeySizes := Cfg.Section("service.minimum_key_sizes").Keys()
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for _, key := range minimumKeySizes {
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if key.MustInt() != -1 {
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Service.MinimumKeySizes[strings.ToLower(key.Name())] = key.MustInt()
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}
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}
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}
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var logLevels = map[string]string{
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