Source file src/golang.org/x/crypto/ssh/keys.go

Documentation: golang.org/x/crypto/ssh

     1  // Copyright 2012 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package ssh
     6  
     7  import (
     8  	"bytes"
     9  	"crypto"
    10  	"crypto/aes"
    11  	"crypto/cipher"
    12  	"crypto/dsa"
    13  	"crypto/ecdsa"
    14  	"crypto/ed25519"
    15  	"crypto/elliptic"
    16  	"crypto/md5"
    17  	"crypto/rand"
    18  	"crypto/rsa"
    19  	"crypto/sha256"
    20  	"crypto/x509"
    21  	"encoding/asn1"
    22  	"encoding/base64"
    23  	"encoding/binary"
    24  	"encoding/hex"
    25  	"encoding/pem"
    26  	"errors"
    27  	"fmt"
    28  	"io"
    29  	"math/big"
    30  	"strings"
    31  
    32  	"golang.org/x/crypto/ssh/internal/bcrypt_pbkdf"
    33  )
    34  
    35  // Public key algorithms names. These values can appear in PublicKey.Type,
    36  // ClientConfig.HostKeyAlgorithms, Signature.Format, or as AlgorithmSigner
    37  // arguments.
    38  const (
    39  	KeyAlgoRSA        = "ssh-rsa"
    40  	KeyAlgoDSA        = "ssh-dss"
    41  	KeyAlgoECDSA256   = "ecdsa-sha2-nistp256"
    42  	KeyAlgoSKECDSA256 = "sk-ecdsa-sha2-nistp256@openssh.com"
    43  	KeyAlgoECDSA384   = "ecdsa-sha2-nistp384"
    44  	KeyAlgoECDSA521   = "ecdsa-sha2-nistp521"
    45  	KeyAlgoED25519    = "ssh-ed25519"
    46  	KeyAlgoSKED25519  = "sk-ssh-ed25519@openssh.com"
    47  
    48  	// KeyAlgoRSASHA256 and KeyAlgoRSASHA512 are only public key algorithms, not
    49  	// public key formats, so they can't appear as a PublicKey.Type. The
    50  	// corresponding PublicKey.Type is KeyAlgoRSA. See RFC 8332, Section 2.
    51  	KeyAlgoRSASHA256 = "rsa-sha2-256"
    52  	KeyAlgoRSASHA512 = "rsa-sha2-512"
    53  )
    54  
    55  const (
    56  	// Deprecated: use KeyAlgoRSA.
    57  	SigAlgoRSA = KeyAlgoRSA
    58  	// Deprecated: use KeyAlgoRSASHA256.
    59  	SigAlgoRSASHA2256 = KeyAlgoRSASHA256
    60  	// Deprecated: use KeyAlgoRSASHA512.
    61  	SigAlgoRSASHA2512 = KeyAlgoRSASHA512
    62  )
    63  
    64  // parsePubKey parses a public key of the given algorithm.
    65  // Use ParsePublicKey for keys with prepended algorithm.
    66  func parsePubKey(in []byte, algo string) (pubKey PublicKey, rest []byte, err error) {
    67  	switch algo {
    68  	case KeyAlgoRSA:
    69  		return parseRSA(in)
    70  	case KeyAlgoDSA:
    71  		return parseDSA(in)
    72  	case KeyAlgoECDSA256, KeyAlgoECDSA384, KeyAlgoECDSA521:
    73  		return parseECDSA(in)
    74  	case KeyAlgoSKECDSA256:
    75  		return parseSKECDSA(in)
    76  	case KeyAlgoED25519:
    77  		return parseED25519(in)
    78  	case KeyAlgoSKED25519:
    79  		return parseSKEd25519(in)
    80  	case CertAlgoRSAv01, CertAlgoDSAv01, CertAlgoECDSA256v01, CertAlgoECDSA384v01, CertAlgoECDSA521v01, CertAlgoSKECDSA256v01, CertAlgoED25519v01, CertAlgoSKED25519v01:
    81  		cert, err := parseCert(in, certKeyAlgoNames[algo])
    82  		if err != nil {
    83  			return nil, nil, err
    84  		}
    85  		return cert, nil, nil
    86  	}
    87  	return nil, nil, fmt.Errorf("ssh: unknown key algorithm: %v", algo)
    88  }
    89  
    90  // parseAuthorizedKey parses a public key in OpenSSH authorized_keys format
    91  // (see sshd(8) manual page) once the options and key type fields have been
    92  // removed.
    93  func parseAuthorizedKey(in []byte) (out PublicKey, comment string, err error) {
    94  	in = bytes.TrimSpace(in)
    95  
    96  	i := bytes.IndexAny(in, " \t")
    97  	if i == -1 {
    98  		i = len(in)
    99  	}
   100  	base64Key := in[:i]
   101  
   102  	key := make([]byte, base64.StdEncoding.DecodedLen(len(base64Key)))
   103  	n, err := base64.StdEncoding.Decode(key, base64Key)
   104  	if err != nil {
   105  		return nil, "", err
   106  	}
   107  	key = key[:n]
   108  	out, err = ParsePublicKey(key)
   109  	if err != nil {
   110  		return nil, "", err
   111  	}
   112  	comment = string(bytes.TrimSpace(in[i:]))
   113  	return out, comment, nil
   114  }
   115  
   116  // ParseKnownHosts parses an entry in the format of the known_hosts file.
   117  //
   118  // The known_hosts format is documented in the sshd(8) manual page. This
   119  // function will parse a single entry from in. On successful return, marker
   120  // will contain the optional marker value (i.e. "cert-authority" or "revoked")
   121  // or else be empty, hosts will contain the hosts that this entry matches,
   122  // pubKey will contain the public key and comment will contain any trailing
   123  // comment at the end of the line. See the sshd(8) manual page for the various
   124  // forms that a host string can take.
   125  //
   126  // The unparsed remainder of the input will be returned in rest. This function
   127  // can be called repeatedly to parse multiple entries.
   128  //
   129  // If no entries were found in the input then err will be io.EOF. Otherwise a
   130  // non-nil err value indicates a parse error.
   131  func ParseKnownHosts(in []byte) (marker string, hosts []string, pubKey PublicKey, comment string, rest []byte, err error) {
   132  	for len(in) > 0 {
   133  		end := bytes.IndexByte(in, '\n')
   134  		if end != -1 {
   135  			rest = in[end+1:]
   136  			in = in[:end]
   137  		} else {
   138  			rest = nil
   139  		}
   140  
   141  		end = bytes.IndexByte(in, '\r')
   142  		if end != -1 {
   143  			in = in[:end]
   144  		}
   145  
   146  		in = bytes.TrimSpace(in)
   147  		if len(in) == 0 || in[0] == '#' {
   148  			in = rest
   149  			continue
   150  		}
   151  
   152  		i := bytes.IndexAny(in, " \t")
   153  		if i == -1 {
   154  			in = rest
   155  			continue
   156  		}
   157  
   158  		// Strip out the beginning of the known_host key.
   159  		// This is either an optional marker or a (set of) hostname(s).
   160  		keyFields := bytes.Fields(in)
   161  		if len(keyFields) < 3 || len(keyFields) > 5 {
   162  			return "", nil, nil, "", nil, errors.New("ssh: invalid entry in known_hosts data")
   163  		}
   164  
   165  		// keyFields[0] is either "@cert-authority", "@revoked" or a comma separated
   166  		// list of hosts
   167  		marker := ""
   168  		if keyFields[0][0] == '@' {
   169  			marker = string(keyFields[0][1:])
   170  			keyFields = keyFields[1:]
   171  		}
   172  
   173  		hosts := string(keyFields[0])
   174  		// keyFields[1] contains the key type (e.g. “ssh-rsa”).
   175  		// However, that information is duplicated inside the
   176  		// base64-encoded key and so is ignored here.
   177  
   178  		key := bytes.Join(keyFields[2:], []byte(" "))
   179  		if pubKey, comment, err = parseAuthorizedKey(key); err != nil {
   180  			return "", nil, nil, "", nil, err
   181  		}
   182  
   183  		return marker, strings.Split(hosts, ","), pubKey, comment, rest, nil
   184  	}
   185  
   186  	return "", nil, nil, "", nil, io.EOF
   187  }
   188  
   189  // ParseAuthorizedKey parses a public key from an authorized_keys
   190  // file used in OpenSSH according to the sshd(8) manual page.
   191  func ParseAuthorizedKey(in []byte) (out PublicKey, comment string, options []string, rest []byte, err error) {
   192  	for len(in) > 0 {
   193  		end := bytes.IndexByte(in, '\n')
   194  		if end != -1 {
   195  			rest = in[end+1:]
   196  			in = in[:end]
   197  		} else {
   198  			rest = nil
   199  		}
   200  
   201  		end = bytes.IndexByte(in, '\r')
   202  		if end != -1 {
   203  			in = in[:end]
   204  		}
   205  
   206  		in = bytes.TrimSpace(in)
   207  		if len(in) == 0 || in[0] == '#' {
   208  			in = rest
   209  			continue
   210  		}
   211  
   212  		i := bytes.IndexAny(in, " \t")
   213  		if i == -1 {
   214  			in = rest
   215  			continue
   216  		}
   217  
   218  		if out, comment, err = parseAuthorizedKey(in[i:]); err == nil {
   219  			return out, comment, options, rest, nil
   220  		}
   221  
   222  		// No key type recognised. Maybe there's an options field at
   223  		// the beginning.
   224  		var b byte
   225  		inQuote := false
   226  		var candidateOptions []string
   227  		optionStart := 0
   228  		for i, b = range in {
   229  			isEnd := !inQuote && (b == ' ' || b == '\t')
   230  			if (b == ',' && !inQuote) || isEnd {
   231  				if i-optionStart > 0 {
   232  					candidateOptions = append(candidateOptions, string(in[optionStart:i]))
   233  				}
   234  				optionStart = i + 1
   235  			}
   236  			if isEnd {
   237  				break
   238  			}
   239  			if b == '"' && (i == 0 || (i > 0 && in[i-1] != '\\')) {
   240  				inQuote = !inQuote
   241  			}
   242  		}
   243  		for i < len(in) && (in[i] == ' ' || in[i] == '\t') {
   244  			i++
   245  		}
   246  		if i == len(in) {
   247  			// Invalid line: unmatched quote
   248  			in = rest
   249  			continue
   250  		}
   251  
   252  		in = in[i:]
   253  		i = bytes.IndexAny(in, " \t")
   254  		if i == -1 {
   255  			in = rest
   256  			continue
   257  		}
   258  
   259  		if out, comment, err = parseAuthorizedKey(in[i:]); err == nil {
   260  			options = candidateOptions
   261  			return out, comment, options, rest, nil
   262  		}
   263  
   264  		in = rest
   265  		continue
   266  	}
   267  
   268  	return nil, "", nil, nil, errors.New("ssh: no key found")
   269  }
   270  
   271  // ParsePublicKey parses an SSH public key formatted for use in
   272  // the SSH wire protocol according to RFC 4253, section 6.6.
   273  func ParsePublicKey(in []byte) (out PublicKey, err error) {
   274  	algo, in, ok := parseString(in)
   275  	if !ok {
   276  		return nil, errShortRead
   277  	}
   278  	var rest []byte
   279  	out, rest, err = parsePubKey(in, string(algo))
   280  	if len(rest) > 0 {
   281  		return nil, errors.New("ssh: trailing junk in public key")
   282  	}
   283  
   284  	return out, err
   285  }
   286  
   287  // MarshalAuthorizedKey serializes key for inclusion in an OpenSSH
   288  // authorized_keys file. The return value ends with newline.
   289  func MarshalAuthorizedKey(key PublicKey) []byte {
   290  	b := &bytes.Buffer{}
   291  	b.WriteString(key.Type())
   292  	b.WriteByte(' ')
   293  	e := base64.NewEncoder(base64.StdEncoding, b)
   294  	e.Write(key.Marshal())
   295  	e.Close()
   296  	b.WriteByte('\n')
   297  	return b.Bytes()
   298  }
   299  
   300  // MarshalPrivateKey returns a PEM block with the private key serialized in the
   301  // OpenSSH format.
   302  func MarshalPrivateKey(key crypto.PrivateKey, comment string) (*pem.Block, error) {
   303  	return marshalOpenSSHPrivateKey(key, comment, unencryptedOpenSSHMarshaler)
   304  }
   305  
   306  // MarshalPrivateKeyWithPassphrase returns a PEM block holding the encrypted
   307  // private key serialized in the OpenSSH format.
   308  func MarshalPrivateKeyWithPassphrase(key crypto.PrivateKey, comment string, passphrase []byte) (*pem.Block, error) {
   309  	return marshalOpenSSHPrivateKey(key, comment, passphraseProtectedOpenSSHMarshaler(passphrase))
   310  }
   311  
   312  // PublicKey represents a public key using an unspecified algorithm.
   313  //
   314  // Some PublicKeys provided by this package also implement CryptoPublicKey.
   315  type PublicKey interface {
   316  	// Type returns the key format name, e.g. "ssh-rsa".
   317  	Type() string
   318  
   319  	// Marshal returns the serialized key data in SSH wire format, with the name
   320  	// prefix. To unmarshal the returned data, use the ParsePublicKey function.
   321  	Marshal() []byte
   322  
   323  	// Verify that sig is a signature on the given data using this key. This
   324  	// method will hash the data appropriately first. sig.Format is allowed to
   325  	// be any signature algorithm compatible with the key type, the caller
   326  	// should check if it has more stringent requirements.
   327  	Verify(data []byte, sig *Signature) error
   328  }
   329  
   330  // CryptoPublicKey, if implemented by a PublicKey,
   331  // returns the underlying crypto.PublicKey form of the key.
   332  type CryptoPublicKey interface {
   333  	CryptoPublicKey() crypto.PublicKey
   334  }
   335  
   336  // A Signer can create signatures that verify against a public key.
   337  //
   338  // Some Signers provided by this package also implement MultiAlgorithmSigner.
   339  type Signer interface {
   340  	// PublicKey returns the associated PublicKey.
   341  	PublicKey() PublicKey
   342  
   343  	// Sign returns a signature for the given data. This method will hash the
   344  	// data appropriately first. The signature algorithm is expected to match
   345  	// the key format returned by the PublicKey.Type method (and not to be any
   346  	// alternative algorithm supported by the key format).
   347  	Sign(rand io.Reader, data []byte) (*Signature, error)
   348  }
   349  
   350  // An AlgorithmSigner is a Signer that also supports specifying an algorithm to
   351  // use for signing.
   352  //
   353  // An AlgorithmSigner can't advertise the algorithms it supports, unless it also
   354  // implements MultiAlgorithmSigner, so it should be prepared to be invoked with
   355  // every algorithm supported by the public key format.
   356  type AlgorithmSigner interface {
   357  	Signer
   358  
   359  	// SignWithAlgorithm is like Signer.Sign, but allows specifying a desired
   360  	// signing algorithm. Callers may pass an empty string for the algorithm in
   361  	// which case the AlgorithmSigner will use a default algorithm. This default
   362  	// doesn't currently control any behavior in this package.
   363  	SignWithAlgorithm(rand io.Reader, data []byte, algorithm string) (*Signature, error)
   364  }
   365  
   366  // MultiAlgorithmSigner is an AlgorithmSigner that also reports the algorithms
   367  // supported by that signer.
   368  type MultiAlgorithmSigner interface {
   369  	AlgorithmSigner
   370  
   371  	// Algorithms returns the available algorithms in preference order. The list
   372  	// must not be empty, and it must not include certificate types.
   373  	Algorithms() []string
   374  }
   375  
   376  // NewSignerWithAlgorithms returns a signer restricted to the specified
   377  // algorithms. The algorithms must be set in preference order. The list must not
   378  // be empty, and it must not include certificate types. An error is returned if
   379  // the specified algorithms are incompatible with the public key type.
   380  func NewSignerWithAlgorithms(signer AlgorithmSigner, algorithms []string) (MultiAlgorithmSigner, error) {
   381  	if len(algorithms) == 0 {
   382  		return nil, errors.New("ssh: please specify at least one valid signing algorithm")
   383  	}
   384  	var signerAlgos []string
   385  	supportedAlgos := algorithmsForKeyFormat(underlyingAlgo(signer.PublicKey().Type()))
   386  	if s, ok := signer.(*multiAlgorithmSigner); ok {
   387  		signerAlgos = s.Algorithms()
   388  	} else {
   389  		signerAlgos = supportedAlgos
   390  	}
   391  
   392  	for _, algo := range algorithms {
   393  		if !contains(supportedAlgos, algo) {
   394  			return nil, fmt.Errorf("ssh: algorithm %q is not supported for key type %q",
   395  				algo, signer.PublicKey().Type())
   396  		}
   397  		if !contains(signerAlgos, algo) {
   398  			return nil, fmt.Errorf("ssh: algorithm %q is restricted for the provided signer", algo)
   399  		}
   400  	}
   401  	return &multiAlgorithmSigner{
   402  		AlgorithmSigner:     signer,
   403  		supportedAlgorithms: algorithms,
   404  	}, nil
   405  }
   406  
   407  type multiAlgorithmSigner struct {
   408  	AlgorithmSigner
   409  	supportedAlgorithms []string
   410  }
   411  
   412  func (s *multiAlgorithmSigner) Algorithms() []string {
   413  	return s.supportedAlgorithms
   414  }
   415  
   416  func (s *multiAlgorithmSigner) isAlgorithmSupported(algorithm string) bool {
   417  	if algorithm == "" {
   418  		algorithm = underlyingAlgo(s.PublicKey().Type())
   419  	}
   420  	for _, algo := range s.supportedAlgorithms {
   421  		if algorithm == algo {
   422  			return true
   423  		}
   424  	}
   425  	return false
   426  }
   427  
   428  func (s *multiAlgorithmSigner) SignWithAlgorithm(rand io.Reader, data []byte, algorithm string) (*Signature, error) {
   429  	if !s.isAlgorithmSupported(algorithm) {
   430  		return nil, fmt.Errorf("ssh: algorithm %q is not supported: %v", algorithm, s.supportedAlgorithms)
   431  	}
   432  	return s.AlgorithmSigner.SignWithAlgorithm(rand, data, algorithm)
   433  }
   434  
   435  type rsaPublicKey rsa.PublicKey
   436  
   437  func (r *rsaPublicKey) Type() string {
   438  	return "ssh-rsa"
   439  }
   440  
   441  // parseRSA parses an RSA key according to RFC 4253, section 6.6.
   442  func parseRSA(in []byte) (out PublicKey, rest []byte, err error) {
   443  	var w struct {
   444  		E    *big.Int
   445  		N    *big.Int
   446  		Rest []byte `ssh:"rest"`
   447  	}
   448  	if err := Unmarshal(in, &w); err != nil {
   449  		return nil, nil, err
   450  	}
   451  
   452  	if w.E.BitLen() > 24 {
   453  		return nil, nil, errors.New("ssh: exponent too large")
   454  	}
   455  	e := w.E.Int64()
   456  	if e < 3 || e&1 == 0 {
   457  		return nil, nil, errors.New("ssh: incorrect exponent")
   458  	}
   459  
   460  	var key rsa.PublicKey
   461  	key.E = int(e)
   462  	key.N = w.N
   463  	return (*rsaPublicKey)(&key), w.Rest, nil
   464  }
   465  
   466  func (r *rsaPublicKey) Marshal() []byte {
   467  	e := new(big.Int).SetInt64(int64(r.E))
   468  	// RSA publickey struct layout should match the struct used by
   469  	// parseRSACert in the x/crypto/ssh/agent package.
   470  	wirekey := struct {
   471  		Name string
   472  		E    *big.Int
   473  		N    *big.Int
   474  	}{
   475  		KeyAlgoRSA,
   476  		e,
   477  		r.N,
   478  	}
   479  	return Marshal(&wirekey)
   480  }
   481  
   482  func (r *rsaPublicKey) Verify(data []byte, sig *Signature) error {
   483  	supportedAlgos := algorithmsForKeyFormat(r.Type())
   484  	if !contains(supportedAlgos, sig.Format) {
   485  		return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, r.Type())
   486  	}
   487  	hash := hashFuncs[sig.Format]
   488  	h := hash.New()
   489  	h.Write(data)
   490  	digest := h.Sum(nil)
   491  	return rsa.VerifyPKCS1v15((*rsa.PublicKey)(r), hash, digest, sig.Blob)
   492  }
   493  
   494  func (r *rsaPublicKey) CryptoPublicKey() crypto.PublicKey {
   495  	return (*rsa.PublicKey)(r)
   496  }
   497  
   498  type dsaPublicKey dsa.PublicKey
   499  
   500  func (k *dsaPublicKey) Type() string {
   501  	return "ssh-dss"
   502  }
   503  
   504  func checkDSAParams(param *dsa.Parameters) error {
   505  	// SSH specifies FIPS 186-2, which only provided a single size
   506  	// (1024 bits) DSA key. FIPS 186-3 allows for larger key
   507  	// sizes, which would confuse SSH.
   508  	if l := param.P.BitLen(); l != 1024 {
   509  		return fmt.Errorf("ssh: unsupported DSA key size %d", l)
   510  	}
   511  
   512  	return nil
   513  }
   514  
   515  // parseDSA parses an DSA key according to RFC 4253, section 6.6.
   516  func parseDSA(in []byte) (out PublicKey, rest []byte, err error) {
   517  	var w struct {
   518  		P, Q, G, Y *big.Int
   519  		Rest       []byte `ssh:"rest"`
   520  	}
   521  	if err := Unmarshal(in, &w); err != nil {
   522  		return nil, nil, err
   523  	}
   524  
   525  	param := dsa.Parameters{
   526  		P: w.P,
   527  		Q: w.Q,
   528  		G: w.G,
   529  	}
   530  	if err := checkDSAParams(&param); err != nil {
   531  		return nil, nil, err
   532  	}
   533  
   534  	key := &dsaPublicKey{
   535  		Parameters: param,
   536  		Y:          w.Y,
   537  	}
   538  	return key, w.Rest, nil
   539  }
   540  
   541  func (k *dsaPublicKey) Marshal() []byte {
   542  	// DSA publickey struct layout should match the struct used by
   543  	// parseDSACert in the x/crypto/ssh/agent package.
   544  	w := struct {
   545  		Name       string
   546  		P, Q, G, Y *big.Int
   547  	}{
   548  		k.Type(),
   549  		k.P,
   550  		k.Q,
   551  		k.G,
   552  		k.Y,
   553  	}
   554  
   555  	return Marshal(&w)
   556  }
   557  
   558  func (k *dsaPublicKey) Verify(data []byte, sig *Signature) error {
   559  	if sig.Format != k.Type() {
   560  		return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, k.Type())
   561  	}
   562  	h := hashFuncs[sig.Format].New()
   563  	h.Write(data)
   564  	digest := h.Sum(nil)
   565  
   566  	// Per RFC 4253, section 6.6,
   567  	// The value for 'dss_signature_blob' is encoded as a string containing
   568  	// r, followed by s (which are 160-bit integers, without lengths or
   569  	// padding, unsigned, and in network byte order).
   570  	// For DSS purposes, sig.Blob should be exactly 40 bytes in length.
   571  	if len(sig.Blob) != 40 {
   572  		return errors.New("ssh: DSA signature parse error")
   573  	}
   574  	r := new(big.Int).SetBytes(sig.Blob[:20])
   575  	s := new(big.Int).SetBytes(sig.Blob[20:])
   576  	if dsa.Verify((*dsa.PublicKey)(k), digest, r, s) {
   577  		return nil
   578  	}
   579  	return errors.New("ssh: signature did not verify")
   580  }
   581  
   582  func (k *dsaPublicKey) CryptoPublicKey() crypto.PublicKey {
   583  	return (*dsa.PublicKey)(k)
   584  }
   585  
   586  type dsaPrivateKey struct {
   587  	*dsa.PrivateKey
   588  }
   589  
   590  func (k *dsaPrivateKey) PublicKey() PublicKey {
   591  	return (*dsaPublicKey)(&k.PrivateKey.PublicKey)
   592  }
   593  
   594  func (k *dsaPrivateKey) Sign(rand io.Reader, data []byte) (*Signature, error) {
   595  	return k.SignWithAlgorithm(rand, data, k.PublicKey().Type())
   596  }
   597  
   598  func (k *dsaPrivateKey) Algorithms() []string {
   599  	return []string{k.PublicKey().Type()}
   600  }
   601  
   602  func (k *dsaPrivateKey) SignWithAlgorithm(rand io.Reader, data []byte, algorithm string) (*Signature, error) {
   603  	if algorithm != "" && algorithm != k.PublicKey().Type() {
   604  		return nil, fmt.Errorf("ssh: unsupported signature algorithm %s", algorithm)
   605  	}
   606  
   607  	h := hashFuncs[k.PublicKey().Type()].New()
   608  	h.Write(data)
   609  	digest := h.Sum(nil)
   610  	r, s, err := dsa.Sign(rand, k.PrivateKey, digest)
   611  	if err != nil {
   612  		return nil, err
   613  	}
   614  
   615  	sig := make([]byte, 40)
   616  	rb := r.Bytes()
   617  	sb := s.Bytes()
   618  
   619  	copy(sig[20-len(rb):20], rb)
   620  	copy(sig[40-len(sb):], sb)
   621  
   622  	return &Signature{
   623  		Format: k.PublicKey().Type(),
   624  		Blob:   sig,
   625  	}, nil
   626  }
   627  
   628  type ecdsaPublicKey ecdsa.PublicKey
   629  
   630  func (k *ecdsaPublicKey) Type() string {
   631  	return "ecdsa-sha2-" + k.nistID()
   632  }
   633  
   634  func (k *ecdsaPublicKey) nistID() string {
   635  	switch k.Params().BitSize {
   636  	case 256:
   637  		return "nistp256"
   638  	case 384:
   639  		return "nistp384"
   640  	case 521:
   641  		return "nistp521"
   642  	}
   643  	panic("ssh: unsupported ecdsa key size")
   644  }
   645  
   646  type ed25519PublicKey ed25519.PublicKey
   647  
   648  func (k ed25519PublicKey) Type() string {
   649  	return KeyAlgoED25519
   650  }
   651  
   652  func parseED25519(in []byte) (out PublicKey, rest []byte, err error) {
   653  	var w struct {
   654  		KeyBytes []byte
   655  		Rest     []byte `ssh:"rest"`
   656  	}
   657  
   658  	if err := Unmarshal(in, &w); err != nil {
   659  		return nil, nil, err
   660  	}
   661  
   662  	if l := len(w.KeyBytes); l != ed25519.PublicKeySize {
   663  		return nil, nil, fmt.Errorf("invalid size %d for Ed25519 public key", l)
   664  	}
   665  
   666  	return ed25519PublicKey(w.KeyBytes), w.Rest, nil
   667  }
   668  
   669  func (k ed25519PublicKey) Marshal() []byte {
   670  	w := struct {
   671  		Name     string
   672  		KeyBytes []byte
   673  	}{
   674  		KeyAlgoED25519,
   675  		[]byte(k),
   676  	}
   677  	return Marshal(&w)
   678  }
   679  
   680  func (k ed25519PublicKey) Verify(b []byte, sig *Signature) error {
   681  	if sig.Format != k.Type() {
   682  		return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, k.Type())
   683  	}
   684  	if l := len(k); l != ed25519.PublicKeySize {
   685  		return fmt.Errorf("ssh: invalid size %d for Ed25519 public key", l)
   686  	}
   687  
   688  	if ok := ed25519.Verify(ed25519.PublicKey(k), b, sig.Blob); !ok {
   689  		return errors.New("ssh: signature did not verify")
   690  	}
   691  
   692  	return nil
   693  }
   694  
   695  func (k ed25519PublicKey) CryptoPublicKey() crypto.PublicKey {
   696  	return ed25519.PublicKey(k)
   697  }
   698  
   699  func supportedEllipticCurve(curve elliptic.Curve) bool {
   700  	return curve == elliptic.P256() || curve == elliptic.P384() || curve == elliptic.P521()
   701  }
   702  
   703  // parseECDSA parses an ECDSA key according to RFC 5656, section 3.1.
   704  func parseECDSA(in []byte) (out PublicKey, rest []byte, err error) {
   705  	var w struct {
   706  		Curve    string
   707  		KeyBytes []byte
   708  		Rest     []byte `ssh:"rest"`
   709  	}
   710  
   711  	if err := Unmarshal(in, &w); err != nil {
   712  		return nil, nil, err
   713  	}
   714  
   715  	key := new(ecdsa.PublicKey)
   716  
   717  	switch w.Curve {
   718  	case "nistp256":
   719  		key.Curve = elliptic.P256()
   720  	case "nistp384":
   721  		key.Curve = elliptic.P384()
   722  	case "nistp521":
   723  		key.Curve = elliptic.P521()
   724  	default:
   725  		return nil, nil, errors.New("ssh: unsupported curve")
   726  	}
   727  
   728  	key.X, key.Y = elliptic.Unmarshal(key.Curve, w.KeyBytes)
   729  	if key.X == nil || key.Y == nil {
   730  		return nil, nil, errors.New("ssh: invalid curve point")
   731  	}
   732  	return (*ecdsaPublicKey)(key), w.Rest, nil
   733  }
   734  
   735  func (k *ecdsaPublicKey) Marshal() []byte {
   736  	// See RFC 5656, section 3.1.
   737  	keyBytes := elliptic.Marshal(k.Curve, k.X, k.Y)
   738  	// ECDSA publickey struct layout should match the struct used by
   739  	// parseECDSACert in the x/crypto/ssh/agent package.
   740  	w := struct {
   741  		Name string
   742  		ID   string
   743  		Key  []byte
   744  	}{
   745  		k.Type(),
   746  		k.nistID(),
   747  		keyBytes,
   748  	}
   749  
   750  	return Marshal(&w)
   751  }
   752  
   753  func (k *ecdsaPublicKey) Verify(data []byte, sig *Signature) error {
   754  	if sig.Format != k.Type() {
   755  		return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, k.Type())
   756  	}
   757  
   758  	h := hashFuncs[sig.Format].New()
   759  	h.Write(data)
   760  	digest := h.Sum(nil)
   761  
   762  	// Per RFC 5656, section 3.1.2,
   763  	// The ecdsa_signature_blob value has the following specific encoding:
   764  	//    mpint    r
   765  	//    mpint    s
   766  	var ecSig struct {
   767  		R *big.Int
   768  		S *big.Int
   769  	}
   770  
   771  	if err := Unmarshal(sig.Blob, &ecSig); err != nil {
   772  		return err
   773  	}
   774  
   775  	if ecdsa.Verify((*ecdsa.PublicKey)(k), digest, ecSig.R, ecSig.S) {
   776  		return nil
   777  	}
   778  	return errors.New("ssh: signature did not verify")
   779  }
   780  
   781  func (k *ecdsaPublicKey) CryptoPublicKey() crypto.PublicKey {
   782  	return (*ecdsa.PublicKey)(k)
   783  }
   784  
   785  // skFields holds the additional fields present in U2F/FIDO2 signatures.
   786  // See openssh/PROTOCOL.u2f 'SSH U2F Signatures' for details.
   787  type skFields struct {
   788  	// Flags contains U2F/FIDO2 flags such as 'user present'
   789  	Flags byte
   790  	// Counter is a monotonic signature counter which can be
   791  	// used to detect concurrent use of a private key, should
   792  	// it be extracted from hardware.
   793  	Counter uint32
   794  }
   795  
   796  type skECDSAPublicKey struct {
   797  	// application is a URL-like string, typically "ssh:" for SSH.
   798  	// see openssh/PROTOCOL.u2f for details.
   799  	application string
   800  	ecdsa.PublicKey
   801  }
   802  
   803  func (k *skECDSAPublicKey) Type() string {
   804  	return KeyAlgoSKECDSA256
   805  }
   806  
   807  func (k *skECDSAPublicKey) nistID() string {
   808  	return "nistp256"
   809  }
   810  
   811  func parseSKECDSA(in []byte) (out PublicKey, rest []byte, err error) {
   812  	var w struct {
   813  		Curve       string
   814  		KeyBytes    []byte
   815  		Application string
   816  		Rest        []byte `ssh:"rest"`
   817  	}
   818  
   819  	if err := Unmarshal(in, &w); err != nil {
   820  		return nil, nil, err
   821  	}
   822  
   823  	key := new(skECDSAPublicKey)
   824  	key.application = w.Application
   825  
   826  	if w.Curve != "nistp256" {
   827  		return nil, nil, errors.New("ssh: unsupported curve")
   828  	}
   829  	key.Curve = elliptic.P256()
   830  
   831  	key.X, key.Y = elliptic.Unmarshal(key.Curve, w.KeyBytes)
   832  	if key.X == nil || key.Y == nil {
   833  		return nil, nil, errors.New("ssh: invalid curve point")
   834  	}
   835  
   836  	return key, w.Rest, nil
   837  }
   838  
   839  func (k *skECDSAPublicKey) Marshal() []byte {
   840  	// See RFC 5656, section 3.1.
   841  	keyBytes := elliptic.Marshal(k.Curve, k.X, k.Y)
   842  	w := struct {
   843  		Name        string
   844  		ID          string
   845  		Key         []byte
   846  		Application string
   847  	}{
   848  		k.Type(),
   849  		k.nistID(),
   850  		keyBytes,
   851  		k.application,
   852  	}
   853  
   854  	return Marshal(&w)
   855  }
   856  
   857  func (k *skECDSAPublicKey) Verify(data []byte, sig *Signature) error {
   858  	if sig.Format != k.Type() {
   859  		return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, k.Type())
   860  	}
   861  
   862  	h := hashFuncs[sig.Format].New()
   863  	h.Write([]byte(k.application))
   864  	appDigest := h.Sum(nil)
   865  
   866  	h.Reset()
   867  	h.Write(data)
   868  	dataDigest := h.Sum(nil)
   869  
   870  	var ecSig struct {
   871  		R *big.Int
   872  		S *big.Int
   873  	}
   874  	if err := Unmarshal(sig.Blob, &ecSig); err != nil {
   875  		return err
   876  	}
   877  
   878  	var skf skFields
   879  	if err := Unmarshal(sig.Rest, &skf); err != nil {
   880  		return err
   881  	}
   882  
   883  	blob := struct {
   884  		ApplicationDigest []byte `ssh:"rest"`
   885  		Flags             byte
   886  		Counter           uint32
   887  		MessageDigest     []byte `ssh:"rest"`
   888  	}{
   889  		appDigest,
   890  		skf.Flags,
   891  		skf.Counter,
   892  		dataDigest,
   893  	}
   894  
   895  	original := Marshal(blob)
   896  
   897  	h.Reset()
   898  	h.Write(original)
   899  	digest := h.Sum(nil)
   900  
   901  	if ecdsa.Verify((*ecdsa.PublicKey)(&k.PublicKey), digest, ecSig.R, ecSig.S) {
   902  		return nil
   903  	}
   904  	return errors.New("ssh: signature did not verify")
   905  }
   906  
   907  type skEd25519PublicKey struct {
   908  	// application is a URL-like string, typically "ssh:" for SSH.
   909  	// see openssh/PROTOCOL.u2f for details.
   910  	application string
   911  	ed25519.PublicKey
   912  }
   913  
   914  func (k *skEd25519PublicKey) Type() string {
   915  	return KeyAlgoSKED25519
   916  }
   917  
   918  func parseSKEd25519(in []byte) (out PublicKey, rest []byte, err error) {
   919  	var w struct {
   920  		KeyBytes    []byte
   921  		Application string
   922  		Rest        []byte `ssh:"rest"`
   923  	}
   924  
   925  	if err := Unmarshal(in, &w); err != nil {
   926  		return nil, nil, err
   927  	}
   928  
   929  	if l := len(w.KeyBytes); l != ed25519.PublicKeySize {
   930  		return nil, nil, fmt.Errorf("invalid size %d for Ed25519 public key", l)
   931  	}
   932  
   933  	key := new(skEd25519PublicKey)
   934  	key.application = w.Application
   935  	key.PublicKey = ed25519.PublicKey(w.KeyBytes)
   936  
   937  	return key, w.Rest, nil
   938  }
   939  
   940  func (k *skEd25519PublicKey) Marshal() []byte {
   941  	w := struct {
   942  		Name        string
   943  		KeyBytes    []byte
   944  		Application string
   945  	}{
   946  		KeyAlgoSKED25519,
   947  		[]byte(k.PublicKey),
   948  		k.application,
   949  	}
   950  	return Marshal(&w)
   951  }
   952  
   953  func (k *skEd25519PublicKey) Verify(data []byte, sig *Signature) error {
   954  	if sig.Format != k.Type() {
   955  		return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, k.Type())
   956  	}
   957  	if l := len(k.PublicKey); l != ed25519.PublicKeySize {
   958  		return fmt.Errorf("invalid size %d for Ed25519 public key", l)
   959  	}
   960  
   961  	h := hashFuncs[sig.Format].New()
   962  	h.Write([]byte(k.application))
   963  	appDigest := h.Sum(nil)
   964  
   965  	h.Reset()
   966  	h.Write(data)
   967  	dataDigest := h.Sum(nil)
   968  
   969  	var edSig struct {
   970  		Signature []byte `ssh:"rest"`
   971  	}
   972  
   973  	if err := Unmarshal(sig.Blob, &edSig); err != nil {
   974  		return err
   975  	}
   976  
   977  	var skf skFields
   978  	if err := Unmarshal(sig.Rest, &skf); err != nil {
   979  		return err
   980  	}
   981  
   982  	blob := struct {
   983  		ApplicationDigest []byte `ssh:"rest"`
   984  		Flags             byte
   985  		Counter           uint32
   986  		MessageDigest     []byte `ssh:"rest"`
   987  	}{
   988  		appDigest,
   989  		skf.Flags,
   990  		skf.Counter,
   991  		dataDigest,
   992  	}
   993  
   994  	original := Marshal(blob)
   995  
   996  	if ok := ed25519.Verify(k.PublicKey, original, edSig.Signature); !ok {
   997  		return errors.New("ssh: signature did not verify")
   998  	}
   999  
  1000  	return nil
  1001  }
  1002  
  1003  // NewSignerFromKey takes an *rsa.PrivateKey, *dsa.PrivateKey,
  1004  // *ecdsa.PrivateKey or any other crypto.Signer and returns a
  1005  // corresponding Signer instance. ECDSA keys must use P-256, P-384 or
  1006  // P-521. DSA keys must use parameter size L1024N160.
  1007  func NewSignerFromKey(key interface{}) (Signer, error) {
  1008  	switch key := key.(type) {
  1009  	case crypto.Signer:
  1010  		return NewSignerFromSigner(key)
  1011  	case *dsa.PrivateKey:
  1012  		return newDSAPrivateKey(key)
  1013  	default:
  1014  		return nil, fmt.Errorf("ssh: unsupported key type %T", key)
  1015  	}
  1016  }
  1017  
  1018  func newDSAPrivateKey(key *dsa.PrivateKey) (Signer, error) {
  1019  	if err := checkDSAParams(&key.PublicKey.Parameters); err != nil {
  1020  		return nil, err
  1021  	}
  1022  
  1023  	return &dsaPrivateKey{key}, nil
  1024  }
  1025  
  1026  type wrappedSigner struct {
  1027  	signer crypto.Signer
  1028  	pubKey PublicKey
  1029  }
  1030  
  1031  // NewSignerFromSigner takes any crypto.Signer implementation and
  1032  // returns a corresponding Signer interface. This can be used, for
  1033  // example, with keys kept in hardware modules.
  1034  func NewSignerFromSigner(signer crypto.Signer) (Signer, error) {
  1035  	pubKey, err := NewPublicKey(signer.Public())
  1036  	if err != nil {
  1037  		return nil, err
  1038  	}
  1039  
  1040  	return &wrappedSigner{signer, pubKey}, nil
  1041  }
  1042  
  1043  func (s *wrappedSigner) PublicKey() PublicKey {
  1044  	return s.pubKey
  1045  }
  1046  
  1047  func (s *wrappedSigner) Sign(rand io.Reader, data []byte) (*Signature, error) {
  1048  	return s.SignWithAlgorithm(rand, data, s.pubKey.Type())
  1049  }
  1050  
  1051  func (s *wrappedSigner) Algorithms() []string {
  1052  	return algorithmsForKeyFormat(s.pubKey.Type())
  1053  }
  1054  
  1055  func (s *wrappedSigner) SignWithAlgorithm(rand io.Reader, data []byte, algorithm string) (*Signature, error) {
  1056  	if algorithm == "" {
  1057  		algorithm = s.pubKey.Type()
  1058  	}
  1059  
  1060  	if !contains(s.Algorithms(), algorithm) {
  1061  		return nil, fmt.Errorf("ssh: unsupported signature algorithm %q for key format %q", algorithm, s.pubKey.Type())
  1062  	}
  1063  
  1064  	hashFunc := hashFuncs[algorithm]
  1065  	var digest []byte
  1066  	if hashFunc != 0 {
  1067  		h := hashFunc.New()
  1068  		h.Write(data)
  1069  		digest = h.Sum(nil)
  1070  	} else {
  1071  		digest = data
  1072  	}
  1073  
  1074  	signature, err := s.signer.Sign(rand, digest, hashFunc)
  1075  	if err != nil {
  1076  		return nil, err
  1077  	}
  1078  
  1079  	// crypto.Signer.Sign is expected to return an ASN.1-encoded signature
  1080  	// for ECDSA and DSA, but that's not the encoding expected by SSH, so
  1081  	// re-encode.
  1082  	switch s.pubKey.(type) {
  1083  	case *ecdsaPublicKey, *dsaPublicKey:
  1084  		type asn1Signature struct {
  1085  			R, S *big.Int
  1086  		}
  1087  		asn1Sig := new(asn1Signature)
  1088  		_, err := asn1.Unmarshal(signature, asn1Sig)
  1089  		if err != nil {
  1090  			return nil, err
  1091  		}
  1092  
  1093  		switch s.pubKey.(type) {
  1094  		case *ecdsaPublicKey:
  1095  			signature = Marshal(asn1Sig)
  1096  
  1097  		case *dsaPublicKey:
  1098  			signature = make([]byte, 40)
  1099  			r := asn1Sig.R.Bytes()
  1100  			s := asn1Sig.S.Bytes()
  1101  			copy(signature[20-len(r):20], r)
  1102  			copy(signature[40-len(s):40], s)
  1103  		}
  1104  	}
  1105  
  1106  	return &Signature{
  1107  		Format: algorithm,
  1108  		Blob:   signature,
  1109  	}, nil
  1110  }
  1111  
  1112  // NewPublicKey takes an *rsa.PublicKey, *dsa.PublicKey, *ecdsa.PublicKey,
  1113  // or ed25519.PublicKey returns a corresponding PublicKey instance.
  1114  // ECDSA keys must use P-256, P-384 or P-521.
  1115  func NewPublicKey(key interface{}) (PublicKey, error) {
  1116  	switch key := key.(type) {
  1117  	case *rsa.PublicKey:
  1118  		return (*rsaPublicKey)(key), nil
  1119  	case *ecdsa.PublicKey:
  1120  		if !supportedEllipticCurve(key.Curve) {
  1121  			return nil, errors.New("ssh: only P-256, P-384 and P-521 EC keys are supported")
  1122  		}
  1123  		return (*ecdsaPublicKey)(key), nil
  1124  	case *dsa.PublicKey:
  1125  		return (*dsaPublicKey)(key), nil
  1126  	case ed25519.PublicKey:
  1127  		if l := len(key); l != ed25519.PublicKeySize {
  1128  			return nil, fmt.Errorf("ssh: invalid size %d for Ed25519 public key", l)
  1129  		}
  1130  		return ed25519PublicKey(key), nil
  1131  	default:
  1132  		return nil, fmt.Errorf("ssh: unsupported key type %T", key)
  1133  	}
  1134  }
  1135  
  1136  // ParsePrivateKey returns a Signer from a PEM encoded private key. It supports
  1137  // the same keys as ParseRawPrivateKey. If the private key is encrypted, it
  1138  // will return a PassphraseMissingError.
  1139  func ParsePrivateKey(pemBytes []byte) (Signer, error) {
  1140  	key, err := ParseRawPrivateKey(pemBytes)
  1141  	if err != nil {
  1142  		return nil, err
  1143  	}
  1144  
  1145  	return NewSignerFromKey(key)
  1146  }
  1147  
  1148  // ParsePrivateKeyWithPassphrase returns a Signer from a PEM encoded private
  1149  // key and passphrase. It supports the same keys as
  1150  // ParseRawPrivateKeyWithPassphrase.
  1151  func ParsePrivateKeyWithPassphrase(pemBytes, passphrase []byte) (Signer, error) {
  1152  	key, err := ParseRawPrivateKeyWithPassphrase(pemBytes, passphrase)
  1153  	if err != nil {
  1154  		return nil, err
  1155  	}
  1156  
  1157  	return NewSignerFromKey(key)
  1158  }
  1159  
  1160  // encryptedBlock tells whether a private key is
  1161  // encrypted by examining its Proc-Type header
  1162  // for a mention of ENCRYPTED
  1163  // according to RFC 1421 Section 4.6.1.1.
  1164  func encryptedBlock(block *pem.Block) bool {
  1165  	return strings.Contains(block.Headers["Proc-Type"], "ENCRYPTED")
  1166  }
  1167  
  1168  // A PassphraseMissingError indicates that parsing this private key requires a
  1169  // passphrase. Use ParsePrivateKeyWithPassphrase.
  1170  type PassphraseMissingError struct {
  1171  	// PublicKey will be set if the private key format includes an unencrypted
  1172  	// public key along with the encrypted private key.
  1173  	PublicKey PublicKey
  1174  }
  1175  
  1176  func (*PassphraseMissingError) Error() string {
  1177  	return "ssh: this private key is passphrase protected"
  1178  }
  1179  
  1180  // ParseRawPrivateKey returns a private key from a PEM encoded private key. It supports
  1181  // RSA, DSA, ECDSA, and Ed25519 private keys in PKCS#1, PKCS#8, OpenSSL, and OpenSSH
  1182  // formats. If the private key is encrypted, it will return a PassphraseMissingError.
  1183  func ParseRawPrivateKey(pemBytes []byte) (interface{}, error) {
  1184  	block, _ := pem.Decode(pemBytes)
  1185  	if block == nil {
  1186  		return nil, errors.New("ssh: no key found")
  1187  	}
  1188  
  1189  	if encryptedBlock(block) {
  1190  		return nil, &PassphraseMissingError{}
  1191  	}
  1192  
  1193  	switch block.Type {
  1194  	case "RSA PRIVATE KEY":
  1195  		return x509.ParsePKCS1PrivateKey(block.Bytes)
  1196  	// RFC5208 - https://tools.ietf.org/html/rfc5208
  1197  	case "PRIVATE KEY":
  1198  		return x509.ParsePKCS8PrivateKey(block.Bytes)
  1199  	case "EC PRIVATE KEY":
  1200  		return x509.ParseECPrivateKey(block.Bytes)
  1201  	case "DSA PRIVATE KEY":
  1202  		return ParseDSAPrivateKey(block.Bytes)
  1203  	case "OPENSSH PRIVATE KEY":
  1204  		return parseOpenSSHPrivateKey(block.Bytes, unencryptedOpenSSHKey)
  1205  	default:
  1206  		return nil, fmt.Errorf("ssh: unsupported key type %q", block.Type)
  1207  	}
  1208  }
  1209  
  1210  // ParseRawPrivateKeyWithPassphrase returns a private key decrypted with
  1211  // passphrase from a PEM encoded private key. If the passphrase is wrong, it
  1212  // will return x509.IncorrectPasswordError.
  1213  func ParseRawPrivateKeyWithPassphrase(pemBytes, passphrase []byte) (interface{}, error) {
  1214  	block, _ := pem.Decode(pemBytes)
  1215  	if block == nil {
  1216  		return nil, errors.New("ssh: no key found")
  1217  	}
  1218  
  1219  	if block.Type == "OPENSSH PRIVATE KEY" {
  1220  		return parseOpenSSHPrivateKey(block.Bytes, passphraseProtectedOpenSSHKey(passphrase))
  1221  	}
  1222  
  1223  	if !encryptedBlock(block) || !x509.IsEncryptedPEMBlock(block) {
  1224  		return nil, errors.New("ssh: not an encrypted key")
  1225  	}
  1226  
  1227  	buf, err := x509.DecryptPEMBlock(block, passphrase)
  1228  	if err != nil {
  1229  		if err == x509.IncorrectPasswordError {
  1230  			return nil, err
  1231  		}
  1232  		return nil, fmt.Errorf("ssh: cannot decode encrypted private keys: %v", err)
  1233  	}
  1234  
  1235  	var result interface{}
  1236  
  1237  	switch block.Type {
  1238  	case "RSA PRIVATE KEY":
  1239  		result, err = x509.ParsePKCS1PrivateKey(buf)
  1240  	case "EC PRIVATE KEY":
  1241  		result, err = x509.ParseECPrivateKey(buf)
  1242  	case "DSA PRIVATE KEY":
  1243  		result, err = ParseDSAPrivateKey(buf)
  1244  	default:
  1245  		err = fmt.Errorf("ssh: unsupported key type %q", block.Type)
  1246  	}
  1247  	// Because of deficiencies in the format, DecryptPEMBlock does not always
  1248  	// detect an incorrect password. In these cases decrypted DER bytes is
  1249  	// random noise. If the parsing of the key returns an asn1.StructuralError
  1250  	// we return x509.IncorrectPasswordError.
  1251  	if _, ok := err.(asn1.StructuralError); ok {
  1252  		return nil, x509.IncorrectPasswordError
  1253  	}
  1254  
  1255  	return result, err
  1256  }
  1257  
  1258  // ParseDSAPrivateKey returns a DSA private key from its ASN.1 DER encoding, as
  1259  // specified by the OpenSSL DSA man page.
  1260  func ParseDSAPrivateKey(der []byte) (*dsa.PrivateKey, error) {
  1261  	var k struct {
  1262  		Version int
  1263  		P       *big.Int
  1264  		Q       *big.Int
  1265  		G       *big.Int
  1266  		Pub     *big.Int
  1267  		Priv    *big.Int
  1268  	}
  1269  	rest, err := asn1.Unmarshal(der, &k)
  1270  	if err != nil {
  1271  		return nil, errors.New("ssh: failed to parse DSA key: " + err.Error())
  1272  	}
  1273  	if len(rest) > 0 {
  1274  		return nil, errors.New("ssh: garbage after DSA key")
  1275  	}
  1276  
  1277  	return &dsa.PrivateKey{
  1278  		PublicKey: dsa.PublicKey{
  1279  			Parameters: dsa.Parameters{
  1280  				P: k.P,
  1281  				Q: k.Q,
  1282  				G: k.G,
  1283  			},
  1284  			Y: k.Pub,
  1285  		},
  1286  		X: k.Priv,
  1287  	}, nil
  1288  }
  1289  
  1290  func unencryptedOpenSSHKey(cipherName, kdfName, kdfOpts string, privKeyBlock []byte) ([]byte, error) {
  1291  	if kdfName != "none" || cipherName != "none" {
  1292  		return nil, &PassphraseMissingError{}
  1293  	}
  1294  	if kdfOpts != "" {
  1295  		return nil, errors.New("ssh: invalid openssh private key")
  1296  	}
  1297  	return privKeyBlock, nil
  1298  }
  1299  
  1300  func passphraseProtectedOpenSSHKey(passphrase []byte) openSSHDecryptFunc {
  1301  	return func(cipherName, kdfName, kdfOpts string, privKeyBlock []byte) ([]byte, error) {
  1302  		if kdfName == "none" || cipherName == "none" {
  1303  			return nil, errors.New("ssh: key is not password protected")
  1304  		}
  1305  		if kdfName != "bcrypt" {
  1306  			return nil, fmt.Errorf("ssh: unknown KDF %q, only supports %q", kdfName, "bcrypt")
  1307  		}
  1308  
  1309  		var opts struct {
  1310  			Salt   string
  1311  			Rounds uint32
  1312  		}
  1313  		if err := Unmarshal([]byte(kdfOpts), &opts); err != nil {
  1314  			return nil, err
  1315  		}
  1316  
  1317  		k, err := bcrypt_pbkdf.Key(passphrase, []byte(opts.Salt), int(opts.Rounds), 32+16)
  1318  		if err != nil {
  1319  			return nil, err
  1320  		}
  1321  		key, iv := k[:32], k[32:]
  1322  
  1323  		c, err := aes.NewCipher(key)
  1324  		if err != nil {
  1325  			return nil, err
  1326  		}
  1327  		switch cipherName {
  1328  		case "aes256-ctr":
  1329  			ctr := cipher.NewCTR(c, iv)
  1330  			ctr.XORKeyStream(privKeyBlock, privKeyBlock)
  1331  		case "aes256-cbc":
  1332  			if len(privKeyBlock)%c.BlockSize() != 0 {
  1333  				return nil, fmt.Errorf("ssh: invalid encrypted private key length, not a multiple of the block size")
  1334  			}
  1335  			cbc := cipher.NewCBCDecrypter(c, iv)
  1336  			cbc.CryptBlocks(privKeyBlock, privKeyBlock)
  1337  		default:
  1338  			return nil, fmt.Errorf("ssh: unknown cipher %q, only supports %q or %q", cipherName, "aes256-ctr", "aes256-cbc")
  1339  		}
  1340  
  1341  		return privKeyBlock, nil
  1342  	}
  1343  }
  1344  
  1345  func unencryptedOpenSSHMarshaler(privKeyBlock []byte) ([]byte, string, string, string, error) {
  1346  	key := generateOpenSSHPadding(privKeyBlock, 8)
  1347  	return key, "none", "none", "", nil
  1348  }
  1349  
  1350  func passphraseProtectedOpenSSHMarshaler(passphrase []byte) openSSHEncryptFunc {
  1351  	return func(privKeyBlock []byte) ([]byte, string, string, string, error) {
  1352  		salt := make([]byte, 16)
  1353  		if _, err := rand.Read(salt); err != nil {
  1354  			return nil, "", "", "", err
  1355  		}
  1356  
  1357  		opts := struct {
  1358  			Salt   []byte
  1359  			Rounds uint32
  1360  		}{salt, 16}
  1361  
  1362  		// Derive key to encrypt the private key block.
  1363  		k, err := bcrypt_pbkdf.Key(passphrase, salt, int(opts.Rounds), 32+aes.BlockSize)
  1364  		if err != nil {
  1365  			return nil, "", "", "", err
  1366  		}
  1367  
  1368  		// Add padding matching the block size of AES.
  1369  		keyBlock := generateOpenSSHPadding(privKeyBlock, aes.BlockSize)
  1370  
  1371  		// Encrypt the private key using the derived secret.
  1372  
  1373  		dst := make([]byte, len(keyBlock))
  1374  		key, iv := k[:32], k[32:]
  1375  		block, err := aes.NewCipher(key)
  1376  		if err != nil {
  1377  			return nil, "", "", "", err
  1378  		}
  1379  
  1380  		stream := cipher.NewCTR(block, iv)
  1381  		stream.XORKeyStream(dst, keyBlock)
  1382  
  1383  		return dst, "aes256-ctr", "bcrypt", string(Marshal(opts)), nil
  1384  	}
  1385  }
  1386  
  1387  const privateKeyAuthMagic = "openssh-key-v1\x00"
  1388  
  1389  type openSSHDecryptFunc func(CipherName, KdfName, KdfOpts string, PrivKeyBlock []byte) ([]byte, error)
  1390  type openSSHEncryptFunc func(PrivKeyBlock []byte) (ProtectedKeyBlock []byte, cipherName, kdfName, kdfOptions string, err error)
  1391  
  1392  type openSSHEncryptedPrivateKey struct {
  1393  	CipherName   string
  1394  	KdfName      string
  1395  	KdfOpts      string
  1396  	NumKeys      uint32
  1397  	PubKey       []byte
  1398  	PrivKeyBlock []byte
  1399  }
  1400  
  1401  type openSSHPrivateKey struct {
  1402  	Check1  uint32
  1403  	Check2  uint32
  1404  	Keytype string
  1405  	Rest    []byte `ssh:"rest"`
  1406  }
  1407  
  1408  type openSSHRSAPrivateKey struct {
  1409  	N       *big.Int
  1410  	E       *big.Int
  1411  	D       *big.Int
  1412  	Iqmp    *big.Int
  1413  	P       *big.Int
  1414  	Q       *big.Int
  1415  	Comment string
  1416  	Pad     []byte `ssh:"rest"`
  1417  }
  1418  
  1419  type openSSHEd25519PrivateKey struct {
  1420  	Pub     []byte
  1421  	Priv    []byte
  1422  	Comment string
  1423  	Pad     []byte `ssh:"rest"`
  1424  }
  1425  
  1426  type openSSHECDSAPrivateKey struct {
  1427  	Curve   string
  1428  	Pub     []byte
  1429  	D       *big.Int
  1430  	Comment string
  1431  	Pad     []byte `ssh:"rest"`
  1432  }
  1433  
  1434  // parseOpenSSHPrivateKey parses an OpenSSH private key, using the decrypt
  1435  // function to unwrap the encrypted portion. unencryptedOpenSSHKey can be used
  1436  // as the decrypt function to parse an unencrypted private key. See
  1437  // https://github.com/openssh/openssh-portable/blob/master/PROTOCOL.key.
  1438  func parseOpenSSHPrivateKey(key []byte, decrypt openSSHDecryptFunc) (crypto.PrivateKey, error) {
  1439  	if len(key) < len(privateKeyAuthMagic) || string(key[:len(privateKeyAuthMagic)]) != privateKeyAuthMagic {
  1440  		return nil, errors.New("ssh: invalid openssh private key format")
  1441  	}
  1442  	remaining := key[len(privateKeyAuthMagic):]
  1443  
  1444  	var w openSSHEncryptedPrivateKey
  1445  	if err := Unmarshal(remaining, &w); err != nil {
  1446  		return nil, err
  1447  	}
  1448  	if w.NumKeys != 1 {
  1449  		// We only support single key files, and so does OpenSSH.
  1450  		// https://github.com/openssh/openssh-portable/blob/4103a3ec7/sshkey.c#L4171
  1451  		return nil, errors.New("ssh: multi-key files are not supported")
  1452  	}
  1453  
  1454  	privKeyBlock, err := decrypt(w.CipherName, w.KdfName, w.KdfOpts, w.PrivKeyBlock)
  1455  	if err != nil {
  1456  		if err, ok := err.(*PassphraseMissingError); ok {
  1457  			pub, errPub := ParsePublicKey(w.PubKey)
  1458  			if errPub != nil {
  1459  				return nil, fmt.Errorf("ssh: failed to parse embedded public key: %v", errPub)
  1460  			}
  1461  			err.PublicKey = pub
  1462  		}
  1463  		return nil, err
  1464  	}
  1465  
  1466  	var pk1 openSSHPrivateKey
  1467  	if err := Unmarshal(privKeyBlock, &pk1); err != nil || pk1.Check1 != pk1.Check2 {
  1468  		if w.CipherName != "none" {
  1469  			return nil, x509.IncorrectPasswordError
  1470  		}
  1471  		return nil, errors.New("ssh: malformed OpenSSH key")
  1472  	}
  1473  
  1474  	switch pk1.Keytype {
  1475  	case KeyAlgoRSA:
  1476  		var key openSSHRSAPrivateKey
  1477  		if err := Unmarshal(pk1.Rest, &key); err != nil {
  1478  			return nil, err
  1479  		}
  1480  
  1481  		if err := checkOpenSSHKeyPadding(key.Pad); err != nil {
  1482  			return nil, err
  1483  		}
  1484  
  1485  		pk := &rsa.PrivateKey{
  1486  			PublicKey: rsa.PublicKey{
  1487  				N: key.N,
  1488  				E: int(key.E.Int64()),
  1489  			},
  1490  			D:      key.D,
  1491  			Primes: []*big.Int{key.P, key.Q},
  1492  		}
  1493  
  1494  		if err := pk.Validate(); err != nil {
  1495  			return nil, err
  1496  		}
  1497  
  1498  		pk.Precompute()
  1499  
  1500  		return pk, nil
  1501  	case KeyAlgoED25519:
  1502  		var key openSSHEd25519PrivateKey
  1503  		if err := Unmarshal(pk1.Rest, &key); err != nil {
  1504  			return nil, err
  1505  		}
  1506  
  1507  		if len(key.Priv) != ed25519.PrivateKeySize {
  1508  			return nil, errors.New("ssh: private key unexpected length")
  1509  		}
  1510  
  1511  		if err := checkOpenSSHKeyPadding(key.Pad); err != nil {
  1512  			return nil, err
  1513  		}
  1514  
  1515  		pk := ed25519.PrivateKey(make([]byte, ed25519.PrivateKeySize))
  1516  		copy(pk, key.Priv)
  1517  		return &pk, nil
  1518  	case KeyAlgoECDSA256, KeyAlgoECDSA384, KeyAlgoECDSA521:
  1519  		var key openSSHECDSAPrivateKey
  1520  		if err := Unmarshal(pk1.Rest, &key); err != nil {
  1521  			return nil, err
  1522  		}
  1523  
  1524  		if err := checkOpenSSHKeyPadding(key.Pad); err != nil {
  1525  			return nil, err
  1526  		}
  1527  
  1528  		var curve elliptic.Curve
  1529  		switch key.Curve {
  1530  		case "nistp256":
  1531  			curve = elliptic.P256()
  1532  		case "nistp384":
  1533  			curve = elliptic.P384()
  1534  		case "nistp521":
  1535  			curve = elliptic.P521()
  1536  		default:
  1537  			return nil, errors.New("ssh: unhandled elliptic curve: " + key.Curve)
  1538  		}
  1539  
  1540  		X, Y := elliptic.Unmarshal(curve, key.Pub)
  1541  		if X == nil || Y == nil {
  1542  			return nil, errors.New("ssh: failed to unmarshal public key")
  1543  		}
  1544  
  1545  		if key.D.Cmp(curve.Params().N) >= 0 {
  1546  			return nil, errors.New("ssh: scalar is out of range")
  1547  		}
  1548  
  1549  		x, y := curve.ScalarBaseMult(key.D.Bytes())
  1550  		if x.Cmp(X) != 0 || y.Cmp(Y) != 0 {
  1551  			return nil, errors.New("ssh: public key does not match private key")
  1552  		}
  1553  
  1554  		return &ecdsa.PrivateKey{
  1555  			PublicKey: ecdsa.PublicKey{
  1556  				Curve: curve,
  1557  				X:     X,
  1558  				Y:     Y,
  1559  			},
  1560  			D: key.D,
  1561  		}, nil
  1562  	default:
  1563  		return nil, errors.New("ssh: unhandled key type")
  1564  	}
  1565  }
  1566  
  1567  func marshalOpenSSHPrivateKey(key crypto.PrivateKey, comment string, encrypt openSSHEncryptFunc) (*pem.Block, error) {
  1568  	var w openSSHEncryptedPrivateKey
  1569  	var pk1 openSSHPrivateKey
  1570  
  1571  	// Random check bytes.
  1572  	var check uint32
  1573  	if err := binary.Read(rand.Reader, binary.BigEndian, &check); err != nil {
  1574  		return nil, err
  1575  	}
  1576  
  1577  	pk1.Check1 = check
  1578  	pk1.Check2 = check
  1579  	w.NumKeys = 1
  1580  
  1581  	// Use a []byte directly on ed25519 keys.
  1582  	if k, ok := key.(*ed25519.PrivateKey); ok {
  1583  		key = *k
  1584  	}
  1585  
  1586  	switch k := key.(type) {
  1587  	case *rsa.PrivateKey:
  1588  		E := new(big.Int).SetInt64(int64(k.PublicKey.E))
  1589  		// Marshal public key:
  1590  		// E and N are in reversed order in the public and private key.
  1591  		pubKey := struct {
  1592  			KeyType string
  1593  			E       *big.Int
  1594  			N       *big.Int
  1595  		}{
  1596  			KeyAlgoRSA,
  1597  			E, k.PublicKey.N,
  1598  		}
  1599  		w.PubKey = Marshal(pubKey)
  1600  
  1601  		// Marshal private key.
  1602  		key := openSSHRSAPrivateKey{
  1603  			N:       k.PublicKey.N,
  1604  			E:       E,
  1605  			D:       k.D,
  1606  			Iqmp:    k.Precomputed.Qinv,
  1607  			P:       k.Primes[0],
  1608  			Q:       k.Primes[1],
  1609  			Comment: comment,
  1610  		}
  1611  		pk1.Keytype = KeyAlgoRSA
  1612  		pk1.Rest = Marshal(key)
  1613  	case ed25519.PrivateKey:
  1614  		pub := make([]byte, ed25519.PublicKeySize)
  1615  		priv := make([]byte, ed25519.PrivateKeySize)
  1616  		copy(pub, k[32:])
  1617  		copy(priv, k)
  1618  
  1619  		// Marshal public key.
  1620  		pubKey := struct {
  1621  			KeyType string
  1622  			Pub     []byte
  1623  		}{
  1624  			KeyAlgoED25519, pub,
  1625  		}
  1626  		w.PubKey = Marshal(pubKey)
  1627  
  1628  		// Marshal private key.
  1629  		key := openSSHEd25519PrivateKey{
  1630  			Pub:     pub,
  1631  			Priv:    priv,
  1632  			Comment: comment,
  1633  		}
  1634  		pk1.Keytype = KeyAlgoED25519
  1635  		pk1.Rest = Marshal(key)
  1636  	case *ecdsa.PrivateKey:
  1637  		var curve, keyType string
  1638  		switch name := k.Curve.Params().Name; name {
  1639  		case "P-256":
  1640  			curve = "nistp256"
  1641  			keyType = KeyAlgoECDSA256
  1642  		case "P-384":
  1643  			curve = "nistp384"
  1644  			keyType = KeyAlgoECDSA384
  1645  		case "P-521":
  1646  			curve = "nistp521"
  1647  			keyType = KeyAlgoECDSA521
  1648  		default:
  1649  			return nil, errors.New("ssh: unhandled elliptic curve " + name)
  1650  		}
  1651  
  1652  		pub := elliptic.Marshal(k.Curve, k.PublicKey.X, k.PublicKey.Y)
  1653  
  1654  		// Marshal public key.
  1655  		pubKey := struct {
  1656  			KeyType string
  1657  			Curve   string
  1658  			Pub     []byte
  1659  		}{
  1660  			keyType, curve, pub,
  1661  		}
  1662  		w.PubKey = Marshal(pubKey)
  1663  
  1664  		// Marshal private key.
  1665  		key := openSSHECDSAPrivateKey{
  1666  			Curve:   curve,
  1667  			Pub:     pub,
  1668  			D:       k.D,
  1669  			Comment: comment,
  1670  		}
  1671  		pk1.Keytype = keyType
  1672  		pk1.Rest = Marshal(key)
  1673  	default:
  1674  		return nil, fmt.Errorf("ssh: unsupported key type %T", k)
  1675  	}
  1676  
  1677  	var err error
  1678  	// Add padding and encrypt the key if necessary.
  1679  	w.PrivKeyBlock, w.CipherName, w.KdfName, w.KdfOpts, err = encrypt(Marshal(pk1))
  1680  	if err != nil {
  1681  		return nil, err
  1682  	}
  1683  
  1684  	b := Marshal(w)
  1685  	block := &pem.Block{
  1686  		Type:  "OPENSSH PRIVATE KEY",
  1687  		Bytes: append([]byte(privateKeyAuthMagic), b...),
  1688  	}
  1689  	return block, nil
  1690  }
  1691  
  1692  func checkOpenSSHKeyPadding(pad []byte) error {
  1693  	for i, b := range pad {
  1694  		if int(b) != i+1 {
  1695  			return errors.New("ssh: padding not as expected")
  1696  		}
  1697  	}
  1698  	return nil
  1699  }
  1700  
  1701  func generateOpenSSHPadding(block []byte, blockSize int) []byte {
  1702  	for i, l := 0, len(block); (l+i)%blockSize != 0; i++ {
  1703  		block = append(block, byte(i+1))
  1704  	}
  1705  	return block
  1706  }
  1707  
  1708  // FingerprintLegacyMD5 returns the user presentation of the key's
  1709  // fingerprint as described by RFC 4716 section 4.
  1710  func FingerprintLegacyMD5(pubKey PublicKey) string {
  1711  	md5sum := md5.Sum(pubKey.Marshal())
  1712  	hexarray := make([]string, len(md5sum))
  1713  	for i, c := range md5sum {
  1714  		hexarray[i] = hex.EncodeToString([]byte{c})
  1715  	}
  1716  	return strings.Join(hexarray, ":")
  1717  }
  1718  
  1719  // FingerprintSHA256 returns the user presentation of the key's
  1720  // fingerprint as unpadded base64 encoded sha256 hash.
  1721  // This format was introduced from OpenSSH 6.8.
  1722  // https://www.openssh.com/txt/release-6.8
  1723  // https://tools.ietf.org/html/rfc4648#section-3.2 (unpadded base64 encoding)
  1724  func FingerprintSHA256(pubKey PublicKey) string {
  1725  	sha256sum := sha256.Sum256(pubKey.Marshal())
  1726  	hash := base64.RawStdEncoding.EncodeToString(sha256sum[:])
  1727  	return "SHA256:" + hash
  1728  }
  1729  

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