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keys.go
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keys.go
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// Copyright 2012 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package ssh
import (
"bytes"
"crypto"
"crypto/dsa"
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rsa"
"crypto/x509"
"encoding/asn1"
"encoding/base64"
"encoding/pem"
"errors"
"fmt"
"io"
"math/big"
)
// These constants represent the algorithm names for key types supported by this
// package.
const (
KeyAlgoRSA = "ssh-rsa"
KeyAlgoDSA = "ssh-dss"
KeyAlgoECDSA256 = "ecdsa-sha2-nistp256"
KeyAlgoECDSA384 = "ecdsa-sha2-nistp384"
KeyAlgoECDSA521 = "ecdsa-sha2-nistp521"
)
// parsePubKey parses a public key of the given algorithm.
// Use ParsePublicKey for keys with prepended algorithm.
func parsePubKey(in []byte, algo string) (pubKey PublicKey, rest []byte, err error) {
switch algo {
case KeyAlgoRSA:
return parseRSA(in)
case KeyAlgoDSA:
return parseDSA(in)
case KeyAlgoECDSA256, KeyAlgoECDSA384, KeyAlgoECDSA521:
return parseECDSA(in)
case CertAlgoRSAv01, CertAlgoDSAv01, CertAlgoECDSA256v01, CertAlgoECDSA384v01, CertAlgoECDSA521v01:
cert, err := parseCert(in, certToPrivAlgo(algo))
if err != nil {
return nil, nil, err
}
return cert, nil, nil
}
return nil, nil, fmt.Errorf("ssh: unknown key algorithm: %v", err)
}
// parseAuthorizedKey parses a public key in OpenSSH authorized_keys format
// (see sshd(8) manual page) once the options and key type fields have been
// removed.
func parseAuthorizedKey(in []byte) (out PublicKey, comment string, err error) {
in = bytes.TrimSpace(in)
i := bytes.IndexAny(in, " \t")
if i == -1 {
i = len(in)
}
base64Key := in[:i]
key := make([]byte, base64.StdEncoding.DecodedLen(len(base64Key)))
n, err := base64.StdEncoding.Decode(key, base64Key)
if err != nil {
return nil, "", err
}
key = key[:n]
out, err = ParsePublicKey(key)
if err != nil {
return nil, "", err
}
comment = string(bytes.TrimSpace(in[i:]))
return out, comment, nil
}
// ParseAuthorizedKeys parses a public key from an authorized_keys
// file used in OpenSSH according to the sshd(8) manual page.
func ParseAuthorizedKey(in []byte) (out PublicKey, comment string, options []string, rest []byte, err error) {
for len(in) > 0 {
end := bytes.IndexByte(in, '\n')
if end != -1 {
rest = in[end+1:]
in = in[:end]
} else {
rest = nil
}
end = bytes.IndexByte(in, '\r')
if end != -1 {
in = in[:end]
}
in = bytes.TrimSpace(in)
if len(in) == 0 || in[0] == '#' {
in = rest
continue
}
i := bytes.IndexAny(in, " \t")
if i == -1 {
in = rest
continue
}
if out, comment, err = parseAuthorizedKey(in[i:]); err == nil {
return out, comment, options, rest, nil
}
// No key type recognised. Maybe there's an options field at
// the beginning.
var b byte
inQuote := false
var candidateOptions []string
optionStart := 0
for i, b = range in {
isEnd := !inQuote && (b == ' ' || b == '\t')
if (b == ',' && !inQuote) || isEnd {
if i-optionStart > 0 {
candidateOptions = append(candidateOptions, string(in[optionStart:i]))
}
optionStart = i + 1
}
if isEnd {
break
}
if b == '"' && (i == 0 || (i > 0 && in[i-1] != '\\')) {
inQuote = !inQuote
}
}
for i < len(in) && (in[i] == ' ' || in[i] == '\t') {
i++
}
if i == len(in) {
// Invalid line: unmatched quote
in = rest
continue
}
in = in[i:]
i = bytes.IndexAny(in, " \t")
if i == -1 {
in = rest
continue
}
if out, comment, err = parseAuthorizedKey(in[i:]); err == nil {
options = candidateOptions
return out, comment, options, rest, nil
}
in = rest
continue
}
return nil, "", nil, nil, errors.New("ssh: no key found")
}
// ParsePublicKey parses an SSH public key formatted for use in
// the SSH wire protocol according to RFC 4253, section 6.6.
func ParsePublicKey(in []byte) (out PublicKey, err error) {
algo, in, ok := parseString(in)
if !ok {
return nil, errShortRead
}
var rest []byte
out, rest, err = parsePubKey(in, string(algo))
if len(rest) > 0 {
return nil, errors.New("ssh: trailing junk in public key")
}
return out, err
}
// MarshalAuthorizedKey serializes key for inclusion in an OpenSSH
// authorized_keys file. The return value ends with newline.
func MarshalAuthorizedKey(key PublicKey) []byte {
b := &bytes.Buffer{}
b.WriteString(key.Type())
b.WriteByte(' ')
e := base64.NewEncoder(base64.StdEncoding, b)
e.Write(key.Marshal())
e.Close()
b.WriteByte('\n')
return b.Bytes()
}
// PublicKey is an abstraction of different types of public keys.
type PublicKey interface {
// Type returns the key's type, e.g. "ssh-rsa".
Type() string
// Marshal returns the serialized key data in SSH wire format,
// with the name prefix.
Marshal() []byte
// Verify that sig is a signature on the given data using this
// key. This function will hash the data appropriately first.
Verify(data []byte, sig *Signature) error
}
// A Signer can create signatures that verify against a public key.
type Signer interface {
// PublicKey returns an associated PublicKey instance.
PublicKey() PublicKey
// Sign returns raw signature for the given data. This method
// will apply the hash specified for the keytype to the data.
Sign(rand io.Reader, data []byte) (*Signature, error)
}
type rsaPublicKey rsa.PublicKey
func (r *rsaPublicKey) Type() string {
return "ssh-rsa"
}
// parseRSA parses an RSA key according to RFC 4253, section 6.6.
func parseRSA(in []byte) (out PublicKey, rest []byte, err error) {
var w struct {
E *big.Int
N *big.Int
Rest []byte `ssh:"rest"`
}
if err := Unmarshal(in, &w); err != nil {
return nil, nil, err
}
if w.E.BitLen() > 24 {
return nil, nil, errors.New("ssh: exponent too large")
}
e := w.E.Int64()
if e < 3 || e&1 == 0 {
return nil, nil, errors.New("ssh: incorrect exponent")
}
var key rsa.PublicKey
key.E = int(e)
key.N = w.N
return (*rsaPublicKey)(&key), w.Rest, nil
}
func (r *rsaPublicKey) Marshal() []byte {
e := new(big.Int).SetInt64(int64(r.E))
wirekey := struct {
Name string
E *big.Int
N *big.Int
}{
KeyAlgoRSA,
e,
r.N,
}
return Marshal(&wirekey)
}
func (r *rsaPublicKey) Verify(data []byte, sig *Signature) error {
if sig.Format != r.Type() {
return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, r.Type())
}
h := crypto.SHA1.New()
h.Write(data)
digest := h.Sum(nil)
return rsa.VerifyPKCS1v15((*rsa.PublicKey)(r), crypto.SHA1, digest, sig.Blob)
}
type rsaPrivateKey struct {
*rsa.PrivateKey
}
func (r *rsaPrivateKey) PublicKey() PublicKey {
return (*rsaPublicKey)(&r.PrivateKey.PublicKey)
}
func (r *rsaPrivateKey) Sign(rand io.Reader, data []byte) (*Signature, error) {
h := crypto.SHA1.New()
h.Write(data)
digest := h.Sum(nil)
blob, err := rsa.SignPKCS1v15(rand, r.PrivateKey, crypto.SHA1, digest)
if err != nil {
return nil, err
}
return &Signature{
Format: r.PublicKey().Type(),
Blob: blob,
}, nil
}
type dsaPublicKey dsa.PublicKey
func (r *dsaPublicKey) Type() string {
return "ssh-dss"
}
// parseDSA parses an DSA key according to RFC 4253, section 6.6.
func parseDSA(in []byte) (out PublicKey, rest []byte, err error) {
var w struct {
P, Q, G, Y *big.Int
Rest []byte `ssh:"rest"`
}
if err := Unmarshal(in, &w); err != nil {
return nil, nil, err
}
key := &dsaPublicKey{
Parameters: dsa.Parameters{
P: w.P,
Q: w.Q,
G: w.G,
},
Y: w.Y,
}
return key, w.Rest, nil
}
func (k *dsaPublicKey) Marshal() []byte {
w := struct {
Name string
P, Q, G, Y *big.Int
}{
k.Type(),
k.P,
k.Q,
k.G,
k.Y,
}
return Marshal(&w)
}
func (k *dsaPublicKey) Verify(data []byte, sig *Signature) error {
if sig.Format != k.Type() {
return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, k.Type())
}
h := crypto.SHA1.New()
h.Write(data)
digest := h.Sum(nil)
// Per RFC 4253, section 6.6,
// The value for 'dss_signature_blob' is encoded as a string containing
// r, followed by s (which are 160-bit integers, without lengths or
// padding, unsigned, and in network byte order).
// For DSS purposes, sig.Blob should be exactly 40 bytes in length.
if len(sig.Blob) != 40 {
return errors.New("ssh: DSA signature parse error")
}
r := new(big.Int).SetBytes(sig.Blob[:20])
s := new(big.Int).SetBytes(sig.Blob[20:])
if dsa.Verify((*dsa.PublicKey)(k), digest, r, s) {
return nil
}
return errors.New("ssh: signature did not verify")
}
type dsaPrivateKey struct {
*dsa.PrivateKey
}
func (k *dsaPrivateKey) PublicKey() PublicKey {
return (*dsaPublicKey)(&k.PrivateKey.PublicKey)
}
func (k *dsaPrivateKey) Sign(rand io.Reader, data []byte) (*Signature, error) {
h := crypto.SHA1.New()
h.Write(data)
digest := h.Sum(nil)
r, s, err := dsa.Sign(rand, k.PrivateKey, digest)
if err != nil {
return nil, err
}
sig := make([]byte, 40)
rb := r.Bytes()
sb := s.Bytes()
copy(sig[20-len(rb):20], rb)
copy(sig[40-len(sb):], sb)
return &Signature{
Format: k.PublicKey().Type(),
Blob: sig,
}, nil
}
type ecdsaPublicKey ecdsa.PublicKey
func (key *ecdsaPublicKey) Type() string {
return "ecdsa-sha2-" + key.nistID()
}
func (key *ecdsaPublicKey) nistID() string {
switch key.Params().BitSize {
case 256:
return "nistp256"
case 384:
return "nistp384"
case 521:
return "nistp521"
}
panic("ssh: unsupported ecdsa key size")
}
func supportedEllipticCurve(curve elliptic.Curve) bool {
return curve == elliptic.P256() || curve == elliptic.P384() || curve == elliptic.P521()
}
// ecHash returns the hash to match the given elliptic curve, see RFC
// 5656, section 6.2.1
func ecHash(curve elliptic.Curve) crypto.Hash {
bitSize := curve.Params().BitSize
switch {
case bitSize <= 256:
return crypto.SHA256
case bitSize <= 384:
return crypto.SHA384
}
return crypto.SHA512
}
// parseECDSA parses an ECDSA key according to RFC 5656, section 3.1.
func parseECDSA(in []byte) (out PublicKey, rest []byte, err error) {
identifier, in, ok := parseString(in)
if !ok {
return nil, nil, errShortRead
}
key := new(ecdsa.PublicKey)
switch string(identifier) {
case "nistp256":
key.Curve = elliptic.P256()
case "nistp384":
key.Curve = elliptic.P384()
case "nistp521":
key.Curve = elliptic.P521()
default:
return nil, nil, errors.New("ssh: unsupported curve")
}
var keyBytes []byte
if keyBytes, in, ok = parseString(in); !ok {
return nil, nil, errShortRead
}
key.X, key.Y = elliptic.Unmarshal(key.Curve, keyBytes)
if key.X == nil || key.Y == nil {
return nil, nil, errors.New("ssh: invalid curve point")
}
return (*ecdsaPublicKey)(key), in, nil
}
func (key *ecdsaPublicKey) Marshal() []byte {
// See RFC 5656, section 3.1.
keyBytes := elliptic.Marshal(key.Curve, key.X, key.Y)
w := struct {
Name string
ID string
Key []byte
}{
key.Type(),
key.nistID(),
keyBytes,
}
return Marshal(&w)
}
func (key *ecdsaPublicKey) Verify(data []byte, sig *Signature) error {
if sig.Format != key.Type() {
return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, key.Type())
}
h := ecHash(key.Curve).New()
h.Write(data)
digest := h.Sum(nil)
// Per RFC 5656, section 3.1.2,
// The ecdsa_signature_blob value has the following specific encoding:
// mpint r
// mpint s
var ecSig struct {
R *big.Int
S *big.Int
}
if err := Unmarshal(sig.Blob, &ecSig); err != nil {
return err
}
if ecdsa.Verify((*ecdsa.PublicKey)(key), digest, ecSig.R, ecSig.S) {
return nil
}
return errors.New("ssh: signature did not verify")
}
type ecdsaPrivateKey struct {
*ecdsa.PrivateKey
}
func (k *ecdsaPrivateKey) PublicKey() PublicKey {
return (*ecdsaPublicKey)(&k.PrivateKey.PublicKey)
}
func (k *ecdsaPrivateKey) Sign(rand io.Reader, data []byte) (*Signature, error) {
h := ecHash(k.PrivateKey.PublicKey.Curve).New()
h.Write(data)
digest := h.Sum(nil)
r, s, err := ecdsa.Sign(rand, k.PrivateKey, digest)
if err != nil {
return nil, err
}
sig := make([]byte, intLength(r)+intLength(s))
rest := marshalInt(sig, r)
marshalInt(rest, s)
return &Signature{
Format: k.PublicKey().Type(),
Blob: sig,
}, nil
}
// NewSignerFromKey takes a pointer to rsa, dsa or ecdsa PrivateKey
// returns a corresponding Signer instance. EC keys should use P256,
// P384 or P521.
func NewSignerFromKey(k interface{}) (Signer, error) {
var sshKey Signer
switch t := k.(type) {
case *rsa.PrivateKey:
sshKey = &rsaPrivateKey{t}
case *dsa.PrivateKey:
sshKey = &dsaPrivateKey{t}
case *ecdsa.PrivateKey:
if !supportedEllipticCurve(t.Curve) {
return nil, errors.New("ssh: only P256, P384 and P521 EC keys are supported.")
}
sshKey = &ecdsaPrivateKey{t}
default:
return nil, fmt.Errorf("ssh: unsupported key type %T", k)
}
return sshKey, nil
}
// NewPublicKey takes a pointer to rsa, dsa or ecdsa PublicKey
// and returns a corresponding ssh PublicKey instance. EC keys should use P256, P384 or P521.
func NewPublicKey(k interface{}) (PublicKey, error) {
var sshKey PublicKey
switch t := k.(type) {
case *rsa.PublicKey:
sshKey = (*rsaPublicKey)(t)
case *ecdsa.PublicKey:
if !supportedEllipticCurve(t.Curve) {
return nil, errors.New("ssh: only P256, P384 and P521 EC keys are supported.")
}
sshKey = (*ecdsaPublicKey)(t)
case *dsa.PublicKey:
sshKey = (*dsaPublicKey)(t)
default:
return nil, fmt.Errorf("ssh: unsupported key type %T", k)
}
return sshKey, nil
}
// ParsePrivateKey returns a Signer from a PEM encoded private key. It supports
// the same keys as ParseRawPrivateKey.
func ParsePrivateKey(pemBytes []byte) (Signer, error) {
key, err := ParseRawPrivateKey(pemBytes)
if err != nil {
return nil, err
}
return NewSignerFromKey(key)
}
// ParseRawPrivateKey returns a private key from a PEM encoded private key. It
// supports RSA (PKCS#1), DSA (OpenSSL), and ECDSA private keys.
func ParseRawPrivateKey(pemBytes []byte) (interface{}, error) {
block, _ := pem.Decode(pemBytes)
if block == nil {
return nil, errors.New("ssh: no key found")
}
switch block.Type {
case "RSA PRIVATE KEY":
return x509.ParsePKCS1PrivateKey(block.Bytes)
case "EC PRIVATE KEY":
return x509.ParseECPrivateKey(block.Bytes)
case "DSA PRIVATE KEY":
return ParseDSAPrivateKey(block.Bytes)
default:
return nil, fmt.Errorf("ssh: unsupported key type %q", block.Type)
}
}
// ParseDSAPrivateKey returns a DSA private key from its ASN.1 DER encoding, as
// specified by the OpenSSL DSA man page.
func ParseDSAPrivateKey(der []byte) (*dsa.PrivateKey, error) {
var k struct {
Version int
P *big.Int
Q *big.Int
G *big.Int
Priv *big.Int
Pub *big.Int
}
rest, err := asn1.Unmarshal(der, &k)
if err != nil {
return nil, errors.New("ssh: failed to parse DSA key: " + err.Error())
}
if len(rest) > 0 {
return nil, errors.New("ssh: garbage after DSA key")
}
return &dsa.PrivateKey{
PublicKey: dsa.PublicKey{
Parameters: dsa.Parameters{
P: k.P,
Q: k.Q,
G: k.G,
},
Y: k.Priv,
},
X: k.Pub,
}, nil
}