diff --git a/ssh/internal/bcrypt_pbkdf/bcrypt_pbkdf.go b/ssh/internal/bcrypt_pbkdf/bcrypt_pbkdf.go new file mode 100644 index 0000000..af81d26 --- /dev/null +++ b/ssh/internal/bcrypt_pbkdf/bcrypt_pbkdf.go @@ -0,0 +1,93 @@ +// Copyright 2014 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 bcrypt_pbkdf implements bcrypt_pbkdf(3) from OpenBSD. +// +// See https://flak.tedunangst.com/post/bcrypt-pbkdf and +// https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/lib/libutil/bcrypt_pbkdf.c. +package bcrypt_pbkdf + +import ( + "crypto/sha512" + "errors" + "golang.org/x/crypto/blowfish" +) + +const blockSize = 32 + +// Key derives a key from the password, salt and rounds count, returning a +// []byte of length keyLen that can be used as cryptographic key. +func Key(password, salt []byte, rounds, keyLen int) ([]byte, error) { + if rounds < 1 { + return nil, errors.New("bcrypt_pbkdf: number of rounds is too small") + } + if len(password) == 0 { + return nil, errors.New("bcrypt_pbkdf: empty password") + } + if len(salt) == 0 || len(salt) > 1<<20 { + return nil, errors.New("bcrypt_pbkdf: bad salt length") + } + if keyLen > 1024 { + return nil, errors.New("bcrypt_pbkdf: keyLen is too large") + } + + numBlocks := (keyLen + blockSize - 1) / blockSize + key := make([]byte, numBlocks*blockSize) + + h := sha512.New() + h.Write(password) + shapass := h.Sum(nil) + + shasalt := make([]byte, 0, sha512.Size) + cnt, tmp := make([]byte, 4), make([]byte, blockSize) + for block := 1; block <= numBlocks; block++ { + h.Reset() + h.Write(salt) + cnt[0] = byte(block >> 24) + cnt[1] = byte(block >> 16) + cnt[2] = byte(block >> 8) + cnt[3] = byte(block) + h.Write(cnt) + bcryptHash(tmp, shapass, h.Sum(shasalt)) + + out := make([]byte, blockSize) + copy(out, tmp) + for i := 2; i <= rounds; i++ { + h.Reset() + h.Write(tmp) + bcryptHash(tmp, shapass, h.Sum(shasalt)) + for j := 0; j < len(out); j++ { + out[j] ^= tmp[j] + } + } + + for i, v := range out { + key[i*numBlocks+(block-1)] = v + } + } + return key[:keyLen], nil +} + +var magic = []byte("OxychromaticBlowfishSwatDynamite") + +func bcryptHash(out, shapass, shasalt []byte) { + c, err := blowfish.NewSaltedCipher(shapass, shasalt) + if err != nil { + panic(err) + } + for i := 0; i < 64; i++ { + blowfish.ExpandKey(shasalt, c) + blowfish.ExpandKey(shapass, c) + } + copy(out, magic) + for i := 0; i < 32; i += 8 { + for j := 0; j < 64; j++ { + c.Encrypt(out[i:i+8], out[i:i+8]) + } + } + // Swap bytes due to different endianness. + for i := 0; i < 32; i += 4 { + out[i+3], out[i+2], out[i+1], out[i] = out[i], out[i+1], out[i+2], out[i+3] + } +} diff --git a/ssh/internal/bcrypt_pbkdf/bcrypt_pbkdf_test.go b/ssh/internal/bcrypt_pbkdf/bcrypt_pbkdf_test.go new file mode 100644 index 0000000..20b7889 --- /dev/null +++ b/ssh/internal/bcrypt_pbkdf/bcrypt_pbkdf_test.go @@ -0,0 +1,97 @@ +// Copyright 2014 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 bcrypt_pbkdf + +import ( + "bytes" + "testing" +) + +// Test vectors generated by the reference implementation from OpenBSD. +var golden = []struct { + rounds int + password, salt, result []byte +}{ + { + 12, + []byte("password"), + []byte("salt"), + []byte{ + 0x1a, 0xe4, 0x2c, 0x05, 0xd4, 0x87, 0xbc, 0x02, 0xf6, + 0x49, 0x21, 0xa4, 0xeb, 0xe4, 0xea, 0x93, 0xbc, 0xac, + 0xfe, 0x13, 0x5f, 0xda, 0x99, 0x97, 0x4c, 0x06, 0xb7, + 0xb0, 0x1f, 0xae, 0x14, 0x9a, + }, + }, + { + 3, + []byte("passwordy\x00PASSWORD\x00"), + []byte("salty\x00SALT\x00"), + []byte{ + 0x7f, 0x31, 0x0b, 0xd3, 0xe7, 0x8c, 0x32, 0x80, 0xc5, + 0x9c, 0xe4, 0x59, 0x52, 0x11, 0xa2, 0x92, 0x8e, 0x8d, + 0x4e, 0xc7, 0x44, 0xc1, 0xed, 0x2e, 0xfc, 0x9f, 0x76, + 0x4e, 0x33, 0x88, 0xe0, 0xad, + }, + }, + { + // See http://thread.gmane.org/gmane.os.openbsd.bugs/20542 + 8, + []byte("секретное слово"), + []byte("посолить немножко"), + []byte{ + 0x8d, 0xf4, 0x3f, 0xc6, 0xfe, 0x13, 0x1f, 0xc4, 0x7f, + 0x0c, 0x9e, 0x39, 0x22, 0x4b, 0xd9, 0x4c, 0x70, 0xb6, + 0xfc, 0xc8, 0xee, 0x81, 0x35, 0xfa, 0xdd, 0xf6, 0x11, + 0x56, 0xe6, 0xcb, 0x27, 0x33, 0xea, 0x76, 0x5f, 0x31, + 0x5a, 0x3e, 0x1e, 0x4a, 0xfc, 0x35, 0xbf, 0x86, 0x87, + 0xd1, 0x89, 0x25, 0x4c, 0x1e, 0x05, 0xa6, 0xfe, 0x80, + 0xc0, 0x61, 0x7f, 0x91, 0x83, 0xd6, 0x72, 0x60, 0xd6, + 0xa1, 0x15, 0xc6, 0xc9, 0x4e, 0x36, 0x03, 0xe2, 0x30, + 0x3f, 0xbb, 0x43, 0xa7, 0x6a, 0x64, 0x52, 0x3f, 0xfd, + 0xa6, 0x86, 0xb1, 0xd4, 0x51, 0x85, 0x43, + }, + }, +} + +func TestKey(t *testing.T) { + for i, v := range golden { + k, err := Key(v.password, v.salt, v.rounds, len(v.result)) + if err != nil { + t.Errorf("%d: %s", i, err) + continue + } + if !bytes.Equal(k, v.result) { + t.Errorf("%d: expected\n%x\n, got\n%x\n", i, v.result, k) + } + } +} + +func TestBcryptHash(t *testing.T) { + good := []byte{ + 0x87, 0x90, 0x48, 0x70, 0xee, 0xf9, 0xde, 0xdd, 0xf8, 0xe7, + 0x61, 0x1a, 0x14, 0x01, 0x06, 0xe6, 0xaa, 0xf1, 0xa3, 0x63, + 0xd9, 0xa2, 0xc5, 0x04, 0xdb, 0x35, 0x64, 0x43, 0x72, 0x1e, + 0xb5, 0x55, + } + var pass, salt [64]byte + var result [32]byte + for i := 0; i < 64; i++ { + pass[i] = byte(i) + salt[i] = byte(i + 64) + } + bcryptHash(result[:], pass[:], salt[:]) + if !bytes.Equal(result[:], good) { + t.Errorf("expected %x, got %x", good, result) + } +} + +func BenchmarkKey(b *testing.B) { + pass := []byte("password") + salt := []byte("salt") + for i := 0; i < b.N; i++ { + Key(pass, salt, 10, 32) + } +} diff --git a/ssh/keys.go b/ssh/keys.go index c148ad4..5377ec8 100644 --- a/ssh/keys.go +++ b/ssh/keys.go @@ -7,6 +7,8 @@ package ssh import ( "bytes" "crypto" + "crypto/aes" + "crypto/cipher" "crypto/dsa" "crypto/ecdsa" "crypto/elliptic" @@ -25,6 +27,7 @@ import ( "strings" "golang.org/x/crypto/ed25519" + "golang.org/x/crypto/ssh/internal/bcrypt_pbkdf" ) // These constants represent the algorithm names for key types supported by this @@ -1122,21 +1125,25 @@ func ParseRawPrivateKey(pemBytes []byte) (interface{}, error) { case "DSA PRIVATE KEY": return ParseDSAPrivateKey(block.Bytes) case "OPENSSH PRIVATE KEY": - return parseOpenSSHPrivateKey(block.Bytes) + return parseOpenSSHPrivateKey(block.Bytes, unencryptedOpenSSHKey) default: return nil, fmt.Errorf("ssh: unsupported key type %q", block.Type) } } // ParseRawPrivateKeyWithPassphrase returns a private key decrypted with -// passphrase from a PEM encoded private key. If wrong passphrase, return -// x509.IncorrectPasswordError. +// passphrase from a PEM encoded private key. If the passphrase is wrong, it +// will return x509.IncorrectPasswordError. func ParseRawPrivateKeyWithPassphrase(pemBytes, passphrase []byte) (interface{}, error) { block, _ := pem.Decode(pemBytes) if block == nil { return nil, errors.New("ssh: no key found") } + if block.Type == "OPENSSH PRIVATE KEY" { + return parseOpenSSHPrivateKey(block.Bytes, passphraseProtectedOpenSSHKey(passphrase)) + } + if !encryptedBlock(block) || !x509.IsEncryptedPEMBlock(block) { return nil, errors.New("ssh: not an encrypted key") } @@ -1193,9 +1200,60 @@ func ParseDSAPrivateKey(der []byte) (*dsa.PrivateKey, error) { }, nil } -// Implemented based on the documentation at -// https://github.com/openssh/openssh-portable/blob/master/PROTOCOL.key -func parseOpenSSHPrivateKey(key []byte) (crypto.PrivateKey, error) { +func unencryptedOpenSSHKey(cipherName, kdfName, kdfOpts string, privKeyBlock []byte) ([]byte, error) { + if kdfName != "none" || cipherName != "none" { + return nil, &PassphraseMissingError{} + } + if kdfOpts != "" { + return nil, errors.New("ssh: invalid openssh private key") + } + return privKeyBlock, nil +} + +func passphraseProtectedOpenSSHKey(passphrase []byte) openSSHDecryptFunc { + return func(cipherName, kdfName, kdfOpts string, privKeyBlock []byte) ([]byte, error) { + if kdfName == "none" || cipherName == "none" { + return nil, errors.New("ssh: key is not password protected") + } + if kdfName != "bcrypt" { + return nil, fmt.Errorf("ssh: unknown KDF %q, only supports %q", kdfName, "bcrypt") + } + + var opts struct { + Salt string + Rounds uint32 + } + if err := Unmarshal([]byte(kdfOpts), &opts); err != nil { + return nil, err + } + + k, err := bcrypt_pbkdf.Key(passphrase, []byte(opts.Salt), int(opts.Rounds), 32+16) + if err != nil { + return nil, err + } + key, iv := k[:32], k[32:] + + if cipherName != "aes256-ctr" { + return nil, fmt.Errorf("ssh: unknown cipher %q, only supports %q", cipherName, "aes256-ctr") + } + c, err := aes.NewCipher(key) + if err != nil { + return nil, err + } + ctr := cipher.NewCTR(c, iv) + ctr.XORKeyStream(privKeyBlock, privKeyBlock) + + return privKeyBlock, nil + } +} + +type openSSHDecryptFunc func(CipherName, KdfName, KdfOpts string, PrivKeyBlock []byte) ([]byte, error) + +// parseOpenSSHPrivateKey parses an OpenSSH private key, using the decrypt +// function to unwrap the encrypted portion. unencryptedOpenSSHKey can be used +// as the decrypt function to parse an unencrypted private key. See +// https://github.com/openssh/openssh-portable/blob/master/PROTOCOL.key. +func parseOpenSSHPrivateKey(key []byte, decrypt openSSHDecryptFunc) (crypto.PrivateKey, error) { const magic = "openssh-key-v1\x00" if len(key) < len(magic) || string(key[:len(magic)]) != magic { return nil, errors.New("ssh: invalid openssh private key format") @@ -1214,9 +1272,22 @@ func parseOpenSSHPrivateKey(key []byte) (crypto.PrivateKey, error) { if err := Unmarshal(remaining, &w); err != nil { return nil, err } + if w.NumKeys != 1 { + // We only support single key files, and so does OpenSSH. + // https://github.com/openssh/openssh-portable/blob/4103a3ec7/sshkey.c#L4171 + return nil, errors.New("ssh: multi-key files are not supported") + } - if w.KdfName != "none" || w.CipherName != "none" { - return nil, errors.New("ssh: cannot decode encrypted private keys") + privKeyBlock, err := decrypt(w.CipherName, w.KdfName, w.KdfOpts, w.PrivKeyBlock) + if err != nil { + if err, ok := err.(*PassphraseMissingError); ok { + pub, errPub := ParsePublicKey(w.PubKey) + if errPub != nil { + return nil, fmt.Errorf("ssh: failed to parse embedded public key: %v", errPub) + } + err.PublicKey = pub + } + return nil, err } pk1 := struct { @@ -1226,12 +1297,11 @@ func parseOpenSSHPrivateKey(key []byte) (crypto.PrivateKey, error) { Rest []byte `ssh:"rest"` }{} - if err := Unmarshal(w.PrivKeyBlock, &pk1); err != nil { - return nil, err - } - - if pk1.Check1 != pk1.Check2 { - return nil, errors.New("ssh: checkint mismatch") + if err := Unmarshal(privKeyBlock, &pk1); err != nil || pk1.Check1 != pk1.Check2 { + if w.CipherName != "none" { + return nil, x509.IncorrectPasswordError + } + return nil, errors.New("ssh: malformed OpenSSH key") } // we only handle ed25519 and rsa keys currently @@ -1253,10 +1323,8 @@ func parseOpenSSHPrivateKey(key []byte) (crypto.PrivateKey, error) { return nil, err } - for i, b := range key.Pad { - if int(b) != i+1 { - return nil, errors.New("ssh: padding not as expected") - } + if err := checkOpenSSHKeyPadding(key.Pad); err != nil { + return nil, err } pk := &rsa.PrivateKey{ @@ -1291,10 +1359,8 @@ func parseOpenSSHPrivateKey(key []byte) (crypto.PrivateKey, error) { return nil, errors.New("ssh: private key unexpected length") } - for i, b := range key.Pad { - if int(b) != i+1 { - return nil, errors.New("ssh: padding not as expected") - } + if err := checkOpenSSHKeyPadding(key.Pad); err != nil { + return nil, err } pk := ed25519.PrivateKey(make([]byte, ed25519.PrivateKeySize)) @@ -1305,6 +1371,15 @@ func parseOpenSSHPrivateKey(key []byte) (crypto.PrivateKey, error) { } } +func checkOpenSSHKeyPadding(pad []byte) error { + for i, b := range pad { + if int(b) != i+1 { + return errors.New("ssh: padding not as expected") + } + } + return nil +} + // FingerprintLegacyMD5 returns the user presentation of the key's // fingerprint as described by RFC 4716 section 4. func FingerprintLegacyMD5(pubKey PublicKey) string { diff --git a/ssh/testdata/keys.go b/ssh/testdata/keys.go index 0df38cd..72cfaa0 100644 --- a/ssh/testdata/keys.go +++ b/ssh/testdata/keys.go @@ -223,6 +223,21 @@ R/4X3HWfIdOHsDUvJ8xVWZ4BZk9Zk9qol045DcFCehpr/3hslCrKSZHakLt9GI58 vVQJ4L0aYp5nloLfzhViZtKJXRLkySMKdzYkIlNmW1oVGl7tce5UCNI8Nok4j6yn IiHM7GBn+0nJoKTXsOGMIBe3ulKlKVxLjEuk9yivh/8= -----END DSA PRIVATE KEY----- +`), + }, + + 2: { + Name: "ed25519-encrypted", + EncryptionKey: "password", + IncludesPublicKey: true, + PEMBytes: []byte(`-----BEGIN OPENSSH PRIVATE KEY----- +b3BlbnNzaC1rZXktdjEAAAAACmFlczI1Ni1jdHIAAAAGYmNyeXB0AAAAGAAAABDKj29BlC +ocEWuVhQ94/RjoAAAAEAAAAAEAAAAzAAAAC3NzaC1lZDI1NTE5AAAAIIw1gSurPTDwZidA +2AIjQZgoQi3IFn9jBtFdP10/Jj7DAAAAoFGkQbB2teSU7ikUsnc7ct2aH3pitM359lNVUh +7DQbJWMjbQFbrBYyDJP+ALj1/RZmP2yoIf7/wr99q53/pm28Xp1gGP5V2RGRJYCA6kgFIH +xdB6KEw1Ce7Bz8JaDIeagAGd3xtQTH3cuuleVxCZZnk9NspsPxigADKCls/RUiK7F+z3Qf +Lvs9+PH8nIuhFMYZgo3liqZbVS5z4Fqhyzyq4= +-----END OPENSSH PRIVATE KEY----- `), }, }