x/crypto/ssh: support encrypted private keys

ssh/certs.go

@@ -17,12 +17,14 @@ import (
 // These constants from [PROTOCOL.certkeys] represent the algorithm names
 // for certificate types supported by this package.
 const (
-	CertAlgoRSAv01      = "[email protected]"
-	CertAlgoDSAv01      = "[email protected]"
-	CertAlgoECDSA256v01 = "[email protected]"
-	CertAlgoECDSA384v01 = "[email protected]"
-	CertAlgoECDSA521v01 = "[email protected]"
-	CertAlgoED25519v01  = "[email protected]"
+	CertAlgoRSAv01        = "[email protected]"
+	CertAlgoDSAv01        = "[email protected]"
+	CertAlgoECDSA256v01   = "[email protected]"
+	CertAlgoECDSA384v01   = "[email protected]"
+	CertAlgoECDSA521v01   = "[email protected]"
+	CertAlgoSKECDSA256v01 = "[email protected]"
+	CertAlgoED25519v01    = "[email protected]"
+	CertAlgoSKED25519v01  = "[email protected]"
 )
 
 // Certificate types distinguish between host and user
@@ -37,6 +39,7 @@ const (
 type Signature struct {
 	Format string
 	Blob   []byte
+	Rest   []byte `ssh:"rest"`
 }
 
 // CertTimeInfinity can be used for OpenSSHCertV01.ValidBefore to indicate that
@@ -411,8 +414,8 @@ func (c *CertChecker) CheckCert(principal string, cert *Certificate) error {
 	return nil
 }
 
-// SignCert sets c.SignatureKey to the authority's public key and stores a
-// Signature, by authority, in the certificate.
+// SignCert signs the certificate with an authority, setting the Nonce,
+// SignatureKey, and Signature fields.
 func (c *Certificate) SignCert(rand io.Reader, authority Signer) error {
 	c.Nonce = make([]byte, 32)
 	if _, err := io.ReadFull(rand, c.Nonce); err != nil {
@@ -429,12 +432,14 @@ func (c *Certificate) SignCert(rand io.Reader, authority Signer) error {
 }
 
 var certAlgoNames = map[string]string{
-	KeyAlgoRSA:      CertAlgoRSAv01,
-	KeyAlgoDSA:      CertAlgoDSAv01,
-	KeyAlgoECDSA256: CertAlgoECDSA256v01,
-	KeyAlgoECDSA384: CertAlgoECDSA384v01,
-	KeyAlgoECDSA521: CertAlgoECDSA521v01,
-	KeyAlgoED25519:  CertAlgoED25519v01,
+	KeyAlgoRSA:        CertAlgoRSAv01,
+	KeyAlgoDSA:        CertAlgoDSAv01,
+	KeyAlgoECDSA256:   CertAlgoECDSA256v01,
+	KeyAlgoECDSA384:   CertAlgoECDSA384v01,
+	KeyAlgoECDSA521:   CertAlgoECDSA521v01,
+	KeyAlgoSKECDSA256: CertAlgoSKECDSA256v01,
+	KeyAlgoED25519:    CertAlgoED25519v01,
+	KeyAlgoSKED25519:  CertAlgoSKED25519v01,
 }
 
 // certToPrivAlgo returns the underlying algorithm for a certificate algorithm.
@@ -518,6 +523,12 @@ func parseSignatureBody(in []byte) (out *Signature, rest []byte, ok bool) {
 		return
 	}
 
+	switch out.Format {
+	case KeyAlgoSKECDSA256, CertAlgoSKECDSA256v01, KeyAlgoSKED25519, CertAlgoSKED25519v01:
+		out.Rest = in
+		return out, nil, ok
+	}
+
 	return out, in, ok
 }
 

ssh/internal/bcrypt_pbkdf/bcrypt_pbkdf.go

@@ -0,0 +1,94 @@
+// 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]
+	}
+}
+