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Add RSA support to ssh key signing #21

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Merged
cjslep merged 1 commit into from
Jul 2, 2020
Merged

Add RSA support to ssh key signing #21

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37 changes: 27 additions & 10 deletions algorithms.go
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@ import (
"crypto/ecdsa"
"crypto/hmac"
"crypto/rsa"
"crypto/sha1"
"crypto/sha256"
"crypto/sha512"
"crypto/subtle" // Use should trigger great care
Expand All @@ -27,6 +28,7 @@ import (
const (
hmacPrefix = "hmac"
rsaPrefix = "rsa"
sshPrefix = "ssh"
ecdsaPrefix = "ecdsa"
ed25519Prefix = "ed25519"
md4String = "md4"
Expand Down Expand Up @@ -66,9 +68,10 @@ var hashToDef = map[crypto.Hash]struct {
// http://www.iana.org/assignments/signature-algorithms
//
// Note that the forbidden hashes have an invalid 'new' function.
crypto.MD4: {md4String, func(key []byte) (hash.Hash, error) { return nil, nil }},
crypto.MD5: {md5String, func(key []byte) (hash.Hash, error) { return nil, nil }},
crypto.SHA1: {sha1String, func(key []byte) (hash.Hash, error) { return nil, nil }},
crypto.MD4: {md4String, func(key []byte) (hash.Hash, error) { return nil, nil }},
crypto.MD5: {md5String, func(key []byte) (hash.Hash, error) { return nil, nil }},
// Temporarily enable SHA1 because of issue https://github.com/golang/go/issues/37278
crypto.SHA1: {sha1String, func(key []byte) (hash.Hash, error) { return sha1.New(), nil }},
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crypto.SHA224: {sha224String, func(key []byte) (hash.Hash, error) { return sha256.New224(), nil }},
crypto.SHA256: {sha256String, func(key []byte) (hash.Hash, error) { return sha256.New(), nil }},
crypto.SHA384: {sha384String, func(key []byte) (hash.Hash, error) { return sha512.New384(), nil }},
Expand Down Expand Up @@ -115,8 +118,6 @@ func isForbiddenHash(h crypto.Hash) bool {
fallthrough
case crypto.MD5:
fallthrough
case crypto.SHA1:
fallthrough
case crypto.MD5SHA1: // shorthand for crypto/tls, not actually implemented
return true
}
Expand Down Expand Up @@ -175,7 +176,8 @@ var _ signer = &rsaAlgorithm{}

type rsaAlgorithm struct {
hash.Hash
kind crypto.Hash
kind crypto.Hash
sshSigner ssh.Signer
}

func (r *rsaAlgorithm) setSig(b []byte) error {
Expand All @@ -191,7 +193,16 @@ func (r *rsaAlgorithm) setSig(b []byte) error {
}

func (r *rsaAlgorithm) Sign(rand io.Reader, p crypto.PrivateKey, sig []byte) ([]byte, error) {
if r.sshSigner != nil {
sshsig, err := r.sshSigner.Sign(rand, sig)
if err != nil {
return nil, err
}

return sshsig.Blob, nil
}
defer r.Reset()

if err := r.setSig(sig); err != nil {
return nil, err
}
Expand Down Expand Up @@ -430,12 +441,18 @@ func newAlgorithm(algo string, key []byte) (hash.Hash, crypto.Hash, error) {
}

func signerFromSSHSigner(sshSigner ssh.Signer, s string) (signer, error) {
if !strings.HasPrefix(s, ed25519Prefix) {
switch {
case strings.HasPrefix(s, rsaPrefix):
return &rsaAlgorithm{
sshSigner: sshSigner,
}, nil
case strings.HasPrefix(s, ed25519Prefix):
return &ed25519Algorithm{
sshSigner: sshSigner,
}, nil
default:
return nil, fmt.Errorf("no signer matching %q", s)
}
return &ed25519Algorithm{
sshSigner: sshSigner,
}, nil
}

// signerFromString is an internally public method constructor
Expand Down
5 changes: 4 additions & 1 deletion httpsig.go
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Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,7 @@ const (
BLAKE2B_384 Algorithm = blake2b_384String
BLAKE2B_512 Algorithm = blake2b_512String
// RSA-based algorithms.
RSA_SHA1 Algorithm = rsaPrefix + "-" + sha1String
RSA_SHA224 Algorithm = rsaPrefix + "-" + sha224String
// RSA_SHA256 is the default algorithm.
RSA_SHA256 Algorithm = rsaPrefix + "-" + sha256String
Expand Down Expand Up @@ -229,8 +230,10 @@ func NewSSHSigner(s ssh.Signer, dAlgo DigestAlgorithm, headers []string, scheme

func getSSHAlgorithm(pkType string) Algorithm {
switch pkType {
case "ssh-ed25519":
case sshPrefix + "-" + ed25519Prefix:
return ED25519
case sshPrefix + "-" + rsaPrefix:
return RSA_SHA1
}

return ""
Expand Down