x/crypto/openpgp: Treat PubKeyAlgoRSA and PubKeyAlgoRSASignOnly as equivalent for signatures

[Merovius]

What version of Go are you using (go version)?

go version go1.11 linux/amd64

Also golang/crypto@0e37d00

Does this issue reproduce with the latest release?

yes.

What operating system and processor architecture are you using (go env)?

GOARCH="amd64"
GOOS="linux"

What did you do?

This program is a slightly modified version of TestRSAPrivateKey using NewSignerPrivateKey:

package main

import (
	"crypto"
	"crypto/rsa"
	"crypto/x509"
	"encoding/hex"
	"hash"
	"time"

	"golang.org/x/crypto/openpgp/packet"
)

func main() {
	privKeyDER, _ := hex.DecodeString(pkcs1PrivKeyHex)
	rsaPriv, err := x509.ParsePKCS1PrivateKey(privKeyDER)
	if err != nil {
		panic(err)
	}

	priv := packet.NewSignerPrivateKey(time.Now(), &rsaSigner{*rsaPriv})

	sig := &packet.Signature{
		PubKeyAlgo: packet.PubKeyAlgoRSA,
		Hash:       crypto.SHA256,
	}
	msg := []byte("Hello World!")

	h, err := populateHash(sig.Hash, msg)
	if err != nil {
		panic(err)
	}
	if err := sig.Sign(h, priv, nil); err != nil {
		panic(err)
	}

	if h, err = populateHash(sig.Hash, msg); err != nil {
		panic(err)
	}
	if err := priv.VerifySignature(h, sig); err != nil {
		panic(err)
	}
}

type rsaSigner struct {
	rsa.PrivateKey
}

func (s *rsaSigner) Public() crypto.PublicKey {
	return s.PublicKey
}

func populateHash(hashFunc crypto.Hash, msg []byte) (hash.Hash, error) {
	h := hashFunc.New()
	if _, err := h.Write(msg); err != nil {
		return nil, err
	}
	return h, nil
}

const pkcs1PrivKeyHex = "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"

What did you expect to see?

No output.

What did you see instead?

panic: openpgp: invalid argument: public key and signature use different algorithms

goroutine 1 [running]:
main.main()
	/home/mero/tmp/rsa.go:41 +0x341
exit status 2

---

NewSignerPrivateKey sets the signature algorithm to RSASignOnly, which is unequal to RSA, causing the signature verification to fail. I have a fix prepared, this is just to track the issue.

[gopherbot]

Change https://golang.org/cl/137896 mentions this issue: openpgp: treat PubKeyAlgoRSA and PubKeyAlgoRSASignOnly as equivalent for signatures