9f46cf9e2d
This adds support for RSASSA-PSS signatures in handshake messages as required by TLS 1.3. Even if TLS 1.2 is negotiated, it must support PSS when advertised in the Client Hello (this will be done later as the testdata will change). Updates #9671 Change-Id: I8006b92e017453ae408c153233ce5ccef99b5c3f
103 lines
3.3 KiB
Go
103 lines
3.3 KiB
Go
// Copyright 2017 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package tls
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import (
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"crypto"
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"crypto/ecdsa"
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"crypto/rsa"
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"encoding/asn1"
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"errors"
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"fmt"
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)
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// pickSignatureAlgorithm selects a signature algorithm that is compatible with
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// the given public key and the list of algorithms from the peer and this side.
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//
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// The returned SignatureScheme codepoint is only meaningful for TLS 1.2,
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// previous TLS versions have a fixed hash function.
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func pickSignatureAlgorithm(pubkey crypto.PublicKey, peerSigAlgs, ourSigAlgs []SignatureScheme, tlsVersion uint16) (SignatureScheme, uint8, crypto.Hash, error) {
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if tlsVersion < VersionTLS12 || len(peerSigAlgs) == 0 {
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// If the client didn't specify any signature_algorithms
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// extension then we can assume that it supports SHA1. See
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// http://tools.ietf.org/html/rfc5246#section-7.4.1.4.1
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switch pubkey.(type) {
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case *rsa.PublicKey:
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if tlsVersion < VersionTLS12 {
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return 0, signaturePKCS1v15, crypto.MD5SHA1, nil
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} else {
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return PKCS1WithSHA1, signaturePKCS1v15, crypto.SHA1, nil
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}
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case *ecdsa.PublicKey:
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return ECDSAWithSHA1, signatureECDSA, crypto.SHA1, nil
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default:
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return 0, 0, 0, fmt.Errorf("tls: unsupported public key: %T", pubkey)
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}
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}
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for _, sigAlg := range peerSigAlgs {
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if !isSupportedSignatureAlgorithm(sigAlg, ourSigAlgs) {
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continue
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}
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hashAlg, err := lookupTLSHash(sigAlg)
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if err != nil {
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panic("tls: supported signature algorithm has an unknown hash function")
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}
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sigType := signatureFromSignatureScheme(sigAlg)
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switch pubkey.(type) {
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case *rsa.PublicKey:
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if sigType == signaturePKCS1v15 || sigType == signatureRSAPSS {
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return sigAlg, sigType, hashAlg, nil
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}
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case *ecdsa.PublicKey:
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if sigType == signatureECDSA {
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return sigAlg, sigType, hashAlg, nil
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}
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}
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}
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return 0, 0, 0, errors.New("tls: peer doesn't support any common signature algorithms")
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}
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// verifyHandshakeSignature verifies a signature against pre-hashed handshake
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// contents.
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func verifyHandshakeSignature(sigType uint8, pubkey crypto.PublicKey, hashFunc crypto.Hash, digest, sig []byte) error {
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switch sigType {
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case signatureECDSA:
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pubKey, ok := pubkey.(*ecdsa.PublicKey)
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if !ok {
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return errors.New("tls: ECDSA signing requires a ECDSA public key")
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}
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ecdsaSig := new(ecdsaSignature)
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if _, err := asn1.Unmarshal(sig, ecdsaSig); err != nil {
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return err
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}
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if ecdsaSig.R.Sign() <= 0 || ecdsaSig.S.Sign() <= 0 {
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return errors.New("tls: ECDSA signature contained zero or negative values")
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}
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if !ecdsa.Verify(pubKey, digest, ecdsaSig.R, ecdsaSig.S) {
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return errors.New("tls: ECDSA verification failure")
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}
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case signaturePKCS1v15:
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pubKey, ok := pubkey.(*rsa.PublicKey)
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if !ok {
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return errors.New("tls: RSA signing requires a RSA public key")
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}
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if err := rsa.VerifyPKCS1v15(pubKey, hashFunc, digest, sig); err != nil {
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return err
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}
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case signatureRSAPSS:
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pubKey, ok := pubkey.(*rsa.PublicKey)
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if !ok {
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return errors.New("tls: RSA signing requires a RSA public key")
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}
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signOpts := &rsa.PSSOptions{SaltLength: rsa.PSSSaltLengthEqualsHash}
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if err := rsa.VerifyPSS(pubKey, hashFunc, digest, sig, signOpts); err != nil {
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return err
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}
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default:
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return errors.New("tls: unknown signature algorithm")
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}
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return nil
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}
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