blob: 2c5fc7087a8e893f8f23f48c0dc1e2692563a8ed [file] [log] [blame]
// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <openssl/asn1.h>
#include <openssl/bytestring.h>
#include <openssl/evp.h>
#include <openssl/obj.h>
#include <openssl/x509.h>
#include "base/logging.h"
#include "crypto/scoped_openssl_types.h"
#include "net/cert/sha256_legacy_support_win.h"
namespace net {
namespace sha256_interception {
namespace {
using ScopedX509_ALGOR = crypto::ScopedOpenSSL<X509_ALGOR, X509_ALGOR_free>;
// Parses |subject_signature| and writes the components into |*out_tbs_data|,
// |*out_algor|, and |*out_signature|. The BIT STRING in the signature must be
// a multiple of 8 bits. |*out_signature| will have the padding byte removed.
// It returns true on success and false on failure.
bool ParseSubjectSignature(const base::StringPiece& subject_signature,
CBS* out_tbs_data,
ScopedX509_ALGOR* out_algor,
CBS* out_signature) {
CBS cbs, sequence, tbs_data, algorithm, signature;
CBS_init(&cbs, reinterpret_cast<const uint8_t*>(subject_signature.data()),
subject_signature.size());
if (!CBS_get_asn1(&cbs, &sequence, CBS_ASN1_SEQUENCE) ||
CBS_len(&cbs) != 0 ||
!CBS_get_any_asn1_element(&sequence, &tbs_data, nullptr, nullptr) ||
!CBS_get_asn1_element(&sequence, &algorithm,
CBS_ASN1_SEQUENCE) ||
!CBS_get_asn1(&sequence, &signature, CBS_ASN1_BITSTRING) ||
CBS_len(&sequence) != 0) {
return false;
}
// Decode the algorithm.
const uint8_t* ptr = CBS_data(&algorithm);
ScopedX509_ALGOR algor(d2i_X509_ALGOR(NULL, &ptr, CBS_len(&algorithm)));
if (!algor || ptr != CBS_data(&algorithm) + CBS_len(&algorithm))
return false;
// An ASN.1 BIT STRING is encoded with a leading byte denoting the number of
// padding bits. All supported signature algorithms output octets, so the
// leading byte must be zero.
uint8_t padding;
if (!CBS_get_u8(&signature, &padding) || padding != 0)
return false;
*out_tbs_data = tbs_data;
*out_algor = algor.Pass();
*out_signature = signature;
return true;
}
} // namespace
BOOL CryptVerifyCertificateSignatureExHook(
CryptVerifyCertificateSignatureExFunc original_func,
HCRYPTPROV_LEGACY provider,
DWORD encoding_type,
DWORD subject_type,
void* subject_data,
DWORD issuer_type,
void* issuer_data,
DWORD flags,
void* extra) {
CHECK(original_func);
// Only intercept if the arguments are supported.
if (provider != NULL || (encoding_type != X509_ASN_ENCODING) ||
!IsSupportedSubjectType(subject_type) || subject_data == NULL ||
!IsSupportedIssuerType(issuer_type) || issuer_data == NULL) {
return original_func(provider, encoding_type, subject_type, subject_data,
issuer_type, issuer_data, flags, extra);
}
base::StringPiece subject_signature =
GetSubjectSignature(subject_type, subject_data);
bool should_intercept = false;
// Parse out the data, AlgorithmIdentifier, and signature.
CBS tbs_data, signature;
ScopedX509_ALGOR algor;
if (ParseSubjectSignature(subject_signature, &tbs_data, &algor,
&signature)) {
// If the signature algorithm is RSA with one of the SHA-2 algorithms
// supported by BoringSSL (excluding SHA-224, which is pointless), then
// defer to the BoringSSL implementation. Otherwise, fall back and let the
// OS handle it (e.g. in case there are any algorithm policies in effect).
int nid = OBJ_obj2nid(algor->algorithm);
if (nid == NID_sha256WithRSAEncryption ||
nid == NID_sha384WithRSAEncryption ||
nid == NID_sha512WithRSAEncryption) {
should_intercept = true;
}
}
if (!should_intercept) {
return original_func(provider, encoding_type, subject_type, subject_data,
issuer_type, issuer_data, flags, extra);
}
// Rather than attempting to synthesize an EVP_PKEY by hand, just force the
// OS to do an ASN.1 encoding and then decode it back into BoringSSL. This
// is silly for performance, but safest for consistency.
PCERT_PUBLIC_KEY_INFO issuer_public_key =
GetIssuerPublicKey(issuer_type, issuer_data);
if (!issuer_public_key) {
SetLastError(static_cast<DWORD>(NTE_BAD_ALGID));
return FALSE;
}
uint8_t* issuer_spki_data = NULL;
DWORD issuer_spki_len = 0;
if (!CryptEncodeObjectEx(X509_ASN_ENCODING, X509_PUBLIC_KEY_INFO,
issuer_public_key, CRYPT_ENCODE_ALLOC_FLAG, NULL,
&issuer_spki_data, &issuer_spki_len)) {
return FALSE;
}
const uint8_t* ptr = issuer_spki_data;
crypto::ScopedEVP_PKEY pubkey(d2i_PUBKEY(NULL, &ptr, issuer_spki_len));
if (!pubkey.get() || ptr != issuer_spki_data + issuer_spki_len) {
::LocalFree(issuer_spki_data);
SetLastError(static_cast<DWORD>(NTE_BAD_ALGID));
return FALSE;
}
::LocalFree(issuer_spki_data);
crypto::ScopedEVP_MD_CTX md_ctx(EVP_MD_CTX_create());
if (!EVP_DigestVerifyInitFromAlgorithm(md_ctx.get(), algor.get(),
pubkey.get()) ||
!EVP_DigestVerifyUpdate(md_ctx.get(), CBS_data(&tbs_data),
CBS_len(&tbs_data)) ||
!EVP_DigestVerifyFinal(md_ctx.get(), CBS_data(&signature),
CBS_len(&signature))) {
SetLastError(static_cast<DWORD>(NTE_BAD_SIGNATURE));
return FALSE;
}
return TRUE;
}
} // namespace sha256_interception
} // namespace net