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1 // Copyright 2014 The Chromium Authors. All rights reserved. | |
2 // Use of this source code is governed by a BSD-style license that can be | |
3 // found in the LICENSE file. | |
4 | |
5 #include <openssl/asn1.h> | |
6 #include <openssl/bytestring.h> | |
7 #include <openssl/evp.h> | |
8 #include <openssl/obj.h> | |
9 #include <openssl/x509.h> | |
10 | |
11 #include "base/logging.h" | |
12 #include "crypto/scoped_openssl_types.h" | |
13 #include "net/cert/sha256_legacy_support_win.h" | |
14 | |
15 namespace net { | |
16 | |
17 namespace sha256_interception { | |
18 | |
19 namespace { | |
20 | |
21 typedef crypto::ScopedOpenSSL<X509_ALGOR, X509_ALGOR_free>::Type | |
22 ScopedX509_ALGOR; | |
23 | |
24 // Parses |subject_signature| and writes the components into |*out_tbs_data|, | |
25 // |*out_algor|, and |*out_signature|. The BIT STRING in the signature must be | |
26 // a multiple of 8 bits. |*out_signature| will have the padding byte removed. | |
27 // It returns true on success and false on failure. | |
28 bool ParseSubjectSignature(const base::StringPiece& subject_signature, | |
29 CBS* out_tbs_data, | |
30 ScopedX509_ALGOR* out_algor, | |
31 CBS* out_signature) { | |
32 CBS cbs, sequence, tbs_data, algorithm, signature; | |
33 CBS_init(&cbs, reinterpret_cast<const uint8_t*>(subject_signature.data()), | |
34 subject_signature.size()); | |
35 if (!CBS_get_asn1(&cbs, &sequence, CBS_ASN1_SEQUENCE) || | |
36 CBS_len(&cbs) != 0 || | |
37 !CBS_get_any_asn1_element(&sequence, &tbs_data, nullptr, nullptr) || | |
38 !CBS_get_asn1_element(&sequence, &algorithm, | |
39 CBS_ASN1_SEQUENCE) || | |
40 !CBS_get_asn1(&sequence, &signature, CBS_ASN1_BITSTRING) || | |
41 CBS_len(&sequence) != 0) { | |
42 return false; | |
43 } | |
44 | |
45 // Decode the algorithm. | |
46 const uint8_t* ptr = CBS_data(&algorithm); | |
47 ScopedX509_ALGOR algor(d2i_X509_ALGOR(NULL, &ptr, CBS_len(&algorithm))); | |
48 if (!algor || ptr != CBS_data(&algorithm) + CBS_len(&algorithm)) | |
49 return false; | |
50 | |
51 // An ASN.1 BIT STRING is encoded with a leading byte denoting the number of | |
52 // padding bits. All supported signature algorithms output octets, so the | |
53 // leading byte must be zero. | |
54 uint8_t padding; | |
55 if (!CBS_get_u8(&signature, &padding) || padding != 0) | |
56 return false; | |
57 | |
58 *out_tbs_data = tbs_data; | |
59 *out_algor = algor.Pass(); | |
60 *out_signature = signature; | |
61 return true; | |
62 } | |
63 | |
64 } // namespace | |
65 | |
66 BOOL CryptVerifyCertificateSignatureExHook( | |
67 CryptVerifyCertificateSignatureExFunc original_func, | |
68 HCRYPTPROV_LEGACY provider, | |
69 DWORD encoding_type, | |
70 DWORD subject_type, | |
71 void* subject_data, | |
72 DWORD issuer_type, | |
73 void* issuer_data, | |
74 DWORD flags, | |
75 void* extra) { | |
76 CHECK(original_func); | |
77 | |
78 // Only intercept if the arguments are supported. | |
79 if (provider != NULL || (encoding_type != X509_ASN_ENCODING) || | |
80 !IsSupportedSubjectType(subject_type) || subject_data == NULL || | |
81 !IsSupportedIssuerType(issuer_type) || issuer_data == NULL) { | |
82 return original_func(provider, encoding_type, subject_type, subject_data, | |
83 issuer_type, issuer_data, flags, extra); | |
84 } | |
85 | |
86 base::StringPiece subject_signature = | |
87 GetSubjectSignature(subject_type, subject_data); | |
88 bool should_intercept = false; | |
89 | |
90 // Parse out the data, AlgorithmIdentifier, and signature. | |
91 CBS tbs_data, signature; | |
92 ScopedX509_ALGOR algor; | |
93 if (ParseSubjectSignature(subject_signature, &tbs_data, &algor, | |
94 &signature)) { | |
95 // If the signature algorithm is RSA with one of the SHA-2 algorithms | |
96 // supported by BoringSSL (excluding SHA-224, which is pointless), then | |
97 // defer to the BoringSSL implementation. Otherwise, fall back and let the | |
98 // OS handle it (e.g. in case there are any algorithm policies in effect). | |
99 int nid = OBJ_obj2nid(algor->algorithm); | |
100 if (nid == NID_sha256WithRSAEncryption || | |
101 nid == NID_sha384WithRSAEncryption || | |
102 nid == NID_sha512WithRSAEncryption) { | |
103 should_intercept = true; | |
104 } | |
105 } | |
106 | |
107 if (!should_intercept) { | |
108 return original_func(provider, encoding_type, subject_type, subject_data, | |
109 issuer_type, issuer_data, flags, extra); | |
110 } | |
111 | |
112 // Rather than attempting to synthesize an EVP_PKEY by hand, just force the | |
113 // OS to do an ASN.1 encoding and then decode it back into BoringSSL. This | |
114 // is silly for performance, but safest for consistency. | |
115 PCERT_PUBLIC_KEY_INFO issuer_public_key = | |
116 GetIssuerPublicKey(issuer_type, issuer_data); | |
117 if (!issuer_public_key) { | |
118 SetLastError(static_cast<DWORD>(NTE_BAD_ALGID)); | |
119 return FALSE; | |
120 } | |
121 | |
122 uint8_t* issuer_spki_data = NULL; | |
123 DWORD issuer_spki_len = 0; | |
124 if (!CryptEncodeObjectEx(X509_ASN_ENCODING, X509_PUBLIC_KEY_INFO, | |
125 issuer_public_key, CRYPT_ENCODE_ALLOC_FLAG, NULL, | |
126 &issuer_spki_data, &issuer_spki_len)) { | |
127 return FALSE; | |
128 } | |
129 | |
130 const uint8_t* ptr = issuer_spki_data; | |
131 crypto::ScopedEVP_PKEY pubkey(d2i_PUBKEY(NULL, &ptr, issuer_spki_len)); | |
132 if (!pubkey.get() || ptr != issuer_spki_data + issuer_spki_len) { | |
133 ::LocalFree(issuer_spki_data); | |
134 SetLastError(static_cast<DWORD>(NTE_BAD_ALGID)); | |
135 return FALSE; | |
136 } | |
137 ::LocalFree(issuer_spki_data); | |
138 | |
139 crypto::ScopedEVP_MD_CTX md_ctx(EVP_MD_CTX_create()); | |
140 if (!EVP_DigestVerifyInitFromAlgorithm(md_ctx.get(), algor.get(), | |
141 pubkey.get()) || | |
142 !EVP_DigestVerifyUpdate(md_ctx.get(), CBS_data(&tbs_data), | |
143 CBS_len(&tbs_data)) || | |
144 !EVP_DigestVerifyFinal(md_ctx.get(), CBS_data(&signature), | |
145 CBS_len(&signature))) { | |
146 SetLastError(static_cast<DWORD>(NTE_BAD_SIGNATURE)); | |
147 return FALSE; | |
148 } | |
149 return TRUE; | |
150 } | |
151 | |
152 } // namespace sha256_interception | |
153 | |
154 } // namespace net | |
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