Implement ct_objects_extractor for OpenSSL.

net/cert/ct_objects_extractor_openssl.cc

Index: net/cert/ct_objects_extractor_openssl.cc
diff --git a/net/cert/ct_objects_extractor_openssl.cc b/net/cert/ct_objects_extractor_openssl.cc
index f6bd8b0e867dfd519043ec7c6f9250f719e3695c..ccc94fe42dc8fecfcc034265a8b8f05c9dd9394f 100644
--- a/net/cert/ct_objects_extractor_openssl.cc
+++ b/net/cert/ct_objects_extractor_openssl.cc
@@ -4,36 +4,359 @@
 
 #include "net/cert/ct_objects_extractor.h"
 
+#include <string.h>
+
+#include <openssl/bytestring.h>
+#include <openssl/obj.h>
+#include <openssl/x509.h>
+
 #include "base/logging.h"
+#include "base/sha1.h"
+#include "base/strings/string_util.h"
+#include "crypto/scoped_openssl_types.h"
+#include "crypto/sha2.h"
+#include "net/cert/asn1_util.h"
+#include "net/cert/signed_certificate_timestamp.h"
 
 namespace net {
 
 namespace ct {
 
+namespace {
+
+typedef crypto::ScopedOpenSSL<X509, X509_free>::Type ScopedX509;
+
+void FreeX509_EXTENSIONS(X509_EXTENSIONS* ptr) {
+  sk_X509_EXTENSION_pop_free(ptr, X509_EXTENSION_free);
+}
+
+typedef crypto::ScopedOpenSSL<X509_EXTENSIONS, FreeX509_EXTENSIONS>::Type
+    ScopedX509_EXTENSIONS;
+
+// The wire form of the OID 1.3.6.1.4.1.11129.2.4.2. See Section 3.3 of
+// RFC6962.
+const uint8_t kEmbeddedSCTOid[] = {0x2B, 0x06, 0x01, 0x04, 0x01, 0xD6, 0x79,
+                                   0x02, 0x04, 0x02};
+
+// The wire form of the OID 1.3.6.1.4.1.11129.2.4.5 - OCSP SingleExtension for
+// X.509v3 Certificate Transparency Signed Certificate Timestamp List, see
+// Section 3.3 of RFC6962.
+const uint8_t kOCSPExtensionOid[] = {0x2B, 0x06, 0x01, 0x04, 0x01, 0xD6, 0x79,
+                                     0x02, 0x04, 0x05};
+
+bool StringEqualToCBS(const std::string& value1, const CBS* value2) {
+  if (CBS_len(value2) != value1.size())
+    return false;
+  return memcmp(value1.data(), CBS_data(value2), CBS_len(value2)) == 0;
+}
+
+ScopedX509 OSCertHandleToOpenSSL(X509Certificate::OSCertHandle os_handle) {
+#if defined(USE_OPENSSL_CERTS)
+  return ScopedX509(X509Certificate::DupOSCertHandle(os_handle));
+#else
+  std::string der_encoded;
+  if (!X509Certificate::GetDEREncoded(os_handle, &der_encoded))
+    return ScopedX509();
+  const uint8_t* bytes = reinterpret_cast<const uint8_t*>(der_encoded.data());
+  return ScopedX509(d2i_X509(NULL, &bytes, der_encoded.size()));
+#endif
+}
+
+// Finds the SignedCertificateTimestampList in an extension with OID |oid| in
+// |x509_exts|. If found, returns true and sets |*out_sct_list| to the encoded
+// SCT list. |out_sct_list| may be NULL.
+bool GetSCTListFromX509_EXTENSIONS(const X509_EXTENSIONS* x509_exts,
+                                   const uint8_t* oid,
+                                   size_t oid_len,
+                                   std::string* out_sct_list) {
+  for (size_t i = 0; i < sk_X509_EXTENSION_num(x509_exts); i++) {
+    X509_EXTENSION* x509_ext = sk_X509_EXTENSION_value(x509_exts, i);
+    if (static_cast<size_t>(x509_ext->object->length) == oid_len &&
+        memcmp(x509_ext->object->data, oid, oid_len) == 0) {
+      // The SCT list is an OCTET STRING inside the extension.
+      CBS ext_value, sct_list;
+      CBS_init(&ext_value, x509_ext->value->data, x509_ext->value->length);
+      if (!CBS_get_asn1(&ext_value, &sct_list, CBS_ASN1_OCTETSTRING) ||
+          CBS_len(&ext_value) != 0) {
+        return false;
+      }
+      if (out_sct_list) {
+        *out_sct_list = std::string(
+            reinterpret_cast<const char*>(CBS_data(&sct_list)),
+            CBS_len(&sct_list));
+      }
+      return true;
+    }
+  }
+  return false;
+}
+
+// Finds the SingleResponse in |responses| which matches |issuer| and
+// |cert_serial_number|. On success, returns true and sets
+// |*out_single_response| to the body of the SingleResponse starting at the
+// |certStatus| field.
+bool FindMatchingSingleResponse(CBS* responses,
+                                X509Certificate::OSCertHandle issuer,
+                                const std::string& cert_serial_number,
+                                CBS* out_single_response) {
+  std::string issuer_der;
+  if (!X509Certificate::GetDEREncoded(issuer, &issuer_der))
+    return false;
+
+  base::StringPiece issuer_spki;
+  if (!asn1::ExtractSPKIFromDERCert(issuer_der, &issuer_spki))
+    return false;
+
+  // In OCSP, only the key itself is under hash.
+  base::StringPiece issuer_spk;
+  if (!asn1::ExtractSubjectPublicKeyFromSPKI(issuer_spki, &issuer_spk))
+    return false;
+
+  // ExtractSubjectPublicKey... does not remove the initial octet encoding the
+  // number of unused bits in the ASN.1 BIT STRING so we do it here. For public
+  // keys, the bitstring is in practice always byte-aligned.
+  if (issuer_spk.empty() || issuer_spk[0] != 0)
+    return false;
+  issuer_spk.remove_prefix(1);
+
+  // TODO(ekasper): add SHA-384 to crypto/sha2.h and here if it proves
+  // necessary.
+  // TODO(ekasper): only compute the hashes on demand.
+  std::string issuer_key_sha256_hash = crypto::SHA256HashString(issuer_spk);
+  std::string issuer_key_sha1_hash = base::SHA1HashString(
+      issuer_spk.as_string());
+
+  while (CBS_len(responses) > 0) {
+    CBS single_response, cert_id;
+    if (!CBS_get_asn1(responses, &single_response, CBS_ASN1_SEQUENCE) ||
+        !CBS_get_asn1(&single_response, &cert_id, CBS_ASN1_SEQUENCE)) {
+      return false;
+    }
+
+    CBS hash_algorithm, hash, serial_number, issuer_name_hash, issuer_key_hash;
+    if (!CBS_get_asn1(&cert_id, &hash_algorithm, CBS_ASN1_SEQUENCE) ||
+        !CBS_get_asn1(&hash_algorithm, &hash, CBS_ASN1_OBJECT) ||
+        !CBS_get_asn1(&cert_id, &issuer_name_hash, CBS_ASN1_OCTETSTRING) ||
+        !CBS_get_asn1(&cert_id, &issuer_key_hash, CBS_ASN1_OCTETSTRING) ||
+        !CBS_get_asn1(&cert_id, &serial_number, CBS_ASN1_INTEGER) ||
+        CBS_len(&cert_id) != 0) {
+      return false;
+    }
+
+    // Check the serial number matches.
+    if (!StringEqualToCBS(cert_serial_number, &serial_number))

[agl, 2014/09/03 20:04:18]

In some places we remove leading zeros from serial numbers but I've checked this
case and an exact match is correct.

+      continue;
+
+    // Check if the issuer_key_hash matches.
+    // TODO(ekasper): also use the issuer name hash in matching.
+    switch (OBJ_cbs2nid(&hash)) {
+      case NID_sha1:
+        if (StringEqualToCBS(issuer_key_sha1_hash, &issuer_key_hash)) {
+          *out_single_response = single_response;
+          return true;
+        }
+        break;
+      case NID_sha256:
+        if (StringEqualToCBS(issuer_key_sha256_hash, &issuer_key_hash)) {
+          *out_single_response = single_response;
+          return true;
+        }
+        break;
+    }
+  }
+
+  return false;
+}
+
+}  // namespace
+
 bool ExtractEmbeddedSCTList(X509Certificate::OSCertHandle cert,
                             std::string* sct_list) {
-  NOTIMPLEMENTED();
-  return false;
+  ScopedX509 x509(OSCertHandleToOpenSSL(cert));
+  if (!x509)
+    return false;
+  X509_EXTENSIONS* x509_exts = x509->cert_info->extensions;
+  if (!x509_exts)
+    return false;
+  return GetSCTListFromX509_EXTENSIONS(
+      x509->cert_info->extensions, kEmbeddedSCTOid, sizeof(kEmbeddedSCTOid),
+      sct_list);
 }
 
 bool GetPrecertLogEntry(X509Certificate::OSCertHandle leaf,
                         X509Certificate::OSCertHandle issuer,
                         LogEntry* result) {
-  NOTIMPLEMENTED();
-  return false;
+  result->Reset();
+
+  ScopedX509 leaf_x509(OSCertHandleToOpenSSL(leaf));
+  if (!leaf_x509)
+    return false;
+
+  // XXX(rsleevi): This check may be overkill, since we should be able to
+  // generate precerts for certs without the extension. For now, just a sanity
+  // check to match the reference implementation.
+  if (!leaf_x509->cert_info->extensions ||
+      !GetSCTListFromX509_EXTENSIONS(leaf_x509->cert_info->extensions,
+                                     kEmbeddedSCTOid, sizeof(kEmbeddedSCTOid),
+                                     NULL)) {
+    return false;
+  }
+
+  // The Precertificate log entry is the final certificate's TBSCertificate
+  // without the SCT extension (RFC6962, section 3.2).
+  ScopedX509 leaf_copy(X509_dup(leaf_x509.get()));
+  if (!leaf_copy || !leaf_copy->cert_info->extensions) {
+    NOTREACHED();
+    return false;
+  }
+  X509_EXTENSIONS* leaf_copy_exts = leaf_copy->cert_info->extensions;
+  for (size_t i = 0; i < sk_X509_EXTENSION_num(leaf_copy_exts); i++) {
+    X509_EXTENSION* ext = sk_X509_EXTENSION_value(leaf_copy_exts, i);
+    if (static_cast<size_t>(ext->object->length) == sizeof(kEmbeddedSCTOid) &&
+        memcmp(ext->object->data,
+               kEmbeddedSCTOid, sizeof(kEmbeddedSCTOid)) == 0) {
+      X509_EXTENSION_free(sk_X509_EXTENSION_delete(leaf_copy_exts, i));
+      X509_CINF_set_modified(leaf_copy->cert_info);
+      break;
+    }
+  }
+
+  std::string to_be_signed;
+  int len = i2d_X509_CINF(leaf_copy->cert_info, NULL);
+  if (len < 0)
+    return false;
+  uint8_t* ptr = reinterpret_cast<uint8_t*>(WriteInto(&to_be_signed, len + 1));
+  if (i2d_X509_CINF(leaf_copy->cert_info, &ptr) < 0)
+    return false;
+
+  // Extract the issuer's public key.
+  std::string issuer_der;
+  if (!X509Certificate::GetDEREncoded(issuer, &issuer_der))
+    return ScopedX509();
+  base::StringPiece issuer_key;
+  if (!asn1::ExtractSPKIFromDERCert(issuer_der, &issuer_key))
+    return false;
+
+  // Fill in the LogEntry.
+  result->type = ct::LogEntry::LOG_ENTRY_TYPE_PRECERT;
+  result->tbs_certificate.swap(to_be_signed);
+  crypto::SHA256HashString(issuer_key,
+                           result->issuer_key_hash.data,
+                           sizeof(result->issuer_key_hash.data));
+
+  return true;
 }
 
 bool GetX509LogEntry(X509Certificate::OSCertHandle leaf, LogEntry* result) {
-  NOTIMPLEMENTED();
-  return false;
+  DCHECK(leaf);
+
+  std::string encoded;
+  if (!X509Certificate::GetDEREncoded(leaf, &encoded))
+    return false;
+
+  result->Reset();
+  result->type = ct::LogEntry::LOG_ENTRY_TYPE_X509;
+  result->leaf_certificate.swap(encoded);
+  return true;
 }
 
 bool ExtractSCTListFromOCSPResponse(X509Certificate::OSCertHandle issuer,
                                     const std::string& cert_serial_number,
                                     const std::string& ocsp_response,
                                     std::string* sct_list) {
-  NOTIMPLEMENTED();
-  return false;
+  // The input is an OCSPResponse. See RFC2560, section 4.2.1. The SCT list is
+  // in the extensions field of the SingleResponse which matches the input
+  // certificate.
+  CBS cbs;
+  CBS_init(&cbs,
+           reinterpret_cast<const uint8_t*>(ocsp_response.data()),
+           ocsp_response.size());
+
+  // Parse down to the ResponseBytes. The ResponseBytes is optional, but if it's
+  // missing, this can't include an SCT list.
+  CBS sequence, response_status, tagged_response_bytes, response_bytes;
+  CBS response_type, response;
+  if (!CBS_get_asn1(&cbs, &sequence, CBS_ASN1_SEQUENCE) ||
+      CBS_len(&cbs) != 0 ||
+      !CBS_get_asn1(&sequence, &response_status, CBS_ASN1_ENUMERATED) ||
+      !CBS_get_asn1(&sequence, &tagged_response_bytes,
+                    CBS_ASN1_CONTEXT_SPECIFIC | CBS_ASN1_CONSTRUCTED | 0) ||
+      CBS_len(&sequence) != 0 ||
+      !CBS_get_asn1(&tagged_response_bytes, &response_bytes,
+                    CBS_ASN1_SEQUENCE) ||
+      CBS_len(&tagged_response_bytes) != 0 ||
+      !CBS_get_asn1(&response_bytes, &response_type, CBS_ASN1_OBJECT) ||
+      !CBS_get_asn1(&response_bytes, &response, CBS_ASN1_OCTETSTRING) ||
+      CBS_len(&response_bytes) != 0) {
+    return false;
+  }
+
+  // The only relevant ResponseType is id-pkix-ocsp-basic.
+  if (OBJ_cbs2nid(&response_type) != NID_id_pkix_OCSP_basic)
+    return false;
+
+  // Parse the ResponseData out of the BasicOCSPResponse. Ignore the rest.
+  CBS basic_response, response_data, responses;
+  if (!CBS_get_asn1(&response, &basic_response, CBS_ASN1_SEQUENCE) ||
+      CBS_len(&response) != 0 ||
+      !CBS_get_asn1(&basic_response, &response_data, CBS_ASN1_SEQUENCE)) {
+  }
+
+  // Skip the optional version.
+  const int kVersionTag =
+      CBS_ASN1_CONTEXT_SPECIFIC | CBS_ASN1_CONSTRUCTED | 0;
+  if (CBS_len(&response_data) > 0 &&
+      CBS_data(&response_data)[0] == kVersionTag &&
+      !CBS_get_asn1(&response_data, NULL /* version */, kVersionTag)) {
+    return false;
+  }
+
+  // Extract the list of SingleResponses.
+  if (!CBS_get_any_asn1_element(&response_data,
+                                NULL /* responderID */, NULL, NULL) ||
+      !CBS_get_any_asn1_element(&response_data,
+                                NULL /* producedAt */, NULL, NULL) ||
+      !CBS_get_asn1(&response_data, &responses, CBS_ASN1_SEQUENCE)) {
+    return false;
+  }
+
+  CBS single_response;
+  if (!FindMatchingSingleResponse(&responses, issuer, cert_serial_number,
+                                  &single_response)) {
+    return false;
+  }
+
+  // Skip the certStatus and thisUpdate fields.
+  if (!CBS_get_any_asn1_element(&single_response,
+                                NULL /* certStatus */, NULL, NULL) ||
+      !CBS_get_any_asn1_element(&single_response,
+                                NULL /* thisUpdate */, NULL, NULL)) {
+    return false;
+  }
+
+  const int kNextUpdateTag =
+      CBS_ASN1_CONTEXT_SPECIFIC | CBS_ASN1_CONSTRUCTED | 0;
+  const int kSingleExtensionsTag =
+      CBS_ASN1_CONTEXT_SPECIFIC | CBS_ASN1_CONSTRUCTED | 1;
+
+  // Skip the optional nextUpdate field.
+  if (CBS_len(&single_response) > 0 &&
+      CBS_data(&single_response)[0] == kNextUpdateTag &&
+      !CBS_get_asn1(&single_response, NULL /* nextUpdate */, kNextUpdateTag)) {
+    return false;
+  }
+
+  CBS extensions;
+  if (!CBS_get_asn1(&single_response, &extensions, kSingleExtensionsTag))
+    return false;
+  const uint8_t* ptr = CBS_data(&extensions);
+  ScopedX509_EXTENSIONS x509_exts(
+      d2i_X509_EXTENSIONS(NULL, &ptr, CBS_len(&extensions)));
+  if (!x509_exts || ptr != CBS_data(&extensions) + CBS_len(&extensions))
+    return false;
+
+  return GetSCTListFromX509_EXTENSIONS(
+      x509_exts.get(), kOCSPExtensionOid, sizeof(kOCSPExtensionOid), sct_list);
 }
 
 }  // namespace ct