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// Copyright (c) 2012 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 "net/cert/x509_certificate.h"
#include <stdlib.h>
#include <algorithm>
#include <map>
#include <string>
#include <vector>
#include "base/base64.h"
#include "base/lazy_instance.h"
#include "base/logging.h"
#include "base/memory/singleton.h"
#include "base/metrics/histogram.h"
#include "base/pickle.h"
#include "base/sha1.h"
#include "base/strings/string_piece.h"
#include "base/strings/string_util.h"
#include "base/synchronization/lock.h"
#include "base/time/time.h"
#include "net/base/net_util.h"
#include "net/base/registry_controlled_domains/registry_controlled_domain.h"
#include "net/cert/pem_tokenizer.h"
#include "url/url_canon.h"
namespace net {
namespace {
// Indicates the order to use when trying to decode binary data, which is
// based on (speculation) as to what will be most common -> least common
const X509Certificate::Format kFormatDecodePriority[] = {
// The PEM block header used for DER certificates
const char kCertificateHeader[] = "CERTIFICATE";
// The PEM block header used for PKCS#7 data
const char kPKCS7Header[] = "PKCS7";
#if !defined(USE_NSS)
// A thread-safe cache for OS certificate handles.
// Within each of the supported underlying crypto libraries, a certificate
// handle is represented as a ref-counted object that contains the parsed
// data for the certificate. In addition, the underlying OS handle may also
// contain a copy of the original ASN.1 DER used to constructed the handle.
// In order to reduce the memory usage when multiple SSL connections exist,
// with each connection storing the server's identity certificate plus any
// intermediates supplied, the certificate handles are cached. Any two
// X509Certificates that were created from the same ASN.1 DER data,
// regardless of where that data came from, will share the same underlying
// OS certificate handle.
class X509CertificateCache {
// Performs a compare-and-swap like operation. If an OS certificate handle
// for the same certificate data as |*cert_handle| already exists in the
// cache, the original |*cert_handle| will be freed and |cert_handle|
// will be updated to point to a duplicated reference to the existing cached
// certificate, with the caller taking ownership of this duplicated handle.
// If an equivalent OS certificate handle is not found, a duplicated
// reference to |*cert_handle| will be added to the cache. In either case,
// upon return, the caller fully owns |*cert_handle| and is responsible for
// calling FreeOSCertHandle(), after first calling Remove().
void InsertOrUpdate(X509Certificate::OSCertHandle* cert_handle);
// Decrements the cache reference count for |cert_handle|, a handle that was
// previously obtained by calling InsertOrUpdate(). If this is the last
// cached reference held, this will remove the handle from the cache. The
// caller retains ownership of |cert_handle| and remains responsible for
// calling FreeOSCertHandle() to release the underlying OS certificate
void Remove(X509Certificate::OSCertHandle cert_handle);
// A single entry in the cache. Certificates will be keyed by their SHA1
// fingerprints, but will not be considered equivalent unless the entire
// certificate data matches.
struct Entry {
Entry() : cert_handle(NULL), ref_count(0) {}
X509Certificate::OSCertHandle cert_handle;
// Increased by each call to InsertOrUpdate(), and balanced by each call
// to Remove(). When it equals 0, all references created by
// InsertOrUpdate() have been released, so the cache entry will be removed
// the cached OS certificate handle will be freed.
int ref_count;
typedef std::map<SHA1HashValue, Entry, SHA1HashValueLessThan> CertMap;
// Obtain an instance of X509CertificateCache via a LazyInstance.
X509CertificateCache() {}
~X509CertificateCache() {}
friend struct base::DefaultLazyInstanceTraits<X509CertificateCache>;
// You must acquire this lock before using any private data of this object
// You must not block while holding this lock.
base::Lock lock_;
// The certificate cache. You must acquire |lock_| before using |cache_|.
CertMap cache_;
g_x509_certificate_cache = LAZY_INSTANCE_INITIALIZER;
void X509CertificateCache::InsertOrUpdate(
X509Certificate::OSCertHandle* cert_handle) {
SHA1HashValue fingerprint =
X509Certificate::OSCertHandle old_handle = NULL;
base::AutoLock lock(lock_);
CertMap::iterator pos = cache_.find(fingerprint);
if (pos == cache_.end()) {
// A cached entry was not found, so initialize a new entry. The entry
// assumes ownership of the current |*cert_handle|.
Entry cache_entry;
cache_entry.cert_handle = *cert_handle;
cache_entry.ref_count = 0;
CertMap::value_type cache_value(fingerprint, cache_entry);
pos = cache_.insert(cache_value).first;
} else {
bool is_same_cert =
X509Certificate::IsSameOSCert(*cert_handle, pos->second.cert_handle);
if (!is_same_cert) {
// Two certificates don't match, due to a SHA1 hash collision. Given
// the low probability, the simplest solution is to not cache the
// certificate, which should not affect performance too negatively.
// A cached entry was found and will be used instead of the caller's
// handle. Ensure the caller's original handle will be freed, since
// ownership is assumed.
old_handle = *cert_handle;
// Whether an existing cached handle or a new handle, increment the
// cache's reference count and return a handle that the caller can own.
*cert_handle = X509Certificate::DupOSCertHandle(pos->second.cert_handle);
// If the caller's handle was replaced with a cached handle, free the
// original handle now. This is done outside of the lock because
// |old_handle| may be the only handle for this particular certificate, so
// freeing it may be complex or resource-intensive and does not need to
// be guarded by the lock.
if (old_handle) {
DHISTOGRAM_COUNTS("X509CertificateReuseCount", 1);
void X509CertificateCache::Remove(X509Certificate::OSCertHandle cert_handle) {
SHA1HashValue fingerprint =
base::AutoLock lock(lock_);
CertMap::iterator pos = cache_.find(fingerprint);
if (pos == cache_.end())
return; // A hash collision where the winning cert was already freed.
bool is_same_cert = X509Certificate::IsSameOSCert(cert_handle,
if (!is_same_cert)
return; // A hash collision where the winning cert is still around.
if (--pos->second.ref_count == 0) {
// The last reference to |cert_handle| has been removed, so release the
// Entry's OS handle and remove the Entry. The caller still holds a
// reference to |cert_handle| and is responsible for freeing it.
#endif // !defined(USE_NSS)
// See X509CertificateCache::InsertOrUpdate. NSS has a built-in cache, so there
// is no point in wrapping another cache around it.
void InsertOrUpdateCache(X509Certificate::OSCertHandle* cert_handle) {
#if !defined(USE_NSS)
// See X509CertificateCache::Remove.
void RemoveFromCache(X509Certificate::OSCertHandle cert_handle) {
#if !defined(USE_NSS)
// Utility to split |src| on the first occurrence of |c|, if any. |right| will
// either be empty if |c| was not found, or will contain the remainder of the
// string including the split character itself.
void SplitOnChar(const base::StringPiece& src,
char c,
base::StringPiece* left,
base::StringPiece* right) {
size_t pos = src.find(c);
if (pos == base::StringPiece::npos) {
*left = src;
} else {
*left = src.substr(0, pos);
*right = src.substr(pos);
} // namespace
bool X509Certificate::LessThan::operator()(
const scoped_refptr<X509Certificate>& lhs,
const scoped_refptr<X509Certificate>& rhs) const {
if (lhs.get() == rhs.get())
return false;
int rv = memcmp(lhs->, rhs->,
if (rv != 0)
return rv < 0;
rv = memcmp(lhs->, rhs->,
return rv < 0;
X509Certificate::X509Certificate(const std::string& subject,
const std::string& issuer,
base::Time start_date,
base::Time expiration_date)
: subject_(subject),
cert_handle_(NULL) {
memset(, 0, sizeof(;
memset(, 0, sizeof(;
// static
X509Certificate* X509Certificate::CreateFromHandle(
OSCertHandle cert_handle,
const OSCertHandles& intermediates) {
return new X509Certificate(cert_handle, intermediates);
// static
X509Certificate* X509Certificate::CreateFromDERCertChain(
const std::vector<base::StringPiece>& der_certs) {
if (der_certs.empty())
return NULL;
X509Certificate::OSCertHandles intermediate_ca_certs;
for (size_t i = 1; i < der_certs.size(); i++) {
OSCertHandle handle = CreateOSCertHandleFromBytes(
const_cast<char*>(der_certs[i].data()), der_certs[i].size());
if (!handle)
OSCertHandle handle = NULL;
// Return NULL if we failed to parse any of the certs.
if (der_certs.size() - 1 == intermediate_ca_certs.size()) {
handle = CreateOSCertHandleFromBytes(
const_cast<char*>(der_certs[0].data()), der_certs[0].size());
X509Certificate* cert = NULL;
if (handle) {
cert = CreateFromHandle(handle, intermediate_ca_certs);
for (size_t i = 0; i < intermediate_ca_certs.size(); i++)
return cert;
// static
X509Certificate* X509Certificate::CreateFromBytes(const char* data,
int length) {
OSCertHandle cert_handle = CreateOSCertHandleFromBytes(data, length);
if (!cert_handle)
return NULL;
X509Certificate* cert = CreateFromHandle(cert_handle, OSCertHandles());
return cert;
// static
X509Certificate* X509Certificate::CreateFromPickle(const Pickle& pickle,
PickleIterator* pickle_iter,
PickleType type) {
int chain_length = 0;
if (!pickle_iter->ReadLength(&chain_length))
return NULL;
std::vector<base::StringPiece> cert_chain;
const char* data = NULL;
int data_length = 0;
for (int i = 0; i < chain_length; ++i) {
if (!pickle_iter->ReadData(&data, &data_length))
return NULL;
cert_chain.push_back(base::StringPiece(data, data_length));
return CreateFromDERCertChain(cert_chain);
// Legacy / Migration code. This should eventually be removed once
// sufficient time has passed that all pickles serialized prior to
OSCertHandle cert_handle = ReadOSCertHandleFromPickle(pickle_iter);
if (!cert_handle)
return NULL;
OSCertHandles intermediates;
uint32 num_intermediates = 0;
if (!pickle_iter->ReadUInt32(&num_intermediates)) {
return NULL;
#if defined(OS_POSIX) && !defined(OS_MACOSX) && defined(__x86_64__)
// On 64-bit Linux (and any other 64-bit platforms), the intermediate count
// might really be a 64-bit field since we used to use Pickle::WriteSize(),
// which writes either 32 or 64 bits depending on the architecture. Since
// x86-64 is little-endian, if that happens, the next 32 bits will be all
// zeroes (the high bits) and the 32 bits we already read above are the
// correct value (we assume there are never more than 2^32 - 1 intermediate
// certificates in a chain; in practice, more than a dozen or so is
// basically unheard of). Since it's invalid for a certificate to start with
// 32 bits of zeroes, we check for that here and skip it if we find it. We
// save a copy of the pickle iterator to restore in case we don't get 32
// bits of zeroes. Now we always write 32 bits, so after a while, these old
// cached pickles will all get replaced.
// TODO(mdm): remove this compatibility code in April 2013 or so.
PickleIterator saved_iter = *pickle_iter;
uint32 zero_check = 0;
if (!pickle_iter->ReadUInt32(&zero_check)) {
// This may not be an error. If there are no intermediates, and we're
// reading an old 32-bit pickle, and there's nothing else after this in
// the pickle, we should report success. Note that it is technically
// possible for us to skip over zeroes that should have occurred after
// an empty certificate list; to avoid this going forward, only do this
// backward-compatibility stuff for PICKLETYPE_CERTIFICATE_CHAIN_V1
// which comes from the pickle version number in
if (num_intermediates) {
return NULL;
if (zero_check)
*pickle_iter = saved_iter;
#endif // defined(OS_POSIX) && !defined(OS_MACOSX) && defined(__x86_64__)
for (uint32 i = 0; i < num_intermediates; ++i) {
OSCertHandle intermediate = ReadOSCertHandleFromPickle(pickle_iter);
if (!intermediate)
X509Certificate* cert = NULL;
if (intermediates.size() == num_intermediates)
cert = CreateFromHandle(cert_handle, intermediates);
for (size_t i = 0; i < intermediates.size(); ++i)
return cert;
// static
CertificateList X509Certificate::CreateCertificateListFromBytes(
const char* data, int length, int format) {
OSCertHandles certificates;
// Check to see if it is in a PEM-encoded form. This check is performed
// first, as both OS X and NSS will both try to convert if they detect
// PEM encoding, except they don't do it consistently between the two.
base::StringPiece data_string(data, length);
std::vector<std::string> pem_headers;
// To maintain compatibility with NSS/Firefox, CERTIFICATE is a universally
// valid PEM block header for any format.
if (format & FORMAT_PKCS7)
PEMTokenizer pem_tok(data_string, pem_headers);
while (pem_tok.GetNext()) {
std::string decoded(;
OSCertHandle handle = NULL;
handle = CreateOSCertHandleFromBytes(decoded.c_str(), decoded.size());
if (handle != NULL) {
// Parsed a DER encoded certificate. All PEM blocks that follow must
// also be DER encoded certificates wrapped inside of PEM blocks.
// If the first block failed to parse as a DER certificate, and
// formats other than PEM are acceptable, check to see if the decoded
// data is one of the accepted formats.
for (size_t i = 0; certificates.empty() &&
i < arraysize(kFormatDecodePriority); ++i) {
if (format & kFormatDecodePriority[i]) {
certificates = CreateOSCertHandlesFromBytes(decoded.c_str(),
decoded.size(), kFormatDecodePriority[i]);
// Stop parsing after the first block for any format but a sequence of
// PEM-encoded DER certificates. The case of FORMAT_PEM_CERT_SEQUENCE
// is handled above, and continues processing until a certificate fails
// to parse.
// Try each of the formats, in order of parse preference, to see if |data|
// contains the binary representation of a Format, if it failed to parse
// as a PEM certificate/chain.
for (size_t i = 0; certificates.empty() &&
i < arraysize(kFormatDecodePriority); ++i) {
if (format & kFormatDecodePriority[i])
certificates = CreateOSCertHandlesFromBytes(data, length,
CertificateList results;
// No certificates parsed.
if (certificates.empty())
return results;
for (OSCertHandles::iterator it = certificates.begin();
it != certificates.end(); ++it) {
X509Certificate* result = CreateFromHandle(*it, OSCertHandles());
return results;
void X509Certificate::Persist(Pickle* pickle) {
// This would be an absolutely insane number of intermediates.
if (intermediate_ca_certs_.size() > static_cast<size_t>(INT_MAX) - 1) {
if (!pickle->WriteInt(
static_cast<int>(intermediate_ca_certs_.size() + 1)) ||
!WriteOSCertHandleToPickle(cert_handle_, pickle)) {
for (size_t i = 0; i < intermediate_ca_certs_.size(); ++i) {
if (!WriteOSCertHandleToPickle(intermediate_ca_certs_[i], pickle)) {
void X509Certificate::GetDNSNames(std::vector<std::string>* dns_names) const {
GetSubjectAltName(dns_names, NULL);
if (dns_names->empty())
bool X509Certificate::HasExpired() const {
return base::Time::Now() > valid_expiry();
bool X509Certificate::Equals(const X509Certificate* other) const {
return IsSameOSCert(cert_handle_, other->cert_handle_);
// static
bool X509Certificate::VerifyHostname(
const std::string& hostname,
const std::string& cert_common_name,
const std::vector<std::string>& cert_san_dns_names,
const std::vector<std::string>& cert_san_ip_addrs,
bool* common_name_fallback_used) {
// Perform name verification following
// The terminology used in this method is as per that RFC:-
// Reference identifier == the host the local user/agent is intending to
// access, i.e. the thing displayed in the URL bar.
// Presented identifier(s) == name(s) the server knows itself as, in its cert.
// CanonicalizeHost requires surrounding brackets to parse an IPv6 address.
const std::string host_or_ip = hostname.find(':') != std::string::npos ?
"[" + hostname + "]" : hostname;
url::CanonHostInfo host_info;
std::string reference_name = CanonicalizeHost(host_or_ip, &host_info);
// CanonicalizeHost does not normalize absolute vs relative DNS names. If
// the input name was absolute (included trailing .), normalize it as if it
// was relative.
if (!reference_name.empty() && *reference_name.rbegin() == '.')
reference_name.resize(reference_name.size() - 1);
if (reference_name.empty())
return false;
// Allow fallback to Common name matching?
const bool common_name_fallback = cert_san_dns_names.empty() &&
*common_name_fallback_used = common_name_fallback;
// Fully handle all cases where |hostname| contains an IP address.
if (host_info.IsIPAddress()) {
if (common_name_fallback && == url::CanonHostInfo::IPV4) {
// Fallback to Common name matching. As this is deprecated and only
// supported for compatibility refuse it for IPv6 addresses.
return reference_name == cert_common_name;
base::StringPiece ip_addr_string(
reinterpret_cast<const char*>(host_info.address),
return std::find(cert_san_ip_addrs.begin(), cert_san_ip_addrs.end(),
ip_addr_string) != cert_san_ip_addrs.end();
// |reference_domain| is the remainder of |host| after the leading host
// component is stripped off, but includes the leading dot e.g.
// "" -> "".
// If there is no meaningful domain part to |host| (e.g. it contains no dots)
// then |reference_domain| will be empty.
base::StringPiece reference_host, reference_domain;
SplitOnChar(reference_name, '.', &reference_host, &reference_domain);
bool allow_wildcards = false;
if (!reference_domain.empty()) {
// Do not allow wildcards for public/ICANN registry controlled domains -
// that is, prevent *.com or * as valid presented names, but do not
// prevent * (a private registry controlled domain).
// In addition, unknown top-level domains (such as 'intranet' domains or
// new TLDs/gTLDs not yet added to the registry controlled domain dataset)
// are also implicitly prevented.
// Because |reference_domain| must contain at least one name component that
// is not registry controlled, this ensures that all reference domains
// contain at least three domain components when using wildcards.
size_t registry_length =
// Because |reference_name| was already canonicalized, the following
// should never happen.
CHECK_NE(std::string::npos, registry_length);
// Account for the leading dot in |reference_domain|.
bool is_registry_controlled =
registry_length != 0 &&
registry_length == (reference_domain.size() - 1);
// Additionally, do not attempt wildcard matching for purely numeric
// hostnames.
allow_wildcards =
!is_registry_controlled &&
reference_name.find_first_not_of("0123456789.") != std::string::npos;
// Now step through the DNS names doing wild card comparison (if necessary)
// on each against the reference name. If subjectAltName is empty, then
// fallback to use the common name instead.
std::vector<std::string> common_name_as_vector;
const std::vector<std::string>* presented_names = &cert_san_dns_names;
if (common_name_fallback) {
// Note: there's a small possibility cert_common_name is an international
// domain name in non-standard encoding (e.g. UTF8String or BMPString
// instead of A-label). As common name fallback is deprecated we're not
// doing anything specific to deal with this.
presented_names = &common_name_as_vector;
for (std::vector<std::string>::const_iterator it =
it != presented_names->end(); ++it) {
// Catch badly corrupt cert names up front.
if (it->empty() || it->find('\0') != std::string::npos) {
DVLOG(1) << "Bad name in cert: " << *it;
std::string presented_name(StringToLowerASCII(*it));
// Remove trailing dot, if any.
if (*presented_name.rbegin() == '.')
presented_name.resize(presented_name.length() - 1);
// The hostname must be at least as long as the cert name it is matching,
// as we require the wildcard (if present) to match at least one character.
if (presented_name.length() > reference_name.length())
base::StringPiece presented_host, presented_domain;
SplitOnChar(presented_name, '.', &presented_host, &presented_domain);
if (presented_domain != reference_domain)
base::StringPiece pattern_begin, pattern_end;
SplitOnChar(presented_host, '*', &pattern_begin, &pattern_end);
if (pattern_end.empty()) { // No '*' in the presented_host
if (presented_host == reference_host)
return true;
pattern_end.remove_prefix(1); // move past the *
if (!allow_wildcards)
// * must not match a substring of an IDN A label; just a whole fragment.
if (reference_host.starts_with("xn--") &&
!(pattern_begin.empty() && pattern_end.empty()))
if (reference_host.starts_with(pattern_begin) &&
return true;
return false;
bool X509Certificate::VerifyNameMatch(const std::string& hostname,
bool* common_name_fallback_used) const {
std::vector<std::string> dns_names, ip_addrs;
GetSubjectAltName(&dns_names, &ip_addrs);
return VerifyHostname(hostname, subject_.common_name, dns_names, ip_addrs,
// static
bool X509Certificate::GetPEMEncodedFromDER(const std::string& der_encoded,
std::string* pem_encoded) {
if (der_encoded.empty())
return false;
std::string b64_encoded;
base::Base64Encode(der_encoded, &b64_encoded);
*pem_encoded = "-----BEGIN CERTIFICATE-----\n";
// Divide the Base-64 encoded data into 64-character chunks, as per
// of RFC 1421.
static const size_t kChunkSize = 64;
size_t chunks = (b64_encoded.size() + (kChunkSize - 1)) / kChunkSize;
for (size_t i = 0, chunk_offset = 0; i < chunks;
++i, chunk_offset += kChunkSize) {
pem_encoded->append(b64_encoded, chunk_offset, kChunkSize);
pem_encoded->append("-----END CERTIFICATE-----\n");
return true;
// static
bool X509Certificate::GetPEMEncoded(OSCertHandle cert_handle,
std::string* pem_encoded) {
std::string der_encoded;
if (!GetDEREncoded(cert_handle, &der_encoded))
return false;
return GetPEMEncodedFromDER(der_encoded, pem_encoded);
bool X509Certificate::GetPEMEncodedChain(
std::vector<std::string>* pem_encoded) const {
std::vector<std::string> encoded_chain;
std::string pem_data;
if (!GetPEMEncoded(os_cert_handle(), &pem_data))
return false;
for (size_t i = 0; i < intermediate_ca_certs_.size(); ++i) {
if (!GetPEMEncoded(intermediate_ca_certs_[i], &pem_data))
return false;
return true;
X509Certificate::X509Certificate(OSCertHandle cert_handle,
const OSCertHandles& intermediates)
: cert_handle_(DupOSCertHandle(cert_handle)) {
for (size_t i = 0; i < intermediates.size(); ++i) {
// Duplicate the incoming certificate, as the caller retains ownership
// of |intermediates|.
OSCertHandle intermediate = DupOSCertHandle(intermediates[i]);
// Update the cache, which will assume ownership of the duplicated
// handle and return a suitable equivalent, potentially from the cache.
// Platform-specific initialization.
X509Certificate::~X509Certificate() {
if (cert_handle_) {
for (size_t i = 0; i < intermediate_ca_certs_.size(); ++i) {
} // namespace net