// Copyright 2016 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "net/cert/cert_verify_proc_ios.h"
#include <CommonCrypto/CommonDigest.h>
#include <string_view>
#include "base/apple/foundation_util.h"
#include "base/apple/osstatus_logging.h"
#include "base/apple/scoped_cftyperef.h"
#include "base/logging.h"
#include "base/notreached.h"
#include "crypto/sha2.h"
#include "net/base/net_errors.h"
#include "net/cert/asn1_util.h"
#include "net/cert/cert_verify_result.h"
#include "net/cert/crl_set.h"
#include "net/cert/ct_serialization.h"
#include "net/cert/known_roots.h"
#include "net/cert/test_root_certs.h"
#include "net/cert/x509_certificate.h"
#include "net/cert/x509_util.h"
#include "net/cert/x509_util_apple.h"
using base::apple::ScopedCFTypeRef;
namespace net {
namespace {
int NetErrorFromOSStatus(OSStatus status) {
switch (status) {
case noErr:
return OK;
case errSecNotAvailable:
return ERR_NOT_IMPLEMENTED;
case errSecAuthFailed:
return ERR_ACCESS_DENIED;
default:
return ERR_FAILED;
}
}
// Maps errors from OSStatus codes to CertStatus flags.
//
// The selection of errors is based off of Apple's SecPolicyChecks.list, and
// any unknown errors are mapped to CERT_STATUS_INVALID for safety.
CertStatus CertStatusFromOSStatus(OSStatus status) {
switch (status) {
case errSecHostNameMismatch:
return CERT_STATUS_COMMON_NAME_INVALID;
case errSecCertificateExpired:
case errSecCertificateNotValidYet:
return CERT_STATUS_DATE_INVALID;
case errSecCreateChainFailed:
case errSecNotTrusted:
// errSecVerifyActionFailed is used when CT is required
// and not present. The OS rejected this chain, and so mapping
// to CERT_STATUS_CT_COMPLIANCE_FAILED (which is informational,
// as policy enforcement is not handled in the CertVerifier)
// would cause this error to be ignored and mapped to
// CERT_STATUS_INVALID. Rather than do that, mark it simply as
// "untrusted". The CT_COMPLIANCE_FAILED bit is not set, since
// it's not necessarily a compliance failure with the embedder's
// CT policy. It's a bit of a hack, but hopefully temporary.
// errSecNotTrusted is somewhat similar. It applies for
// situations where a root isn't trusted or an intermediate
// isn't trusted, when a key is restricted, or when the calling
// application requested CT enforcement (which CertVerifier
// should never being doing).
case errSecVerifyActionFailed:
return CERT_STATUS_AUTHORITY_INVALID;
case errSecInvalidIDLinkage:
case errSecNoBasicConstraintsCA:
case errSecInvalidSubjectName:
case errSecInvalidExtendedKeyUsage:
case errSecInvalidKeyUsageForPolicy:
case errSecMissingRequiredExtension:
case errSecNoBasicConstraints:
case errSecPathLengthConstraintExceeded:
case errSecUnknownCertExtension:
case errSecUnknownCriticalExtensionFlag:
// errSecCertificatePolicyNotAllowed and errSecCertificateNameNotAllowed
// are used for certificates that violate the constraints imposed upon the
// issuer. Nominally this could be mapped to CERT_STATUS_AUTHORITY_INVALID,
// except the trustd behaviour is to treat this as a fatal
// (non-recoverable) error. That behavior is preserved here for consistency
// with Safari.
case errSecCertificatePolicyNotAllowed:
case errSecCertificateNameNotAllowed:
return CERT_STATUS_INVALID;
// Unfortunately, iOS's handling of weak digest algorithms and key sizes
// doesn't map exactly to Chrome's. errSecInvalidDigestAlgorithm and
// errSecUnsupportedKeySize may indicate errors that iOS considers fatal
// (too weak to process at all) or recoverable (too weak according to
// compliance policies).
// Further, because SecTrustEvaluateWithError only returns a single error
// code, a fatal error may have occurred elsewhere in the chain, so the
// overall result can't be used to distinguish individual certificate
// errors. For this complicated reason, the weak key and weak digest cases
// also map to CERT_STATUS_INVALID for safety.
case errSecInvalidDigestAlgorithm:
return CERT_STATUS_WEAK_SIGNATURE_ALGORITHM | CERT_STATUS_INVALID;
case errSecUnsupportedKeySize:
return CERT_STATUS_WEAK_KEY | CERT_STATUS_INVALID;
case errSecCertificateRevoked:
return CERT_STATUS_REVOKED;
case errSecIncompleteCertRevocationCheck:
return CERT_STATUS_UNABLE_TO_CHECK_REVOCATION;
case errSecCertificateValidityPeriodTooLong:
return CERT_STATUS_VALIDITY_TOO_LONG;
case errSecInvalidCertificateRef:
case errSecInvalidName:
case errSecInvalidPolicyIdentifiers:
return CERT_STATUS_INVALID;
// This function should only be called on errors, so should always return a
// CertStatus code that is considered an error. If the input is unexpectedly
// errSecSuccess, return CERT_STATUS_INVALID for safety.
case errSecSuccess:
default:
OSSTATUS_LOG(WARNING, status)
<< "Unknown error mapped to CERT_STATUS_INVALID";
return CERT_STATUS_INVALID;
}
}
// Creates a series of SecPolicyRefs to be added to a SecTrustRef used to
// validate a certificate for an SSL server. |hostname| contains the name of
// the SSL server that the certificate should be verified against. If
// successful, returns noErr, and stores the resultant array of SecPolicyRefs
// in |policies|.
OSStatus CreateTrustPolicies(ScopedCFTypeRef<CFArrayRef>* policies) {
ScopedCFTypeRef<CFMutableArrayRef> local_policies(
CFArrayCreateMutable(kCFAllocatorDefault, 0, &kCFTypeArrayCallBacks));
if (!local_policies)
return errSecAllocate;
base::apple::ScopedCFTypeRef<SecPolicyRef> ssl_policy(
SecPolicyCreateBasicX509());
CFArrayAppendValue(local_policies.get(), ssl_policy.get());
ssl_policy.reset(SecPolicyCreateSSL(/*server=*/true, /*hostname=*/nullptr));
CFArrayAppendValue(local_policies.get(), ssl_policy.get());
*policies = std::move(local_policies);
return noErr;
}
// Builds and evaluates a SecTrustRef for the certificate chain contained
// in |cert_array|, using the verification policies in |trust_policies|. On
// success, returns OK, and updates |trust_ref|, |is_trusted|, and
// |trust_error|. On failure, no output parameters are modified.
//
// Note: An OK return does not mean that |cert_array| is trusted, merely that
// verification was performed successfully.
int BuildAndEvaluateSecTrustRef(CFArrayRef cert_array,
CFArrayRef trust_policies,
CFDataRef ocsp_response_ref,
CFArrayRef sct_array_ref,
ScopedCFTypeRef<SecTrustRef>* trust_ref,
ScopedCFTypeRef<CFArrayRef>* verified_chain,
bool* is_trusted,
ScopedCFTypeRef<CFErrorRef>* trust_error) {
ScopedCFTypeRef<SecTrustRef> tmp_trust;
OSStatus status = SecTrustCreateWithCertificates(cert_array, trust_policies,
tmp_trust.InitializeInto());
if (status)
return NetErrorFromOSStatus(status);
if (TestRootCerts::HasInstance()) {
status = TestRootCerts::GetInstance()->FixupSecTrustRef(tmp_trust.get());
if (status)
return NetErrorFromOSStatus(status);
}
if (ocsp_response_ref) {
status = SecTrustSetOCSPResponse(tmp_trust.get(), ocsp_response_ref);
if (status)
return NetErrorFromOSStatus(status);
}
if (sct_array_ref) {
if (__builtin_available(iOS 12.1.1, *)) {
status = SecTrustSetSignedCertificateTimestamps(tmp_trust.get(),
sct_array_ref);
if (status)
return NetErrorFromOSStatus(status);
}
}
ScopedCFTypeRef<CFErrorRef> tmp_error;
bool tmp_is_trusted = false;
if (__builtin_available(iOS 12.0, *)) {
tmp_is_trusted =
SecTrustEvaluateWithError(tmp_trust.get(), tmp_error.InitializeInto());
} else {
#if !defined(__IPHONE_12_0) || __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_12_0
SecTrustResultType tmp_trust_result;
status = SecTrustEvaluate(tmp_trust.get(), &tmp_trust_result);
if (status)
return NetErrorFromOSStatus(status);
switch (tmp_trust_result) {
case kSecTrustResultUnspecified:
case kSecTrustResultProceed:
tmp_is_trusted = true;
break;
case kSecTrustResultInvalid:
return ERR_FAILED;
default:
tmp_is_trusted = false;
}
#endif
}
trust_ref->swap(tmp_trust);
trust_error->swap(tmp_error);
*verified_chain = x509_util::CertificateChainFromSecTrust(trust_ref->get());
*is_trusted = tmp_is_trusted;
return OK;
}
void GetCertChainInfo(CFArrayRef cert_chain, CertVerifyResult* verify_result) {
DCHECK_LT(0, CFArrayGetCount(cert_chain));
base::apple::ScopedCFTypeRef<SecCertificateRef> verified_cert;
std::vector<base::apple::ScopedCFTypeRef<SecCertificateRef>> verified_chain;
for (CFIndex i = 0, count = CFArrayGetCount(cert_chain); i < count; ++i) {
SecCertificateRef chain_cert = reinterpret_cast<SecCertificateRef>(
const_cast<void*>(CFArrayGetValueAtIndex(cert_chain, i)));
if (i == 0) {
verified_cert.reset(chain_cert, base::scoped_policy::RETAIN);
} else {
verified_chain.emplace_back(chain_cert, base::scoped_policy::RETAIN);
}
base::apple::ScopedCFTypeRef<CFDataRef> der_data(
SecCertificateCopyData(chain_cert));
if (!der_data) {
verify_result->cert_status |= CERT_STATUS_INVALID;
return;
}
std::string_view spki_bytes;
if (!asn1::ExtractSPKIFromDERCert(
std::string_view(
reinterpret_cast<const char*>(CFDataGetBytePtr(der_data.get())),
CFDataGetLength(der_data.get())),
&spki_bytes)) {
verify_result->cert_status |= CERT_STATUS_INVALID;
return;
}
HashValue sha256(HASH_VALUE_SHA256);
CC_SHA256(spki_bytes.data(), spki_bytes.size(), sha256.data());
verify_result->public_key_hashes.push_back(sha256);
}
if (!verified_cert.get()) {
NOTREACHED_IN_MIGRATION();
verify_result->cert_status |= CERT_STATUS_INVALID;
return;
}
scoped_refptr<X509Certificate> verified_cert_with_chain =
x509_util::CreateX509CertificateFromSecCertificate(verified_cert,
verified_chain);
if (verified_cert_with_chain)
verify_result->verified_cert = std::move(verified_cert_with_chain);
else
verify_result->cert_status |= CERT_STATUS_INVALID;
}
} // namespace
CertVerifyProcIOS::CertVerifyProcIOS(scoped_refptr<CRLSet> crl_set)
: CertVerifyProc(std::move(crl_set)) {}
// static
CertStatus CertVerifyProcIOS::GetCertFailureStatusFromError(CFErrorRef error) {
if (!error)
return CERT_STATUS_INVALID;
base::apple::ScopedCFTypeRef<CFStringRef> error_domain(
CFErrorGetDomain(error));
CFIndex error_code = CFErrorGetCode(error);
if (error_domain.get() != kCFErrorDomainOSStatus) {
LOG(WARNING) << "Unhandled error domain: " << error;
return CERT_STATUS_INVALID;
}
return CertStatusFromOSStatus(error_code);
}
#if !defined(__IPHONE_12_0) || __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_12_0
// The iOS APIs don't expose an API-stable set of reasons for certificate
// validation failures. However, internally, the reason is tracked, and it's
// converted to user-facing localized strings.
//
// In the absence of a consistent API, convert the English strings to their
// localized counterpart, and then compare that with the error properties. If
// they're equal, it's a strong sign that this was the cause for the error.
// While this will break if/when iOS changes the contents of these strings,
// it's sufficient enough for now.
//
// TODO(rsleevi): https://crbug.com/601915 - Use a less brittle solution when
// possible.
// static
CertStatus CertVerifyProcIOS::GetCertFailureStatusFromTrust(SecTrustRef trust) {
CertStatus reason = 0;
base::apple::ScopedCFTypeRef<CFArrayRef> properties(
SecTrustCopyProperties(trust));
if (!properties)
return CERT_STATUS_INVALID;
const CFIndex properties_length = CFArrayGetCount(properties.get());
if (properties_length == 0)
return CERT_STATUS_INVALID;
CFBundleRef bundle =
CFBundleGetBundleWithIdentifier(CFSTR("com.apple.Security"));
CFStringRef date_string =
CFSTR("One or more certificates have expired or are not valid yet.");
ScopedCFTypeRef<CFStringRef> date_error(CFBundleCopyLocalizedString(
bundle, date_string, date_string, CFSTR("SecCertificate")));
CFStringRef trust_string = CFSTR("Root certificate is not trusted.");
ScopedCFTypeRef<CFStringRef> trust_error(CFBundleCopyLocalizedString(
bundle, trust_string, trust_string, CFSTR("SecCertificate")));
CFStringRef weak_string =
CFSTR("One or more certificates is using a weak key size.");
ScopedCFTypeRef<CFStringRef> weak_error(CFBundleCopyLocalizedString(
bundle, weak_string, weak_string, CFSTR("SecCertificate")));
CFStringRef hostname_mismatch_string = CFSTR("Hostname mismatch.");
ScopedCFTypeRef<CFStringRef> hostname_mismatch_error(
CFBundleCopyLocalizedString(bundle, hostname_mismatch_string,
hostname_mismatch_string,
CFSTR("SecCertificate")));
CFStringRef root_certificate_string =
CFSTR("Unable to build chain to root certificate.");
ScopedCFTypeRef<CFStringRef> root_certificate_error(
CFBundleCopyLocalizedString(bundle, root_certificate_string,
root_certificate_string,
CFSTR("SecCertificate")));
CFStringRef policy_requirements_not_met_string =
CFSTR("Policy requirements not met.");
ScopedCFTypeRef<CFStringRef> policy_requirements_not_met_error(
CFBundleCopyLocalizedString(bundle, policy_requirements_not_met_string,
policy_requirements_not_met_string,
CFSTR("SecCertificate")));
for (CFIndex i = 0; i < properties_length; ++i) {
CFDictionaryRef dict = reinterpret_cast<CFDictionaryRef>(
const_cast<void*>(CFArrayGetValueAtIndex(properties.get(), i)));
CFStringRef error = reinterpret_cast<CFStringRef>(
const_cast<void*>(CFDictionaryGetValue(dict, CFSTR("value"))));
if (CFEqual(error, date_error.get())) {
reason |= CERT_STATUS_DATE_INVALID;
} else if (CFEqual(error, trust_error.get())) {
reason |= CERT_STATUS_AUTHORITY_INVALID;
} else if (CFEqual(error, weak_error.get())) {
reason |= CERT_STATUS_WEAK_KEY;
} else if (CFEqual(error, hostname_mismatch_error.get())) {
reason |= CERT_STATUS_COMMON_NAME_INVALID;
} else if (CFEqual(error, policy_requirements_not_met_error.get())) {
reason |= CERT_STATUS_INVALID | CERT_STATUS_AUTHORITY_INVALID;
} else if (CFEqual(error, root_certificate_error.get())) {
reason |= CERT_STATUS_AUTHORITY_INVALID;
} else {
LOG(ERROR) << "Unrecognized error: " << error;
reason |= CERT_STATUS_INVALID;
}
}
return reason;
}
#endif // !defined(__IPHONE_12_0) || __IPHONE_OS_VERSION_MIN_REQUIRED <
// __IPHONE_12_0
CertVerifyProcIOS::~CertVerifyProcIOS() = default;
int CertVerifyProcIOS::VerifyInternal(X509Certificate* cert,
const std::string& hostname,
const std::string& ocsp_response,
const std::string& sct_list,
int flags,
CertVerifyResult* verify_result,
const NetLogWithSource& net_log) {
ScopedCFTypeRef<CFArrayRef> trust_policies;
OSStatus status = CreateTrustPolicies(&trust_policies);
if (status)
return NetErrorFromOSStatus(status);
ScopedCFTypeRef<CFMutableArrayRef> cert_array(
x509_util::CreateSecCertificateArrayForX509Certificate(
cert, x509_util::InvalidIntermediateBehavior::kIgnore));
if (!cert_array) {
verify_result->cert_status |= CERT_STATUS_INVALID;
return ERR_CERT_INVALID;
}
ScopedCFTypeRef<CFDataRef> ocsp_response_ref;
if (!ocsp_response.empty()) {
ocsp_response_ref.reset(
CFDataCreate(kCFAllocatorDefault,
reinterpret_cast<const UInt8*>(ocsp_response.data()),
base::checked_cast<CFIndex>(ocsp_response.size())));
if (!ocsp_response_ref)
return ERR_OUT_OF_MEMORY;
}
ScopedCFTypeRef<CFMutableArrayRef> sct_array_ref;
if (!sct_list.empty()) {
if (__builtin_available(iOS 12.1.1, *)) {
std::vector<std::string_view> decoded_sct_list;
if (ct::DecodeSCTList(sct_list, &decoded_sct_list)) {
sct_array_ref.reset(CFArrayCreateMutable(kCFAllocatorDefault,
decoded_sct_list.size(),
&kCFTypeArrayCallBacks));
if (!sct_array_ref)
return ERR_OUT_OF_MEMORY;
for (const auto& sct : decoded_sct_list) {
ScopedCFTypeRef<CFDataRef> sct_ref(CFDataCreate(
kCFAllocatorDefault, reinterpret_cast<const UInt8*>(sct.data()),
base::checked_cast<CFIndex>(sct.size())));
if (!sct_ref)
return ERR_OUT_OF_MEMORY;
CFArrayAppendValue(sct_array_ref.get(), sct_ref.get());
}
}
}
}
ScopedCFTypeRef<SecTrustRef> trust_ref;
bool is_trusted = false;
ScopedCFTypeRef<CFArrayRef> final_chain;
ScopedCFTypeRef<CFErrorRef> trust_error;
int err = BuildAndEvaluateSecTrustRef(
cert_array.get(), trust_policies.get(), ocsp_response_ref.get(),
sct_array_ref.get(), &trust_ref, &final_chain, &is_trusted, &trust_error);
if (err)
return err;
if (CFArrayGetCount(final_chain.get()) == 0) {
return ERR_FAILED;
}
// TODO(rsleevi): Support CRLSet revocation.
if (!is_trusted) {
if (__builtin_available(iOS 12.0, *)) {
verify_result->cert_status |=
GetCertFailureStatusFromError(trust_error.get());
} else {
#if !defined(__IPHONE_12_0) || __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_12_0
SecTrustResultType trust_result = kSecTrustResultInvalid;
status = SecTrustGetTrustResult(trust_ref.get(), &trust_result);
if (status)
return NetErrorFromOSStatus(status);
switch (trust_result) {
case kSecTrustResultUnspecified:
case kSecTrustResultProceed:
NOTREACHED_IN_MIGRATION();
break;
case kSecTrustResultDeny:
verify_result->cert_status |= CERT_STATUS_AUTHORITY_INVALID;
break;
default:
verify_result->cert_status |=
GetCertFailureStatusFromTrust(trust_ref.get());
}
#else
// It should be impossible to reach this code, but if somehow it is
// reached it would allow any certificate as valid since no errors would
// be added to cert_status. Therefore, add a CHECK as a fail safe.
CHECK(false);
#endif
}
}
GetCertChainInfo(final_chain.get(), verify_result);
// While iOS lacks the ability to distinguish system-trusted versus
// user-installed roots, the set of roots that are expected to comply with
// the Baseline Requirements can be determined by
// GetNetTrustAnchorHistogramForSPKI() - a non-zero value means that it is
// known as a publicly trusted, and therefore subject to the BRs, cert.
for (auto it = verify_result->public_key_hashes.rbegin();
it != verify_result->public_key_hashes.rend() &&
!verify_result->is_issued_by_known_root;
++it) {
verify_result->is_issued_by_known_root =
GetNetTrustAnchorHistogramIdForSPKI(*it) != 0;
}
if (IsCertStatusError(verify_result->cert_status))
return MapCertStatusToNetError(verify_result->cert_status);
if (TestRootCerts::HasInstance() &&
!verify_result->verified_cert->intermediate_buffers().empty() &&
TestRootCerts::GetInstance()->IsKnownRoot(x509_util::CryptoBufferAsSpan(
verify_result->verified_cert->intermediate_buffers().back().get()))) {
verify_result->is_issued_by_known_root = true;
}
LogNameNormalizationMetrics(".IOS", verify_result->verified_cert.get(),
verify_result->is_issued_by_known_root);
return OK;
}
} // namespace net
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