gecko-dev/security/certverifier/CTObjectsExtractor.cpp

397 строки
12 KiB
C++

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "CTObjectsExtractor.h"
#include "hasht.h"
#include "mozilla/Assertions.h"
#include "mozilla/Casting.h"
#include "mozilla/Move.h"
#include "mozilla/PodOperations.h"
#include "mozilla/RangedPtr.h"
#include "mozilla/Vector.h"
#include "pkix/pkixnss.h"
#include "pkixutil.h"
namespace mozilla { namespace ct {
using namespace mozilla::pkix;
// Holds a non-owning pointer to a byte buffer and allows writing chunks of data
// to the buffer, placing the later chunks after the earlier ones
// in a stream-like fashion.
// Note that writing to Output always succeeds. If the internal buffer
// overflows, an error flag is turned on and you won't be able to retrieve
// the final data.
class Output
{
public:
Output(uint8_t* buffer, size_t length)
: begin(buffer)
, end(buffer + length)
, current(buffer, begin, end)
, overflowed(false)
{
}
template <size_t N>
explicit Output(uint8_t (&buffer)[N])
: Output(buffer, N)
{
}
void Write(Input data)
{
Write(data.UnsafeGetData(), data.GetLength());
}
void Write(uint8_t b)
{
Write(&b, 1);
}
bool IsOverflowed() const { return overflowed; }
Result GetInput(/*out*/ Input& input) const
{
if (overflowed) {
return Result::FATAL_ERROR_INVALID_STATE;
}
size_t length = AssertedCast<size_t>(current.get() - begin);
return input.Init(begin, length);
}
private:
uint8_t* begin;
uint8_t* end;
RangedPtr<uint8_t> current;
bool overflowed;
Output(const Output&) = delete;
void operator=(const Output&) = delete;
void Write(const uint8_t* data, size_t length)
{
size_t available = AssertedCast<size_t>(end - current.get());
if (available < length) {
overflowed = true;
}
if (overflowed) {
return;
}
PodCopy(current.get(), data, length);
current += length;
}
};
// For reference:
//
// Certificate ::= SEQUENCE {
// tbsCertificate TBSCertificate,
// signatureAlgorithm AlgorithmIdentifier,
// signatureValue BIT STRING }
//
// TBSCertificate ::= SEQUENCE {
// version [0] EXPLICIT Version DEFAULT v1,
// serialNumber CertificateSerialNumber,
// signature AlgorithmIdentifier,
// issuer Name,
// validity Validity,
// subject Name,
// subjectPublicKeyInfo SubjectPublicKeyInfo,
// issuerUniqueID [1] IMPLICIT UniqueIdentifier OPTIONAL,
// -- If present, version MUST be v2 or v3
// subjectUniqueID [2] IMPLICIT UniqueIdentifier OPTIONAL,
// -- If present, version MUST be v2 or v3
// extensions [3] EXPLICIT Extensions OPTIONAL
// -- If present, version MUST be v3
// }
// python DottedOIDToCode.py id-embeddedSctList 1.3.6.1.4.1.11129.2.4.2
// See Section 3.3 of RFC 6962.
static const uint8_t EMBEDDED_SCT_LIST_OID[] = {
0x2b, 0x06, 0x01, 0x04, 0x01, 0xd6, 0x79, 0x02, 0x04, 0x02
};
// Maximum length of DER TLV header
static const size_t MAX_TLV_HEADER_LENGTH = 4;
// DER tag of the "extensions [3]" field from TBSCertificate
static const uint8_t EXTENSIONS_CONTEXT_TAG =
der::CONTEXT_SPECIFIC | der::CONSTRUCTED | 3;
// Given a leaf certificate, extracts the DER-encoded TBSCertificate component
// of the corresponding Precertificate.
// Basically, the extractor needs to remove the embedded SCTs extension
// from the certificate and return its TBSCertificate. We do it in an ad hoc
// manner by breaking the source DER into several parts and then joining
// the right parts, taking care to update the relevant TLV headers.
// See WriteOutput for more details on the parts involved.
class PrecertTBSExtractor
{
public:
// |buffer| is the buffer to be used for writing the output. Since the
// required buffer size is not generally known in advance, it's best
// to use at least the size of the input certificate DER.
PrecertTBSExtractor(Input der, uint8_t* buffer, size_t bufferLength)
: mDER(der)
, mOutput(buffer, bufferLength)
{
}
// Performs the extraction.
Result Init()
{
Reader tbsReader;
Result rv = GetTBSCertificate(tbsReader);
if (rv != Success) {
return rv;
}
rv = ExtractTLVsBeforeExtensions(tbsReader);
if (rv != Success) {
return rv;
}
rv = ExtractOptionalExtensionsExceptSCTs(tbsReader);
if (rv != Success) {
return rv;
}
return WriteOutput();
}
// Use to retrieve the result after a successful call to Init.
// The returned Input points to the buffer supplied in the constructor.
Input GetPrecertTBS()
{
return mPrecertTBS;
}
private:
Result GetTBSCertificate(Reader& tbsReader)
{
Reader certificateReader;
Result rv = der::ExpectTagAndGetValueAtEnd(mDER, der::SEQUENCE,
certificateReader);
if (rv != Success) {
return rv;
}
return ExpectTagAndGetValue(certificateReader, der::SEQUENCE, tbsReader);
}
Result ExtractTLVsBeforeExtensions(Reader& tbsReader)
{
Reader::Mark tbsBegin = tbsReader.GetMark();
while (!tbsReader.AtEnd()) {
if (tbsReader.Peek(EXTENSIONS_CONTEXT_TAG)) {
break;
}
uint8_t tag;
Input tagValue;
Result rv = der::ReadTagAndGetValue(tbsReader, tag, tagValue);
if (rv != Success) {
return rv;
}
}
return tbsReader.GetInput(tbsBegin, mTLVsBeforeExtensions);
}
Result ExtractOptionalExtensionsExceptSCTs(Reader& tbsReader)
{
if (!tbsReader.Peek(EXTENSIONS_CONTEXT_TAG)) {
return Success;
}
Reader extensionsContextReader;
Result rv = der::ExpectTagAndGetValueAtEnd(tbsReader,
EXTENSIONS_CONTEXT_TAG,
extensionsContextReader);
if (rv != Success) {
return rv;
}
Reader extensionsReader;
rv = der::ExpectTagAndGetValueAtEnd(extensionsContextReader, der::SEQUENCE,
extensionsReader);
if (rv != Success) {
return rv;
}
while (!extensionsReader.AtEnd()) {
Reader::Mark extensionTLVBegin = extensionsReader.GetMark();
Reader extension;
rv = der::ExpectTagAndGetValue(extensionsReader, der::SEQUENCE,
extension);
if (rv != Success) {
return rv;
}
Reader extensionID;
rv = der::ExpectTagAndGetValue(extension, der::OIDTag, extensionID);
if (rv != Success) {
return rv;
}
if (!extensionID.MatchRest(EMBEDDED_SCT_LIST_OID)) {
Input extensionTLV;
rv = extensionsReader.GetInput(extensionTLVBegin, extensionTLV);
if (rv != Success) {
return rv;
}
if (!mExtensionTLVs.append(Move(extensionTLV))) {
return Result::FATAL_ERROR_NO_MEMORY;
}
}
}
return Success;
}
Result WriteOutput()
{
// What should be written here:
//
// TBSCertificate ::= SEQUENCE (TLV with header |tbsHeader|)
// dump of |mTLVsBeforeExtensions|
// extensions [3] OPTIONAL (TLV with header |extensionsContextHeader|)
// SEQUENCE (TLV with with header |extensionsHeader|)
// dump of |mExtensionTLVs|
Result rv;
if (mExtensionTLVs.length() > 0) {
uint8_t tbsHeaderBuffer[MAX_TLV_HEADER_LENGTH];
uint8_t extensionsContextHeaderBuffer[MAX_TLV_HEADER_LENGTH];
uint8_t extensionsHeaderBuffer[MAX_TLV_HEADER_LENGTH];
Input tbsHeader;
Input extensionsContextHeader;
Input extensionsHeader;
// Count the total size of the extensions. Note that since
// the extensions data is contained within mDER (an Input),
// their combined length won't overflow Input::size_type.
Input::size_type extensionsValueLength = 0;
for (auto& extensionTLV : mExtensionTLVs) {
extensionsValueLength += extensionTLV.GetLength();
}
rv = MakeTLVHeader(der::SEQUENCE, extensionsValueLength,
extensionsHeaderBuffer, extensionsHeader);
if (rv != Success) {
return rv;
}
Input::size_type extensionsContextLength =
AssertedCast<Input::size_type>(extensionsHeader.GetLength() +
extensionsValueLength);
rv = MakeTLVHeader(EXTENSIONS_CONTEXT_TAG,
extensionsContextLength,
extensionsContextHeaderBuffer,
extensionsContextHeader);
if (rv != Success) {
return rv;
}
Input::size_type tbsLength =
AssertedCast<Input::size_type>(mTLVsBeforeExtensions.GetLength() +
extensionsContextHeader.GetLength() +
extensionsHeader.GetLength() +
extensionsValueLength);
rv = MakeTLVHeader(der::SEQUENCE, tbsLength, tbsHeaderBuffer, tbsHeader);
if (rv != Success) {
return rv;
}
mOutput.Write(tbsHeader);
mOutput.Write(mTLVsBeforeExtensions);
mOutput.Write(extensionsContextHeader);
mOutput.Write(extensionsHeader);
for (auto& extensionTLV : mExtensionTLVs) {
mOutput.Write(extensionTLV);
}
} else {
uint8_t tbsHeaderBuffer[MAX_TLV_HEADER_LENGTH];
Input tbsHeader;
rv = MakeTLVHeader(der::SEQUENCE, mTLVsBeforeExtensions.GetLength(),
tbsHeaderBuffer, tbsHeader);
if (rv != Success) {
return rv;
}
mOutput.Write(tbsHeader);
mOutput.Write(mTLVsBeforeExtensions);
}
return mOutput.GetInput(mPrecertTBS);
}
Result MakeTLVHeader(uint8_t tag, size_t length,
uint8_t (&buffer)[MAX_TLV_HEADER_LENGTH],
/*out*/ Input& header)
{
Output output(buffer);
output.Write(tag);
if (length < 128) {
output.Write(AssertedCast<uint8_t>(length));
} else if (length < 256) {
output.Write(0x81u);
output.Write(AssertedCast<uint8_t>(length));
} else if (length < 65536) {
output.Write(0x82u);
output.Write(AssertedCast<uint8_t>(length / 256));
output.Write(AssertedCast<uint8_t>(length % 256));
} else {
return Result::FATAL_ERROR_INVALID_ARGS;
}
return output.GetInput(header);
}
Input mDER;
Input mTLVsBeforeExtensions;
Vector<Input, 16> mExtensionTLVs;
Output mOutput;
Input mPrecertTBS;
};
Result
GetPrecertLogEntry(Input leafCertificate, Input issuerSubjectPublicKeyInfo,
LogEntry& output)
{
MOZ_ASSERT(leafCertificate.GetLength() > 0);
MOZ_ASSERT(issuerSubjectPublicKeyInfo.GetLength() > 0);
output.Reset();
Buffer precertTBSBuffer;
if (!precertTBSBuffer.resize(leafCertificate.GetLength())) {
return Result::FATAL_ERROR_NO_MEMORY;
}
PrecertTBSExtractor extractor(leafCertificate,
precertTBSBuffer.begin(),
precertTBSBuffer.length());
Result rv = extractor.Init();
if (rv != Success) {
return rv;
}
Input precertTBS(extractor.GetPrecertTBS());
MOZ_ASSERT(precertTBS.UnsafeGetData() == precertTBSBuffer.begin());
precertTBSBuffer.shrinkTo(precertTBS.GetLength());
output.type = LogEntry::Type::Precert;
output.tbsCertificate = Move(precertTBSBuffer);
if (!output.issuerKeyHash.resizeUninitialized(SHA256_LENGTH)) {
return Result::FATAL_ERROR_NO_MEMORY;
}
return DigestBufNSS(issuerSubjectPublicKeyInfo, DigestAlgorithm::sha256,
output.issuerKeyHash.begin(),
output.issuerKeyHash.length());
}
Result
GetX509LogEntry(Input leafCertificate, LogEntry& output)
{
MOZ_ASSERT(leafCertificate.GetLength() > 0);
output.Reset();
output.type = LogEntry::Type::X509;
return InputToBuffer(leafCertificate, output.leafCertificate);
}
} } // namespace mozilla::ct