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Diffstat (limited to 'security/certverifier/CTObjectsExtractor.cpp')
| -rw-r--r-- | security/certverifier/CTObjectsExtractor.cpp | 396 |
1 files changed, 396 insertions, 0 deletions
diff --git a/security/certverifier/CTObjectsExtractor.cpp b/security/certverifier/CTObjectsExtractor.cpp new file mode 100644 index 0000000000..33354f97be --- /dev/null +++ b/security/certverifier/CTObjectsExtractor.cpp @@ -0,0 +1,396 @@ +/* -*- 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 |