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