1 files changed, 221 insertions, 0 deletions
diff --git a/mozglue/linker/XZStream.cpp b/mozglue/linker/XZStream.cpp
new file mode 100644
index 0000000000..db154d12aa
--- /dev/null
+++ b/mozglue/linker/XZStream.cpp
@@ -0,0 +1,221 @@
+/* -*- 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 "XZStream.h"
+
+#include <algorithm>
+#include <cstring>
+#include "mozilla/Assertions.h"
+#include "mozilla/CheckedInt.h"
+#include "Logging.h"
+
+// LZMA dictionary size, should have a minimum size for the given compression
+// rate, see XZ Utils docs for details.
+static const uint32_t kDictSize = 1 << 24;
+
+static const size_t kFooterSize = 12;
+
+// Parses a variable-length integer (VLI),
+// see http://tukaani.org/xz/xz-file-format.txt for details.
+static size_t ParseVarLenInt(const uint8_t* aBuf, size_t aBufSize,
+                             uint64_t* aValue) {
+  if (!aBufSize) {
+    return 0;
+  }
+  aBufSize = std::min(size_t(9), aBufSize);
+
+  *aValue = aBuf[0] & 0x7F;
+  size_t i = 0;
+
+  while (aBuf[i++] & 0x80) {
+    if (i >= aBufSize || aBuf[i] == 0x0) {
+      return 0;
+    }
+    *aValue |= static_cast<uint64_t>(aBuf[i] & 0x7F) << (i * 7);
+  }
+  return i;
+}
+
+/* static */
+bool XZStream::IsXZ(const void* aBuf, size_t aBufSize) {
+  static const uint8_t kXzMagic[] = {0xfd, '7', 'z', 'X', 'Z', 0x0};
+  MOZ_ASSERT(aBuf);
+  return aBufSize > sizeof(kXzMagic) &&
+         !memcmp(reinterpret_cast<const void*>(kXzMagic), aBuf,
+                 sizeof(kXzMagic));
+}
+
+XZStream::XZStream(const void* aInBuf, size_t aInSize)
+    : mInBuf(static_cast<const uint8_t*>(aInBuf)),
+      mUncompSize(0),
+      mDec(nullptr) {
+  mBuffers.in = mInBuf;
+  mBuffers.in_pos = 0;
+  mBuffers.in_size = aInSize;
+}
+
+XZStream::~XZStream() { xz_dec_end(mDec); }
+
+bool XZStream::Init() {
+#ifdef XZ_USE_CRC64
+  xz_crc64_init();
+#endif
+  xz_crc32_init();
+
+  mDec = xz_dec_init(XZ_DYNALLOC, kDictSize);
+
+  if (!mDec) {
+    return false;
+  }
+
+  mUncompSize = ParseUncompressedSize();
+  if (!mUncompSize) {
+    return false;
+  }
+
+  return true;
+}
+
+size_t XZStream::Decode(void* aOutBuf, size_t aOutSize) {
+  if (!mDec) {
+    return 0;
+  }
+
+  mBuffers.out = static_cast<uint8_t*>(aOutBuf);
+  mBuffers.out_pos = 0;
+  mBuffers.out_size = aOutSize;
+
+  while (mBuffers.in_pos < mBuffers.in_size &&
+         mBuffers.out_pos < mBuffers.out_size) {
+    const xz_ret ret = xz_dec_run(mDec, &mBuffers);
+
+    switch (ret) {
+      case XZ_STREAM_END:
+        // Stream ended, the next loop iteration should terminate.
+        MOZ_ASSERT(mBuffers.in_pos == mBuffers.in_size);
+        [[fallthrough]];
+#ifdef XZ_DEC_ANY_CHECK
+      case XZ_UNSUPPORTED_CHECK:
+        // Ignore unsupported check.
+        [[fallthrough]];
+#endif
+      case XZ_OK:
+        // Chunk decoded, proceed.
+        break;
+
+      case XZ_MEM_ERROR:
+        ERROR("XZ decoding: memory allocation failed");
+        return 0;
+
+      case XZ_MEMLIMIT_ERROR:
+        ERROR("XZ decoding: memory usage limit reached");
+        return 0;
+
+      case XZ_FORMAT_ERROR:
+        ERROR("XZ decoding: invalid stream format");
+        return 0;
+
+      case XZ_OPTIONS_ERROR:
+        ERROR("XZ decoding: unsupported header options");
+        return 0;
+
+      case XZ_DATA_ERROR:
+        [[fallthrough]];
+      case XZ_BUF_ERROR:
+        ERROR("XZ decoding: corrupt input stream");
+        return 0;
+
+      default:
+        MOZ_ASSERT_UNREACHABLE("XZ decoding: unknown error condition");
+        return 0;
+    }
+  }
+  return mBuffers.out_pos;
+}
+
+size_t XZStream::RemainingInput() const {
+  return mBuffers.in_size - mBuffers.in_pos;
+}
+
+size_t XZStream::Size() const { return mBuffers.in_size; }
+
+size_t XZStream::UncompressedSize() const { return mUncompSize; }
+
+size_t XZStream::ParseIndexSize() const {
+  static const uint8_t kFooterMagic[] = {'Y', 'Z'};
+
+  const uint8_t* footer = mInBuf + mBuffers.in_size - kFooterSize;
+  // The magic bytes are at the end of the footer.
+  if (memcmp(reinterpret_cast<const void*>(kFooterMagic),
+             footer + kFooterSize - sizeof(kFooterMagic),
+             sizeof(kFooterMagic))) {
+    // Not a valid footer at stream end.
+    ERROR("XZ parsing: Invalid footer at end of stream");
+    return 0;
+  }
+  // Backward size is a 32 bit LE integer field positioned after the 32 bit
+  // CRC32 code. It encodes the index size as a multiple of 4 bytes with a
+  // minimum size of 4 bytes.
+  const uint32_t backwardSizeRaw = *(footer + 4);
+  // Check for overflow.
+  mozilla::CheckedInt<size_t> backwardSizeBytes(backwardSizeRaw);
+  backwardSizeBytes = (backwardSizeBytes + 1) * 4;
+  if (!backwardSizeBytes.isValid()) {
+    ERROR("XZ parsing: Cannot parse index size");
+    return 0;
+  }
+  return backwardSizeBytes.value();
+}
+
+size_t XZStream::ParseUncompressedSize() const {
+  static const uint8_t kIndexIndicator[] = {0x0};
+
+  const size_t indexSize = ParseIndexSize();
+  if (!indexSize) {
+    return 0;
+  }
+  // The footer follows directly the index, so we can use it as a reference.
+  const uint8_t* end = mInBuf + mBuffers.in_size;
+  const uint8_t* index = end - kFooterSize - indexSize;
+
+  // The xz stream index consists of three concatenated elements:
+  //  (1) 1 byte indicator (always OxOO)
+  //  (2) a Variable Length Integer (VLI) field for the number of records
+  //  (3) a list of records
+  // See https://tukaani.org/xz/xz-file-format-1.0.4.txt
+  // Each record contains a VLI field for unpadded size followed by a var field
+  // for uncompressed size. We only support xz streams with a single record.
+
+  if (memcmp(reinterpret_cast<const void*>(kIndexIndicator), index,
+             sizeof(kIndexIndicator))) {
+    ERROR("XZ parsing: Invalid stream index");
+    return 0;
+  }
+
+  index += sizeof(kIndexIndicator);
+  uint64_t numRecords = 0;
+  index += ParseVarLenInt(index, end - index, &numRecords);
+  // Only streams with a single record are supported.
+  if (numRecords != 1) {
+    ERROR("XZ parsing: Multiple records not supported");
+    return 0;
+  }
+  uint64_t unpaddedSize = 0;
+  index += ParseVarLenInt(index, end - index, &unpaddedSize);
+  if (!unpaddedSize) {
+    ERROR("XZ parsing: Unpadded size is 0");
+    return 0;
+  }
+  uint64_t uncompressedSize = 0;
+  index += ParseVarLenInt(index, end - index, &uncompressedSize);
+  mozilla::CheckedInt<size_t> checkedSize(uncompressedSize);
+  if (!checkedSize.isValid()) {
+    ERROR("XZ parsing: Uncompressed stream size is too large");
+    return 0;
+  }
+
+  return checkedSize.value();
+}