1 files changed, 289 insertions, 0 deletions
diff --git a/nss/fuzz/tls_mutators.cc b/nss/fuzz/tls_mutators.cc
new file mode 100644
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--- /dev/null
+++ b/nss/fuzz/tls_mutators.cc
@@ -0,0 +1,289 @@
+/* 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 "shared.h"
+#include "tls_parser.h"
+
+#include "ssl.h"
+#include "sslimpl.h"
+
+using namespace nss_test;
+
+// Number of additional bytes in the TLS header.
+// Used to properly skip DTLS seqnums.
+static size_t gExtraHeaderBytes = 0;
+
+// Helper class to simplify TLS record manipulation.
+class Record {
+ public:
+  static std::unique_ptr<Record> Create(const uint8_t *data, size_t size,
+                                        size_t remaining) {
+    return std::unique_ptr<Record>(new Record(data, size, remaining));
+  }
+
+  void insert_before(const std::unique_ptr<Record> &other) {
+    assert(data_ && size_ > 0);
+
+    // Copy data in case other == this.
+    uint8_t buf[size_];
+    memcpy(buf, data_, size_);
+
+    uint8_t *dest = const_cast<uint8_t *>(other->data());
+    // Make room for the record we want to insert.
+    memmove(dest + size_, other->data(), other->size() + other->remaining());
+    // Insert the record.
+    memcpy(dest, buf, size_);
+  }
+
+  void truncate(size_t length) {
+    assert(length >= 5 + gExtraHeaderBytes);
+    uint8_t *dest = const_cast<uint8_t *>(data_);
+    (void)ssl_EncodeUintX(length - 5 - gExtraHeaderBytes, 2, &dest[3]);
+    memmove(dest + length, data_ + size_, remaining_);
+  }
+
+  void drop() {
+    uint8_t *dest = const_cast<uint8_t *>(data_);
+    memmove(dest, data_ + size_, remaining_);
+  }
+
+  const uint8_t *data() { return data_; }
+  size_t remaining() { return remaining_; }
+  size_t size() { return size_; }
+
+ private:
+  Record(const uint8_t *data, size_t size, size_t remaining)
+      : data_(data), remaining_(remaining), size_(size) {}
+
+  const uint8_t *data_;
+  size_t remaining_;
+  size_t size_;
+};
+
+// Parse records contained in a given TLS transcript.
+std::vector<std::unique_ptr<Record>> ParseRecords(const uint8_t *data,
+                                                  size_t size) {
+  std::vector<std::unique_ptr<Record>> records;
+  TlsParser parser(data, size);
+
+  while (parser.remaining()) {
+    size_t offset = parser.consumed();
+
+    // Skip type, version, and DTLS seqnums.
+    if (!parser.Skip(3 + gExtraHeaderBytes)) {
+      break;
+    }
+
+    DataBuffer fragment;
+    if (!parser.ReadVariable(&fragment, 2)) {
+      break;
+    }
+
+    records.push_back(Record::Create(data + offset,
+                                     fragment.len() + 5 + gExtraHeaderBytes,
+                                     parser.remaining()));
+  }
+
+  return records;
+}
+
+namespace TlsMutators {
+
+// Handle seqnums in DTLS transcripts.
+void SetIsDTLS() { gExtraHeaderBytes = 8; }
+
+// Mutator that drops whole TLS records.
+size_t DropRecord(uint8_t *data, size_t size, size_t max_size,
+                  unsigned int seed) {
+  std::mt19937 rng(seed);
+
+  // Find TLS records in the corpus.
+  auto records = ParseRecords(data, size);
+  if (records.empty()) {
+    return 0;
+  }
+
+  // Pick a record to drop at random.
+  std::uniform_int_distribution<size_t> dist(0, records.size() - 1);
+  auto &rec = records.at(dist(rng));
+
+  // Drop the record.
+  rec->drop();
+
+  // Return the new final size.
+  return size - rec->size();
+}
+
+// Mutator that shuffles TLS records in a transcript.
+size_t ShuffleRecords(uint8_t *data, size_t size, size_t max_size,
+                      unsigned int seed) {
+  std::mt19937 rng(seed);
+
+  // Store the original corpus.
+  uint8_t buf[size];
+  memcpy(buf, data, size);
+
+  // Find TLS records in the corpus.
+  auto records = ParseRecords(buf, sizeof(buf));
+  if (records.empty()) {
+    return 0;
+  }
+
+  // Find offset of first record in target buffer.
+  uint8_t *dest = const_cast<uint8_t *>(ParseRecords(data, size).at(0)->data());
+
+  // Shuffle record order.
+  std::shuffle(records.begin(), records.end(), rng);
+
+  // Write records to their new positions.
+  for (auto &rec : records) {
+    memcpy(dest, rec->data(), rec->size());
+    dest += rec->size();
+  }
+
+  // Final size hasn't changed.
+  return size;
+}
+
+// Mutator that duplicates a single TLS record and randomly inserts it.
+size_t DuplicateRecord(uint8_t *data, size_t size, size_t max_size,
+                       unsigned int seed) {
+  std::mt19937 rng(seed);
+
+  // Find TLS records in the corpus.
+  const auto records = ParseRecords(data, size);
+  if (records.empty()) {
+    return 0;
+  }
+
+  // Pick a record to duplicate at random.
+  std::uniform_int_distribution<size_t> dist(0, records.size() - 1);
+  auto &rec = records.at(dist(rng));
+  if (size + rec->size() > max_size) {
+    return 0;
+  }
+
+  // Insert before random record.
+  rec->insert_before(records.at(dist(rng)));
+
+  // Return the new final size.
+  return size + rec->size();
+}
+
+// Mutator that truncates a TLS record.
+size_t TruncateRecord(uint8_t *data, size_t size, size_t max_size,
+                      unsigned int seed) {
+  std::mt19937 rng(seed);
+
+  // Find TLS records in the corpus.
+  const auto records = ParseRecords(data, size);
+  if (records.empty()) {
+    return 0;
+  }
+
+  // Pick a record to truncate at random.
+  std::uniform_int_distribution<size_t> dist(0, records.size() - 1);
+  auto &rec = records.at(dist(rng));
+
+  // Need a record with data.
+  if (rec->size() <= 5 + gExtraHeaderBytes) {
+    return 0;
+  }
+
+  // Truncate.
+  std::uniform_int_distribution<size_t> dist2(5 + gExtraHeaderBytes,
+                                              rec->size() - 1);
+  size_t new_length = dist2(rng);
+  rec->truncate(new_length);
+
+  // Return the new final size.
+  return size + new_length - rec->size();
+}
+
+// Mutator that splits a TLS record in two.
+size_t FragmentRecord(uint8_t *data, size_t size, size_t max_size,
+                      unsigned int seed) {
+  std::mt19937 rng(seed);
+
+  // We can't deal with DTLS yet.
+  if (gExtraHeaderBytes > 0) {
+    return 0;
+  }
+
+  if (size + 5 > max_size) {
+    return 0;
+  }
+
+  // Find TLS records in the corpus.
+  const auto records = ParseRecords(data, size);
+  if (records.empty()) {
+    return 0;
+  }
+
+  // Pick a record to fragment at random.
+  std::uniform_int_distribution<size_t> dist(0, records.size() - 1);
+  auto &rec = records.at(dist(rng));
+  uint8_t *rdata = const_cast<uint8_t *>(rec->data());
+  size_t length = rec->size();
+  size_t content_length = length - 5;
+
+  if (content_length < 2) {
+    return 0;
+  }
+
+  // Assign a new length to the first fragment.
+  size_t new_length = content_length / 2;
+  uint8_t *content = ssl_EncodeUintX(new_length, 2, &rdata[3]);
+
+  // Make room for one more header.
+  memmove(content + new_length + 5, content + new_length,
+          rec->remaining() + content_length - new_length);
+
+  // Write second header.
+  memcpy(content + new_length, rdata, 3);
+  (void)ssl_EncodeUintX(content_length - new_length, 2,
+                        &content[new_length + 3]);
+
+  return size + 5;
+}
+
+// Cross-over function that merges and shuffles two transcripts.
+size_t CrossOver(const uint8_t *data1, size_t size1, const uint8_t *data2,
+                 size_t size2, uint8_t *out, size_t max_out_size,
+                 unsigned int seed) {
+  std::mt19937 rng(seed);
+
+  // Find TLS records in the corpus.
+  auto records1 = ParseRecords(data1, size1);
+  if (records1.empty()) {
+    return 0;
+  }
+
+  {  // Merge the two vectors.
+    auto records2 = ParseRecords(data2, size2);
+    if (records2.empty()) {
+      return 0;
+    }
+    std::move(records2.begin(), records2.end(), std::back_inserter(records1));
+  }
+
+  // Shuffle record order.
+  std::shuffle(records1.begin(), records1.end(), rng);
+
+  size_t total = 0;
+  for (auto &rec : records1) {
+    size_t length = rec->size();
+    if (total + length > max_out_size) {
+      break;
+    }
+
+    // Write record to its new position.
+    memcpy(out + total, rec->data(), length);
+    total += length;
+  }
+
+  return total;
+}
+
+}  // namespace TlsMutators