crypto: convert OpenPGP code to NSS

(This is a reland of r91350 which was reverted in r91355.)

BUG=none
TEST=crypto_unittests

Review URL: http://codereview.chromium.org/7273080

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@91559 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 790 insertions, 0 deletions

diff --git a/crypto/openpgp_symmetric_encryption.cc b/crypto/openpgp_symmetric_encryption.cc
new file mode 100644
index 0000000..62223f9
--- /dev/null
+++ b/crypto/openpgp_symmetric_encryption.cc
@@ -0,0 +1,790 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "crypto/openpgp_symmetric_encryption.h"
+
+#include <stdlib.h>
+
+#include <sechash.h>
+#include <cryptohi.h>
+
+#include <vector>
+
+#include "base/logging.h"
+#include "base/rand_util.h"
+#include "crypto/scoped_nss_types.h"
+
+namespace crypto {
+
+namespace {
+
+// Reader wraps a StringPiece and provides methods to read several datatypes
+// while advancing the StringPiece.
+class Reader {
+ public:
+  Reader(base::StringPiece input)
+      : data_(input) {
+  }
+
+  bool U8(uint8* out) {
+    if (data_.size() < 1)
+      return false;
+    *out = static_cast<uint8>(data_[0]);
+    data_.remove_prefix(1);
+    return true;
+  }
+
+  bool U32(uint32* out) {
+    if (data_.size() < 4)
+      return false;
+    *out = static_cast<uint32>(data_[0]) << 24 |
+           static_cast<uint32>(data_[1]) << 16 |
+           static_cast<uint32>(data_[2]) << 8 |
+           static_cast<uint32>(data_[3]);
+    data_.remove_prefix(4);
+    return true;
+  }
+
+  // Prefix sets |*out| to the first |n| bytes of the StringPiece and advances
+  // the StringPiece by |n|.
+  bool Prefix(size_t n, base::StringPiece *out) {
+    if (data_.size() < n)
+      return false;
+    *out = base::StringPiece(data_.data(), n);
+    data_.remove_prefix(n);
+    return true;
+  }
+
+  // Remainder returns the remainer of the StringPiece and advances it to the
+  // end.
+  base::StringPiece Remainder() {
+    base::StringPiece ret = data_;
+    data_ = base::StringPiece();
+    return ret;
+  }
+
+  typedef base::StringPiece Position;
+
+  Position tell() const {
+    return data_;
+  }
+
+  void Seek(Position p) {
+    data_ = p;
+  }
+
+  bool Skip(size_t n) {
+    if (data_.size() < n)
+      return false;
+    data_.remove_prefix(n);
+    return true;
+  }
+
+  bool empty() const {
+    return data_.empty();
+  }
+
+  size_t size() const {
+    return data_.size();
+  }
+
+ private:
+  base::StringPiece data_;
+};
+
+// SaltedIteratedS2K implements the salted and iterated string-to-key
+// convertion. See RFC 4880, section 3.7.1.3.
+void SaltedIteratedS2K(unsigned cipher_key_length,
+                       HASH_HashType hash_function,
+                       base::StringPiece passphrase,
+                       base::StringPiece salt,
+                       unsigned count,
+                       uint8 *out_key) {
+  const std::string combined = salt.as_string() + passphrase.as_string();
+  const size_t combined_len = combined.size();
+
+  unsigned done = 0;
+  uint8 zero[1] = {0};
+
+  HASHContext* hash_context = HASH_Create(hash_function);
+
+  for (unsigned i = 0; done < cipher_key_length; i++) {
+    HASH_Begin(hash_context);
+
+    for (unsigned j = 0; j < i; j++)
+      HASH_Update(hash_context, zero, sizeof(zero));
+
+    unsigned written = 0;
+    while (written < count) {
+      if (written + combined_len > count) {
+        unsigned todo = count - written;
+        HASH_Update(hash_context,
+                     reinterpret_cast<const uint8*>(combined.data()),
+                     todo);
+        written = count;
+      } else {
+        HASH_Update(hash_context,
+                     reinterpret_cast<const uint8*>(combined.data()),
+                     combined_len);
+        written += combined_len;
+      }
+    }
+
+    unsigned num_hash_bytes;
+    uint8 digest[HASH_LENGTH_MAX];
+    HASH_End(hash_context, digest, &num_hash_bytes, sizeof(digest));
+
+    unsigned todo = cipher_key_length - done;
+    if (todo > num_hash_bytes)
+      todo = num_hash_bytes;
+    memcpy(out_key + done, digest, todo);
+    done += todo;
+  }
+
+  HASH_Destroy(hash_context);
+}
+
+// CreateAESContext sets up |out_key| to be an AES context, with the given key,
+// in ECB mode and with no IV.
+bool CreateAESContext(const uint8* key, unsigned key_len,
+                      ScopedPK11Context* out_decryption_context) {
+  ScopedPK11Slot slot(PK11_GetBestSlot(CKM_AES_ECB, NULL));
+  if (!slot.get())
+    return false;
+  SECItem key_item;
+  key_item.type = siBuffer;
+  key_item.data = const_cast<uint8*>(key);
+  key_item.len = key_len;
+  ScopedPK11SymKey pk11_key(PK11_ImportSymKey(
+      slot.get(), CKM_AES_ECB, PK11_OriginUnwrap, CKA_ENCRYPT, &key_item,
+      NULL));
+  if (!pk11_key.get())
+    return false;
+  ScopedSECItem iv_param(PK11_ParamFromIV(CKM_AES_ECB, NULL));
+  out_decryption_context->reset(
+      PK11_CreateContextBySymKey(CKM_AES_ECB, CKA_ENCRYPT, pk11_key.get(),
+                                 iv_param.get()));
+  return out_decryption_context->get() != NULL;
+}
+
+
+// These constants are the tag numbers for the various packet types that we
+// use.
+static const unsigned kSymmetricKeyEncryptedTag = 3;
+static const unsigned kSymmetricallyEncryptedTag = 18;
+static const unsigned kCompressedTag = 8;
+static const unsigned kLiteralDataTag = 11;
+
+class Decrypter {
+ public:
+  ~Decrypter() {
+    for (std::vector<void*>::iterator
+         i = arena_.begin(); i != arena_.end(); i++) {
+      free(*i);
+    }
+    arena_.clear();
+  }
+
+  OpenPGPSymmetricEncrytion::Result Decrypt(base::StringPiece in,
+                                            base::StringPiece passphrase,
+                                            base::StringPiece *out_contents) {
+    Reader reader(in);
+    unsigned tag;
+    base::StringPiece contents;
+    ScopedPK11Context decryption_context;
+
+    if (!ParsePacket(&reader, &tag, &contents))
+      return OpenPGPSymmetricEncrytion::PARSE_ERROR;
+    if (tag != kSymmetricKeyEncryptedTag)
+      return OpenPGPSymmetricEncrytion::NOT_SYMMETRICALLY_ENCRYPTED;
+    Reader inner(contents);
+    OpenPGPSymmetricEncrytion::Result result =
+      ParseSymmetricKeyEncrypted(&inner, passphrase, &decryption_context);
+    if (result != OpenPGPSymmetricEncrytion::OK)
+      return result;
+
+    if (!ParsePacket(&reader, &tag, &contents))
+      return OpenPGPSymmetricEncrytion::PARSE_ERROR;
+    if (tag != kSymmetricallyEncryptedTag)
+      return OpenPGPSymmetricEncrytion::NOT_SYMMETRICALLY_ENCRYPTED;
+    if (!reader.empty())
+      return OpenPGPSymmetricEncrytion::PARSE_ERROR;
+    inner = Reader(contents);
+    if (!ParseSymmetricallyEncrypted(&inner, &decryption_context, &contents))
+      return OpenPGPSymmetricEncrytion::PARSE_ERROR;
+
+    reader = Reader(contents);
+    if (!ParsePacket(&reader, &tag, &contents))
+      return OpenPGPSymmetricEncrytion::PARSE_ERROR;
+    if (tag == kCompressedTag)
+      return OpenPGPSymmetricEncrytion::COMPRESSED;
+    if (tag != kLiteralDataTag)
+      return OpenPGPSymmetricEncrytion::NOT_SYMMETRICALLY_ENCRYPTED;
+    inner = Reader(contents);
+    if (!ParseLiteralData(&inner, out_contents))
+      return OpenPGPSymmetricEncrytion::PARSE_ERROR;
+
+    return OpenPGPSymmetricEncrytion::OK;
+  }
+
+ private:
+  // ParsePacket parses an OpenPGP packet from reader. See RFC 4880, section
+  // 4.2.2.
+  bool ParsePacket(Reader *reader,
+                   unsigned *out_tag,
+                   base::StringPiece *out_contents) {
+    uint8 header;
+    if (!reader->U8(&header))
+      return false;
+    if ((header & 0x80) == 0) {
+      // Tag byte must have MSB set.
+      return false;
+    }
+
+    if ((header & 0x40) == 0) {
+      // Old format packet.
+      *out_tag = (header & 0x3f) >> 2;
+
+      uint8 length_type = header & 3;
+      if (length_type == 3) {
+        *out_contents = reader->Remainder();
+        return true;
+      }
+
+      const unsigned length_bytes = 1 << length_type;
+      size_t length = 0;
+      for (unsigned i = 0; i < length_bytes; i++) {
+        uint8 length_byte;
+        if (!reader->U8(&length_byte))
+          return false;
+        length <<= 8;
+        length |= length_byte;
+      }
+
+      return reader->Prefix(length, out_contents);
+    }
+
+    // New format packet.
+    *out_tag = header & 0x3f;
+    size_t length;
+    bool is_partial;
+    if (!ParseLength(reader, &length, &is_partial))
+      return false;
+    if (is_partial)
+      return ParseStreamContents(reader, length, out_contents);
+    return reader->Prefix(length, out_contents);
+  }
+
+  // ParseStreamContents parses all the chunks of a partial length stream from
+  // reader. See http://tools.ietf.org/html/rfc4880#section-4.2.2.4
+  bool ParseStreamContents(Reader *reader,
+                           size_t length,
+                           base::StringPiece *out_contents) {
+    const Reader::Position beginning_of_stream = reader->tell();
+    const size_t first_chunk_length = length;
+
+    // First we parse the stream to find its length.
+    if (!reader->Skip(length))
+      return false;
+
+    for (;;) {
+      size_t chunk_length;
+      bool is_partial;
+
+      if (!ParseLength(reader, &chunk_length, &is_partial))
+        return false;
+      if (length + chunk_length < length)
+        return false;
+      length += chunk_length;
+      if (!reader->Skip(chunk_length))
+        return false;
+      if (!is_partial)
+        break;
+    }
+
+    // Now we have the length of the whole stream in |length|.
+    char* buf = reinterpret_cast<char*>(malloc(length));
+    arena_.push_back(buf);
+    size_t j = 0;
+    reader->Seek(beginning_of_stream);
+
+    base::StringPiece first_chunk;
+    if (!reader->Prefix(first_chunk_length, &first_chunk))
+      return false;
+    memcpy(buf + j, first_chunk.data(), first_chunk_length);
+    j += first_chunk_length;
+
+    // Now we parse the stream again, this time copying into |buf|
+    for (;;) {
+      size_t chunk_length;
+      bool is_partial;
+
+      if (!ParseLength(reader, &chunk_length, &is_partial))
+        return false;
+      base::StringPiece chunk;
+      if (!reader->Prefix(chunk_length, &chunk))
+        return false;
+      memcpy(buf + j, chunk.data(), chunk_length);
+      j += chunk_length;
+      if (!is_partial)
+        break;
+    }
+
+    *out_contents = base::StringPiece(buf, length);
+    return true;
+  }
+
+  // ParseLength parses an OpenPGP length from reader. See RFC 4880, section
+  // 4.2.2.
+  bool ParseLength(Reader *reader, size_t *out_length, bool *out_is_prefix) {
+    uint8 length_spec;
+    if (!reader->U8(&length_spec))
+      return false;
+
+    *out_is_prefix = false;
+    if (length_spec < 192) {
+      *out_length = length_spec;
+      return true;
+    } else if (length_spec < 224) {
+      uint8 next_byte;
+      if (!reader->U8(&next_byte))
+        return false;
+
+      *out_length = (length_spec - 192) << 8;
+      *out_length += next_byte;
+      return true;
+    } else if (length_spec < 255) {
+      *out_length = 1u << (length_spec & 0x1f);
+      *out_is_prefix = true;
+      return true;
+    } else {
+      uint32 length32;
+      if (!reader->U32(&length32))
+        return false;
+      *out_length = length32;
+      return true;
+    }
+  }
+
+  // ParseSymmetricKeyEncrypted parses a passphrase protected session key. See
+  // RFC 4880, section 5.3.
+  OpenPGPSymmetricEncrytion::Result ParseSymmetricKeyEncrypted(
+      Reader *reader,
+      base::StringPiece passphrase,
+      ScopedPK11Context *decryption_context) {
+    uint8 version, cipher, s2k_type, hash_func_id;
+    if (!reader->U8(&version) || version != 4)
+      return OpenPGPSymmetricEncrytion::PARSE_ERROR;
+
+    if (!reader->U8(&cipher) ||
+        !reader->U8(&s2k_type) ||
+        !reader->U8(&hash_func_id)) {
+      return OpenPGPSymmetricEncrytion::PARSE_ERROR;
+    }
+
+    uint8 cipher_key_length = OpenPGPCipherIdToKeyLength(cipher);
+    if (cipher_key_length == 0)
+      return OpenPGPSymmetricEncrytion::UNKNOWN_CIPHER;
+
+    HASH_HashType hash_function;
+    switch (hash_func_id) {
+    case 2:  // SHA-1
+      hash_function = HASH_AlgSHA1;
+      break;
+    case 8:  // SHA-256
+      hash_function = HASH_AlgSHA256;
+      break;
+    default:
+      return OpenPGPSymmetricEncrytion::UNKNOWN_HASH;
+    }
+
+    // This chunk of code parses the S2K specifier. See RFC 4880, section 3.7.1.
+    base::StringPiece salt;
+    uint8 key[32];
+    uint8 count_spec;
+    switch (s2k_type) {
+    case 1:
+      if (!reader->Prefix(8, &salt))
+        return OpenPGPSymmetricEncrytion::PARSE_ERROR;
+      // Fall through.
+    case 0:
+      SaltedIteratedS2K(cipher_key_length, hash_function, passphrase, salt,
+                        passphrase.size() + salt.size(), key);
+      break;
+    case 3:
+      if (!reader->Prefix(8, &salt) ||
+          !reader->U8(&count_spec)) {
+        return OpenPGPSymmetricEncrytion::PARSE_ERROR;
+      }
+      SaltedIteratedS2K(
+          cipher_key_length, hash_function, passphrase, salt,
+          static_cast<unsigned>(
+            16 + (count_spec&15)) << ((count_spec >> 4) + 6), key);
+      break;
+    default:
+      return OpenPGPSymmetricEncrytion::PARSE_ERROR;
+    }
+
+    if (!CreateAESContext(key, cipher_key_length, decryption_context))
+      return OpenPGPSymmetricEncrytion::INTERNAL_ERROR;
+
+    if (reader->empty()) {
+      // The resulting key is used directly.
+      return OpenPGPSymmetricEncrytion::OK;
+    }
+
+    // The S2K derived key encrypts another key that follows:
+    base::StringPiece encrypted_key = reader->Remainder();
+    if (encrypted_key.size() < 1)
+      return OpenPGPSymmetricEncrytion::PARSE_ERROR;
+
+    uint8* plaintext_key = reinterpret_cast<uint8*>(
+        malloc(encrypted_key.size()));
+    arena_.push_back(plaintext_key);
+
+    CFBDecrypt(encrypted_key, decryption_context, plaintext_key);
+
+    cipher_key_length = OpenPGPCipherIdToKeyLength(plaintext_key[0]);
+    if (cipher_key_length == 0)
+      return OpenPGPSymmetricEncrytion::UNKNOWN_CIPHER;
+    if (encrypted_key.size() != 1u + cipher_key_length)
+      return OpenPGPSymmetricEncrytion::PARSE_ERROR;
+    if (!CreateAESContext(plaintext_key + 1, cipher_key_length,
+                          decryption_context)) {
+      return OpenPGPSymmetricEncrytion::INTERNAL_ERROR;
+    }
+    return OpenPGPSymmetricEncrytion::OK;
+  }
+
+  // CFBDecrypt decrypts the cipher-feedback encrypted data in |in| to |out|
+  // using |decryption_context| and assumes an IV of all zeros.
+  void CFBDecrypt(base::StringPiece in, ScopedPK11Context* decryption_context,
+                  uint8* out) {
+    // We need this for PK11_CipherOp to write to, but we never check it as we
+    // work in ECB mode, one block at a time.
+    int out_len;
+
+    uint8 mask[AES_BLOCK_SIZE];
+    memset(mask, 0, sizeof(mask));
+
+    unsigned used = AES_BLOCK_SIZE;
+
+    for (size_t i = 0; i < in.size(); i++) {
+      if (used == AES_BLOCK_SIZE) {
+        PK11_CipherOp(decryption_context->get(), mask, &out_len, sizeof(mask),
+                      mask, AES_BLOCK_SIZE);
+        used = 0;
+      }
+
+      uint8 t = in[i];
+      out[i] = t ^ mask[used];
+      mask[used] = t;
+      used++;
+    }
+  }
+
+  // OpenPGPCipherIdToKeyLength converts an OpenPGP cipher id (see RFC 4880,
+  // section 9.2) to the key length of that cipher. It returns 0 on error.
+  unsigned OpenPGPCipherIdToKeyLength(uint8 cipher) {
+    switch (cipher) {
+    case 7:  // AES-128
+      return 16;
+    case 8:  // AES-192
+      return 24;
+    case 9:  // AES-256
+      return 32;
+    default:
+      return 0;
+    }
+  }
+
+  // ParseSymmetricallyEncrypted parses a Symmetrically Encrypted packet. See
+  // RFC 4880, sections 5.7 and 5.13.
+  bool ParseSymmetricallyEncrypted(Reader *reader,
+                                   ScopedPK11Context *decryption_context,
+                                   base::StringPiece *out_plaintext) {
+    // We need this for PK11_CipherOp to write to, but we never check it as we
+    // work in ECB mode, one block at a time.
+    int out_len;
+
+    uint8 version;
+    if (!reader->U8(&version) || version != 1)
+      return false;
+
+    base::StringPiece prefix_sp;
+    if (!reader->Prefix(AES_BLOCK_SIZE + 2, &prefix_sp))
+      return false;
+    uint8 prefix[AES_BLOCK_SIZE + 2];
+    memcpy(prefix, prefix_sp.data(), sizeof(prefix));
+
+    uint8 prefix_copy[AES_BLOCK_SIZE + 2];
+    uint8 fre[AES_BLOCK_SIZE];
+
+    memset(prefix_copy, 0, AES_BLOCK_SIZE);
+    PK11_CipherOp(decryption_context->get(), fre, &out_len, sizeof(fre),
+                  prefix_copy, AES_BLOCK_SIZE);
+    for (unsigned i = 0; i < AES_BLOCK_SIZE; i++)
+      prefix_copy[i] = fre[i] ^ prefix[i];
+    PK11_CipherOp(decryption_context->get(), fre, &out_len, sizeof(fre), prefix,
+                  AES_BLOCK_SIZE);
+    prefix_copy[AES_BLOCK_SIZE] = prefix[AES_BLOCK_SIZE] ^ fre[0];
+    prefix_copy[AES_BLOCK_SIZE + 1] = prefix[AES_BLOCK_SIZE + 1] ^ fre[1];
+
+    if (prefix_copy[AES_BLOCK_SIZE - 2] != prefix_copy[AES_BLOCK_SIZE] ||
+        prefix_copy[AES_BLOCK_SIZE - 1] != prefix_copy[AES_BLOCK_SIZE + 1]) {
+      return false;
+    }
+
+    fre[0] = prefix[AES_BLOCK_SIZE];
+    fre[1] = prefix[AES_BLOCK_SIZE + 1];
+
+    unsigned out_used = 2;
+
+    const size_t plaintext_size = reader->size();
+    if (plaintext_size < SHA1_LENGTH + 2) {
+      // Too small to contain an MDC trailer.
+      return false;
+    }
+
+    uint8* plaintext = reinterpret_cast<uint8*>(malloc(plaintext_size));
+    arena_.push_back(plaintext);
+
+    for (size_t i = 0; i < plaintext_size; i++) {
+      uint8 b;
+      if (!reader->U8(&b))
+        return false;
+      if (out_used == AES_BLOCK_SIZE) {
+        PK11_CipherOp(decryption_context->get(), fre, &out_len, sizeof(fre),
+                      fre, AES_BLOCK_SIZE);
+        out_used = 0;
+      }
+
+      plaintext[i] = b ^ fre[out_used];
+      fre[out_used++] = b;
+    }
+
+    // The plaintext should be followed by a Modification Detection Code
+    // packet. This packet is specified such that the header is always
+    // serialized as exactly these two bytes:
+    if (plaintext[plaintext_size - SHA1_LENGTH - 2] != 0xd3 ||
+        plaintext[plaintext_size - SHA1_LENGTH - 1] != 0x14) {
+      return false;
+    }
+
+    HASHContext* hash_context = HASH_Create(HASH_AlgSHA1);
+    HASH_Begin(hash_context);
+    HASH_Update(hash_context, prefix_copy, sizeof(prefix_copy));
+    HASH_Update(hash_context, plaintext, plaintext_size - SHA1_LENGTH);
+    uint8 digest[SHA1_LENGTH];
+    unsigned num_hash_bytes;
+    HASH_End(hash_context, digest, &num_hash_bytes, sizeof(digest));
+    HASH_Destroy(hash_context);
+
+    if (memcmp(digest, &plaintext[plaintext_size - SHA1_LENGTH],
+               SHA1_LENGTH) != 0) {
+      return false;
+    }
+
+    *out_plaintext = base::StringPiece(reinterpret_cast<char*>(plaintext),
+                                       plaintext_size - SHA1_LENGTH);
+    return true;
+  }
+
+  // ParseLiteralData parses a Literal Data packet. See RFC 4880, section 5.9.
+  bool ParseLiteralData(Reader *reader, base::StringPiece *out_data) {
+    uint8 is_binary, filename_len;
+    if (!reader->U8(&is_binary) ||
+        !reader->U8(&filename_len) ||
+        !reader->Skip(filename_len) ||
+        !reader->Skip(sizeof(uint32) /* mtime */)) {
+      return false;
+    }
+
+    *out_data = reader->Remainder();
+    return true;
+  }
+
+  // arena_ contains malloced pointers that are used as temporary space during
+  // the decryption.
+  std::vector<void*> arena_;
+};
+
+class Encrypter {
+ public:
+  // ByteString is used throughout in order to avoid signedness issues with a
+  // std::string.
+  typedef std::basic_string<uint8> ByteString;
+
+  static ByteString Encrypt(base::StringPiece plaintext,
+                            base::StringPiece passphrase) {
+    ByteString key;
+    ByteString ske = SerializeSymmetricKeyEncrypted(passphrase, &key);
+
+    ByteString literal_data = SerializeLiteralData(plaintext);
+    ByteString se = SerializeSymmetricallyEncrypted(literal_data, key);
+    return ske + se;
+  }
+
+ private:
+  // MakePacket returns an OpenPGP packet tagged as type |tag|. It always uses
+  // new-format headers. See RFC 4880, section 4.2.
+  static ByteString MakePacket(unsigned tag, const ByteString& contents) {
+    ByteString header;
+    header.push_back(0x80 | 0x40 | tag);
+
+    if (contents.size() < 192) {
+      header.push_back(contents.size());
+    } else if (contents.size() < 8384) {
+      size_t length = contents.size();
+      length -= 192;
+      header.push_back(192 + (length >> 8));
+      header.push_back(length & 0xff);
+    } else {
+      size_t length = contents.size();
+      header.push_back(255);
+      header.push_back(length >> 24);
+      header.push_back(length >> 16);
+      header.push_back(length >> 8);
+      header.push_back(length);
+    }
+
+    return header + contents;
+  }
+
+  // SerializeLiteralData returns a Literal Data packet containing |contents|
+  // as binary data with no filename nor mtime specified. See RFC 4880, section
+  // 5.9.
+  static ByteString SerializeLiteralData(base::StringPiece contents) {
+    ByteString literal_data;
+    literal_data.push_back(0x74);  // text mode
+    literal_data.push_back(0x00);  // no filename
+    literal_data.push_back(0x00);  // zero mtime
+    literal_data.push_back(0x00);
+    literal_data.push_back(0x00);
+    literal_data.push_back(0x00);
+    literal_data += ByteString(reinterpret_cast<const uint8*>(contents.data()),
+                               contents.size());
+    return MakePacket(kLiteralDataTag, literal_data);
+  }
+
+  // SerializeSymmetricKeyEncrypted generates a random AES-128 key from
+  // |passphrase|, sets |out_key| to it and returns a Symmetric Key Encrypted
+  // packet. See RFC 4880, section 5.3.
+  static ByteString SerializeSymmetricKeyEncrypted(base::StringPiece passphrase,
+                                                   ByteString *out_key) {
+    ByteString ske;
+    ske.push_back(4);  // version 4
+    ske.push_back(7);  // AES-128
+    ske.push_back(3);  // iterated and salted S2K
+    ske.push_back(2);  // SHA-1
+
+    uint64 salt64 = base::RandUint64();
+    ByteString salt(sizeof(salt64), 0);
+
+    // It's a random value, so endianness doesn't matter.
+    ske += ByteString(reinterpret_cast<uint8*>(&salt64), sizeof(salt64));
+    ske.push_back(96);  // iteration count of 65536
+
+    uint8 key[16];
+    SaltedIteratedS2K(
+        sizeof(key), HASH_AlgSHA1, passphrase,
+        base::StringPiece(reinterpret_cast<char*>(&salt64), sizeof(salt64)),
+        65536, key);
+    *out_key = ByteString(key, sizeof(key));
+    return MakePacket(kSymmetricKeyEncryptedTag, ske);
+  }
+
+  // SerializeSymmetricallyEncrypted encrypts |plaintext| with |key| and
+  // returns a Symmetrically Encrypted packet containing the ciphertext. See
+  // RFC 4880, section 5.7.
+  static ByteString SerializeSymmetricallyEncrypted(ByteString plaintext,
+                                                    const ByteString& key) {
+    // We need this for PK11_CipherOp to write to, but we never check it as we
+    // work in ECB mode, one block at a time.
+    int out_len;
+
+    ByteString packet;
+    packet.push_back(1);  // version 1
+    static const unsigned kBlockSize = 16;  // AES block size
+
+    uint8 prefix[kBlockSize + 2], fre[kBlockSize], iv[kBlockSize];
+    base::RandBytes(iv, kBlockSize);
+    memset(fre, 0, sizeof(fre));
+
+    ScopedPK11Context aes_context;
+    CHECK(CreateAESContext(key.data(), key.size(), &aes_context));
+
+    PK11_CipherOp(aes_context.get(), fre, &out_len, sizeof(fre), fre,
+                  AES_BLOCK_SIZE);
+    for (unsigned i = 0; i < 16; i++)
+      prefix[i] = iv[i] ^ fre[i];
+    PK11_CipherOp(aes_context.get(), fre, &out_len, sizeof(fre), prefix,
+                  AES_BLOCK_SIZE);
+    prefix[kBlockSize] = iv[kBlockSize - 2] ^ fre[0];
+    prefix[kBlockSize + 1] = iv[kBlockSize - 1] ^ fre[1];
+
+    packet += ByteString(prefix, sizeof(prefix));
+
+    ByteString plaintext_copy = plaintext;
+    plaintext_copy.push_back(0xd3);  // MDC packet
+    plaintext_copy.push_back(20);  // packet length (20 bytes)
+
+    HASHContext* hash_context = HASH_Create(HASH_AlgSHA1);
+    HASH_Begin(hash_context);
+    HASH_Update(hash_context, iv, sizeof(iv));
+    HASH_Update(hash_context, iv + kBlockSize - 2, 2);
+    HASH_Update(hash_context, plaintext_copy.data(), plaintext_copy.size());
+    uint8 digest[SHA1_LENGTH];
+    unsigned num_hash_bytes;
+    HASH_End(hash_context, digest, &num_hash_bytes, sizeof(digest));
+    HASH_Destroy(hash_context);
+
+    plaintext_copy += ByteString(digest, sizeof(digest));
+
+    fre[0] = prefix[kBlockSize];
+    fre[1] = prefix[kBlockSize+1];
+    unsigned out_used = 2;
+
+    for (size_t i = 0; i < plaintext_copy.size(); i++) {
+      if (out_used == kBlockSize) {
+        PK11_CipherOp(aes_context.get(), fre, &out_len, sizeof(fre), fre,
+                      AES_BLOCK_SIZE);
+        out_used = 0;
+      }
+
+      uint8 c = plaintext_copy[i] ^ fre[out_used];
+      fre[out_used++] = c;
+      packet.push_back(c);
+    }
+
+    return MakePacket(kSymmetricallyEncryptedTag, packet);
+  }
+};
+
+}  // anonymous namespace
+
+// static
+OpenPGPSymmetricEncrytion::Result OpenPGPSymmetricEncrytion::Decrypt(
+    base::StringPiece encrypted,
+    base::StringPiece passphrase,
+    std::string *out) {
+  Decrypter decrypter;
+
+  base::StringPiece result;
+  Result reader = decrypter.Decrypt(encrypted, passphrase, &result);
+  if (reader == OK)
+    *out = result.as_string();
+  return reader;
+}
+
+// static
+std::string OpenPGPSymmetricEncrytion::Encrypt(
+    base::StringPiece plaintext,
+    base::StringPiece passphrase) {
+  Encrypter::ByteString b =
+      Encrypter::Encrypt(plaintext, passphrase);
+  return std::string(reinterpret_cast<const char*>(b.data()), b.size());
+}
+
+}  // namespace crypto