Update on feedback, update dbus API, add unit tests. TEST=manual,unit,BVT BUG=3628 323

crypto.cc

+// Copyright (c) 2009-2010 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Contains the implementation of class Crypto
+
+#include "crypto.h"
+
+#include <openssl/err.h>
+#include <openssl/evp.h>
+#include <openssl/rand.h>
+#include <openssl/sha.h>
+
+#include <base/file_util.h>
+#include <base/logging.h>
+#include <chromeos/utility.h>
+
+#include "cryptohome_common.h"
+#include "platform.h"
+#include "username_passkey.h"
+
+// Included last because it has conflicting defines
+extern "C" {
+#include <ecryptfs.h>
+}
+
+using std::string;
+
+namespace cryptohome {
+
+const std::string kDefaultEntropySource = "/dev/urandom";
+const std::string kOpenSSLMagic = "Salted__";
+
+Crypto::Crypto()
+    : entropy_source_(kDefaultEntropySource) {
+}
+
+Crypto::~Crypto() {
+}
+
+void Crypto::GetSecureRandom(unsigned char *rand, int length) const {
+  // TODO(fes): Get assistance from the TPM when it is available
+  // Seed the OpenSSL random number generator until it is happy
+  while (!RAND_status()) {
+    char buffer[256];
+    file_util::ReadFile(FilePath(entropy_source_), buffer, sizeof(buffer));
+    RAND_add(buffer, sizeof(buffer), sizeof(buffer));
+  }
+
+  // Have OpenSSL generate the random bytes
+  RAND_bytes(rand, length);
+}
+
+bool Crypto::UnwrapVaultKeyset(const chromeos::Blob& wrapped_keyset,
+                               const chromeos::Blob& vault_wrapper,
+                               VaultKeyset* vault_keyset) const {
+  unsigned int header_size = kOpenSSLMagic.length() + PKCS5_SALT_LEN;
+
+  if (wrapped_keyset.size() < header_size) {
+    LOG(ERROR) << "Master key file too short";
+    return false;
+  }
+
+  // Grab the salt used in converting the passkey to a key (OpenSSL
+  // passkey-encrypted files have the format:
+  // Salted__<8-byte-salt><ciphertext>)
+  unsigned char salt[PKCS5_SALT_LEN];
+  memcpy(salt, &wrapped_keyset[kOpenSSLMagic.length()], PKCS5_SALT_LEN);
+
+  unsigned char wrapper_key[EVP_MAX_KEY_LENGTH];
+  unsigned char iv[EVP_MAX_IV_LENGTH];
+
+  // Convert the passkey to a key encryption key
+  if (!EVP_BytesToKey(EVP_aes_256_cbc(), EVP_sha1(), salt, &vault_wrapper[0],
+                          vault_wrapper.size(), 1, wrapper_key, iv)) {
+    LOG(ERROR) << "Failure converting bytes to key";
+    return false;
+  }
+
+  int cipher_text_size = wrapped_keyset.size() - header_size;
+  SecureBlob plain_text(cipher_text_size);
+
+  int final_size = 0;
+  int decrypt_size = plain_text.size();
+
+  // Do the actual decryption
+  EVP_CIPHER_CTX d_ctx;
+  EVP_CIPHER_CTX_init(&d_ctx);
+  EVP_DecryptInit_ex(&d_ctx, EVP_aes_256_ecb(), NULL, wrapper_key, iv);
+  if (!EVP_DecryptUpdate(&d_ctx, &plain_text[0], &decrypt_size,
+                        &wrapped_keyset[header_size],
+                        cipher_text_size)) {
+    LOG(ERROR) << "DecryptUpdate failed";
+    return false;
+  }
+  if (!EVP_DecryptFinal_ex(&d_ctx, &plain_text[decrypt_size], &final_size)) {
+    unsigned long err = ERR_get_error();
+    ERR_load_ERR_strings();
+    ERR_load_crypto_strings();
+
+    LOG(ERROR) << "DecryptFinal Error: " << err
+               << ": " << ERR_lib_error_string(err)
+               << ", " << ERR_func_error_string(err)
+               << ", " << ERR_reason_error_string(err);
+
+    return false;
+  }
+  final_size += decrypt_size;
+
+  plain_text.resize(final_size);
+
+  if (plain_text.size() != VaultKeyset::SerializedSize()) {
+    LOG(ERROR) << "Plain text was not the correct size: " << plain_text.size()
+               << ", expected: " << VaultKeyset::SerializedSize();
+    return false;
+  }
+
+  (*vault_keyset).AssignBuffer(plain_text);
+  return true;
+}
+
+bool Crypto::WrapVaultKeyset(const VaultKeyset& vault_keyset,
+                             const SecureBlob& vault_wrapper,
+                             const SecureBlob& vault_wrapper_salt,
+                             SecureBlob* wrapped_keyset) const {
+  unsigned char wrapper_key[EVP_MAX_KEY_LENGTH];
+  unsigned char iv[EVP_MAX_IV_LENGTH];
+
+  if (vault_wrapper_salt.size() < PKCS5_SALT_LEN) {
+    LOG(ERROR) << "Vault wrapper salt was not the correct length";
+    return false;
+  }
+
+  // Convert the passkey wrapper to a key encryption key
+  if (!EVP_BytesToKey(EVP_aes_256_cbc(), EVP_sha1(), &vault_wrapper_salt[0],
+                      &vault_wrapper[0], vault_wrapper.size(), 1,
+                      wrapper_key, iv)) {
+    LOG(ERROR) << "Failure converting bytes to key";
+    return false;
+  }
+
+  SecureBlob keyset_blob;
+  if (!vault_keyset.ToBuffer(&keyset_blob)) {
+    LOG(ERROR) << "Failure serializing keyset to buffer";
+    return false;
+  }
+
+  // Store the salt and encrypt the master key
+  unsigned int header_size = kOpenSSLMagic.length() + PKCS5_SALT_LEN;
+  SecureBlob cipher_text(header_size
+                         + keyset_blob.size()
+                         + EVP_CIPHER_block_size(EVP_aes_256_ecb()));
+  memcpy(&cipher_text[0], kOpenSSLMagic.c_str(), kOpenSSLMagic.length());
+  memcpy(&cipher_text[kOpenSSLMagic.length()], vault_wrapper_salt.const_data(),
+         PKCS5_SALT_LEN);
+
+  int current_size = header_size;
+  int encrypt_size = 0;
+  EVP_CIPHER_CTX e_ctx;
+  EVP_CIPHER_CTX_init(&e_ctx);
+
+  // Encrypt the keyset
+  EVP_EncryptInit_ex(&e_ctx, EVP_aes_256_ecb(), NULL, wrapper_key, iv);
+  if (!EVP_EncryptUpdate(&e_ctx, &cipher_text[current_size], &encrypt_size,
+                         &keyset_blob[0],
+                         keyset_blob.size())) {
+    LOG(ERROR) << "EncryptUpdate failed";
+    chromeos::SecureMemset(wrapper_key, 0, sizeof(wrapper_key));
+    return false;
+  }
+  current_size += encrypt_size;
+  encrypt_size = 0;
+
+  // Finish the encryption
+  if (!EVP_EncryptFinal_ex(&e_ctx, &cipher_text[current_size], &encrypt_size)) {
+    LOG(ERROR) << "EncryptFinal failed";
+    chromeos::SecureMemset(wrapper_key, 0, sizeof(wrapper_key));
+    return false;
+  }
+  current_size += encrypt_size;
+  cipher_text.resize(current_size);
+
+  chromeos::SecureMemset(wrapper_key, 0, sizeof(wrapper_key));
+
+  wrapped_keyset->swap(cipher_text);
+  return true;
+}
+
+void Crypto::PasskeyToWrapper(const chromeos::Blob& passkey,
+                              const chromeos::Blob& salt, int iters,
+                              SecureBlob* wrapper) const {
+  // TODO(fes): Update this when TPM support is available, or use a memory-
+  // bound strengthening algorithm.
+  int update_length = passkey.size();
+  int holder_size = SHA_DIGEST_LENGTH;
+  if (update_length > SHA_DIGEST_LENGTH) {
+    holder_size = update_length;
+  }
+  SecureBlob holder(holder_size);
+  memcpy(&holder[0], &passkey[0], update_length);
+
+  // Repeatedly hash the user passkey and salt to generate the wrapper
+  for (int i = 0; i < iters; ++i) {
+    SHA_CTX ctx;
+    unsigned char md_value[SHA_DIGEST_LENGTH];
+
+    SHA1_Init(&ctx);
+    SHA1_Update(&ctx, &salt[0], salt.size());
+    SHA1_Update(&ctx, &holder[0], update_length);
+    SHA1_Final(md_value, &ctx);
+
+    memcpy(&holder[0], md_value, SHA_DIGEST_LENGTH);
+    update_length = SHA_DIGEST_LENGTH;
+  }
+
+  holder.resize(update_length);
+  SecureBlob local_wrapper(update_length * 2);
+  AsciiEncodeToBuffer(holder, static_cast<char*>(local_wrapper.data()),
+                      local_wrapper.size());
+  wrapper->swap(local_wrapper);
+}
+
+bool Crypto::GetOrCreateSalt(const FilePath& path, int length, bool force,
+                             SecureBlob* salt) const {
+  SecureBlob local_salt;
+  if (force || !file_util::PathExists(path)) {
+    // If this salt doesn't exist, automatically create it
+    local_salt.resize(length);
+    GetSecureRandom(static_cast<unsigned char*>(local_salt.data()),
+                    local_salt.size());
+    int data_written = file_util::WriteFile(path,
+        static_cast<const char*>(local_salt.const_data()),
+        length);
+    if (data_written != length) {
+      LOG(ERROR) << "Could not write user salt";
+      return false;
+    }
+  } else {
+    // Otherwise just load the contents of the salt
+    int64 file_size;
+    if (!file_util::GetFileSize(path, &file_size)) {
+      LOG(ERROR) << "Could not get size of " << path.value();
+      return false;
+    }
+    if (file_size > INT_MAX) {
+      LOG(ERROR) << "File " << path.value() << " is too large: " << file_size;
+      return false;
+    }
+    local_salt.resize(file_size);
+    int data_read = file_util::ReadFile(path,
+                                        static_cast<char*>(local_salt.data()),
+                                        local_salt.size());
+    if (data_read != file_size) {
+      LOG(ERROR) << "Could not read entire file " << file_size;
+      return false;
+    }
+  }
+  salt->swap(local_salt);
+  return true;
+}
+
+bool Crypto::AddKeyset(const VaultKeyset& vault_keyset,
+                       std::string* key_signature,
+                       std::string* fnek_signature) const {
+  // Add the FEK
+  *key_signature = chromeos::AsciiEncode(vault_keyset.FEK_SIG());
+  if (!PushVaultKey(vault_keyset.FEK(), *key_signature,
+                    vault_keyset.FEK_SALT())) {
+    LOG(ERROR) << "Couldn't add ecryptfs key to keyring";
+    return false;
+  }
+
+  // Add the FNEK
+  *fnek_signature = chromeos::AsciiEncode(vault_keyset.FNEK_SIG());
+  if (!PushVaultKey(vault_keyset.FNEK(), *fnek_signature,
+                    vault_keyset.FNEK_SALT())) {
+    LOG(ERROR) << "Couldn't add ecryptfs fnek key to keyring";
+    return false;
+  }
+
+  return true;
+}
+
+void Crypto::ClearKeyset() const {
+  Platform::ClearUserKeyring();
+}
+
+bool Crypto::PushVaultKey(const SecureBlob& key, const std::string& key_sig,
+                          const SecureBlob& salt) const {
+  DCHECK(key.size() == ECRYPTFS_MAX_KEY_BYTES);
+  DCHECK(key_sig.length() == (ECRYPTFS_SIG_SIZE * 2));
+  DCHECK(salt.size() == ECRYPTFS_SALT_SIZE);
+
+  struct ecryptfs_auth_tok auth_token;
+
+  generate_payload(&auth_token, const_cast<char*>(key_sig.c_str()),
+                   const_cast<char*>(reinterpret_cast<const char*>(&salt[0])),
+                   const_cast<char*>(reinterpret_cast<const char*>(&key[0])));
+
+  if (ecryptfs_add_auth_tok_to_keyring(&auth_token,
+      const_cast<char*>(key_sig.c_str())) < 0) {
+    LOG(ERROR) << "PushVaultKey failed";
+  }
+
+  return true;
+}
+
+void Crypto::PasswordToPasskey(const char *password,
+                               const chromeos::Blob& salt,
+                               SecureBlob* passkey) {
+  CHECK(password);
+
+  std::string ascii_salt = chromeos::AsciiEncode(salt);
+  // Convert a raw password to a password hash
+  SHA256_CTX sha_ctx;
+  SecureBlob md_value(SHA256_DIGEST_LENGTH);
+
+  SHA256_Init(&sha_ctx);
+  SHA256_Update(&sha_ctx,
+                reinterpret_cast<const unsigned char*>(ascii_salt.data()),
+                static_cast<unsigned int>(ascii_salt.length()));
+  SHA256_Update(&sha_ctx, password, strlen(password));
+  SHA256_Final(static_cast<unsigned char*>(md_value.data()), &sha_ctx);
+
+  md_value.resize(SHA256_DIGEST_LENGTH / 2);
+  SecureBlob local_passkey(SHA256_DIGEST_LENGTH);
+  AsciiEncodeToBuffer(md_value, static_cast<char*>(local_passkey.data()),
+                      local_passkey.size());
+  passkey->swap(local_passkey);
+}
+
+void Crypto::AsciiEncodeToBuffer(const chromeos::Blob& blob, char* buffer,
+                                 int buffer_length) {
+  const char hex_chars[] = "0123456789abcdef";
+  int i = 0;
+  for (chromeos::Blob::const_iterator it = blob.begin();
+      it < blob.end() && (i + 1) < buffer_length; ++it) {
+    buffer[i++] = hex_chars[((*it) >> 4) & 0x0f];
+    buffer[i++] = hex_chars[(*it) & 0x0f];
+  }
+  if (i < buffer_length) {
+    buffer[i] = '\0';
+  }
+}
+
+} // namespace cryptohome