* the functions in this file, so this is the only point where we interface
* with an external cryptographic library. */
+/* TODO: We ought to switch to an authenticated encryption mode like EAX. */
+
GCRY_THREAD_OPTION_PTHREAD_IMPL;
void bluesky_crypt_init()
memcpy(out, raw_csum, CRYPTO_KEY_SIZE);
}
+/* Compute an HMAC of a given data block with the given key. The key and
+ * output should both as large as the hash output size. */
+#define MD_ALGO GCRY_MD_SHA256
+void bluesky_crypt_hmac(const char *buf, size_t bufsize,
+ const uint8_t key[CRYPTO_HASH_SIZE],
+ uint8_t output[CRYPTO_HASH_SIZE])
+{
+ gcry_error_t status;
+ gcry_md_hd_t handle;
+
+ g_assert(gcry_md_get_algo_dlen(MD_ALGO) == CRYPTO_HASH_SIZE);
+
+ status = gcry_md_open(&handle, MD_ALGO, GCRY_MD_FLAG_HMAC);
+ if (status) {
+ g_error("gcrypt error setting up message digest: %s\n",
+ gcry_strerror(status));
+ g_assert(FALSE);
+ }
+
+ status = gcry_md_setkey(handle, key, CRYPTO_HASH_SIZE);
+ if (status) {
+ g_error("gcrypt error setting HMAC key: %s\n",
+ gcry_strerror(status));
+ g_assert(FALSE);
+ }
+
+ gcry_md_write(handle, buf, bufsize);
+
+ unsigned char *digest = gcry_md_read(handle, MD_ALGO);
+ memcpy(output, digest, CRYPTO_HASH_SIZE);
+
+ gcry_md_close(handle);
+}
+
+void bluesky_crypt_derive_keys(BlueSkyCryptKeys *keys, const gchar *master)
+{
+ uint8_t outbuf[CRYPTO_HASH_SIZE];
+
+ const char *key_type = "ENCRYPT";
+ bluesky_crypt_hmac(key_type, strlen(key_type),
+ (const uint8_t *)master, outbuf);
+ memcpy(keys->encryption_key, outbuf, sizeof(keys->encryption_key));
+
+ key_type = "AUTH";
+ bluesky_crypt_hmac(key_type, strlen(key_type),
+ (const uint8_t *)master, outbuf);
+ memcpy(keys->authentication_key, outbuf, sizeof(keys->authentication_key));
+}
+
+void bluesky_crypt_block_encrypt(gchar *cloud_block, size_t len,
+ BlueSkyCryptKeys *keys)
+{
+ gcry_error_t status;
+ gcry_cipher_hd_t handle;
+
+ status = gcry_cipher_open(&handle, GCRY_CIPHER_AES, GCRY_CIPHER_MODE_CTR,
+ 0);
+ if (status) {
+ g_error("gcrypt error setting up encryption: %s\n",
+ gcry_strerror(status));
+ }
+
+ struct cloudlog_header *header = (struct cloudlog_header *)cloud_block;
+ g_assert(memcmp(header->magic, CLOUDLOG_MAGIC, sizeof(header->magic)) == 0);
+
+ gcry_cipher_setkey(handle, keys->encryption_key, CRYPTO_KEY_SIZE);
+ if (status) {
+ g_error("gcrypt error setting key: %s\n",
+ gcry_strerror(status));
+ }
+
+ bluesky_crypt_random_bytes(header->crypt_iv, sizeof(header->crypt_iv));
+ status = gcry_cipher_setctr(handle, header->crypt_iv,
+ sizeof(header->crypt_iv));
+ if (status) {
+ g_error("gcrypt error setting IV: %s\n",
+ gcry_strerror(status));
+ }
+
+ status = gcry_cipher_encrypt(handle,
+ cloud_block + sizeof(struct cloudlog_header),
+ GUINT32_FROM_LE(header->size1),
+ NULL, 0);
+ if (status) {
+ g_error("gcrypt error encrypting: %s\n",
+ gcry_strerror(status));
+ }
+
+ bluesky_crypt_hmac((char *)&header->crypt_iv,
+ cloud_block + len - (char *)&header->crypt_iv,
+ keys->authentication_key,
+ header->crypt_auth);
+}
+
+#if 0
/* Encrypt a data block. */
BlueSkyRCStr *bluesky_crypt_encrypt(BlueSkyRCStr *in, const uint8_t *key)
{
gcry_error_t status;
gcry_cipher_hd_t handle;
- status = gcry_cipher_open(&handle, GCRY_CIPHER_AES, GCRY_CIPHER_MODE_CBC,
- GCRY_CIPHER_CBC_CTS);
+ status = gcry_cipher_open(&handle, GCRY_CIPHER_AES, GCRY_CIPHER_MODE_CTR,
+ 0);
if (status) {
g_error("gcrypt error setting up encryption: %s\n",
gcry_strerror(status));
}
bluesky_crypt_random_bytes(out, CRYPTO_BLOCK_SIZE);
- status = gcry_cipher_setiv(handle, out, CRYPTO_BLOCK_SIZE);
+ status = gcry_cipher_setctr(handle, out, CRYPTO_BLOCK_SIZE);
if (status) {
g_error("gcrypt error setting IV: %s\n",
gcry_strerror(status));
g_return_val_if_fail(in->len > CRYPTO_BLOCK_SIZE, NULL);
- status = gcry_cipher_open(&handle, GCRY_CIPHER_AES, GCRY_CIPHER_MODE_CBC,
- GCRY_CIPHER_CBC_CTS);
+ status = gcry_cipher_open(&handle, GCRY_CIPHER_AES, GCRY_CIPHER_MODE_CTR,
+ 0);
if (status) {
g_error("gcrypt error setting up encryption: %s\n",
gcry_strerror(status));
gcry_strerror(status));
}
- status = gcry_cipher_setiv(handle, in->data, CRYPTO_BLOCK_SIZE);
+ status = gcry_cipher_setctr(handle, in->data, CRYPTO_BLOCK_SIZE);
if (status) {
g_error("gcrypt error setting IV: %s\n",
gcry_strerror(status));
gcry_cipher_close(handle);
- return bluesky_string_new(out, in->len + CRYPTO_BLOCK_SIZE);
+ return bluesky_string_new(out, in->len - CRYPTO_BLOCK_SIZE);
}
+#endif