Add in header fields for per-object encryption/authentication.

[bluesky.git] / bluesky / crypto.c

diff --git a/bluesky/crypto.c b/bluesky/crypto.c
index c40c15c..5b22357 100644 (file)
--- a/bluesky/crypto.c
+++ b/bluesky/crypto.c
@@ -7,6 +7,7 @@
  */
 
 #include <stdint.h>
+#include <assert.h>
 #include <errno.h>
 #include <pthread.h>
 #include <glib.h>
@@ -15,12 +16,12 @@
 
 #include "bluesky-private.h"
 
-static int DISABLE_CRYPTO = 1;
-
 /* Cryptographic operations.  The rest of the BlueSky code merely calls into
  * 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()
@@ -43,19 +44,30 @@ void bluesky_crypt_random_bytes(guchar *buf, gint len)
     gcry_randomize(buf, len, GCRY_STRONG_RANDOM);
 }
 
+/* Hash a string down to an encryption key. */
+void bluesky_crypt_hash_key(const char *keystr, uint8_t *out)
+{
+    guint8 raw_csum[32];
+    gsize csum_len = sizeof(raw_csum);
+
+    assert(CRYPTO_KEY_SIZE == 16);
+
+    GChecksum *csum = g_checksum_new(G_CHECKSUM_SHA256);
+    g_checksum_update(csum, (const guchar *)keystr, strlen(keystr));
+    g_checksum_get_digest(csum, raw_csum, &csum_len);
+    g_checksum_free(csum);
+
+    memcpy(out, raw_csum, CRYPTO_KEY_SIZE);
+}
+
 /* Encrypt a data block. */
 BlueSkyRCStr *bluesky_crypt_encrypt(BlueSkyRCStr *in, const uint8_t *key)
 {
-    if (DISABLE_CRYPTO) {
-        bluesky_string_ref(in);
-        return in;
-    }
-
     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));
@@ -70,7 +82,7 @@ BlueSkyRCStr *bluesky_crypt_encrypt(BlueSkyRCStr *in, const uint8_t *key)
     }
 
     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));
@@ -91,18 +103,13 @@ BlueSkyRCStr *bluesky_crypt_encrypt(BlueSkyRCStr *in, const uint8_t *key)
 /* Decrypt a data block. */
 BlueSkyRCStr *bluesky_crypt_decrypt(BlueSkyRCStr *in, const uint8_t *key)
 {
-    if (DISABLE_CRYPTO) {
-        bluesky_string_ref(in);
-        return in;
-    }
-
     gcry_error_t status;
     gcry_cipher_hd_t handle;
 
     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));
@@ -116,7 +123,7 @@ BlueSkyRCStr *bluesky_crypt_decrypt(BlueSkyRCStr *in, const uint8_t *key)
                 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));
@@ -132,5 +139,5 @@ BlueSkyRCStr *bluesky_crypt_decrypt(BlueSkyRCStr *in, const uint8_t *key)
 
     gcry_cipher_close(handle);
 
-    return bluesky_string_new(out, in->len + CRYPTO_BLOCK_SIZE);
+    return bluesky_string_new(out, in->len - CRYPTO_BLOCK_SIZE);
 }