1 files changed, 45 insertions, 9 deletions

diff --git a/src/lib/libcrypto/aes/aes_ctr.c b/src/lib/libcrypto/aes/aes_ctr.c
index 59088499a0..79e1c18f19 100644
--- a/src/lib/libcrypto/aes/aes_ctr.c
+++ b/src/lib/libcrypto/aes/aes_ctr.c
@@ -62,19 +62,49 @@
 /* NOTE: CTR mode is big-endian.  The rest of the AES code
  * is endian-neutral. */
 
-/* increment counter (128-bit int) by 2^64 */
+/* increment counter (128-bit int) by 1 */
 static void AES_ctr128_inc(unsigned char *counter) {
         unsigned long c;
 
-        /* Grab 3rd dword of counter and increment */
+        /* Grab bottom dword of counter and increment */
 #ifdef L_ENDIAN
-        c = GETU32(counter + 8);
+        c = GETU32(counter +  0);
         c++;
-        PUTU32(counter + 8, c);
+        PUTU32(counter +  0, c);
 #else
-        c = GETU32(counter + 4);
+        c = GETU32(counter + 12);
         c++;
-        PUTU32(counter + 4, c);
+        PUTU32(counter + 12, c);
+#endif
+
+        /* if no overflow, we're done */
+        if (c)
+                return;
+
+        /* Grab 1st dword of counter and increment */
+#ifdef L_ENDIAN
+        c = GETU32(counter +  4);
+        c++;
+        PUTU32(counter +  4, c);
+#else
+        c = GETU32(counter +  8);
+        c++;
+        PUTU32(counter +  8, c);
+#endif
+
+        /* if no overflow, we're done */
+        if (c)
+                return;
+
+        /* Grab 2nd dword of counter and increment */
+#ifdef L_ENDIAN
+        c = GETU32(counter +  8);
+        c++;
+        PUTU32(counter +  8, c);
+#else
+        c = GETU32(counter +  4);
+        c++;
+        PUTU32(counter +  4, c);
 #endif
 
         /* if no overflow, we're done */
@@ -100,10 +130,16 @@ static void AES_ctr128_inc(unsigned char *counter) {
  * encrypted counter is kept in ecount_buf.  Both *num and
  * ecount_buf must be initialised with zeros before the first
  * call to AES_ctr128_encrypt().
+ *
+ * This algorithm assumes that the counter is in the x lower bits
+ * of the IV (ivec), and that the application has full control over
+ * overflow and the rest of the IV.  This implementation takes NO
+ * responsability for checking that the counter doesn't overflow
+ * into the rest of the IV when incremented.
  */
 void AES_ctr128_encrypt(const unsigned char *in, unsigned char *out,
         const unsigned long length, const AES_KEY *key,
-        unsigned char counter[AES_BLOCK_SIZE],
+        unsigned char ivec[AES_BLOCK_SIZE],
         unsigned char ecount_buf[AES_BLOCK_SIZE],
         unsigned int *num) {
 
@@ -117,8 +153,8 @@ void AES_ctr128_encrypt(const unsigned char *in, unsigned char *out,
 
         while (l--) {
                 if (n == 0) {
-                        AES_encrypt(counter, ecount_buf, key);
-                        AES_ctr128_inc(counter);
+                        AES_encrypt(ivec, ecount_buf, key);
+                        AES_ctr128_inc(ivec);
                 }
                 *(out++) = *(in++) ^ ecount_buf[n];
                 n = (n+1) % AES_BLOCK_SIZE;