aes: Implement AES-128-CBC decryption function

[karo-tx-uboot.git] / lib / aes.c

diff --git a/lib/aes.c b/lib/aes.c
index a6648f90db29f714ef52bab78eafecf0bcadbcaa..9dadb22c3ad9b6bb4e738b3b1e91bfd7db6fa846 100644 (file)
--- a/lib/aes.c
+++ b/lib/aes.c
@@ -632,3 +632,31 @@ void aes_cbc_encrypt_blocks(u8 *key_exp, u8 *src, u8 *dst, u32 num_aes_blocks)
                dst += AES_KEY_LENGTH;
        }
 }
+
+void aes_cbc_decrypt_blocks(u8 *key_exp, u8 *src, u8 *dst, u32 num_aes_blocks)
+{
+       u8 tmp_data[AES_KEY_LENGTH], tmp_block[AES_KEY_LENGTH];
+       /* Convenient array of 0's for IV */
+       u8 cbc_chain_data[AES_KEY_LENGTH] = { 0 };
+       u32 i;
+
+       for (i = 0; i < num_aes_blocks; i++) {
+               debug("encrypt_object: block %d of %d\n", i, num_aes_blocks);
+               debug_print_vector("AES Src", AES_KEY_LENGTH, src);
+
+               memcpy(tmp_block, src, AES_KEY_LENGTH);
+
+               /* Decrypt the AES block */
+               aes_decrypt(src, key_exp, tmp_data);
+               debug_print_vector("AES Xor", AES_KEY_LENGTH, tmp_data);
+
+               /* Apply the chain data */
+               apply_cbc_chain_data(cbc_chain_data, tmp_data, dst);
+               debug_print_vector("AES Dst", AES_KEY_LENGTH, dst);
+
+               /* Update pointers for next loop. */
+               memcpy(cbc_chain_data, tmp_block, AES_KEY_LENGTH);
+               src += AES_KEY_LENGTH;
+               dst += AES_KEY_LENGTH;
+       }
+}