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-rw-r--r--include/aes.h10
-rw-r--r--lib/aes.c28
2 files changed, 38 insertions, 0 deletions
diff --git a/include/aes.h b/include/aes.h
index d9bb387..4897e6f 100644
--- a/include/aes.h
+++ b/include/aes.h
@@ -63,4 +63,14 @@ void aes_decrypt(u8 *in, u8 *expkey, u8 *out);
*/
void aes_cbc_encrypt_blocks(u8 *key_exp, u8 *src, u8 *dst, u32 num_aes_blocks);
+/**
+ * Decrypt multiple blocks of data with AES CBC.
+ *
+ * @key_exp Expanded key to use
+ * @src Source data to decrypt
+ * @dst Destination buffer
+ * @num_aes_blocks Number of AES blocks to decrypt
+ */
+void aes_cbc_decrypt_blocks(u8 *key_exp, u8 *src, u8 *dst, u32 num_aes_blocks);
+
#endif /* _AES_REF_H_ */
diff --git a/lib/aes.c b/lib/aes.c
index a6648f9..9dadb22 100644
--- 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;
+ }
+}