Implement a compatible AES-128-CBC decryption function as a counterpart of the encryption function pulled from tegra20-common/crypto.c .
Signed-off-by: Marek Vasut marex@denx.de --- include/aes.h | 10 ++++++++++ lib/aes.c | 28 ++++++++++++++++++++++++++++ 2 files changed, 38 insertions(+)
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; + } +}