crypto-algorithms.c

commit b308d9f801c8c54c84edd0c0a18e0303fedd494d
parent 100f4ff91b5a5b31a84b3999365c3058df6251ea
Author: Brad Conte <brad@bradconte.com>
Date:   Sun, 26 Apr 2015 20:14:41 -0700

Add an AES CBC decryption function for completeness.

Diffstat:
M
aes.c
 | 
37
++++++++++++++++++++++++++++++-------
M
aes_test.c
 | 
11
++++++++++-

2 files changed, 40 insertions(+), 8 deletions(-)
diff --git a/aes.c b/aes.c
@@ -233,7 +233,7 @@ void xor_buf(const BYTE in[], BYTE out[], size_t len)
 *******************/
 int aes_encrypt_cbc(const BYTE in[], size_t in_len, BYTE out[], const WORD key[], int keysize, const BYTE iv[])
 {
-	BYTE buf_in[AES_BLOCK_SIZE], buf_out[AES_BLOCK_SIZE];
+	BYTE buf_in[AES_BLOCK_SIZE], buf_out[AES_BLOCK_SIZE], iv_buf[AES_BLOCK_SIZE];
 	int blocks, idx;
 
 	if (in_len % AES_BLOCK_SIZE != 0)
@@ -241,13 +241,14 @@ int aes_encrypt_cbc(const BYTE in[], size_t in_len, BYTE out[], const WORD key[]
 
 	blocks = in_len / AES_BLOCK_SIZE;
 
-	memcpy(buf_out, iv, AES_BLOCK_SIZE);
+	memcpy(iv_buf, iv, AES_BLOCK_SIZE);
 
 	for (idx = 0; idx < blocks; idx++) {
 		memcpy(buf_in, &in[idx * AES_BLOCK_SIZE], AES_BLOCK_SIZE);
-		xor_buf(buf_out, buf_in, AES_BLOCK_SIZE);
+		xor_buf(iv_buf, buf_in, AES_BLOCK_SIZE);
 		aes_encrypt(buf_in, buf_out, key, keysize);
 		memcpy(&out[idx * AES_BLOCK_SIZE], buf_out, AES_BLOCK_SIZE);
+		memcpy(iv_buf, buf_out, AES_BLOCK_SIZE);
 	}
 
 	return(TRUE);
@@ -255,7 +256,7 @@ int aes_encrypt_cbc(const BYTE in[], size_t in_len, BYTE out[], const WORD key[]
 
 int aes_encrypt_cbc_mac(const BYTE in[], size_t in_len, BYTE out[], const WORD key[], int keysize, const BYTE iv[])
 {
-	BYTE buf_in[AES_BLOCK_SIZE], buf_out[AES_BLOCK_SIZE];
+	BYTE buf_in[AES_BLOCK_SIZE], buf_out[AES_BLOCK_SIZE], iv_buf[AES_BLOCK_SIZE];
 	int blocks, idx;
 
 	if (in_len % AES_BLOCK_SIZE != 0)
@@ -263,12 +264,13 @@ int aes_encrypt_cbc_mac(const BYTE in[], size_t in_len, BYTE out[], const WORD k
 
 	blocks = in_len / AES_BLOCK_SIZE;
 
-	memcpy(buf_out, iv, AES_BLOCK_SIZE);
+	memcpy(iv_buf, iv, AES_BLOCK_SIZE);
 
 	for (idx = 0; idx < blocks; idx++) {
 		memcpy(buf_in, &in[idx * AES_BLOCK_SIZE], AES_BLOCK_SIZE);
-		xor_buf(buf_out, buf_in, AES_BLOCK_SIZE);
+		xor_buf(iv_buf, buf_in, AES_BLOCK_SIZE);
 		aes_encrypt(buf_in, buf_out, key, keysize);
+		memcpy(iv_buf, buf_out, AES_BLOCK_SIZE);
 		// Do not output all encrypted blocks.
 	}
 
@@ -277,7 +279,28 @@ int aes_encrypt_cbc_mac(const BYTE in[], size_t in_len, BYTE out[], const WORD k
 	return(TRUE);
 }
 
-// No need for an aes_decrypt_cbc() for just CCM.
+int aes_decrypt_cbc(const BYTE in[], size_t in_len, BYTE out[], const WORD key[], int keysize, const BYTE iv[])
+{
+	BYTE buf_in[AES_BLOCK_SIZE], buf_out[AES_BLOCK_SIZE], iv_buf[AES_BLOCK_SIZE];
+	int blocks, idx;
+
+	if (in_len % AES_BLOCK_SIZE != 0)
+		return(FALSE);
+
+	blocks = in_len / AES_BLOCK_SIZE;
+
+	memcpy(iv_buf, iv, AES_BLOCK_SIZE);
+
+	for (idx = 0; idx < blocks; idx++) {
+		memcpy(buf_in, &in[idx * AES_BLOCK_SIZE], AES_BLOCK_SIZE);
+		aes_decrypt(buf_in, buf_out, key, keysize);
+		xor_buf(iv_buf, buf_out, AES_BLOCK_SIZE);
+		memcpy(&out[idx * AES_BLOCK_SIZE], buf_out, AES_BLOCK_SIZE);
+		memcpy(iv_buf, buf_in, AES_BLOCK_SIZE);
+	}
+
+	return(TRUE);
+}
 
 /*******************
 * AES - CTR
diff --git a/aes_test.c b/aes_test.c
@@ -77,7 +77,7 @@ int aes_cbc_test()
 	BYTE plaintext[1][32] = {
 		{0x6b,0xc1,0xbe,0xe2,0x2e,0x40,0x9f,0x96,0xe9,0x3d,0x7e,0x11,0x73,0x93,0x17,0x2a,0xae,0x2d,0x8a,0x57,0x1e,0x03,0xac,0x9c,0x9e,0xb7,0x6f,0xac,0x45,0xaf,0x8e,0x51}
 	};
-	BYTE ciphertext[2][32] = {
+	BYTE ciphertext[1][32] = {
 		{0xf5,0x8c,0x4c,0x04,0xd6,0xe5,0xf1,0xba,0x77,0x9e,0xab,0xfb,0x5f,0x7b,0xfb,0xd6,0x9c,0xfc,0x4e,0x96,0x7e,0xdb,0x80,0x8d,0x67,0x9f,0x77,0x7b,0xc6,0x70,0x2c,0x7d}
 	};
 	BYTE iv[1][16] = {
@@ -105,6 +105,15 @@ int aes_cbc_test()
 	//print_hex(ciphertext[0], 32);
 	pass = pass && !memcmp(enc_buf, ciphertext[0], 32);
 
+	aes_decrypt_cbc(ciphertext[0], 32, enc_buf, key_schedule, 256, iv[0]);
+	//printf("\nCiphertext   : ");
+	//print_hex(ciphertext[0], 32);
+	//printf("\n-decrypted to: ");
+	//print_hex(enc_buf, 32);
+	//printf("\nPlaintext   : ");
+	//print_hex(plaintext[0], 32);
+	pass = pass && !memcmp(enc_buf, plaintext[0], 32);
+
 	//printf("\n\n");
 	return(pass);
 }