Problem - Kevin Tafuro

These two functions erase the key from memory before exiting. You
may want to have them erase the plaintext as well.
Here’s the implementation of the above interface:
#include
#include
unsigned char *spc_cbc_encrypt(unsigned char *key, size_t kl, unsigned char *iv,
unsigned char *in, size_t il, size_t *ol) {
SPC_CBC_CTX ctx;
size_t tmp;
unsigned char *result;
if (!(result = (unsigned char *)malloc(((il / SPC_BLOCK_SZ) * SPC_BLOCK_SZ) +
SPC_BLOCK_SZ))) return 0;
spc_cbc_encrypt_init(&ctx, key, kl, iv);
spc_cbc_encrypt_update(&ctx, in, il, result, &tmp);
spc_cbc_encrypt_final(&ctx, result+tmp, ol);
*ol += tmp;
return result;
}
unsigned char *spc_cbc_decrypt(unsigned char *key, size_t kl, unsigned char *iv,
unsigned char *in, size_t il, size_t *ol) {
int success;
size_t tmp;
SPC_CBC_CTX ctx;
unsigned char *result;
if (!(result = (unsigned char *)malloc(il))) return 0;
spc_cbc_decrypt_init(&ctx, key, kl, iv);
spc_cbc_decrypt_update(&ctx, in, il, result, &tmp);
if (!(success = spc_cbc_decrypt_final(&ctx, result+tmp, ol))) {
*ol = 0;
spc_memset(result, 0, il);
free(result);
return 0;
}
*ol += tmp;
result = (unsigned char *)realloc(result, *ol);
return result;
}
Note that this code depends on the SPC_CBC_CTX data type, as well as the incremental
CBC interface, neither of which we have yet discussed.
SPC_CBC_CTX data type
Let’s look at the SPC_CBC_CTX data type. It’s defined as:
178 | Chapter 5: Symmetric Encryption
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