Reputation: 13
For some reason, I am getting 0 from EVP_DecryptUpdate() function when I am passing 32 as its last parameter but when I changed it to 64 it returns 1. The buffer size is 32.
According to the documentation, I should get a 1 if the decrypt is successful.
#include <openssl/evp.h>
#include <stdio.h>
#include <string.h>
void dump_head(unsigned char *buf, size_t len)
{
unsigned end, i;
for (end = len; end > 0; end--)
if (buf[end-1] != 0)
break;
printf("buf = {");
for (i = 0; i < end; i++)
printf(" %02hhx,", buf[i]);
printf(" }\n");
}
int main(void)
{
unsigned char key[] = "0123456789abcdef";
unsigned char iv[] = "1234567887654321";
unsigned char indata[32] = "0123456789abcdeffedcba9876543210";
unsigned char buf[4096];
unsigned pos;
int cipher_len;
EVP_CIPHER_CTX *ctx;
ctx = EVP_CIPHER_CTX_new();
EVP_CIPHER_CTX_init(ctx);
EVP_CIPHER_CTX_set_padding(ctx, 0);
EVP_CIPHER_CTX_set_flags(ctx, EVP_CIPHER_CTX_FLAG_WRAP_ALLOW);
printf("decrypt init: %d\n", EVP_DecryptInit_ex(ctx, EVP_aes_256_wrap_pad(), NULL, key, iv));
printf("decrypt update: %d\n", EVP_DecryptUpdate(ctx, (unsigned char *)buf, &cipher_len, indata, 32));
printf("Got %d\n", cipher_len);
dump_head(buf, sizeof(buf));
printf("Final!\n");
memset(buf, 0, sizeof(buf));
EVP_DecryptFinal_ex(ctx, buf, &cipher_len);
printf("Got %d\n", cipher_len);
dump_head(buf, sizeof(buf));
return 0;
}
In both cases, I am getting cipher_len as 0. Are there some parameters I am missing?
Upvotes: 0
Views: 1176