Difference between code1 and code2

Question

code 1

uint8_t  ucAESKey_BASE64[] = "oFqTg0a0VrjiVU76M1WRVw==";
uint8_t *pucAESKey_BASE64;
pucAESKey_BASE64 = ucAESKey_BASE64;

code 2

uint8_t *pucAESKey_BASE64 = "oFqTg0a0VrjiVU76M1WRVw==";

I use mbedtls_base64_decode() to decode base64 string ,the API of mbedTLS.

int mbedtls_base64_decode( unsigned char *dst, size_t dlen, size_t *olen,
                   const unsigned char *src, size_t slen )

My program like this：

mbedtls_base64_decode(ucAESKey, sizeof(ucAESKey), &olen, 
                      pucAESKey_BASE64, strlen(pucAESKey_BASE64));

If the parameter *src use code 2 , the output is

00 00 00 83 46 b4 56 b8 e2 55 4e fa 33 55 91 57

if *src use code 1, the output is

a0 5a 93 83 46 b4 56 b8 e2 55 4e fa 33 55 91 57

and this is correct. Why?

Why are you using `strlen` on a buffer that is not `const char *`? — PaulMcKenzie, Apr 13 '17 at 06:27
Probably having problems because you are declaring one as an array and the other as not: uint8_t ucAESKey_BASE64[] = "oFqTg0a0VrjiVU76M1WRVw=="; uint8_t *pucAESKey_BASE64 = "oFqTg0a0VrjiVU76M1WRVw=="; Should be: uint8_t ucAESKey_BASE64 = "oFqTg0a0VrjiVU76M1WRVw=="; uint8_t *pucAESKey_BASE64 = "oFqTg0a0VrjiVU76M1WRVw=="; — Edward B., Apr 13 '17 at 06:30
Show the declarations and how `ucAESKey` and `olen` are initialized. — Michael Burr, Apr 13 '17 at 07:22
can you try with this: `char *pcaAESKey_BASE64 = "oFqTg0a0VrjiVU76M1WRVw==";` — Taha Paksu, Apr 13 '17 at 07:26
Usually it's the issue of [using `sizeof` with pointers](http://stackoverflow.com/q/492384/69809), expecting it to return the same as `strlen`. Is `ucAESKey` initialized the same way in both cases? — vgru, Apr 13 '17 at 08:00
It is highly unlikely that the exact thing you describe happens in reality. Please show a [mcve]. — n. m. could be an AI, Apr 13 '17 at 08:22

Ron Eldor · Answer 1 · 2018-03-28T07:27:03.563

Since the input of mbedtls_base64_decode() is a base64 string, it is ok to use strlen, as we don't expect any null character within the input. I have tried reproducing your issue, but both inputs generate the same output, so I assume your other inputs are different, as @n.m. suggests. I have tried the following:

int main( int argc, char *argv[] )
{
    unsigned char ucAESKey[32] = { 0 };
    size_t olen = 32;
    size_t i;
#if 0
    uint8_t  ucAESKey_BASE64[] = "oFqTg0a0VrjiVU76M1WRVw==";
    uint8_t *pucAESKey_BASE64;
    pucAESKey_BASE64 = ucAESKey_BASE64;
#else
    uint8_t *pucAESKey_BASE64 = "oFqTg0a0VrjiVU76M1WRVw==";
#endif
    mbedtls_base64_decode(ucAESKey, sizeof(ucAESKey), &olen,
                   pucAESKey_BASE64, strlen(pucAESKey_BASE64));

    for (i = 0; i < olen; i++)
    {
        mbedtls_printf("0x%x ", ucAESKey[i]); 
    }
return 0;
}

Difference between code1 and code2

1 Answers1