HMAC_Init_ex Corrupting Stack Space - c

Question

I'm trying to create a SHA256 hash with a key using OpenSSL's HMAC functions. My stack keeps getting corrupted (every value set to 0) after I call HMAC_Init_ex. I'm using Xcode and running OS X 10.8.5. Running "openssl version" in my terminal outputs "OpenSSL 0.9.8y 5 Feb 2013".
Here is my function and all my #includes:
#include <stdio.h>
#include <openssl/hmac.h>
char* hash(char *str, char* key){
int inputLen = strlen(str);
int keyLen = strlen(key);
HMAC_CTX ctx;
HMAC_CTX_init(&ctx);
HMAC_Init_ex(&ctx, key, keyLen, EVP_sha256(), NULL); // Everything is fine up to here.
HMAC_Update(&ctx, str, inputLen); // By the time this line runs, str and key are NULL, and inputLen and keyLen are 0.
char* ret = malloc(65*sizeof(char));
HMAC_Final(&ctx, ret, 65);
HMAC_CTX_cleanup(&ctx);
ret[65] = '\0';
return ret;
}
This code should be working. It probably has something to do with my libraries, but I don't know what. Did I do something wrong when importing the libraries?
Update:
I found an example from here that uses the fully encapsulated hmac function and says that this is essentially the same as what I was doing before, and strangely, it works. So I have circumvented my problem, but you could still answer in case it helps somebody else. Except it's probably some weird, specific issue with my libraries. The working function:
char* hash(char *str, char* key){
int inputLen = strlen(str);
int keyLen = strlen(key);
unsigned int retLen = 65;
char* ret = emalloc(retLen*sizeof(char));
ret = HMAC(EVP_sha256(), key, keyLen, (unsigned char*)str, inputLen, NULL, NULL);
return ret;
}

Answer 1

You missed OpenSSL/Initialization.The ENGINE or ssh config provides you with the cipher methods, digest methods, etc.
#include <openssl/engine.h>
#include <openssl/hmac.h>
HMAC_CTX ctx;
result = (unsigned char*) malloc(sizeof(char) * result_len);
ENGINE_load_builtin_engines();
ENGINE_register_all_complete();
HMAC_CTX_init(&ctx);
HMAC_Init_ex(&ctx, key, 16, EVP_sha256(), NULL);
HMAC_Update(&ctx, data, 8);
HMAC_Final(&ctx, result, &result_len);
HMAC_CTX_cleanup(&ctx);

Answer 2

use [ssh -Version] get openssl version,when the version less than 1.0.1e, should use HMAC_Init... instead of HMAC_Init_ex...
in version 1.0.1e, the implement of HMAC like this
unsigned char *HMAC(const EVP_MD *evp_md, const void *key, int key_len,const unsigned char *d, size_t n, unsigned char *md,unsigned int *md_len)
{
HMAC_CTX c;
static unsigned char m[EVP_MAX_MD_SIZE];
if (md == NULL) md=m;
HMAC_CTX_init(&c);
if (!HMAC_Init(&c,key,key_len,evp_md))
goto err;
if (!HMAC_Update(&c,d,n))
goto err;
if (!HMAC_Final(&c,md,md_len))
goto err;
HMAC_CTX_cleanup(&c);
return md;
err:
return NULL;
}
you can compare the HMAC() API in the later version of openssl