hmac.c

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#include "darkplaces.h"
#include "hmac.h"
 
qbool hmac(
    hashfunc_t hfunc, int hlen, int hblock,
    unsigned char *out,
    const unsigned char *in, int n,
    const unsigned char *key, int k
)
{
    unsigned char hashbuf[32];
    unsigned char k_xor_ipad[128];
    unsigned char k_xor_opad[128];
    unsigned char *catbuf;
    int i;
 
    if(sizeof(hashbuf) < (size_t) hlen)
        return false;
    if(sizeof(k_xor_ipad) < (size_t) hblock)
        return false;
    if(sizeof(k_xor_ipad) < (size_t) hlen)
        return false;
 
    catbuf = (unsigned char *)Mem_Alloc(tempmempool, (size_t) hblock + max((size_t) hlen, (size_t) n));
 
    if(k > hblock)
    {
        // hash the key if it is too long
        hfunc(k_xor_opad, key, k);
        key = k_xor_opad;
        k = hlen;
    }
 
    if(k < hblock)
    {
        // zero pad the key if it is too short
        if(key != k_xor_opad)
            memcpy(k_xor_opad, key, k);
        for(i = k; i < hblock; ++i)
            k_xor_opad[i] = 0;
        key = k_xor_opad;
        k = hblock;
    }
 
    for(i = 0; i < hblock; ++i)
    {
        k_xor_ipad[i] = key[i] ^ 0x36;
        k_xor_opad[i] = key[i] ^ 0x5c;
    }
 
    memcpy(catbuf, k_xor_ipad, hblock);
    memcpy(catbuf + hblock, in, n);
    hfunc(hashbuf, catbuf, hblock + n);
    memcpy(catbuf, k_xor_opad, hblock);
    memcpy(catbuf + hblock, hashbuf, hlen);
    hfunc(out, catbuf, hblock + hlen);
 
    Mem_Free(catbuf);
 
    return true;
}