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hmac: HKDF refactory to reduce stack usage: (up to 128 bytes - pointer sizes) moved to the heap.

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--- tmp variable moved to the heap; (up to 64 bytes)
--- prk variable moved to the heap; (up to 64 bytes)
This commit is contained in:
Moisés Guimarães 2014-04-21 11:31:42 -03:00
parent d7e5b604f5
commit 6d0fbfe7e9
1 changed files with 32 additions and 26 deletions
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58
ctaocrypt/src/hmac.c
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@ -732,8 +732,13 @@ int HKDF(int type, const byte* inKey, word32 inKeySz,
byte* out, word32 outSz)
{
Hmac myHmac;
#ifdef CYASSL_SMALL_STACK
byte* tmp;
byte* prk;
#else
byte tmp[MAX_DIGEST_SIZE]; /* localSalt helper and T */
byte prk[MAX_DIGEST_SIZE];
#endif
const byte* localSalt; /* either points to user input or tmp */
int hashSz = GetHashSizeByType(type);
word32 outIdx = 0;
@ -743,6 +748,18 @@ int HKDF(int type, const byte* inKey, word32 inKeySz,
if (hashSz < 0)
return BAD_FUNC_ARG;
#ifdef CYASSL_SMALL_STACK
tmp = (byte*)XMALLOC(MAX_DIGEST_SIZE, NULL, DYNAMIC_TYPE_TMP_BUFFER);
if (tmp == NULL)
return MEMORY_E;
prk = (byte*)XMALLOC(MAX_DIGEST_SIZE, NULL, DYNAMIC_TYPE_TMP_BUFFER);
if (prk == NULL) {
XFREE(tmp, NULL, DYNAMIC_TYPE_TMP_BUFFER);
return MEMORY_E;
}
#endif
localSalt = salt;
if (localSalt == NULL) {
XMEMSET(tmp, 0, hashSz);
@ -750,35 +767,19 @@ int HKDF(int type, const byte* inKey, word32 inKeySz,
saltSz = hashSz;
}
ret = HmacSetKey(&myHmac, type, localSalt, saltSz);
if (ret != 0)
return ret;
ret = HmacUpdate(&myHmac, inKey, inKeySz);
if (ret != 0)
return ret;
ret = HmacFinal(&myHmac, prk);
if (ret != 0)
return ret;
if ((ret = HmacSetKey(&myHmac, type, localSalt, saltSz)) == 0)
if ((ret = HmacUpdate(&myHmac, inKey, inKeySz)) == 0)
ret = HmacFinal(&myHmac, prk);
while (outIdx < outSz) {
while (ret == 0 && outIdx < outSz) {
int tmpSz = (n == 1) ? 0 : hashSz;
word32 left = outSz - outIdx;
ret = HmacSetKey(&myHmac, type, prk, hashSz);
if (ret != 0)
return ret;
ret = HmacUpdate(&myHmac, tmp, tmpSz);
if (ret != 0)
return ret;
ret = HmacUpdate(&myHmac, info, infoSz);
if (ret != 0)
return ret;
ret = HmacUpdate(&myHmac, &n, 1);
if (ret != 0)
return ret;
ret = HmacFinal(&myHmac, tmp);
if (ret != 0)
return ret;
if ((ret = HmacSetKey(&myHmac, type, prk, hashSz)) == 0)
if ((ret = HmacUpdate(&myHmac, tmp, tmpSz)) == 0)
if ((ret = HmacUpdate(&myHmac, info, infoSz)) == 0)
if ((ret = HmacUpdate(&myHmac, &n, 1)) == 0)
ret = HmacFinal(&myHmac, tmp);
left = min(left, (word32)hashSz);
XMEMCPY(out+outIdx, tmp, left);
@ -787,7 +788,12 @@ int HKDF(int type, const byte* inKey, word32 inKeySz,
n++;
}
return 0;
#ifdef CYASSL_SMALL_STACK
XFREE(tmp, NULL, DYNAMIC_TYPE_TMP_BUFFER);
XFREE(prk, NULL, DYNAMIC_TYPE_TMP_BUFFER);
#endif
return ret;
}
#endif /* HAVE_HKDF */