Below is from crypto/evp/evp_key.c.
Notice that `addmd` is never set to 1. *If* the routine needs to loop
back to the top to finish fulfilling a derivation request, then the
previous hash is *not* added back into the computation. That is, this
is never executed:
if (addmd++)
if (!EVP_DigestUpdate(c,(md_buf[0]),mds))
I believe that means the same bit pattern repeats. If MD5 is the
underlying hash (which appears to be used fairly regularly), then the
bits repeat after 16 bytes.
Also, the early out from `if (data == NULL) return(nkey);` should
probably return something other than a successful result. Since
nothing was derived, the function should return 0; and not nkey.
*
int EVP_BytesToKey(const EVP_CIPHER *type, const EVP_MD *md,
const unsigned char *salt, const unsigned char
*data, int datal,
int count, unsigned char *key, unsigned char *iv)
{
EVP_MD_CTX c;
unsigned char md_buf[EVP_MAX_MD_SIZE];
int niv,nkey,addmd=0;
unsigned int mds=0,i;
int rv = 0;
nkey=type-key_len;
niv=type-iv_len;
OPENSSL_assert(nkey = EVP_MAX_KEY_LENGTH);
OPENSSL_assert(niv = EVP_MAX_IV_LENGTH);
if (data == NULL) return(nkey);
EVP_MD_CTX_init(c);
for (;;)
{
if (!EVP_DigestInit_ex(c,md, NULL))
return 0;
if (addmd++)
if (!EVP_DigestUpdate(c,(md_buf[0]),mds))
goto err;
if (!EVP_DigestUpdate(c,data,datal))
goto err;
if (salt != NULL)
if (!EVP_DigestUpdate(c,salt,PKCS5_SALT_LEN))
goto err;
if (!EVP_DigestFinal_ex(c,(md_buf[0]),mds))
goto err;
for (i=1; i(unsigned int)count; i++)
{
if (!EVP_DigestInit_ex(c,md, NULL))
goto err;
if (!EVP_DigestUpdate(c,(md_buf[0]),mds))
goto err;
if (!EVP_DigestFinal_ex(c,(md_buf[0]),mds))
goto err;
}
i=0;
if (nkey)
{
for (;;)
{
if (nkey == 0) break;
if (i == mds) break;
if (key != NULL)
*(key++)=md_buf[i];
nkey--;
i++;
}
}
if (niv (i != mds))
{
for (;;)
{
if (niv == 0) break;
if (i == mds) break;
if (iv != NULL)
*(iv++)=md_buf[i];
niv--;
i++;
}
}
if ((nkey == 0) (niv == 0)) break;
}
rv = type-key_len;
err:
EVP_MD_CTX_cleanup(c);
OPENSSL_cleanse((md_buf[0]),EVP_MAX_MD_SIZE);
return rv;
}
*
$ git pull
...
$ git log
commit 199772e53427ca921c289471c1344d454781fcc0
...
__
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