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More forceful clearing of stack memory with keys

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gcc 8.3.0 was apparently clever enough to optimize away the previously
used os_memset() to explicitly clear a stack buffer that contains keys
when that clearing happened just before returning from the function.
Since memset_s() is not exactly portable (or commonly available yet..),
use a less robust mechanism that is still pretty likely to prevent
current compilers from optimizing the explicit clearing of the memory
away.

Signed-off-by: Jouni Malinen <j@w1.fi>
This commit is contained in:
Jouni Malinen 2019-05-26 00:47:17 +03:00
parent e1923f5b6a
commit 31bc66e4d1
25 changed files with 98 additions and 72 deletions
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6
src/crypto/sha256-kdf.c
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@ -69,7 +69,7 @@ int hmac_sha256_kdf(const u8 *secret, size_t secret_len,
if (iter == 255) {
os_memset(out, 0, outlen);
os_memset(T, 0, SHA256_MAC_LEN);
forced_memzero(T, SHA256_MAC_LEN);
return -1;
}
iter++;
@ -77,11 +77,11 @@ int hmac_sha256_kdf(const u8 *secret, size_t secret_len,
if (hmac_sha256_vector(secret, secret_len, 4, addr, len, T) < 0)
{
os_memset(out, 0, outlen);
os_memset(T, 0, SHA256_MAC_LEN);
forced_memzero(T, SHA256_MAC_LEN);
return -1;
}
}
os_memset(T, 0, SHA256_MAC_LEN);
forced_memzero(T, SHA256_MAC_LEN);
return 0;
}