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sys/hashes/pbkdf2: wipe local variables, prevents leaks.

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Wipe temporary buffers and sha256 contexts so that no remnants of the
password is left on the stack

This ensures that the password is not leaked if some function reads
the stack afterwards.
This commit is contained in:
Juan Carrano 2019-09-13 12:33:28 +02:00 committed by Francisco Molina
parent 62667848c4
commit bc8ce928d4
No known key found for this signature in database
GPG Key ID: 3E94EAC3DBDEEDA8
2 changed files with 16 additions and 0 deletions
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4
sys/Makefile.dep
View File

@ -732,6 +732,10 @@ ifneq (,$(filter random,$(USEMODULE)))
USEMODULE += luid
endif
ifneq (,$(filter hashes,$(USEMODULE)))
USEMODULE += crypto
endif
ifneq (,$(filter asymcute,$(USEMODULE)))
USEMODULE += sock_udp
USEMODULE += sock_util

12
sys/hashes/pbkdf2.c
View File

@ -22,6 +22,7 @@
#include "hashes/sha256.h"
#include "hashes/pbkdf2.h"
#include "crypto/helper.h"
static void inplace_xor_scalar(uint8_t *bytes, size_t len, uint8_t c)
{
@ -75,6 +76,8 @@ void pbkdf2_sha256(const uint8_t *password, size_t password_len,
inplace_xor_scalar(processed_pass, sizeof(processed_pass), 0x36 ^ 0x5C);
sha256_update(&outer, processed_pass, sizeof(processed_pass));
crypto_secure_wipe(&processed_pass, sizeof(processed_pass));
}
memset(output, 0, SHA256_DIGEST_LENGTH);
@ -96,5 +99,14 @@ void pbkdf2_sha256(const uint8_t *password, size_t password_len,
sha256_final(&outer_copy, tmp_digest);
inplace_xor_digests(output, tmp_digest);
if (iterations == 0) {
crypto_secure_wipe(&inner_copy, sizeof(inner_copy));
crypto_secure_wipe(&outer_copy, sizeof(outer_copy));
}
}
crypto_secure_wipe(&inner, sizeof(inner));
crypto_secure_wipe(&outer, sizeof(outer));
crypto_secure_wipe(&tmp_digest, sizeof(tmp_digest));
}