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eapol: Rework eapol_decrypt_key_data

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802.11 uses AES Key Wrap and RC4 with the first 256 bytes skipped.  The
IV is also initialized into the RC4 key.
This commit is contained in:
Denis Kenzior 2015-02-17 17:39:23 -06:00
parent 88d4b36663
commit 89e4538945
1 changed files with 36 additions and 11 deletions
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47
src/eapol.c
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@ -30,6 +30,7 @@
#include "sha1.h"
#include "md5.h"
#include "aes.h"
#include "arc4.h"
#include "eapol.h"
#define VERIFY_IS_ZERO(field) \
@ -72,33 +73,57 @@ uint8_t *eapol_decrypt_key_data(const uint8_t *kek,
const struct eapol_key *frame)
{
size_t key_data_len = L_BE16_TO_CPU(frame->key_data_len);
struct l_cipher *cipher;
const uint8_t *key_data = frame->key_data;
size_t expected_len;
uint8_t *buf;
bool ret;
switch (frame->key_descriptor_version) {
case EAPOL_KEY_DESCRIPTOR_VERSION_HMAC_MD5_ARC4:
/* TODO: This might require an IV from frame->eapol_key_iv */
cipher = l_cipher_new(L_CIPHER_ARC4, kek, 16);
expected_len = key_data_len;
break;
case EAPOL_KEY_DESCRIPTOR_VERSION_HMAC_SHA1_AES:
case EAPOL_KEY_DESCRIPTOR_VERSION_AES_128_CMAC_AES:
cipher = l_cipher_new(L_CIPHER_AES, kek, 16);
expected_len = key_data_len - 8;
break;
default:
return NULL;
};
buf = l_new(uint8_t, key_data_len);
ret = l_cipher_decrypt(cipher, frame->key_data, buf, key_data_len);
l_cipher_free(cipher);
buf = l_new(uint8_t, expected_len);
if (!ret) {
l_free(buf);
return NULL;
switch (frame->key_descriptor_version) {
case EAPOL_KEY_DESCRIPTOR_VERSION_HMAC_MD5_ARC4:
{
uint8_t key[32];
bool ret;
memcpy(key, frame->eapol_key_iv, 16);
memcpy(key + 16, kek, 16);
ret = arc4_skip(key, 32, 256, key_data, key_data_len, buf);
memset(key, 0, sizeof(key));
if (!ret)
goto error;
break;
}
case EAPOL_KEY_DESCRIPTOR_VERSION_HMAC_SHA1_AES:
case EAPOL_KEY_DESCRIPTOR_VERSION_AES_128_CMAC_AES:
if (key_data_len < 8 || key_data_len % 8)
goto error;
if (!aes_unwrap(kek, key_data, key_data_len, buf))
goto error;
break;
}
return buf;
error:
l_free(buf);
return NULL;
}
const struct eapol_key *eapol_key_validate(const uint8_t *frame, size_t len)