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EAP-pwd server: Use os_get_random() for unpredictable token

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Do not use os_random() that uses a low quality PRNG to generate the
anti-clogging token. The construction can be improved upon by replacing
it with a call to os_get_random(), which uses a high quality PRNG. While
the RFC 5931 explictly recommends not to do this ("SHOULD NOT be from a
source of random entropy"), it does still mandate unpredicability ("MUST
be unpredictable"). The anti-clogging token is most unpredictable when
it is taken from a high quality PRNG.

Signed-off-by: Nick Lowe <nick.lowe@lugatech.com>
This commit is contained in:
Nick Lowe 2016-02-09 16:02:32 +00:00 committed by Jouni Malinen
parent 239952b4da
commit 4b16c15bbc
1 changed files with 7 additions and 2 deletions
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9
src/eap_server/eap_server_pwd.c
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@ -178,8 +178,13 @@ static void eap_pwd_build_id_req(struct eap_sm *sm, struct eap_pwd_data *data,
return; return;
} }
/* an lfsr is good enough to generate unpredictable tokens */ if (os_get_random((u8 *) &data->token, sizeof(data->token)) < 0) {
data->token = os_random(); wpabuf_free(data->outbuf);
data->outbuf = NULL;
eap_pwd_state(data, FAILURE);
return;
}
wpabuf_put_be16(data->outbuf, data->group_num); wpabuf_put_be16(data->outbuf, data->group_num);
wpabuf_put_u8(data->outbuf, EAP_PWD_DEFAULT_RAND_FUNC); wpabuf_put_u8(data->outbuf, EAP_PWD_DEFAULT_RAND_FUNC);
wpabuf_put_u8(data->outbuf, EAP_PWD_DEFAULT_PRF); wpabuf_put_u8(data->outbuf, EAP_PWD_DEFAULT_PRF);