Do not use os_random() that uses a low quality PRNG to
generate the anti-clogging token. The current construction can be improved
upon by replacing it with a call to os_get_random(...), which uses a high
quality PRNG. While the RFC explictly recommends not to do this, it does so
because the author(s) either must have had a mistaken notion that there are
always issues where an entropy source/pool can be consumed and did not want
to exacerbate that presumed issue or had notions that there were always
significant performance issues using a source of random entropy. This is
certainly not the case with /dev/urandom in Linux. The anti-clogging token is
most unpredictable when it is taken from a high quality PRNG.
Signed-off-by: Nick Lowe <nick.lowe@xxxxxxxxxxxx>
---
src/eap_server/eap_server_pwd.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/src/eap_server/eap_server_pwd.c b/src/eap_server/eap_server_pwd.c
index 36ac555..eb3e00f 100644
--- a/src/eap_server/eap_server_pwd.c
+++ b/src/eap_server/eap_server_pwd.c
@@ -178,8 +178,11 @@ static void eap_pwd_build_id_req(struct eap_sm
*sm, struct eap_pwd_data *data,
return;
}
- /* an lfsr is good enough to generate unpredictable tokens */
- data->token = os_random();
+ if (os_get_random((u8 *) &data->token, sizeof(data->token)) < 0) {
+ eap_pwd_state(data, FAILURE);
+ return;
+ }
+
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_PRF);
--
2.5.0
From 972f14f773ceabd079f2d7a6bb974b6fa0cc6d9e Mon Sep 17 00:00:00 2001
From: Nick Lowe <nick.lowe@xxxxxxxxxxxx>
Date: Tue, 9 Feb 2016 16:02:32 +0000
Subject: [PATCH 04/10] Do not use os_random() that uses a low quality PRNG to
generate the anti-clogging token. The current construction can be improved
upon by replacing it with a call to os_get_random(...), which uses a high
quality PRNG. While the RFC explictly recommends not to do this, it does so
because the author(s) either must have had a mistaken notion that there are
always issues where an entropy source/pool can be consumed and did not want
to exacerbate that presumed issue or had notions that there were always
significant performance issues using a source of random entropy. This is
certainly not the case with /dev/urandom in Linux. The anti-clogging token is
most unpredictable when it is taken from a high quality PRNG.
Signed-off-by: Nick Lowe <nick.lowe@xxxxxxxxxxxx>
---
src/eap_server/eap_server_pwd.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/src/eap_server/eap_server_pwd.c b/src/eap_server/eap_server_pwd.c
index 36ac555..eb3e00f 100644
--- a/src/eap_server/eap_server_pwd.c
+++ b/src/eap_server/eap_server_pwd.c
@@ -178,8 +178,11 @@ static void eap_pwd_build_id_req(struct eap_sm *sm, struct eap_pwd_data *data,
return;
}
- /* an lfsr is good enough to generate unpredictable tokens */
- data->token = os_random();
+ if (os_get_random((u8 *) &data->token, sizeof(data->token)) < 0) {
+ eap_pwd_state(data, FAILURE);
+ return;
+ }
+
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_PRF);
--
2.5.0
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