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eapol: Do not install the same GTK/IGTK

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Track the contents and size of the GTK and IGTK and if the Authenticator
(or an adversary) tries to set the same GTK/IGTK, process the packet
normally but do not resubmit the GTK/IGTK to the kernel.
This commit is contained in:
Denis Kenzior 2017-10-19 16:41:39 -05:00
parent cd7af67aac
commit 7f8f45220e
1 changed files with 53 additions and 14 deletions
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67
src/eapol.c
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@ -788,6 +788,10 @@ struct eapol_sm {
struct eap_state *eap;
struct eapol_frame *early_frame;
uint32_t watch_id;
uint8_t installed_gtk_len;
uint8_t installed_gtk[CRYPTO_MAX_GTK_LEN];
uint8_t installed_igtk_len;
uint8_t installed_igtk[CRYPTO_MAX_IGTK_LEN];
};
static void eapol_sm_destroy(void *value)
@ -804,6 +808,11 @@ static void eapol_sm_destroy(void *value)
eapol_frame_watch_remove(sm->watch_id);
sm->installed_gtk_len = 0;
memset(sm->installed_gtk, 0, sizeof(sm->installed_gtk));
sm->installed_igtk_len = 0;
memset(sm->installed_igtk, 0, sizeof(sm->installed_igtk));
l_free(sm);
l_queue_remove(state_machines, sm);
@ -872,6 +881,46 @@ static void eapol_write(struct eapol_sm *sm, const struct eapol_frame *ef)
sm->handshake->aa, sm->handshake->spa, ETH_P_PAE, ef);
}
static void eapol_install_gtk(struct eapol_sm *sm, uint8_t gtk_key_index,
const uint8_t *gtk, size_t gtk_len,
const uint8_t *rsc)
{
if (!gtk)
return;
/*
* Don't install the same GTK. On older kernels this resets the
* replay counters, etc and can lead to various attacks
*/
if (sm->installed_gtk_len == gtk_len &&
!memcmp(sm->installed_gtk, gtk, gtk_len))
return;
handshake_state_install_gtk(sm->handshake, gtk_key_index,
gtk, gtk_len, rsc, 6);
memcpy(sm->installed_gtk, gtk, gtk_len);
sm->installed_gtk_len = gtk_len;
}
static void eapol_install_igtk(struct eapol_sm *sm, uint8_t igtk_key_index,
const uint8_t *igtk, size_t igtk_len)
{
if (!igtk)
return;
/*
* Don't install the same IGTK. On older kernels this resets the
* replay counters, etc and can lead to various attacks
*/
if (sm->installed_igtk_len == igtk_len - 6 &&
!memcmp(sm->installed_igtk, igtk + 6, igtk_len - 6))
return;
handshake_state_install_igtk(sm->handshake, igtk_key_index,
igtk + 6, igtk_len - 6, igtk);
memcpy(sm->installed_igtk, igtk + 6, igtk_len - 6);
sm->installed_igtk_len = igtk_len - 6;
}
static void send_eapol_start(struct l_timeout *timeout, void *user_data)
{
struct eapol_sm *sm = user_data;
@ -1293,14 +1342,8 @@ retransmit:
return;
handshake_state_install_ptk(sm->handshake);
if (gtk)
handshake_state_install_gtk(sm->handshake, gtk_key_index,
gtk, gtk_len, ek->key_rsc, 6);
if (igtk)
handshake_state_install_igtk(sm->handshake, igtk_key_index,
igtk + 6, igtk_len - 6, igtk);
eapol_install_gtk(sm, gtk_key_index, gtk, gtk_len, ek->key_rsc);
eapol_install_igtk(sm, igtk_key_index, igtk, igtk_len);
if (rekey_offload)
rekey_offload(sm->handshake->ifindex, ptk->kek, ptk->kck,
@ -1401,12 +1444,8 @@ static void eapol_handle_gtk_1_of_2(struct eapol_sm *sm,
eapol_write(sm, (struct eapol_frame *) step2);
l_free(step2);
handshake_state_install_gtk(sm->handshake, gtk_key_index,
gtk, gtk_len, ek->key_rsc, 6);
if (igtk)
handshake_state_install_igtk(sm->handshake, igtk_key_index,
igtk + 6, igtk_len - 6, igtk);
eapol_install_gtk(sm, gtk_key_index, gtk, gtk_len, ek->key_rsc);
eapol_install_igtk(sm, igtk_key_index, igtk, igtk_len);
}
static struct eapol_sm *eapol_find_sm(uint32_t ifindex, const uint8_t *aa)