eapol: Check the MSK size supplied by EAP
Despite RFC3748 mandating MSKs to be at least 256 bits some EAP methods return shorter MSKs. Since we call handshake_failed when the MSK is too short, EAP methods have to be careful with their calls to set_key_material because it may result in a call to the method's .remove method. EAP-TLS and EAP-TTLS can't handle that currently and would be difficult to adapt because of the TLS internals but they always set msk_len to 64 so handshake_failed will not be called.
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src/eapol.c
26
src/eapol.c
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@ -1419,6 +1419,8 @@ static void eapol_eap_results_cb(const uint8_t *msk_data, size_t msk_len,
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void *user_data)
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void *user_data)
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{
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{
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struct eapol_sm *sm = user_data;
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struct eapol_sm *sm = user_data;
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ssize_t pmk_len;
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const uint8_t *pmk_data;
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l_debug("EAP key material received");
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l_debug("EAP key material received");
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@ -1443,10 +1445,26 @@ static void eapol_eap_results_cb(const uint8_t *msk_data, size_t msk_len,
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* 802.1X authentication), i.e., XXKey = L(MSK, 256, 256)."
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* 802.1X authentication), i.e., XXKey = L(MSK, 256, 256)."
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*/
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*/
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if (sm->handshake->akm_suite == IE_RSN_AKM_SUITE_FT_OVER_8021X)
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if (sm->handshake->akm_suite == IE_RSN_AKM_SUITE_FT_OVER_8021X) {
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handshake_state_set_pmk(sm->handshake, msk_data + 32);
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pmk_len = (ssize_t) msk_len - 32;
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else
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pmk_data = msk_data + 32;
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handshake_state_set_pmk(sm->handshake, msk_data);
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} else {
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pmk_len = msk_len;
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pmk_data = msk_data;
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}
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if (pmk_len < 32)
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goto msk_short;
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handshake_state_set_pmk(sm->handshake, pmk_data);
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return;
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msk_short:
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l_error("EAP method's MSK too short for AKM suite %u",
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sm->handshake->akm_suite);
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handshake_failed(sm, MPDU_REASON_CODE_IEEE8021X_FAILED);
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}
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}
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static void eapol_eap_event_cb(unsigned int event,
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static void eapol_eap_event_cb(unsigned int event,
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