eap-mschapv2: add code for eap method
This commit is contained in:
Markus Ongyerth
Denis Kenzior
parent
dfc852dd3e
commit
9afe21f86f
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@ -201,6 +201,7 @@ unit_test_wsc_SOURCES = unit/test-wsc.c src/wscutil.h src/wscutil.c \
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unit_test_wsc_LDADD = ell/libell-internal.la
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unit_test_eap_mschapv2_SOURCES = src/eap-mschapv2.h src/eap-mschapv2.c \
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src/eap.c src/eap.h \
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unit/test-eap-mschapv2.c
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unit_test_eap_mschapv2_LDADD = ell/libell-internal.la
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@ -20,11 +20,55 @@
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*
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*/
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#include <ell/ell.h>
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#include <ctype.h>
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#include <stdio.h>
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#include <errno.h>
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#include <ell/ell.h>
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#include "eap.h"
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#include "eap-mschapv2.h"
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#define MSCHAPV2_CHAL_LEN 16
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#define MSCHAPV2_NT_RESPONSE_LEN 24
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#define MSCHAPV2_AUTH_RESPONSE_LEN 20
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#define MSCHAPV2_MASTER_KEY_LEN 16
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#define MSCHAPV2_OP_CHALLENGE 1
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#define MSCHAPV2_OP_RESPONSE 2
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#define MSCHAPV2_OP_SUCCESS 3
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#define MSCHAPV2_OP_FAILURE 4
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struct eap_mschapv2_state {
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uint8_t password_hash[16];
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char *user;
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size_t user_len;
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uint8_t current_id;
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uint8_t peer_challenge[MSCHAPV2_CHAL_LEN];
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uint8_t server_challenge[MSCHAPV2_CHAL_LEN];
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};
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struct mschapv2_header {
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uint8_t op_code;
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uint8_t mschap_id;
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uint16_t mschap_len;
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} __attribute__((packed));
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struct mschapv2_value {
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uint8_t peer_challenge[MSCHAPV2_CHAL_LEN];
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uint8_t reserved[8];
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uint8_t nt_response[MSCHAPV2_NT_RESPONSE_LEN];
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uint8_t flags;
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} __attribute__((packed));
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struct mschapv2_response {
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struct mschapv2_header hdr;
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/* This will always be sizeof(value) */
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uint8_t val_length;
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struct mschapv2_value value;
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char name[0];
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} __attribute__((packed));
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/**
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* Generate the asymetric start keys from our mschapv2 master key for MPPE
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* This function is specified in:
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@ -353,3 +397,322 @@ bool mschapv2_generate_authenticator_response(
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return true;
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}
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static int eap_mschapv2_probe(struct eap_state *eap, const char *name)
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{
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struct eap_mschapv2_state *state;
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if (strcasecmp(name, "MSCHAPV2"))
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return -ENOTSUP;
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state = l_new(struct eap_mschapv2_state, 1);
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eap_set_data(eap, state);
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return 0;
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}
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static void eap_mschapv2_free(struct eap_mschapv2_state *state)
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{
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l_free(state->user);
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l_free(state);
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}
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static void eap_mschapv2_remove(struct eap_state *eap)
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{
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struct eap_mschapv2_state *state;
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state = eap_get_data(eap);
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eap_set_data(eap, NULL);
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eap_mschapv2_free(state);
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}
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static bool eap_mschapv2_send_response(struct eap_state *eap)
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{
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struct eap_mschapv2_state *state = eap_get_data(eap);
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size_t size = sizeof(struct mschapv2_response) + state->user_len;
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uint8_t output[size + 5];
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struct mschapv2_response *response =
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(struct mschapv2_response *) (output + 5);
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bool ret;
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ret = mschapv2_generate_nt_response(state->password_hash,
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state->peer_challenge,
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state->server_challenge,
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state->user,
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response->value.nt_response);
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if (!ret)
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return false;
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response->hdr.op_code = MSCHAPV2_OP_RESPONSE;
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response->hdr.mschap_id = state->current_id;
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response->hdr.mschap_len = L_BE16_TO_CPU(size);
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response->val_length = sizeof(struct mschapv2_value);
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memcpy(response->value.peer_challenge, state->peer_challenge,
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MSCHAPV2_CHAL_LEN);
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memcpy(response->name, state->user, state->user_len);
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eap_send_response(eap, EAP_TYPE_MSCHAPV2, output, sizeof(output));
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return true;
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}
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static void eap_mschapv2_handle_challenge(struct eap_state *eap,
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const uint8_t *pkt, size_t len)
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{
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struct eap_mschapv2_state *state = eap_get_data(eap);
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if (pkt[0] != MSCHAPV2_CHAL_LEN) {
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l_error("MSCHAPV2-Challenge had unexpected length: %x",
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pkt[0]);
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goto err;
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}
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if (len - 1 < MSCHAPV2_CHAL_LEN) {
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l_error("MSCHAPV2-Challenge packet was to short for challenge");
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goto err;
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}
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memcpy(state->server_challenge, pkt + 1, MSCHAPV2_CHAL_LEN);
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l_getrandom(state->peer_challenge, MSCHAPV2_CHAL_LEN);
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if (eap_mschapv2_send_response(eap))
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return;
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err:
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eap_method_error(eap);
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}
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/*
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* We need to verify the authenticator response from the server
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* and generate the master session key.
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*/
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static void eap_mschapv2_handle_success(struct eap_state *eap,
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const uint8_t *pkt, size_t len)
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{
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struct eap_mschapv2_state *state = eap_get_data(eap);
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uint8_t nt_response[24];
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uint8_t password_hash_hash[16];
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uint8_t master_key[16];
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uint8_t session_key[32];
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char authenticator_resp[42];
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struct l_checksum *check;
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bool ret;
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uint8_t buffer[5 + 1];
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check = l_checksum_new(L_CHECKSUM_MD4);
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if (!check)
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goto err;
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l_checksum_update(check, state->password_hash, 16);
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l_checksum_get_digest(check, password_hash_hash, 16);
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l_checksum_free(check);
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ret = mschapv2_generate_nt_response(state->password_hash,
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state->peer_challenge,
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state->server_challenge,
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state->user, nt_response);
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if (!ret)
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goto err;
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ret = mschapv2_generate_authenticator_response(password_hash_hash,
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nt_response,
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state->peer_challenge,
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state->server_challenge,
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state->user,
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authenticator_resp);
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if (!ret)
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goto err;
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/*
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* For iwd timing attacks are unlikly because media access will
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* influence timing. If this code is ever taken out of iwd, memcmp
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* should be replaced by a constant time memcmp
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*/
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if (len < 42 || memcmp(authenticator_resp, pkt, 42)) {
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l_warn("Authenticator response didn't match");
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goto err;
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}
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ret = mschapv2_get_master_key(password_hash_hash, nt_response,
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master_key);
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ret &= mschapv2_get_asymmetric_start_key(master_key, session_key,
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16, false, true);
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ret &= mschapv2_get_asymmetric_start_key(master_key, session_key + 16,
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16, false, false);
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if (!ret)
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goto err;
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eap_method_success(eap);
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/* The eapol set_key_material only needs msk, and that's all we got */
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eap_set_key_material(eap, session_key, 32, NULL, 0, NULL, 0);
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buffer[5] = MSCHAPV2_OP_SUCCESS;
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eap_send_response(eap, EAP_TYPE_MSCHAPV2, buffer, sizeof(buffer));
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return;
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err:
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eap_method_error(eap);
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}
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static void eap_mschapv2_handle_failure(struct eap_state *eap,
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const uint8_t *pkt, size_t len)
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{
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/*
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* From what I have seen, we can't prompt the user in any useful way
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* yet, so we can't do any proper error handling.
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* The values we can read from this are defined in:
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* https://tools.ietf.org/html/draft-ietf-pppext-mschap-v2-01
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* Section 9
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*
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* At the current point, this will be a fail.
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*/
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l_debug("");
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eap_method_error(eap);
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}
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static void eap_mschapv2_handle_request(struct eap_state *eap,
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const uint8_t *pkt, size_t len)
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{
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struct eap_mschapv2_state *state = eap_get_data(eap);
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const struct mschapv2_header *hdr = (struct mschapv2_header *) pkt;
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size_t size = sizeof(*hdr);
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if (len < sizeof(struct mschapv2_header) + 1) {
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l_error("EAP-MSCHAPV2 packet too short");
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goto err;
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}
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state->current_id = hdr->mschap_id;
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if (L_BE16_TO_CPU(hdr->mschap_len) != len) {
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l_error("EAP-MSCHAPV2 packet contains invalid length");
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goto err;
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}
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switch (hdr->op_code) {
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case MSCHAPV2_OP_CHALLENGE:
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eap_mschapv2_handle_challenge(eap, pkt + size, len - size);
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break;
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case MSCHAPV2_OP_SUCCESS:
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eap_mschapv2_handle_success(eap, pkt + size, len - size);
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break;
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case MSCHAPV2_OP_FAILURE:
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eap_mschapv2_handle_failure(eap, pkt + size, len - size);
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break;
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default:
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l_error("Got unknown OP-Code in MSCHPV2 packet: %x",
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hdr->op_code);
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goto err;
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}
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return;
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err:
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eap_method_error(eap);
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}
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static bool set_password_from_string(struct eap_mschapv2_state *state,
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const char *password)
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{
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if (!l_utf8_validate(password, strlen(password), NULL))
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return false;
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return mschapv2_nt_password_hash(password, state->password_hash);
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}
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static void set_user_name(struct eap_mschapv2_state *state, const char *user)
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{
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const char *pos;
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if (!user)
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return;
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for (pos = user; *pos; ++pos) {
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if (*pos == '\\') {
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state->user = l_strdup(pos + 1);
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return;
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}
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}
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state->user = l_strdup(user);
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}
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static bool eap_mschapv2_load_settings(struct eap_state *eap,
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struct l_settings *settings,
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const char *prefix)
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{
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struct eap_mschapv2_state *state = eap_get_data(eap);
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const char *password;
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char setting[64];
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snprintf(setting, sizeof(setting), "%sIdentity", prefix);
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set_user_name(state,
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l_settings_get_value(settings, "Security", setting));
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if (!state->user)
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return false;
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state->user_len = strlen(state->user);
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/* Either read the password-hash from hexdump or password and hash it */
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snprintf(setting, sizeof(setting), "%sPassword-Hash", prefix);
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password = l_settings_get_value(settings, "Security", setting);
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if (password) {
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unsigned char *tmp;
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size_t len;
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tmp = l_util_from_hexstring(password, &len);
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if (len != 16) {
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l_error("Read an impossible password hash");
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l_free(tmp);
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return false;
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}
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memcpy(state->password_hash, tmp, 16);
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l_free(tmp);
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} else {
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snprintf(setting, sizeof(setting), "%sPassword", prefix);
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password = l_settings_get_value(settings, "Security",
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setting);
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if (!password || !set_password_from_string(state, password))
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return false;
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}
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return true;
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}
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static struct eap_method eap_mschapv2 = {
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.request_type = EAP_TYPE_MSCHAPV2,
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.exports_msk = true,
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.name = "MSCHAPV2",
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.probe = eap_mschapv2_probe,
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.remove = eap_mschapv2_remove,
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.handle_request = eap_mschapv2_handle_request,
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.load_settings = eap_mschapv2_load_settings,
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};
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static int eap_mschapv2_init(void)
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{
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l_debug("");
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return eap_register_method(&eap_mschapv2);
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}
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static void eap_mschapv2_exit(void)
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{
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l_debug("");
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eap_unregister_method(&eap_mschapv2);
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}
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EAP_METHOD_BUILTIN(eap_mschapv2, eap_mschapv2_init, eap_mschapv2_exit)
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