Previously, the key was installed once the runnel was created despite the outcome of the second authentication phase. Now, the key installation is delayed until the successful completion of the second authentication phase. This excludes the unnecessary operations in the case of a failure and key reinstallation with cypro-binding in use. --- src/eap-peap.c | 27 ++++++++++++++++++++++----- 1 file changed, 22 insertions(+), 5 deletions(-) diff --git a/src/eap-peap.c b/src/eap-peap.c index c400ddee..eb0b0c5f 100644 --- a/src/eap-peap.c +++ b/src/eap-peap.c @@ -43,6 +43,8 @@ struct peap_state { struct eap_state *phase2; + + uint8_t key[128]; }; static void eap_peap_phase2_send_response(const uint8_t *pdu, size_t pdu_len, @@ -66,6 +68,7 @@ static void eap_peap_phase2_send_response(const uint8_t *pdu, size_t pdu_len, static void eap_peap_phase2_complete(enum eap_result result, void *user_data) { struct eap_state *eap = user_data; + struct peap_state *peap_state; l_debug("result: %d", result); @@ -94,6 +97,12 @@ static void eap_peap_phase2_complete(enum eap_result result, void *user_data) return; } + peap_state = eap_tls_common_get_variant_data(eap); + + eap_set_key_material(eap, peap_state->key + 0, 64, NULL, 0, NULL, + 0, NULL, 0); + explicit_bzero(peap_state->key, sizeof(peap_state->key)); + eap_method_success(eap); } @@ -174,6 +183,7 @@ static void eap_extensions_handle_request(struct eap_state *eap, const uint8_t *pkt, size_t len) { + struct peap_state *peap_state; uint8_t response[EAP_EXTENSIONS_HEADER_LEN + EAP_EXTENSIONS_AVP_HEADER_LEN + 2]; int r = eap_extensions_handle_result_avp(eap, pkt, len, response); @@ -199,13 +209,19 @@ static void eap_extensions_handle_request(struct eap_state *eap, return; } + peap_state = eap_tls_common_get_variant_data(eap); + + eap_set_key_material(eap, peap_state->key + 0, 64, NULL, 0, NULL, + 0, NULL, 0); + explicit_bzero(peap_state->key, sizeof(peap_state->key)); + eap_method_success(eap); } static bool eap_peap_tunnel_ready(struct eap_state *eap, const char *peer_identity) { - uint8_t msk_emsk[128]; + struct peap_state *peap_state = eap_tls_common_get_variant_data(eap); /* * PEAPv1: draft-josefsson-pppext-eap-tls-eap-05, Section 2.1.1 @@ -217,10 +233,7 @@ static bool eap_peap_tunnel_ready(struct eap_state *eap, /* MSK, EMSK and challenge derivation */ eap_tls_common_tunnel_prf_get_bytes(eap, true, "client EAP encryption", - msk_emsk, 128); - - eap_set_key_material(eap, msk_emsk + 0, 64, NULL, 0, NULL, 0, NULL, 0); - explicit_bzero(msk_emsk, sizeof(msk_emsk)); + peap_state->key, 128); eap_tls_common_send_empty_response(eap); @@ -286,6 +299,8 @@ static void eap_peap_state_reset(void *variant_data) return; eap_reset(peap_state->phase2); + + explicit_bzero(peap_state->key, sizeof(peap_state->key)); } static void eap_peap_state_destroy(void *variant_data) @@ -298,6 +313,8 @@ static void eap_peap_state_destroy(void *variant_data) eap_reset(peap_state->phase2); eap_free(peap_state->phase2); + explicit_bzero(peap_state->key, sizeof(peap_state->key)); + l_free(peap_state); } -- 2.13.6

The handler for EAP Extensions has been modified to support multiple TLV types instead of the single Result TLV. This will allow to handle the other TLVs such as Crypto-Binding TLV. --- src/eap-peap.c | 90 ++++++++++++++++++++++++++++++++++++++++++---------------- 1 file changed, 65 insertions(+), 25 deletions(-) diff --git a/src/eap-peap.c b/src/eap-peap.c index ed18c667..8cd73c82 100644 --- a/src/eap-peap.c +++ b/src/eap-peap.c @@ -111,6 +111,7 @@ static void eap_peap_phase2_complete(enum eap_result result, void *user_data) */ #define EAP_EXTENSIONS_HEADER_LEN 5 #define EAP_EXTENSIONS_TLV_HEADER_LEN 4 +#define EAP_EXTENSIONS_TLV_M_BIT_MASK 0x8000 enum eap_extensions_tlv_type { /* Reserved = 0x0000, */ @@ -119,6 +120,8 @@ enum eap_extensions_tlv_type { EAP_EXTENSIONS_TLV_TYPE_RESULT = 0x8003, }; +#define TLV_RESULT_VAL_LEN 2 + enum eap_extensions_result { EAP_EXTENSIONS_RESULT_SUCCCESS = 1, EAP_EXTENSIONS_RESULT_FAILURE = 2, @@ -126,31 +129,15 @@ enum eap_extensions_result { static int eap_extensions_handle_result_tlv(struct eap_state *eap, const uint8_t *data, - size_t data_len, + uint16_t tlv_value_len, uint8_t *response) { struct peap_state *peap_state; - uint16_t type; - uint16_t len; uint16_t result; - if (data_len < EAP_EXTENSIONS_TLV_HEADER_LEN + 2) - return -ENOENT; - - type = l_get_be16(data); - - if (type != EAP_EXTENSIONS_TLV_TYPE_RESULT) - return -ENOENT; - - data += 2; - - len = l_get_be16(data); - - if (len != 2) + if (tlv_value_len != TLV_RESULT_VAL_LEN) return -ENOENT; - data += 2; - result = l_get_be16(data); l_debug("result: %d", result); @@ -169,11 +156,62 @@ static int eap_extensions_handle_result_tlv(struct eap_state *eap, return -ENOENT; } - l_put_be16(EAP_EXTENSIONS_TLV_TYPE_RESULT, - &response[EAP_EXTENSIONS_HEADER_LEN]); - l_put_be16(2, &response[EAP_EXTENSIONS_HEADER_LEN + 2]); - l_put_be16(result, &response[EAP_EXTENSIONS_HEADER_LEN + - EAP_EXTENSIONS_TLV_HEADER_LEN]); + /* Build response Result TLV */ + + l_put_be16(EAP_EXTENSIONS_TLV_TYPE_RESULT, response); + response += 2; + + l_put_be16(TLV_RESULT_VAL_LEN, response); + response += 2; + + l_put_be16(result, response); + + return result; +} + +static int eap_extensions_process_tlvs(struct eap_state *eap, + const uint8_t *data, + size_t data_len, + uint8_t *response) +{ + uint16_t tlv_type; + uint16_t tlv_value_len; + int r; + int result = EAP_EXTENSIONS_RESULT_FAILURE; + + while (data_len >= EAP_EXTENSIONS_TLV_HEADER_LEN) { + tlv_type = l_get_be16(data); + data += 2; + + tlv_value_len = l_get_be16(data); + data += 2; + + data_len -= EAP_EXTENSIONS_TLV_HEADER_LEN; + + if (data_len < tlv_value_len) + return -ENOENT; + + switch (tlv_type) { + case EAP_EXTENSIONS_TLV_TYPE_RESULT: + result = r = eap_extensions_handle_result_tlv(eap, + data, tlv_value_len, response); + + response += EAP_EXTENSIONS_TLV_HEADER_LEN + + TLV_RESULT_VAL_LEN; + break; + default: + if (tlv_type & EAP_EXTENSIONS_TLV_M_BIT_MASK) + return -ENOENT; + + break; + } + + if (r < 0) + return r; + + data += tlv_value_len; + data_len -= tlv_value_len; + } return result; } @@ -185,8 +223,10 @@ static void eap_extensions_handle_request(struct eap_state *eap, { struct peap_state *peap_state; uint8_t response[EAP_EXTENSIONS_HEADER_LEN + - EAP_EXTENSIONS_TLV_HEADER_LEN + 2]; - int r = eap_extensions_handle_result_tlv(eap, pkt, len, response); + EAP_EXTENSIONS_TLV_HEADER_LEN + + TLV_RESULT_VAL_LEN]; + int r = eap_extensions_process_tlvs(eap, pkt, len, + &response[EAP_EXTENSIONS_HEADER_LEN]); if (r < 0) return; -- 2.13.6

The PRF+ algorithm is based Internet Key Exchange (IKEv2) Protocol: https://www.ietf.org/rfc/rfc4306.txt --- src/crypto.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ src/crypto.h | 3 +++ 2 files changed, 67 insertions(+) diff --git a/src/crypto.c b/src/crypto.c index 67a042be..c1fe83a2 100644 --- a/src/crypto.c +++ b/src/crypto.c @@ -581,6 +581,70 @@ bool prf_sha1(const void *key, size_t key_len, return true; } +bool prf_plus_sha1(const void *key, size_t key_len, + const void *label, size_t label_len, + const void *seed, size_t seed_len, + void *output, size_t size) +{ + /* + * PRF+ (K, S, LEN) = T1 | T2 | T3 | T4 | ... where: + * + * T1 = HMAC-SHA1 (K, S | LEN | 0x01 | 0x00 | 0x00) + * + * T2 = HMAC-SHA1 (K, T1 | S | LEN | 0x02 | 0x00 | 0x00) + * + * T3 = HMAC-SHA1 (K, T2 | S | LEN | 0x03 | 0x00 | 0x00) + * + * T4 = HMAC-SHA1 (K, T3 | S | LEN | 0x04 | 0x00 | 0x00) + * + * ... + */ + + static const uint8_t SHA1_MAC_LEN = 20; + static const uint8_t nil_bytes[2] = { 0, 0 }; + struct l_checksum *hmac; + uint8_t t[SHA1_MAC_LEN]; + uint8_t counter; + struct iovec iov[5] = { + [0] = { .iov_base = (void *) t, .iov_len = 0 }, + [1] = { .iov_base = (void *) label, .iov_len = label_len }, + [2] = { .iov_base = (void *) seed, .iov_len = seed_len }, + [3] = { .iov_base = &counter, .iov_len = 1 }, + [4] = { .iov_base = (void *) nil_bytes, .iov_len = 2 }, + }; + + hmac = l_checksum_new_hmac(L_CHECKSUM_SHA1, key, key_len); + if (!hmac) + return false; + + /* PRF processes in 160-bit chunks (20 bytes) */ + for (counter = 1;; counter++) { + size_t len; + + if (size > SHA1_MAC_LEN) + len = SHA1_MAC_LEN; + else + len = size; + + l_checksum_updatev(hmac, iov, 5); + l_checksum_get_digest(hmac, t, len); + + memcpy(output, t, len); + + size -= len; + + if (!size) + break; + + output += len; + iov[0].iov_len = len; + } + + l_checksum_free(hmac); + + return true; +} + /* Defined in 802.11-2012, Section 11.6.1.7.2 Key derivation function (KDF) */ bool kdf_sha256(const void *key, size_t key_len, const void *prefix, size_t prefix_len, diff --git a/src/crypto.h b/src/crypto.h index 23ca2450..89e2402c 100644 --- a/src/crypto.h +++ b/src/crypto.h @@ -106,6 +106,9 @@ bool kdf_sha384(const void *key, size_t key_len, bool prf_sha1(const void *key, size_t key_len, const void *prefix, size_t prefix_len, const void *data, size_t data_len, void *output, size_t size); +bool prf_plus_sha1(const void *key, size_t key_len, + const void *prefix, size_t prefix_len, + const void *data, size_t data_len, void *output, size_t size); bool hkdf_extract(enum l_checksum_type type, const uint8_t *key, size_t key_len, uint8_t num_args, uint8_t *out, ...); -- 2.13.6

The Crypto Binding TLV is used to ensure that the EAP peer and the EAP server participated in both the inner and the outer EAP authentications of a PEAP authentication by cryptographically associating the phase 1 and phase 2 authentications. The usage of Crypto-Binding in PEAPv0 is optional and is triggered by the reception of the Crypto-Binding TLV from the server. --- src/eap-peap.c | 179 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 177 insertions(+), 2 deletions(-) diff --git a/src/eap-peap.c b/src/eap-peap.c index 8cd73c82..b2897186 100644 --- a/src/eap-peap.c +++ b/src/eap-peap.c @@ -29,6 +29,7 @@ #include <errno.h> #include <ell/ell.h> +#include "src/crypto.h" #include "src/missing.h" #include "src/eap.h" #include "src/eap-private.h" @@ -113,13 +114,178 @@ static void eap_peap_phase2_complete(enum eap_result result, void *user_data) #define EAP_EXTENSIONS_TLV_HEADER_LEN 4 #define EAP_EXTENSIONS_TLV_M_BIT_MASK 0x8000 +#define TLV_CRYPTOBINDING_VAL_LEN 56 +#define TLV_CRYPTOBINDING_NONCE_LEN 32 +#define TLV_CRYPTOBINDING_COMPOUND_MAC_LEN 20 + enum eap_extensions_tlv_type { /* Reserved = 0x0000, */ /* Reserved = 0x0001, */ /* Reserved = 0x0002, */ - EAP_EXTENSIONS_TLV_TYPE_RESULT = 0x8003, + EAP_EXTENSIONS_TLV_TYPE_RESULT = 0x8003, + EAP_EXTENSIONS_TLV_TYPE_CRYPTOBINDING = 0x000C, +}; + +enum TLV_CRYPTOBINDING_TYPE { + TLV_CRYPTOBINDING_TYPE_REQUEST = 0, + TLV_CRYPTOBINDING_TYPE_RESPONSE = 1, }; +static bool cryptobinding_tlv_generate_csk(struct eap_state *eap, uint8_t *imck) +{ + struct peap_state *peap_state = eap_tls_common_get_variant_data(eap); + char *label; + + label = "Session Key Generating Function"; + + if (!prf_plus_sha1(imck, 40, label, strlen(label), "\00", 1, + peap_state->key, sizeof(peap_state->key))) + return false; + + return true; +} + +static bool cryptobinding_tlv_generate_imck(struct eap_state *eap, + uint8_t *imck_out) +{ + struct peap_state *peap_state = eap_tls_common_get_variant_data(eap); + static uint8_t isk[32]; + char *label; + + label = "Inner Methods Compound Keys"; + memset(isk, 0, sizeof(isk)); + + if (!prf_plus_sha1(peap_state->key, 40, label, strlen(label), + isk, sizeof(isk), imck_out, 60)) + return false; + + return true; +} + +static int eap_extensions_handle_cryptobinding_tlv(struct eap_state *eap, + const uint8_t *data, + uint16_t tlv_value_len, + uint8_t *response) +{ + const uint8_t *nonce; + const uint8_t *server_compound_mac; + uint8_t compound_mac[TLV_CRYPTOBINDING_COMPOUND_MAC_LEN]; + const uint8_t *cryptobinding_tlv_value; + uint8_t buf[61]; + uint8_t imck[60]; + + if (tlv_value_len != TLV_CRYPTOBINDING_VAL_LEN) + return -ENOENT; + + cryptobinding_tlv_value = data; + + /* Reserved byte: must be ignored on receipt. */ + data += 1; + + /* Version byte: must be set to 0. */ + if (*data) + return -ENOENT; + + data += 1; + + /* RecvVersion byte: must be set to 0. */ + if (*data) + return -ENOENT; + + data += 1; + + /* SubType byte: cryptobinding TLV request. */ + if (*data != TLV_CRYPTOBINDING_TYPE_REQUEST) + return -ENOENT; + + data += 1; + + nonce = data; + data += TLV_CRYPTOBINDING_NONCE_LEN; + + server_compound_mac = data; + + l_put_be16(EAP_EXTENSIONS_TLV_TYPE_CRYPTOBINDING, &buf[0]); + l_put_be16(tlv_value_len, &buf[2]); + memcpy(&buf[4], cryptobinding_tlv_value, + 4 + TLV_CRYPTOBINDING_NONCE_LEN); + memset(&buf[EAP_EXTENSIONS_TLV_HEADER_LEN + 4 + + TLV_CRYPTOBINDING_NONCE_LEN], + 0, TLV_CRYPTOBINDING_COMPOUND_MAC_LEN); + buf[60] = EAP_TYPE_PEAP; + + if (!cryptobinding_tlv_generate_imck(eap, imck)) { + l_error("PEAP: Failed to generate IMCK to validate " + "server compound MAC."); + + return -ENOENT; + } + + if (!hmac_sha1(imck + 40, 20, buf, sizeof(buf), compound_mac, + TLV_CRYPTOBINDING_COMPOUND_MAC_LEN)) { + l_error("PEAP: Failed to generate compound MAC to validate " + "server compound MAC."); + + return -ENOENT; + } + + if (memcmp(server_compound_mac, compound_mac, + TLV_CRYPTOBINDING_COMPOUND_MAC_LEN)) { + l_error("PEAP: Generated compound MAC and server compound MAC " + "don't match."); + + return -ENOENT; + } + + /* Build response Crypto-Binding TLV */ + data = response; + + l_put_be16(EAP_EXTENSIONS_TLV_TYPE_CRYPTOBINDING, response); + response += 2; + + l_put_be16(TLV_CRYPTOBINDING_VAL_LEN, response); + response += 2; + + /* Reserved - must be set to 0. */ + l_put_u8(0, response); + response += 1; + + /* Version */ + l_put_u8(EAP_TLS_VERSION_0, response); + response += 1; + + /* Received Version */ + l_put_u8(EAP_TLS_VERSION_0, response); + response += 1; + + /* Sub-Type */ + l_put_u8(TLV_CRYPTOBINDING_TYPE_RESPONSE, response); + response += 1; + + memcpy(response, nonce, TLV_CRYPTOBINDING_NONCE_LEN); + response += TLV_CRYPTOBINDING_NONCE_LEN; + + memcpy(buf, data, EAP_EXTENSIONS_TLV_HEADER_LEN + 4 + + TLV_CRYPTOBINDING_NONCE_LEN); + + if (!hmac_sha1(imck + 40, 20, buf, sizeof(buf), compound_mac, + TLV_CRYPTOBINDING_COMPOUND_MAC_LEN)) { + l_error("PEAP: Failed to generate client compound MAC."); + + return -ENOENT; + } + + memcpy(response, compound_mac, 20); + + if (!cryptobinding_tlv_generate_csk(eap, imck)) { + l_error("PEAP: Failed to generate Compound Session Key."); + + return -ENOENT; + } + + return 0; +} + #define TLV_RESULT_VAL_LEN 2 enum eap_extensions_result { @@ -199,6 +365,13 @@ static int eap_extensions_process_tlvs(struct eap_state *eap, response += EAP_EXTENSIONS_TLV_HEADER_LEN + TLV_RESULT_VAL_LEN; break; + case EAP_EXTENSIONS_TLV_TYPE_CRYPTOBINDING: + r = eap_extensions_handle_cryptobinding_tlv(eap, + data, tlv_value_len, response); + + response += EAP_EXTENSIONS_TLV_HEADER_LEN + + TLV_CRYPTOBINDING_VAL_LEN; + break; default: if (tlv_type & EAP_EXTENSIONS_TLV_M_BIT_MASK) return -ENOENT; @@ -224,7 +397,9 @@ static void eap_extensions_handle_request(struct eap_state *eap, struct peap_state *peap_state; uint8_t response[EAP_EXTENSIONS_HEADER_LEN + EAP_EXTENSIONS_TLV_HEADER_LEN + - TLV_RESULT_VAL_LEN]; + TLV_RESULT_VAL_LEN + + EAP_EXTENSIONS_TLV_HEADER_LEN + + TLV_CRYPTOBINDING_VAL_LEN]; int r = eap_extensions_process_tlvs(eap, pkt, len, &response[EAP_EXTENSIONS_HEADER_LEN]); -- 2.13.6