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-rw-r--r--src/modules/rlm_eap/types/rlm_eap_pwd/eap_pwd.c933
1 files changed, 933 insertions, 0 deletions
diff --git a/src/modules/rlm_eap/types/rlm_eap_pwd/eap_pwd.c b/src/modules/rlm_eap/types/rlm_eap_pwd/eap_pwd.c
new file mode 100644
index 0000000..2626052
--- /dev/null
+++ b/src/modules/rlm_eap/types/rlm_eap_pwd/eap_pwd.c
@@ -0,0 +1,933 @@
+/**
+ * copyright holder grants permission for redistribution and use in source
+ * and binary forms, with or without modification, provided that the
+ * following conditions are met:
+ * 1. Redistribution of source code must retain the above copyright
+ * notice, this list of conditions, and the following disclaimer
+ * in all source files.
+ * 2. Redistribution in binary form must retain the above copyright
+ * notice, this list of conditions, and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *
+ * "DISCLAIMER OF LIABILITY
+ *
+ * THIS SOFTWARE IS PROVIDED BY DAN HARKINS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE INDUSTRIAL LOUNGE BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE."
+ *
+ * This license and distribution terms cannot be changed. In other words,
+ * this code cannot simply be copied and put under a different distribution
+ * license (including the GNU public license).
+ *
+ * @copyright (c) Dan Harkins, 2012
+ */
+
+RCSID("$Id$")
+USES_APPLE_DEPRECATED_API /* OpenSSL API has been deprecated by Apple */
+
+#include "eap_pwd.h"
+#include "const_time.h"
+#include <freeradius-devel/openssl3.h>
+
+static uint8_t allzero[SHA256_DIGEST_LENGTH] = { 0x00 };
+
+/* The random function H(x) = HMAC-SHA256(0^32, x) */
+static void pwd_hmac_final(HMAC_CTX *hmac_ctx, uint8_t *digest)
+{
+ unsigned int mdlen = SHA256_DIGEST_LENGTH;
+ HMAC_Final(hmac_ctx, digest, &mdlen);
+// HMAC_CTX_reset(hmac_ctx);
+}
+
+/* a counter-based KDF based on NIST SP800-108 */
+static void eap_pwd_kdf(uint8_t *key, int keylen, char const *label,
+ int label_len, uint8_t *result, int result_bit_len)
+{
+ HMAC_CTX *hmac_ctx;
+ uint8_t digest[SHA256_DIGEST_LENGTH];
+ uint16_t i, ctr, L;
+ int result_byte_len, len = 0;
+ unsigned int mdlen = SHA256_DIGEST_LENGTH;
+ uint8_t mask = 0xff;
+
+ MEM(hmac_ctx = HMAC_CTX_new());
+ result_byte_len = (result_bit_len + 7) / 8;
+
+ ctr = 0;
+ L = htons(result_bit_len);
+ while (len < result_byte_len) {
+ ctr++; i = htons(ctr);
+
+ HMAC_Init_ex(hmac_ctx, key, keylen, EVP_sha256(), NULL);
+ if (ctr > 1) HMAC_Update(hmac_ctx, digest, mdlen);
+ HMAC_Update(hmac_ctx, (uint8_t *) &i, sizeof(uint16_t));
+ HMAC_Update(hmac_ctx, (uint8_t const *)label, label_len);
+ HMAC_Update(hmac_ctx, (uint8_t *) &L, sizeof(uint16_t));
+ HMAC_Final(hmac_ctx, digest, &mdlen);
+ if ((len + (int) mdlen) > result_byte_len) {
+ memcpy(result + len, digest, result_byte_len - len);
+ } else {
+ memcpy(result + len, digest, mdlen);
+ }
+ len += mdlen;
+// HMAC_CTX_reset(hmac_ctx);
+ }
+
+ /* since we're expanding to a bit length, mask off the excess */
+ if (result_bit_len % 8) {
+ mask <<= (8 - (result_bit_len % 8));
+ result[result_byte_len - 1] &= mask;
+ }
+
+ HMAC_CTX_free(hmac_ctx);
+}
+
+static BIGNUM *consttime_BN (void)
+{
+ BIGNUM *bn;
+
+ bn = BN_new();
+ if (bn) BN_set_flags(bn, BN_FLG_CONSTTIME);
+ return bn;
+}
+
+/*
+ * compute the legendre symbol in constant time
+ */
+static int legendre(BIGNUM *a, BIGNUM *p, BN_CTX *bnctx)
+{
+ int symbol;
+ unsigned int mask;
+ BIGNUM *res, *pm1over2;
+
+ pm1over2 = consttime_BN();
+ res = consttime_BN();
+
+ if (!BN_sub(pm1over2, p, BN_value_one()) ||
+ !BN_rshift1(pm1over2, pm1over2) ||
+ !BN_mod_exp_mont_consttime(res, a, pm1over2, p, bnctx, NULL)) {
+ BN_free(pm1over2);
+ BN_free(res);
+ return -2;
+ }
+
+ symbol = -1;
+ mask = const_time_eq(BN_is_word(res, 1), 1);
+ symbol = const_time_select_int(mask, 1, symbol);
+ mask = const_time_eq(BN_is_zero(res), 1);
+ symbol = const_time_select_int(mask, -1, symbol);
+
+ BN_free(pm1over2);
+ BN_free(res);
+
+ return symbol;
+}
+
+static void do_equation(EC_GROUP *group, BIGNUM *y2, BIGNUM *x, BN_CTX *bnctx)
+{
+ BIGNUM *p, *a, *b, *tmp1, *pm1;
+
+ tmp1 = BN_new();
+ pm1 = BN_new();
+ p = BN_new();
+ a = BN_new();
+ b = BN_new();
+ EC_GROUP_get_curve(group, p, a, b, bnctx);
+
+ BN_sub(pm1, p, BN_value_one());
+
+ /*
+ * y2 = x^3 + ax + b
+ */
+ BN_mod_sqr(tmp1, x, p, bnctx);
+ BN_mod_mul(y2, tmp1, x, p, bnctx);
+ BN_mod_mul(tmp1, a, x, p, bnctx);
+ BN_mod_add_quick(y2, y2, tmp1, p);
+ BN_mod_add_quick(y2, y2, b, p);
+
+ BN_free(tmp1);
+ BN_free(pm1);
+ BN_free(p);
+ BN_free(a);
+ BN_free(b);
+
+ return;
+}
+
+static int is_quadratic_residue(BIGNUM *val, BIGNUM *p, BIGNUM *qr, BIGNUM *qnr, BN_CTX *bnctx)
+{
+ int offset, check, ret = 0;
+ BIGNUM *r = NULL, *pm1 = NULL, *res = NULL, *qr_or_qnr = NULL;
+ unsigned int mask;
+ unsigned char *qr_bin = NULL, *qnr_bin = NULL, *qr_or_qnr_bin = NULL;
+
+ if (((r = consttime_BN()) == NULL) ||
+ ((res = consttime_BN()) == NULL) ||
+ ((qr_or_qnr = consttime_BN()) == NULL) ||
+ ((pm1 = consttime_BN()) == NULL)) {
+ ret = -2;
+ goto fail;
+ }
+
+ if (((qr_bin = (unsigned char *)malloc(BN_num_bytes(p))) == NULL) ||
+ ((qnr_bin = (unsigned char *)malloc(BN_num_bytes(p))) == NULL) ||
+ ((qr_or_qnr_bin = (unsigned char *)malloc(BN_num_bytes(p))) == NULL)) {
+ ret = -2;
+ goto fail;
+ }
+
+ /*
+ * we select binary in constant time so make them binary
+ */
+ memset(qr_bin, 0, BN_num_bytes(p));
+ memset(qnr_bin, 0, BN_num_bytes(p));
+ memset(qr_or_qnr_bin, 0, BN_num_bytes(p));
+
+ offset = BN_num_bytes(p) - BN_num_bytes(qr);
+ BN_bn2bin(qr, qr_bin + offset);
+
+ offset = BN_num_bytes(p) - BN_num_bytes(qnr);
+ BN_bn2bin(qnr, qnr_bin + offset);
+
+ /*
+ * r = (random() mod p-1) + 1
+ */
+ BN_sub(pm1, p, BN_value_one());
+ BN_rand_range(r, pm1);
+ BN_add(r, r, BN_value_one());
+
+ BN_copy(res, val);
+
+ /*
+ * res = val * r * r which ensures res != val but has same quadratic residocity
+ */
+ BN_mod_mul(res, res, r, p, bnctx);
+ BN_mod_mul(res, res, r, p, bnctx);
+
+ /*
+ * if r is even (mask is -1) then multiply by qnr and our check is qnr
+ * otherwise multiply by qr and our check is qr
+ */
+ mask = const_time_is_zero(BN_is_odd(r));
+ const_time_select_bin(mask, qnr_bin, qr_bin, BN_num_bytes(p), qr_or_qnr_bin);
+ BN_bin2bn(qr_or_qnr_bin, BN_num_bytes(p), qr_or_qnr);
+ BN_mod_mul(res, res, qr_or_qnr, p, bnctx);
+ check = const_time_select_int(mask, -1, 1);
+
+ if ((ret = legendre(res, p, bnctx)) == -2) {
+ ret = -1; /* just say no it's not */
+ goto fail;
+ }
+ mask = const_time_eq(ret, check);
+ ret = const_time_select_int(mask, 1, 0);
+
+fail:
+ if (qr_bin != NULL) free(qr_bin);
+ if (qnr_bin != NULL) free(qnr_bin);
+ if (qr_or_qnr_bin != NULL) free(qr_or_qnr_bin);
+ BN_free(r);
+ BN_free(res);
+ BN_free(qr_or_qnr);
+ BN_free(pm1);
+
+ return ret;
+}
+
+int compute_password_element (REQUEST *request, pwd_session_t *session, uint16_t grp_num,
+ char const *password, int password_len,
+ char const *id_server, int id_server_len,
+ char const *id_peer, int id_peer_len,
+ uint32_t *token)
+{
+ BIGNUM *x_candidate = NULL, *rnd = NULL, *y_sqrd = NULL, *qr = NULL, *qnr = NULL, *y1 = NULL, *y2 = NULL, *y = NULL, *exp = NULL;
+ EVP_MD_CTX *hmac_ctx;
+ EVP_PKEY *hmac_pkey;
+ uint8_t pwe_digest[SHA256_DIGEST_LENGTH], *prfbuf = NULL, *xbuf = NULL, *pm1buf = NULL, *y1buf = NULL, *y2buf = NULL, *ybuf = NULL, ctr;
+ int nid, is_odd, primebitlen, primebytelen, ret = 0, found = 0, mask;
+ int save, i, rbits, qr_or_qnr, save_is_odd = 0, cmp;
+ unsigned int skip;
+
+ MEM(hmac_ctx = EVP_MD_CTX_new());
+ MEM(hmac_pkey = EVP_PKEY_new_mac_key(EVP_PKEY_HMAC, NULL, allzero, sizeof(allzero)));
+
+ switch (grp_num) { /* from IANA registry for IKE D-H groups */
+ case 19:
+ nid = NID_X9_62_prime256v1;
+ break;
+
+ case 20:
+ nid = NID_secp384r1;
+ break;
+
+ case 21:
+ nid = NID_secp521r1;
+ break;
+
+ case 25:
+ nid = NID_X9_62_prime192v1;
+ break;
+
+ case 26:
+ nid = NID_secp224r1;
+ break;
+
+ default:
+ DEBUG("unknown group %d", grp_num);
+ goto fail;
+ }
+
+ session->pwe = NULL;
+ session->order = NULL;
+ session->prime = NULL;
+
+ if ((session->group = EC_GROUP_new_by_curve_name(nid)) == NULL) {
+ DEBUG("unable to create EC_GROUP");
+ goto fail;
+ }
+
+ if (((rnd = consttime_BN()) == NULL) ||
+ ((session->pwe = EC_POINT_new(session->group)) == NULL) ||
+ ((session->order = consttime_BN()) == NULL) ||
+ ((session->prime = consttime_BN()) == NULL) ||
+ ((qr = consttime_BN()) == NULL) ||
+ ((qnr = consttime_BN()) == NULL) ||
+ ((x_candidate = consttime_BN()) == NULL) ||
+ ((y_sqrd = consttime_BN()) == NULL) ||
+ ((y1 = consttime_BN()) == NULL) ||
+ ((y2 = consttime_BN()) == NULL) ||
+ ((y = consttime_BN()) == NULL) ||
+ ((exp = consttime_BN()) == NULL)) {
+ DEBUG("unable to create bignums");
+ goto fail;
+ }
+
+ if (!EC_GROUP_get_curve(session->group, session->prime, NULL, NULL, NULL)) {
+ DEBUG("unable to get prime for GFp curve");
+ goto fail;
+ }
+
+ if (!EC_GROUP_get_order(session->group, session->order, NULL)) {
+ DEBUG("unable to get order for curve");
+ goto fail;
+ }
+
+ primebitlen = BN_num_bits(session->prime);
+ primebytelen = BN_num_bytes(session->prime);
+ if ((prfbuf = talloc_zero_array(session, uint8_t, primebytelen)) == NULL) {
+ DEBUG("unable to alloc space for prf buffer");
+ goto fail;
+ }
+ if ((xbuf = talloc_zero_array(request, uint8_t, primebytelen)) == NULL) {
+ DEBUG("unable to alloc space for x buffer");
+ goto fail;
+ }
+ if ((pm1buf = talloc_zero_array(request, uint8_t, primebytelen)) == NULL) {
+ DEBUG("unable to alloc space for pm1 buffer");
+ goto fail;
+ }
+ if ((y1buf = talloc_zero_array(request, uint8_t, primebytelen)) == NULL) {
+ DEBUG("unable to alloc space for y1 buffer");
+ goto fail;
+ }
+ if ((y2buf = talloc_zero_array(request, uint8_t, primebytelen)) == NULL) {
+ DEBUG("unable to alloc space for y2 buffer");
+ goto fail;
+ }
+ if ((ybuf = talloc_zero_array(request, uint8_t, primebytelen)) == NULL) {
+ DEBUG("unable to alloc space for y buffer");
+ goto fail;
+ }
+
+
+ /*
+ * derive random quadradic residue and quadratic non-residue
+ */
+ do {
+ BN_rand_range(qr, session->prime);
+ } while (legendre(qr, session->prime, session->bnctx) != 1);
+
+ do {
+ BN_rand_range(qnr, session->prime);
+ } while (legendre(qnr, session->prime, session->bnctx) != -1);
+
+ if (!BN_sub(rnd, session->prime, BN_value_one())) {
+ goto fail;
+ }
+ BN_bn2bin(rnd, pm1buf);
+
+ save_is_odd = 0;
+ found = 0;
+ memset(xbuf, 0, primebytelen);
+ ctr = 0;
+ while (ctr < 40) {
+ ctr++;
+
+ /*
+ * compute counter-mode password value and stretch to prime
+ * pwd-seed = H(token | peer-id | server-id | password |
+ * counter)
+ */
+ EVP_DigestSignInit(hmac_ctx, NULL, EVP_sha256(), NULL, hmac_pkey);
+ EVP_DigestSignUpdate(hmac_ctx, (uint8_t *)token, sizeof(*token));
+ EVP_DigestSignUpdate(hmac_ctx, (uint8_t const *)id_peer, id_peer_len);
+ EVP_DigestSignUpdate(hmac_ctx, (uint8_t const *)id_server, id_server_len);
+ EVP_DigestSignUpdate(hmac_ctx, (uint8_t const *)password, password_len);
+ EVP_DigestSignUpdate(hmac_ctx, (uint8_t *)&ctr, sizeof(ctr));
+
+ {
+ size_t mdlen = SHA256_DIGEST_LENGTH;
+
+ EVP_DigestSignFinal(hmac_ctx, pwe_digest, &mdlen);
+ EVP_MD_CTX_reset(hmac_ctx);
+ }
+
+ BN_bin2bn(pwe_digest, SHA256_DIGEST_LENGTH, rnd);
+ eap_pwd_kdf(pwe_digest, SHA256_DIGEST_LENGTH, "EAP-pwd Hunting And Pecking",
+ strlen("EAP-pwd Hunting And Pecking"), prfbuf, primebitlen);
+
+ /*
+ * eap_pwd_kdf() returns a string of bits 0..primebitlen but
+ * BN_bin2bn will treat that string of bits as a big endian
+ * number. If the primebitlen is not an even multiple of 8
+ * then excessive bits-- those _after_ primebitlen-- so now
+ * we have to shift right the amount we masked off.
+ */
+ if (primebitlen % 8) {
+ rbits = 8 - (primebitlen % 8);
+ for (i = primebytelen - 1; i > 0; i--) {
+ prfbuf[i] = (prfbuf[i - 1] << (8 - rbits)) | (prfbuf[i] >> rbits);
+ }
+ prfbuf[0] >>= rbits;
+ }
+ BN_bin2bn(prfbuf, primebytelen, x_candidate);
+
+ /*
+ * it would've been better if the spec reduced the candidate
+ * modulo the prime but it didn't. So if the candidate >= prime
+ * we need to skip it but still run through the operations below
+ */
+ cmp = const_time_memcmp(pm1buf, prfbuf, primebytelen);
+ skip = const_time_fill_msb((unsigned int)cmp);
+
+ /*
+ * need to unambiguously identify the solution, if there is
+ * one..
+ */
+ is_odd = BN_is_odd(rnd);
+
+ /*
+ * check whether x^3 + a*x + b is a quadratic residue
+ *
+ * save the first quadratic residue we find in the loop but do
+ * it in constant time.
+ */
+ do_equation(session->group, y_sqrd, x_candidate, session->bnctx);
+ qr_or_qnr = is_quadratic_residue(y_sqrd, session->prime, qr, qnr, session->bnctx);
+
+ /*
+ * if the candidate >= prime then we want to skip it
+ */
+ qr_or_qnr = const_time_select(skip, 0, qr_or_qnr);
+
+ /*
+ * if we haven't found PWE yet (found = 0) then mask will be true,
+ * if we have found PWE then mask will be false
+ */
+ mask = const_time_select(found, 0, -1);
+
+ /*
+ * save will be 1 if we want to save this value-- i.e. we haven't
+ * found PWE yet and this is a quadratic residue-- and 0 otherwise
+ */
+ save = const_time_select(mask, qr_or_qnr, 0);
+
+ /*
+ * mask will be true (-1) if we want to save this and false (0)
+ * otherwise
+ */
+ mask = const_time_eq(save, 1);
+
+ const_time_select_bin(mask, prfbuf, xbuf, primebytelen, xbuf);
+ save_is_odd = const_time_select(mask, is_odd, save_is_odd);
+ found = const_time_select(mask, -1, found);
+ }
+
+ /*
+ * now we can savely construct PWE
+ */
+ BN_bin2bn(xbuf, primebytelen, x_candidate);
+ do_equation(session->group, y_sqrd, x_candidate, session->bnctx);
+ if ( !BN_add(exp, session->prime, BN_value_one()) ||
+ !BN_rshift(exp, exp, 2) ||
+ !BN_mod_exp_mont_consttime(y1, y_sqrd, exp, session->prime, session->bnctx, NULL) ||
+ !BN_sub(y2, session->prime, y1) ||
+ !BN_bn2bin(y1, y1buf) ||
+ !BN_bn2bin(y2, y2buf)) {
+ DEBUG("unable to compute y");
+ goto fail;
+ }
+ mask = const_time_eq(save_is_odd, BN_is_odd(y1));
+ const_time_select_bin(mask, y1buf, y2buf, primebytelen, ybuf);
+ if (BN_bin2bn(ybuf, primebytelen, y) == NULL ||
+ !EC_POINT_set_affine_coordinates(session->group, session->pwe, x_candidate, y, session->bnctx)) {
+ DEBUG("unable to set point coordinate");
+ goto fail;
+ }
+
+ session->group_num = grp_num;
+ if (0) {
+ fail: /* DON'T free session, it's in handler->opaque */
+ ret = -1;
+ }
+
+ /* cleanliness and order.... */
+ BN_clear_free(x_candidate);
+ BN_clear_free(y_sqrd);
+ BN_clear_free(qr);
+ BN_clear_free(qnr);
+ BN_clear_free(rnd);
+ BN_clear_free(y1);
+ BN_clear_free(y2);
+ BN_clear_free(y);
+ BN_clear_free(exp);
+
+ if (prfbuf) talloc_free(prfbuf);
+ if (xbuf) talloc_free(xbuf);
+ if (pm1buf) talloc_free(pm1buf);
+ if (y1buf) talloc_free(y1buf);
+ if (y2buf) talloc_free(y2buf);
+ if (ybuf) talloc_free(ybuf);
+
+ EVP_MD_CTX_free(hmac_ctx);
+ EVP_PKEY_free(hmac_pkey);
+
+ return ret;
+}
+
+int compute_scalar_element(REQUEST *request, pwd_session_t *session, BN_CTX *bn_ctx)
+{
+ BIGNUM *mask = NULL;
+ int ret = -1;
+
+ MEM(session->private_value = BN_new());
+ MEM(session->my_element = EC_POINT_new(session->group));
+ MEM(session->my_scalar = BN_new());
+
+ MEM(mask = BN_new());
+
+ if (BN_rand_range(session->private_value, session->order) != 1) {
+ REDEBUG("Unable to get randomness for private_value");
+ goto error;
+ }
+ if (BN_rand_range(mask, session->order) != 1) {
+ REDEBUG("Unable to get randomness for mask");
+ goto error;
+ }
+ BN_add(session->my_scalar, session->private_value, mask);
+ BN_mod(session->my_scalar, session->my_scalar, session->order, bn_ctx);
+
+ if (!EC_POINT_mul(session->group, session->my_element, NULL, session->pwe, mask, bn_ctx)) {
+ REDEBUG("Server element allocation failed");
+ goto error;
+ }
+
+ if (!EC_POINT_invert(session->group, session->my_element, bn_ctx)) {
+ REDEBUG("Server element inversion failed");
+ goto error;
+ }
+
+ ret = 0;
+
+error:
+ BN_clear_free(mask);
+
+ return ret;
+}
+
+int process_peer_commit(REQUEST *request, pwd_session_t *session, uint8_t *in, size_t in_len, BN_CTX *bn_ctx)
+{
+ uint8_t *ptr;
+ size_t data_len;
+ BIGNUM *x = NULL, *y = NULL, *cofactor = NULL;
+ EC_POINT *K = NULL, *point = NULL;
+ int ret = 1;
+
+ MEM(session->peer_scalar = BN_new());
+ MEM(session->k = BN_new());
+ MEM(session->peer_element = EC_POINT_new(session->group));
+ MEM(point = EC_POINT_new(session->group));
+ MEM(K = EC_POINT_new(session->group));
+
+ MEM(cofactor = BN_new());
+ MEM(x = BN_new());
+ MEM(y = BN_new());
+
+ if (!EC_GROUP_get_cofactor(session->group, cofactor, NULL)) {
+ REDEBUG("Unable to get group co-factor");
+ goto finish;
+ }
+
+ /* element, x then y, followed by scalar */
+ ptr = (uint8_t *)in;
+ data_len = BN_num_bytes(session->prime);
+
+ /*
+ * Did the peer send enough data?
+ */
+ if (in_len < (2 * data_len + BN_num_bytes(session->order))) {
+ REDEBUG("Invalid commit packet");
+ goto finish;
+ }
+
+ BN_bin2bn(ptr, data_len, x);
+ ptr += data_len;
+ BN_bin2bn(ptr, data_len, y);
+ ptr += data_len;
+
+ data_len = BN_num_bytes(session->order);
+ BN_bin2bn(ptr, data_len, session->peer_scalar);
+
+ /* validate received scalar */
+ if (BN_is_zero(session->peer_scalar) ||
+ BN_is_one(session->peer_scalar) ||
+ BN_cmp(session->peer_scalar, session->order) >= 0) {
+ REDEBUG("Peer's scalar is not within the allowed range");
+ goto finish;
+ }
+
+ if (!EC_POINT_set_affine_coordinates(session->group, session->peer_element, x, y, bn_ctx)) {
+ REDEBUG("Unable to get coordinates of peer's element");
+ goto finish;
+ }
+
+ /* validate received element */
+ if (!EC_POINT_is_on_curve(session->group, session->peer_element, bn_ctx) ||
+ EC_POINT_is_at_infinity(session->group, session->peer_element)) {
+ REDEBUG("Peer's element is not a point on the elliptic curve");
+ goto finish;
+ }
+
+ /* check to ensure peer's element is not in a small sub-group */
+ if (BN_cmp(cofactor, BN_value_one())) {
+ if (!EC_POINT_mul(session->group, point, NULL, session->peer_element, cofactor, NULL)) {
+ REDEBUG("Unable to multiply element by co-factor");
+ goto finish;
+ }
+
+ if (EC_POINT_is_at_infinity(session->group, point)) {
+ REDEBUG("Peer's element is in small sub-group");
+ goto finish;
+ }
+ }
+
+ /* detect reflection attacks */
+ if (BN_cmp(session->peer_scalar, session->my_scalar) == 0 ||
+ EC_POINT_cmp(session->group, session->peer_element, session->my_element, bn_ctx) == 0) {
+ REDEBUG("Reflection attack detected");
+ goto finish;
+ }
+
+ /* compute the shared key, k */
+ if ((!EC_POINT_mul(session->group, K, NULL, session->pwe, session->peer_scalar, bn_ctx)) ||
+ (!EC_POINT_add(session->group, K, K, session->peer_element, bn_ctx)) ||
+ (!EC_POINT_mul(session->group, K, NULL, K, session->private_value, bn_ctx))) {
+ REDEBUG("Unable to compute shared key, k");
+ goto finish;
+ }
+
+ /* ensure that the shared key isn't in a small sub-group */
+ if (BN_cmp(cofactor, BN_value_one())) {
+ if (!EC_POINT_mul(session->group, K, NULL, K, cofactor, NULL)) {
+ REDEBUG("Unable to multiply k by co-factor");
+ goto finish;
+ }
+ }
+
+ /*
+ * This check is strictly speaking just for the case above where
+ * co-factor > 1 but it was suggested that even though this is probably
+ * never going to happen it is a simple and safe check "just to be
+ * sure" so let's be safe.
+ */
+ if (EC_POINT_is_at_infinity(session->group, K)) {
+ REDEBUG("K is point-at-infinity");
+ goto finish;
+ }
+
+ if (!EC_POINT_get_affine_coordinates(session->group, K, session->k, NULL, bn_ctx)) {
+ REDEBUG("Unable to get shared secret from K");
+ goto finish;
+ }
+ ret = 0;
+
+finish:
+ EC_POINT_clear_free(K);
+ EC_POINT_clear_free(point);
+ BN_clear_free(cofactor);
+ BN_clear_free(x);
+ BN_clear_free(y);
+
+ return ret;
+}
+
+int compute_server_confirm(REQUEST *request, pwd_session_t *session, uint8_t *out, BN_CTX *bn_ctx)
+{
+ BIGNUM *x = NULL, *y = NULL;
+ HMAC_CTX *hmac_ctx = NULL;
+ uint8_t *cruft = NULL;
+ int offset, req = -1;
+
+ /*
+ * Each component of the cruft will be at most as big as the prime
+ */
+ MEM(cruft = talloc_zero_array(session, uint8_t, BN_num_bytes(session->prime)));
+ MEM(x = BN_new());
+ MEM(y = BN_new());
+
+ /*
+ * commit is H(k | server_element | server_scalar | peer_element |
+ * peer_scalar | ciphersuite)
+ */
+ MEM(hmac_ctx = HMAC_CTX_new());
+ HMAC_Init_ex(hmac_ctx, allzero, SHA256_DIGEST_LENGTH, EVP_sha256(), NULL);
+
+ /*
+ * Zero the memory each time because this is mod prime math and some
+ * value may start with a few zeros and the previous one did not.
+ *
+ * First is k
+ */
+ offset = BN_num_bytes(session->prime) - BN_num_bytes(session->k);
+ BN_bn2bin(session->k, cruft + offset);
+ HMAC_Update(hmac_ctx, cruft, BN_num_bytes(session->prime));
+
+ /*
+ * next is server element: x, y
+ */
+ if (!EC_POINT_get_affine_coordinates(session->group, session->my_element, x, y, bn_ctx)) {
+ REDEBUG("Unable to get coordinates of server element");
+ goto finish;
+ }
+ memset(cruft, 0, BN_num_bytes(session->prime));
+ offset = BN_num_bytes(session->prime) - BN_num_bytes(x);
+ BN_bn2bin(x, cruft + offset);
+ HMAC_Update(hmac_ctx, cruft, BN_num_bytes(session->prime));
+
+ memset(cruft, 0, BN_num_bytes(session->prime));
+ offset = BN_num_bytes(session->prime) - BN_num_bytes(y);
+ BN_bn2bin(y, cruft + offset);
+ HMAC_Update(hmac_ctx, cruft, BN_num_bytes(session->prime));
+
+ /*
+ * and server scalar
+ */
+ memset(cruft, 0, BN_num_bytes(session->prime));
+ offset = BN_num_bytes(session->order) - BN_num_bytes(session->my_scalar);
+ BN_bn2bin(session->my_scalar, cruft + offset);
+ HMAC_Update(hmac_ctx, cruft, BN_num_bytes(session->order));
+
+ /*
+ * next is peer element: x, y
+ */
+ if (!EC_POINT_get_affine_coordinates(session->group, session->peer_element, x, y, bn_ctx)) {
+ REDEBUG("Unable to get coordinates of peer's element");
+ goto finish;
+ }
+
+ memset(cruft, 0, BN_num_bytes(session->prime));
+ offset = BN_num_bytes(session->prime) - BN_num_bytes(x);
+ BN_bn2bin(x, cruft + offset);
+ HMAC_Update(hmac_ctx, cruft, BN_num_bytes(session->prime));
+
+ memset(cruft, 0, BN_num_bytes(session->prime));
+ offset = BN_num_bytes(session->prime) - BN_num_bytes(y);
+ BN_bn2bin(y, cruft + offset);
+ HMAC_Update(hmac_ctx, cruft, BN_num_bytes(session->prime));
+
+ /*
+ * and peer scalar
+ */
+ memset(cruft, 0, BN_num_bytes(session->prime));
+ offset = BN_num_bytes(session->order) - BN_num_bytes(session->peer_scalar);
+ BN_bn2bin(session->peer_scalar, cruft + offset);
+ HMAC_Update(hmac_ctx, cruft, BN_num_bytes(session->order));
+
+ /*
+ * finally, ciphersuite
+ */
+ HMAC_Update(hmac_ctx, (uint8_t *)&session->ciphersuite, sizeof(session->ciphersuite));
+
+ pwd_hmac_final(hmac_ctx, out);
+
+ req = 0;
+
+finish:
+ HMAC_CTX_free(hmac_ctx);
+ talloc_free(cruft);
+ BN_free(x);
+ BN_free(y);
+
+ return req;
+}
+
+int compute_peer_confirm(REQUEST *request, pwd_session_t *session, uint8_t *out, BN_CTX *bn_ctx)
+{
+ BIGNUM *x = NULL, *y = NULL;
+ HMAC_CTX *hmac_ctx = NULL;
+ uint8_t *cruft = NULL;
+ int offset, req = -1;
+
+ /*
+ * Each component of the cruft will be at most as big as the prime
+ */
+ MEM(cruft = talloc_zero_array(session, uint8_t, BN_num_bytes(session->prime)));
+ MEM(x = BN_new());
+ MEM(y = BN_new());
+
+ /*
+ * commit is H(k | server_element | server_scalar | peer_element |
+ * peer_scalar | ciphersuite)
+ */
+ MEM(hmac_ctx = HMAC_CTX_new());
+ HMAC_Init_ex(hmac_ctx, allzero, SHA256_DIGEST_LENGTH, EVP_sha256(), NULL);
+
+ /*
+ * Zero the memory each time because this is mod prime math and some
+ * value may start with a few zeros and the previous one did not.
+ *
+ * First is k
+ */
+ offset = BN_num_bytes(session->prime) - BN_num_bytes(session->k);
+ BN_bn2bin(session->k, cruft + offset);
+ HMAC_Update(hmac_ctx, cruft, BN_num_bytes(session->prime));
+
+ /*
+ * then peer element: x, y
+ */
+ if (!EC_POINT_get_affine_coordinates(session->group, session->peer_element, x, y, bn_ctx)) {
+ REDEBUG("Unable to get coordinates of peer's element");
+ goto finish;
+ }
+
+ memset(cruft, 0, BN_num_bytes(session->prime));
+ offset = BN_num_bytes(session->prime) - BN_num_bytes(x);
+ BN_bn2bin(x, cruft + offset);
+ HMAC_Update(hmac_ctx, cruft, BN_num_bytes(session->prime));
+
+ memset(cruft, 0, BN_num_bytes(session->prime));
+ offset = BN_num_bytes(session->prime) - BN_num_bytes(y);
+ BN_bn2bin(y, cruft + offset);
+ HMAC_Update(hmac_ctx, cruft, BN_num_bytes(session->prime));
+
+ /*
+ * and peer scalar
+ */
+ memset(cruft, 0, BN_num_bytes(session->prime));
+ offset = BN_num_bytes(session->order) - BN_num_bytes(session->peer_scalar);
+ BN_bn2bin(session->peer_scalar, cruft + offset);
+ HMAC_Update(hmac_ctx, cruft, BN_num_bytes(session->order));
+
+ /*
+ * then server element: x, y
+ */
+ if (!EC_POINT_get_affine_coordinates(session->group, session->my_element, x, y, bn_ctx)) {
+ REDEBUG("Unable to get coordinates of server element");
+ goto finish;
+ }
+ memset(cruft, 0, BN_num_bytes(session->prime));
+ offset = BN_num_bytes(session->prime) - BN_num_bytes(x);
+ BN_bn2bin(x, cruft + offset);
+ HMAC_Update(hmac_ctx, cruft, BN_num_bytes(session->prime));
+
+ memset(cruft, 0, BN_num_bytes(session->prime));
+ offset = BN_num_bytes(session->prime) - BN_num_bytes(y);
+ BN_bn2bin(y, cruft + offset);
+ HMAC_Update(hmac_ctx, cruft, BN_num_bytes(session->prime));
+
+ /*
+ * and server scalar
+ */
+ memset(cruft, 0, BN_num_bytes(session->prime));
+ offset = BN_num_bytes(session->order) - BN_num_bytes(session->my_scalar);
+ BN_bn2bin(session->my_scalar, cruft + offset);
+ HMAC_Update(hmac_ctx, cruft, BN_num_bytes(session->order));
+
+ /*
+ * finally, ciphersuite
+ */
+ HMAC_Update(hmac_ctx, (uint8_t *)&session->ciphersuite, sizeof(session->ciphersuite));
+
+ pwd_hmac_final(hmac_ctx, out);
+
+ req = 0;
+finish:
+ HMAC_CTX_free(hmac_ctx);
+ talloc_free(cruft);
+ BN_free(x);
+ BN_free(y);
+
+ return req;
+}
+
+int compute_keys(UNUSED REQUEST *request, pwd_session_t *session, uint8_t *peer_confirm, uint8_t *msk, uint8_t *emsk)
+{
+ HMAC_CTX *hmac_ctx;
+ uint8_t mk[SHA256_DIGEST_LENGTH], *cruft;
+ uint8_t session_id[SHA256_DIGEST_LENGTH + 1];
+ uint8_t msk_emsk[128]; /* 64 each */
+ int offset;
+
+ MEM(cruft = talloc_array(session, uint8_t, BN_num_bytes(session->prime)));
+ MEM(hmac_ctx = HMAC_CTX_new());
+
+ /*
+ * first compute the session-id = TypeCode | H(ciphersuite | scal_p |
+ * scal_s)
+ */
+ session_id[0] = PW_EAP_PWD;
+ HMAC_Init_ex(hmac_ctx, allzero, SHA256_DIGEST_LENGTH, EVP_sha256(), NULL);
+ HMAC_Update(hmac_ctx, (uint8_t *)&session->ciphersuite, sizeof(session->ciphersuite));
+ offset = BN_num_bytes(session->order) - BN_num_bytes(session->peer_scalar);
+ memset(cruft, 0, BN_num_bytes(session->prime));
+ BN_bn2bin(session->peer_scalar, cruft + offset);
+ HMAC_Update(hmac_ctx, cruft, BN_num_bytes(session->order));
+ offset = BN_num_bytes(session->order) - BN_num_bytes(session->my_scalar);
+ memset(cruft, 0, BN_num_bytes(session->prime));
+ BN_bn2bin(session->my_scalar, cruft + offset);
+ HMAC_Update(hmac_ctx, cruft, BN_num_bytes(session->order));
+ pwd_hmac_final(hmac_ctx, (uint8_t *)&session_id[1]);
+
+ /* then compute MK = H(k | commit-peer | commit-server) */
+ HMAC_Init_ex(hmac_ctx, allzero, SHA256_DIGEST_LENGTH, EVP_sha256(), NULL);
+
+ memset(cruft, 0, BN_num_bytes(session->prime));
+ offset = BN_num_bytes(session->prime) - BN_num_bytes(session->k);
+ BN_bn2bin(session->k, cruft + offset);
+ HMAC_Update(hmac_ctx, cruft, BN_num_bytes(session->prime));
+
+ HMAC_Update(hmac_ctx, peer_confirm, SHA256_DIGEST_LENGTH);
+
+ HMAC_Update(hmac_ctx, session->my_confirm, SHA256_DIGEST_LENGTH);
+
+ pwd_hmac_final(hmac_ctx, mk);
+
+ /* stretch the mk with the session-id to get MSK | EMSK */
+ eap_pwd_kdf(mk, SHA256_DIGEST_LENGTH, (char const *)session_id,
+ SHA256_DIGEST_LENGTH + 1, msk_emsk, 1024); /* it's bits, ((64 + 64) * 8) */
+
+ memcpy(msk, msk_emsk, 64);
+ memcpy(emsk, msk_emsk + 64, 64);
+
+ HMAC_CTX_free(hmac_ctx);
+ talloc_free(cruft);
+ return 0;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-05-19 18:02:48 +0000