radius.c

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	struct radius_attr_hdr *attr = NULL;
	int i;

	for (i = 0; i < msg->attr_used; i++) {
		if (msg->attrs[i]->type == RADIUS_ATTR_MESSAGE_AUTHENTICATOR) {
			if (attr != NULL) {
				printf("Multiple Message-Authenticator "
				       "attributes in RADIUS message\n");
				return 1;
			}
			attr = msg->attrs[i];
		}
	}

	if (attr == NULL) {
		printf("No Message-Authenticator attribute found\n");
		return 1;
	}

	memcpy(orig, attr + 1, MD5_MAC_LEN);
	memset(attr + 1, 0, MD5_MAC_LEN);
	if (req_auth) {
		memcpy(orig_authenticator, msg->hdr->authenticator,
		       sizeof(orig_authenticator));
		memcpy(msg->hdr->authenticator, req_auth,
		       sizeof(msg->hdr->authenticator));
	}
	hmac_md5(secret, secret_len, msg->buf, msg->buf_used, auth);
	memcpy(attr + 1, orig, MD5_MAC_LEN);
	if (req_auth) {
		memcpy(msg->hdr->authenticator, orig_authenticator,
		       sizeof(orig_authenticator));
	}

	if (memcmp(orig, auth, MD5_MAC_LEN) != 0) {
		printf("Invalid Message-Authenticator!\n");
		return 1;
	}

	return 0;
}


int radius_msg_verify(struct radius_msg *msg, u8 *secret, size_t secret_len,
		      struct radius_msg *sent_msg)
{
	MD5_CTX context;
	u8 hash[MD5_MAC_LEN];

	if (sent_msg == NULL) {
		printf("No matching Access-Request message found\n");
		return 1;
	}

	if (radius_msg_verify_msg_auth(msg, secret, secret_len,
				       sent_msg->hdr->authenticator)) {
		return 1;
	}

	/* ResponseAuth = MD5(Code+ID+Length+RequestAuth+Attributes+Secret) */
	MD5Init(&context);
	MD5Update(&context, (u8 *) msg->hdr, 1 + 1 + 2);
	MD5Update(&context, sent_msg->hdr->authenticator, MD5_MAC_LEN);
	MD5Update(&context, (u8 *) (msg->hdr + 1),
		  msg->buf_used - sizeof(*msg->hdr));
	MD5Update(&context, secret, secret_len);
	MD5Final(hash, &context);
	if (memcmp(hash, msg->hdr->authenticator, MD5_MAC_LEN) != 0) {
		printf("Response Authenticator invalid!\n");
		return 1;
	}

	return 0;

}


int radius_msg_verify_acct(struct radius_msg *msg, u8 *secret,
			   size_t secret_len, struct radius_msg *sent_msg)
{
	MD5_CTX context;
	u8 hash[MD5_MAC_LEN];

	MD5Init(&context);
	MD5Update(&context, msg->buf, 4);
	MD5Update(&context, sent_msg->hdr->authenticator, MD5_MAC_LEN);
	if (msg->buf_used > sizeof(struct radius_hdr))
		MD5Update(&context, msg->buf + sizeof(struct radius_hdr),
			  msg->buf_used - sizeof(struct radius_hdr));
	MD5Update(&context, secret, secret_len);
	MD5Final(hash, &context);
	if (memcmp(hash, msg->hdr->authenticator, MD5_MAC_LEN) != 0) {
		printf("Response Authenticator invalid!\n");
		return 1;
	}

	return 0;
}


int radius_msg_copy_attr(struct radius_msg *dst, struct radius_msg *src,
			 u8 type)
{
	struct radius_attr_hdr *attr = NULL;
	int i;

	for (i = 0; i < src->attr_used; i++) {
		if (src->attrs[i]->type == type) {
			attr = src->attrs[i];
			break;
		}
	}

	if (attr == NULL)
		return 0;

	if (!radius_msg_add_attr(dst, type, (u8 *) (attr + 1),
				 attr->length - sizeof(*attr)))
		return -1;

	return 1;
}


/* Create Request Authenticator. The value should be unique over the lifetime
 * of the shared secret between authenticator and authentication server.
 * Use one-way MD5 hash calculated from current timestamp and some data given
 * by the caller. */
void radius_msg_make_authenticator(struct radius_msg *msg,
				   u8 *data, size_t len)
{
	struct timeval tv;
	MD5_CTX context;
	long int l;

	gettimeofday(&tv, NULL);
	l = random();
	MD5Init(&context);
	MD5Update(&context, (u8 *) &tv, sizeof(tv));
	MD5Update(&context, data, len);
	MD5Update(&context, (u8 *) &l, sizeof(l));
	MD5Final(msg->hdr->authenticator, &context);
}


/* Get Vendor-specific RADIUS Attribute from a parsed RADIUS message.
 * Returns the Attribute payload and sets alen to indicate the length of the
 * payload if a vendor attribute with subtype is found, otherwise returns NULL.
 * The returned payload is allocated with malloc() and caller must free it.
 */
static u8 *radius_msg_get_vendor_attr(struct radius_msg *msg, u32 vendor,
				      u8 subtype, size_t *alen)
{
	u8 *data, *pos;
	int i;
	size_t len;

	if (msg == NULL)
		return NULL;

	for (i = 0; i < msg->attr_used; i++) {
		struct radius_attr_hdr *attr = msg->attrs[i];
		int left;
		u32 vendor_id;
		struct radius_attr_vendor *vhdr;

		if (attr->type != RADIUS_ATTR_VENDOR_SPECIFIC)
			continue;

		left = attr->length - sizeof(*attr);
		if (left < 4)
			continue;

		pos = (u8 *) (attr + 1);

		memcpy(&vendor_id, pos, 4);
		pos += 4;
		left -= 4;

		if (ntohl(vendor_id) != vendor)
			continue;

		while (left >= sizeof(*vhdr)) {
			vhdr = (struct radius_attr_vendor *) pos;
			if (vhdr->vendor_length > left ||
			    vhdr->vendor_length < sizeof(*vhdr)) {
				left = 0;
				break;
			}
			if (vhdr->vendor_type != subtype) {
				pos += vhdr->vendor_length;
				left -= vhdr->vendor_length;
				continue;
			}

			len = vhdr->vendor_length - sizeof(*vhdr);
			data = malloc(len);
			if (data == NULL)
				return NULL;
			memcpy(data, pos + sizeof(*vhdr), len);
			if (alen)
				*alen = len;
			return data;
		}
	}

	return NULL;
}


static u8 * decrypt_ms_key(const u8 *key, size_t len,
			   const u8 *req_authenticator,
			   const u8 *secret, size_t secret_len, size_t *reslen)
{
	u8 *plain, *ppos, *res;
	const u8 *pos;
	size_t left, plen;
	u8 hash[MD5_MAC_LEN];
	MD5_CTX context;
	int i, first = 1;

	/* key: 16-bit salt followed by encrypted key info */

	if (len < 2 + 16)
		return NULL;

	pos = key + 2;
	left = len - 2;
	if (left % 16) {
		printf("Invalid ms key len %lu\n", (unsigned long) left);
		return NULL;
	}

	plen = left;
	ppos = plain = malloc(plen);
	if (plain == NULL)
		return NULL;

	while (left > 0) {
		/* b(1) = MD5(Secret + Request-Authenticator + Salt)
		 * b(i) = MD5(Secret + c(i - 1)) for i > 1 */

		MD5Init(&context);
		MD5Update(&context, secret, secret_len);
		if (first) {
			MD5Update(&context, req_authenticator, MD5_MAC_LEN);
			MD5Update(&context, key, 2); /* Salt */
			first = 0;
		} else
			MD5Update(&context, pos - MD5_MAC_LEN, MD5_MAC_LEN);
		MD5Final(hash, &context);

		for (i = 0; i < MD5_MAC_LEN; i++)
			*ppos++ = *pos++ ^ hash[i];
		left -= MD5_MAC_LEN;
	}

	if (plain[0] > plen - 1) {
		printf("Failed to decrypt MPPE key\n");
		free(plain);
		return NULL;
	}

	res = malloc(plain[0]);
	if (res == NULL) {
		free(plain);
		return NULL;
	}
	memcpy(res, plain + 1, plain[0]);
	if (reslen)
		*reslen = plain[0];
	free(plain);
	return res;
}


static void encrypt_ms_key(const u8 *key, size_t key_len, u16 salt,
			   const u8 *req_authenticator,
			   const u8 *secret, size_t secret_len,
			   u8 *ebuf, size_t *elen)
{
	int i, len, first = 1;
	u8 hash[MD5_MAC_LEN], saltbuf[2], *pos;
	MD5_CTX context;

	saltbuf[0] = salt >> 8;
	saltbuf[1] = salt;

	len = 1 + key_len;
	if (len & 0x0f) {
		len = (len & 0xf0) + 16;
	}
	memset(ebuf, 0, len);
	ebuf[0] = key_len;
	memcpy(ebuf + 1, key, key_len);

	*elen = len;

	pos = ebuf;
	while (len > 0) {
		/* b(1) = MD5(Secret + Request-Authenticator + Salt)
		 * b(i) = MD5(Secret + c(i - 1)) for i > 1 */
		MD5Init(&context);
		MD5Update(&context, secret, secret_len);
		if (first) {
			MD5Update(&context, req_authenticator, MD5_MAC_LEN);
			MD5Update(&context, saltbuf, sizeof(saltbuf));
			first = 0;
		} else {
			MD5Update(&context, pos - MD5_MAC_LEN, MD5_MAC_LEN);
		}
		MD5Final(hash, &context);

		for (i = 0; i < MD5_MAC_LEN; i++)
			*pos++ ^= hash[i];

		len -= MD5_MAC_LEN;
	}
}


struct radius_ms_mppe_keys *
radius_msg_get_ms_keys(struct radius_msg *msg, struct radius_msg *sent_msg,
		       u8 *secret, size_t secret_len)
{
	u8 *key;
	size_t keylen;
	struct radius_ms_mppe_keys *keys;

	if (msg == NULL || sent_msg == NULL)
		return NULL;

	keys = (struct radius_ms_mppe_keys *) malloc(sizeof(*keys));
	if (keys == NULL)
		return NULL;

	memset(keys, 0, sizeof(*keys));

	key = radius_msg_get_vendor_attr(msg, RADIUS_VENDOR_ID_MICROSOFT,
					 RADIUS_VENDOR_ATTR_MS_MPPE_SEND_KEY,
					 &keylen);
	if (key) {
		keys->send = decrypt_ms_key(key, keylen,
					    sent_msg->hdr->authenticator,
					    secret, secret_len,
					    &keys->send_len);
		free(key);
	}

	key = radius_msg_get_vendor_attr(msg, RADIUS_VENDOR_ID_MICROSOFT,
					 RADIUS_VENDOR_ATTR_MS_MPPE_RECV_KEY,
					 &keylen);
	if (key) {
		keys->recv = decrypt_ms_key(key, keylen,
					    sent_msg->hdr->authenticator,
					    secret, secret_len,
					    &keys->recv_len);
		free(key);
	}

	return keys;
}


struct radius_ms_mppe_keys *
radius_msg_get_cisco_keys(struct radius_msg *msg, struct radius_msg *sent_msg,
			  u8 *secret, size_t secret_len)
{
	u8 *key;
	size_t keylen;
	struct radius_ms_mppe_keys *keys;

	if (msg == NULL || sent_msg == NULL)
		return NULL;

	keys = (struct radius_ms_mppe_keys *) malloc(sizeof(*keys));
	if (keys == NULL)
		return NULL;

	memset(keys, 0, sizeof(*keys));

	key = radius_msg_get_vendor_attr(msg, RADIUS_VENDOR_ID_CISCO,
					 RADIUS_CISCO_AV_PAIR, &keylen);
	if (key && keylen == 51 && memcmp(key, "leap:session-key=", 17) == 0) {
		keys->recv = decrypt_ms_key(key + 17, keylen - 17,
					    sent_msg->hdr->authenticator,
					    secret, secret_len,
					    &keys->recv_len);
		free(key);
	}

	return keys;
}


int radius_msg_add_mppe_keys(struct radius_msg *msg,
			     const u8 *req_authenticator,
			     const u8 *secret, size_t secret_len,
			     const u8 *send_key, size_t send_key_len,
			     const u8 *recv_key, size_t recv_key_len)
{
	struct radius_attr_hdr *attr;
	u32 vendor_id = htonl(RADIUS_VENDOR_ID_MICROSOFT);
	u8 *buf;
	struct radius_attr_vendor *vhdr;
	u8 *pos;
	size_t elen;
	int hlen;
	u16 salt;

	hlen = sizeof(vendor_id) + sizeof(*vhdr) + 2;

	/* MS-MPPE-Send-Key */
	buf = malloc(hlen + send_key_len + 16);
	if (buf == NULL) {
		return 0;
	}
	pos = buf;
	memcpy(pos, &vendor_id, sizeof(vendor_id));
	pos += sizeof(vendor_id);
	vhdr = (struct radius_attr_vendor *) pos;
	vhdr->vendor_type = RADIUS_VENDOR_ATTR_MS_MPPE_SEND_KEY;
	pos = (u8 *) (vhdr + 1);
	salt = random() | 0x8000;
	*pos++ = salt >> 8;
	*pos++ = salt;
	encrypt_ms_key(send_key, send_key_len, salt, req_authenticator, secret,
		       secret_len, pos, &elen);
	vhdr->vendor_length = hlen + elen - sizeof(vendor_id);

	attr = radius_msg_add_attr(msg, RADIUS_ATTR_VENDOR_SPECIFIC,
				   buf, hlen + elen);
	free(buf);
	if (attr == NULL) {
		return 0;
	}

	/* MS-MPPE-Recv-Key */
	buf = malloc(hlen + send_key_len + 16);
	if (buf == NULL) {
		return 0;
	}
	pos = buf;
	memcpy(pos, &vendor_id, sizeof(vendor_id));
	pos += sizeof(vendor_id);
	vhdr = (struct radius_attr_vendor *) pos;
	vhdr->vendor_type = RADIUS_VENDOR_ATTR_MS_MPPE_RECV_KEY;
	pos = (u8 *) (vhdr + 1);
	salt ^= 1;
	*pos++ = salt >> 8;
	*pos++ = salt;
	encrypt_ms_key(recv_key, recv_key_len, salt, req_authenticator, secret,
		       secret_len, pos, &elen);
	vhdr->vendor_length = hlen + elen - sizeof(vendor_id);

	attr = radius_msg_add_attr(msg, RADIUS_ATTR_VENDOR_SPECIFIC,
				   buf, hlen + elen);
	free(buf);
	if (attr == NULL) {
		return 0;
	}

	return 1;
}


/* Add User-Password attribute to a RADIUS message and encrypt it as specified
 * in RFC 2865, Chap. 5.2 */
struct radius_attr_hdr *
radius_msg_add_attr_user_password(struct radius_msg *msg,
				  u8 *data, size_t data_len,
				  u8 *secret, size_t secret_len)
{
	u8 buf[128];
	int padlen, i, pos;
	MD5_CTX context;
	size_t buf_len;
	u8 hash[16];

	if (data_len > 128)
		return NULL;

	memcpy(buf, data, data_len);
	buf_len = data_len;

	padlen = data_len % 16;
	if (padlen) {
		padlen = 16 - padlen;
		memset(buf + data_len, 0, padlen);
		buf_len += padlen;
	}

	MD5Init(&context);
	MD5Update(&context, secret, secret_len);
	MD5Update(&context, msg->hdr->authenticator, 16);
	MD5Final(hash, &context);

	for (i = 0; i < 16; i++)
		buf[i] ^= hash[i];
	pos = 16;

	while (pos < buf_len) {
		MD5Init(&context);
		MD5Update(&context, secret, secret_len);
		MD5Update(&context, &buf[pos - 16], 16);
		MD5Final(hash, &context);

		for (i = 0; i < 16; i++)
			buf[pos + i] ^= hash[i];

		pos += 16;
	}

	return radius_msg_add_attr(msg, RADIUS_ATTR_USER_PASSWORD,
				   buf, buf_len);
}


int radius_msg_get_attr(struct radius_msg *msg, u8 type, u8 *buf, size_t len)
{
	int i;
	struct radius_attr_hdr *attr = NULL;
	size_t dlen;

	for (i = 0; i < msg->attr_used; i++) {
		if (msg->attrs[i]->type == type) {
			attr = msg->attrs[i];
			break;
		}
	}

	if (!attr)
		return -1;

	dlen = attr->length - sizeof(*attr);
	if (buf)
		memcpy(buf, (attr + 1), dlen > len ? len : dlen);
	return dlen;
}


int radius_msg_get_attr_ptr(struct radius_msg *msg, u8 type, u8 **buf,
			    size_t *len, const u8 *start)
{
	int i;
	struct radius_attr_hdr *attr = NULL;

	for (i = 0; i < msg->attr_used; i++) {
		if (msg->attrs[i]->type == type &&
		    (start == NULL || (u8 *) msg->attrs[i] > start)) {
			attr = msg->attrs[i];
			break;
		}
	}

	if (!attr)
		return -1;

	*buf = (u8 *) (attr + 1);
	*len = attr->length - sizeof(*attr);
	return 0;
}


int radius_msg_count_attr(struct radius_msg *msg, u8 type, int min_len)
{
	int i, count;

	for (count = 0, i = 0; i < msg->attr_used; i++) {
		if (msg->attrs[i]->type == type &&
		    msg->attrs[i]->length >=
		    sizeof(struct radius_attr_hdr) + min_len)
			count++;
	}

	return count;
}