lib/libradius/radlib.c

/*-
 * Copyright 1998 Juniper Networks, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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 AUTHOR OR CONTRIBUTORS 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.
 *
 *	$FreeBSD$
 */

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include <errno.h>
#include <md5.h>
#include <netdb.h>
#include <stdarg.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "radlib_private.h"

static void	 clear_password(struct rad_handle *);
static void	 generr(struct rad_handle *, const char *, ...)
		    __printflike(2, 3);
static void	 insert_scrambled_password(struct rad_handle *, int);
static int	 is_valid_response(struct rad_handle *, int,
		    const struct sockaddr_in *);
static int	 put_password_attr(struct rad_handle *, int,
		    const void *, size_t);
static int	 put_raw_attr(struct rad_handle *, int,
		    const void *, size_t);
static int	 split(char *, char *[], int, char *, size_t);

static void
clear_password(struct rad_handle *h)
{
	if (h->pass_len != 0) {
		memset(h->pass, 0, h->pass_len);
		h->pass_len = 0;
		h->pass_pos = 0;
	}
}

static void
generr(struct rad_handle *h, const char *format, ...)
{
	va_list		 ap;

	va_start(ap, format);
	vsnprintf(h->errmsg, ERRSIZE, format, ap);
	va_end(ap);
}

static void
insert_scrambled_password(struct rad_handle *h, int srv)
{
	MD5_CTX ctx;
	unsigned char md5[16];
	const struct rad_server *srvp;
	int padded_len;
	int pos;

	srvp = &h->servers[srv];
	padded_len = h->pass_len == 0 ? 16 : (h->pass_len+15) & ~0xf;

	memcpy(md5, &h->request[POS_AUTH], LEN_AUTH);
	for (pos = 0;  pos < padded_len;  pos += 16) {
		int i;

		/* Calculate the new scrambler */
		MD5Init(&ctx);
		MD5Update(&ctx, srvp->secret, strlen(srvp->secret));
		MD5Update(&ctx, md5, 16);
		MD5Final(md5, &ctx);

		/*
		 * Mix in the current chunk of the password, and copy
		 * the result into the right place in the request.  Also
		 * modify the scrambler in place, since we will use this
		 * in calculating the scrambler for next time.
		 */
		for (i = 0;  i < 16;  i++)
			h->request[h->pass_pos + pos + i] =
			    md5[i] ^= h->pass[pos + i];
	}
}

/*
 * Return true if the current response is valid for a request to the
 * specified server.
 */
static int
is_valid_response(struct rad_handle *h, int srv,
    const struct sockaddr_in *from)
{
	MD5_CTX ctx;
	unsigned char md5[16];
	const struct rad_server *srvp;
	int len;

	srvp = &h->servers[srv];

	/* Check the source address */
	if (from->sin_family != srvp->addr.sin_family ||
	    from->sin_addr.s_addr != srvp->addr.sin_addr.s_addr ||
	    from->sin_port != srvp->addr.sin_port)
		return 0;

	/* Check the message length */
	if (h->resp_len < POS_ATTRS)
		return 0;
	len = h->response[POS_LENGTH] << 8 | h->response[POS_LENGTH+1];
	if (len > h->resp_len)
		return 0;

	/* Check the response authenticator */
	MD5Init(&ctx);
	MD5Update(&ctx, &h->response[POS_CODE], POS_AUTH - POS_CODE);
	MD5Update(&ctx, &h->request[POS_AUTH], LEN_AUTH);
	MD5Update(&ctx, &h->response[POS_ATTRS], len - POS_ATTRS);
	MD5Update(&ctx, srvp->secret, strlen(srvp->secret));
	MD5Final(md5, &ctx);
	if (memcmp(&h->response[POS_AUTH], md5, sizeof md5) != 0)
		return 0;

	return 1;
}

static int
put_password_attr(struct rad_handle *h, int type, const void *value, size_t len)
{
	int padded_len;
	int pad_len;

	if (h->pass_pos != 0) {
		generr(h, "Multiple User-Password attributes specified");
		return -1;
	}
	if (len > PASSSIZE)
		len = PASSSIZE;
	padded_len = len == 0 ? 16 : (len+15) & ~0xf;
	pad_len = padded_len - len;

	/*
	 * Put in a place-holder attribute containing all zeros, and
	 * remember where it is so we can fill it in later.
	 */
	clear_password(h);
	put_raw_attr(h, type, h->pass, padded_len);
	h->pass_pos = h->req_len - padded_len;

	/* Save the cleartext password, padded as necessary */
	memcpy(h->pass, value, len);
	h->pass_len = len;
	memset(h->pass + len, 0, pad_len);
	return 0;
}

static int
put_raw_attr(struct rad_handle *h, int type, const void *value, size_t len)
{
	if (len > 253) {
		generr(h, "Attribute too long");
		return -1;
	}
	if (h->req_len + 2 + len > MSGSIZE) {
		generr(h, "Maximum message length exceeded");
		return -1;
	}
	h->request[h->req_len++] = type;
	h->request[h->req_len++] = len + 2;
	memcpy(&h->request[h->req_len], value, len);
	h->req_len += len;
	return 0;
}

int
rad_add_server(struct rad_handle *h, const char *host, int port,
    const char *secret, int timeout, int tries)
{
	struct rad_server *srvp;

	if (h->num_servers >= MAXSERVERS) {
		generr(h, "Too many RADIUS servers specified");
		return -1;
	}
	srvp = &h->servers[h->num_servers];

	memset(&srvp->addr, 0, sizeof srvp->addr);
	srvp->addr.sin_len = sizeof srvp->addr;
	srvp->addr.sin_family = AF_INET;
	if (!inet_aton(host, &srvp->addr.sin_addr)) {
		struct hostent *hent;

		if ((hent = gethostbyname(host)) == NULL) {
			generr(h, "%s: host not found", host);
			return -1;
		}
		memcpy(&srvp->addr.sin_addr, hent->h_addr,
		    sizeof srvp->addr.sin_addr);
	}
	if (port != 0)
		srvp->addr.sin_port = htons(port);
	else {
		struct servent *sent;

		srvp->addr.sin_port =
		    (sent = getservbyname("radius", "udp")) != NULL ?
			sent->s_port : htons(RADIUS_PORT);
	}
	if ((srvp->secret = strdup(secret)) == NULL) {
		generr(h, "Out of memory");
		return -1;
	}
	srvp->timeout = timeout;
	srvp->max_tries = tries;
	srvp->num_tries = 0;
	h->num_servers++;
	return 0;
}

void
rad_close(struct rad_handle *h)
{
	int srv;

	if (h->fd != -1)
		close(h->fd);
	for (srv = 0;  srv < h->num_servers;  srv++) {
		memset(h->servers[srv].secret, 0,
		    strlen(h->servers[srv].secret));
		free(h->servers[srv].secret);
	}
	clear_password(h);
	free(h);
}

int
rad_config(struct rad_handle *h, const char *path)
{
	FILE *fp;
	char buf[MAXCONFLINE];
	int linenum;
	int retval;

	if (path == NULL)
		path = PATH_RADIUS_CONF;
	if ((fp = fopen(path, "r")) == NULL) {
		generr(h, "Cannot open \"%s\": %s", path, strerror(errno));
		return -1;
	}
	retval = 0;
	linenum = 0;
	while (fgets(buf, sizeof buf, fp) != NULL) {
		int len;
		char *fields[4];
		int nfields;
		char msg[ERRSIZE];
		char *host;
		char *port_str;
		char *secret;
		char *timeout_str;
		char *maxtries_str;
		char *end;
		unsigned long timeout;
		unsigned long maxtries;
		int port;

		linenum++;
		len = strlen(buf);
		/* We know len > 0, else fgets would have returned NULL. */
		if (buf[len - 1] != '\n') {
			if (len == sizeof buf - 1)
				generr(h, "%s:%d: line too long", path,
				    linenum);
			else
				generr(h, "%s:%d: missing newline", path,
				    linenum);
			retval = -1;
			break;
		}
		buf[len - 1] = '\0';

		/* Extract the fields from the line. */
		nfields = split(buf, fields, 4, msg, sizeof msg);
		if (nfields == -1) {
			generr(h, "%s:%d: %s", path, linenum, msg);
			retval = -1;
			break;
		}
		if (nfields == 0)
			continue;
		if (nfields < 2) {
			generr(h, "%s:%d: missing shared secret", path,
			    linenum);
			retval = -1;
			break;
		}
		host = fields[0];
		secret = fields[1];
		timeout_str = fields[2];
		maxtries_str = fields[3];

		/* Parse and validate the fields. */
		host = strtok(host, ":");
		port_str = strtok(NULL, ":");
		if (port_str != NULL) {
			port = strtoul(port_str, &end, 10);
			if (*end != '\0') {
				generr(h, "%s:%d: invalid port", path,
				    linenum);
				retval = -1;
				break;
			}
		} else
			port = 0;
		if (timeout_str != NULL) {
			timeout = strtoul(timeout_str, &end, 10);
			if (*end != '\0') {
				generr(h, "%s:%d: invalid timeout", path,
				    linenum);
				retval = -1;
				break;
			}
		} else
			timeout = TIMEOUT;
		if (maxtries_str != NULL) {
			maxtries = strtoul(maxtries_str, &end, 10);
			if (*end != '\0') {
				generr(h, "%s:%d: invalid maxtries", path,
				    linenum);
				retval = -1;
				break;
			}
		} else
			maxtries = MAXTRIES;

		if (rad_add_server(h, host, port, secret, timeout, maxtries) ==
		    -1) {
			char msg[ERRSIZE];

			strcpy(msg, h->errmsg);
			generr(h, "%s:%d: %s", path, linenum, msg);
			retval = -1;
			break;
		}
	}
	/* Clear out the buffer to wipe a possible copy of a shared secret */
	memset(buf, 0, sizeof buf);
	fclose(fp);
	return retval;
}

int
rad_create_request(struct rad_handle *h, int code)
{
	int i;

	h->request[POS_CODE] = code;
	h->request[POS_IDENT] = ++h->ident;
	/* Create a random authenticator */
	for (i = 0;  i < LEN_AUTH;  i += 2) {
		long r;
		r = random();
		h->request[POS_AUTH+i] = r;
		h->request[POS_AUTH+i+1] = r >> 8;
	}
	h->req_len = POS_ATTRS;
	clear_password(h);
	return 0;
}

struct in_addr
rad_cvt_addr(const void *data)
{
	struct in_addr value;

	memcpy(&value.s_addr, data, sizeof value.s_addr);
	return value;
}

u_int32_t
rad_cvt_int(const void *data)
{
	u_int32_t value;

	memcpy(&value, data, sizeof value);
	return ntohl(value);
}

char *
rad_cvt_string(const void *data, size_t len)
{
	char *s;

	s = malloc(len + 1);
	if (s != NULL) {
		memcpy(s, data, len);
		s[len] = '\0';
	}
	return s;
}

/*
 * Returns the attribute type.  If none are left, returns 0.  On failure,
 * returns -1.
 */
int
rad_get_attr(struct rad_handle *h, const void **value, size_t *len)
{
	int type;

	if (h->resp_pos >= h->resp_len)
		return 0;
	if (h->resp_pos + 2 > h->resp_len) {
		generr(h, "Malformed attribute in response");
		return -1;
	}
	type = h->response[h->resp_pos++];
	*len = h->response[h->resp_pos++] - 2;
	if (h->resp_pos + *len > h->resp_len) {
		generr(h, "Malformed attribute in response");
		return -1;
	}
	*value = &h->response[h->resp_pos];
	h->resp_pos += *len;
	return type;
}

/*
 * Create and initialize a rad_handle structure, and return it to the
 * caller.  Can fail only if the necessary memory cannot be allocated.
 * In that case, it returns NULL.
 */
struct rad_handle *
rad_open(void)
{
	struct rad_handle *h;

	h = (struct rad_handle *)malloc(sizeof(struct rad_handle));
	if (h != NULL) {
		srandomdev();
		h->fd = -1;
		h->num_servers = 0;
		h->ident = random();
		h->errmsg[0] = '\0';
		memset(h->pass, 0, sizeof h->pass);
		h->pass_len = 0;
		h->pass_pos = 0;
	}
	return h;
}

int
rad_put_addr(struct rad_handle *h, int type, struct in_addr addr)
{
	return rad_put_attr(h, type, &addr.s_addr, sizeof addr.s_addr);
}

int
rad_put_attr(struct rad_handle *h, int type, const void *value, size_t len)
{
	return type == RAD_USER_PASSWORD ?
	    put_password_attr(h, type, value, len) :
	    put_raw_attr(h, type, value, len);
}

int
rad_put_int(struct rad_handle *h, int type, u_int32_t value)
{
	u_int32_t nvalue;

	nvalue = htonl(value);
	return rad_put_attr(h, type, &nvalue, sizeof nvalue);
}

int
rad_put_string(struct rad_handle *h, int type, const char *str)
{
	return rad_put_attr(h, type, str, strlen(str));
}

/*
 * Returns the response type code on success, or -1 on failure.
 */
int
rad_send_request(struct rad_handle *h)
{
	int total_tries;
	int try;
	int srv;
	int n;
	int got_valid_response;

	/* Make sure we have a socket to use */
	if (h->fd == -1) {
		struct sockaddr_in sin;

		if ((h->fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1) {
			generr(h, "Cannot create socket: %s", strerror(errno));
			return -1;
		}
		memset(&sin, 0, sizeof sin);
		sin.sin_len = sizeof sin;
		sin.sin_family = AF_INET;
		sin.sin_addr.s_addr = INADDR_ANY;
		sin.sin_port = htons(0);
		if (bind(h->fd, (const struct sockaddr *)&sin,
		    sizeof sin) == -1) {
			generr(h, "bind: %s", strerror(errno));
			close(h->fd);
			h->fd = -1;
			return -1;
		}
	}

	/* Make sure the user gave us a password */
	if (h->pass_pos == 0) {
		generr(h, "No User-Password attribute given");
		return -1;
	}

	/* Fill in the length field in the message */
	h->request[POS_LENGTH] = h->req_len >> 8;
	h->request[POS_LENGTH+1] = h->req_len;

	/*
	 * Count the total number of tries we will make, and zero the
	 * counter for each server.
	 */
	total_tries = 0;
	for (srv = 0;  srv < h->num_servers;  srv++) {
		total_tries += h->servers[srv].max_tries;
		h->servers[srv].num_tries = 0;
	}
	if (total_tries == 0) {
		generr(h, "No RADIUS servers specified");
		return -1;
	}

	srv = 0;
	got_valid_response = 0;
	for (try = 0;  try < total_tries;  try++) {
		struct timeval timelimit;
		struct timeval tv;

		/*
                 * Scan round-robin to the next server that has some
                 * tries left.  There is guaranteed to be one, or we
                 * would have exited this loop by now.
		 */
		while (h->servers[srv].num_tries >=
		    h->servers[srv].max_tries)
			if (++srv >= h->num_servers)
				srv = 0;

		/* Insert the scrambled password into the request */
		insert_scrambled_password(h, srv);

		/* Send the request */
		n = sendto(h->fd, h->request, h->req_len, 0,
		    (const struct sockaddr *)&h->servers[srv].addr,
		    sizeof h->servers[srv].addr);
		if (n != h->req_len) {
			if (n == -1)
				generr(h, "sendto: %s", strerror(errno));
			else
				generr(h, "sendto: short write");
			return -1;
		}
		h->servers[srv].num_tries++;

		/* Wait for a valid response */
		gettimeofday(&timelimit, NULL);
		timelimit.tv_sec += h->servers[srv].timeout;

		tv.tv_sec = h->servers[srv].timeout;
		tv.tv_usec = 0;
		for ( ; ; ) {
			fd_set readfds;

			FD_ZERO(&readfds);
			FD_SET(h->fd, &readfds);
			n = select(h->fd + 1, &readfds, NULL, NULL, &tv);
			if (n == -1) {
				generr(h, "select: %s", strerror(errno));
				return -1;
			}
			if (n == 0)	/* Timed out */
				break;
			if (FD_ISSET(h->fd, &readfds)) {
				struct sockaddr_in from;
				int fromlen;

				fromlen = sizeof from;
				h->resp_len = recvfrom(h->fd, h->response,
				    MSGSIZE, MSG_WAITALL,
				    (struct sockaddr *)&from, &fromlen);
				if (h->resp_len == -1) {
					generr(h, "recvfrom: %s",
					    strerror(errno));
					return -1;
				}
				if (is_valid_response(h, srv, &from)) {
					got_valid_response = 1;
					break;
				}
			}
			/* Compute a new timeout */
			gettimeofday(&tv, NULL);
			timersub(&timelimit, &tv, &tv);
			if (tv.tv_sec < 0)	/* Still poll once more */
				timerclear(&tv);
		}
		if (got_valid_response)
			break;
		/* Advance to the next server */
		if (++srv >= h->num_servers)
			srv = 0;
	}
	if (!got_valid_response) {
		generr(h, "No valid RADIUS responses received");
		return -1;
	}
	h->resp_len = h->response[POS_LENGTH] << 8 | h->response[POS_LENGTH+1];
	h->resp_pos = POS_ATTRS;
	return h->response[POS_CODE];
}

const char *
rad_strerror(struct rad_handle *h)
{
	return h->errmsg;
}

/*
 * Destructively split a string into fields separated by white space.
 * `#' at the beginning of a field begins a comment that extends to the
 * end of the string.  Fields may be quoted with `"'.  Inside quoted
 * strings, the backslash escapes `\"' and `\\' are honored.
 *
 * Pointers to up to the first maxfields fields are stored in the fields
 * array.  Missing fields get NULL pointers.
 *
 * The return value is the actual number of fields parsed, and is always
 * <= maxfields.
 *
 * On a syntax error, places a message in the msg string, and returns -1.
 */
static int
split(char *str, char *fields[], int maxfields, char *msg, size_t msglen)
{
	char *p;
	int i;
	static const char ws[] = " \t";

	for (i = 0;  i < maxfields;  i++)
		fields[i] = NULL;
	p = str;
	i = 0;
	while (*p != '\0') {
		p += strspn(p, ws);
		if (*p == '#' || *p == '\0')
			break;
		if (i >= maxfields) {
			snprintf(msg, msglen, "line has too many fields");
			return -1;
		}
		if (*p == '"') {
			char *dst;

			dst = ++p;
			fields[i] = dst;
			while (*p != '"') {
				if (*p == '\\') {
					p++;
					if (*p != '"' && *p != '\\' &&
					    *p != '\0') {
						snprintf(msg, msglen,
						    "invalid `\\' escape");
						return -1;
					}
				}
				if (*p == '\0') {
					snprintf(msg, msglen,
					    "unterminated quoted string");
					return -1;
				}
				*dst++ = *p++;
			}
			*dst = '\0';
			p++;
			if (*fields[i] == '\0') {
				snprintf(msg, msglen,
				    "empty quoted string not permitted");
				return -1;
			}
			if (*p != '\0' && strspn(p, ws) == 0) {
				snprintf(msg, msglen, "quoted string not"
				    " followed by white space");
				return -1;
			}
		} else {
			fields[i] = p;
			p += strcspn(p, ws);
			if (*p != '\0')
				*p++ = '\0';
		}
		i++;
	}
	return i;
}