chap-new.c

/*
 * chap-new.c - New CHAP implementation.
 *
 * Copyright (c) 2003 Paul Mackerras. 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. The name(s) of the authors of this software must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission.
 *
 * 3. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by Paul Mackerras
 *     <paulus@samba.org>".
 *
 * THE AUTHORS OF THIS SOFTWARE DISCLAIM ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
 * SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
 * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include "netif/ppp/ppp_opts.h"
#if PPP_SUPPORT && CHAP_SUPPORT  /* don't build if not configured for use in lwipopts.h */

#if 0 /* UNUSED */
#include <stdlib.h>
#include <string.h>
#endif /* UNUSED */

#include "netif/ppp/ppp_impl.h"

#if 0 /* UNUSED */
#include "session.h"
#endif /* UNUSED */

#include "netif/ppp/chap-new.h"
#include "netif/ppp/chap-md5.h"
#if MSCHAP_SUPPORT
#include "netif/ppp/chap_ms.h"
#endif
#include "netif/ppp/magic.h"

#if 0 /* UNUSED */
/* Hook for a plugin to validate CHAP challenge */
int (*chap_verify_hook)(const char *name, const char *ourname, int id,
            const struct chap_digest_type *digest,
            const unsigned char *challenge, const unsigned char *response,
            char *message, int message_space) = NULL;
#endif /* UNUSED */

#if PPP_OPTIONS
/*
 * Command-line options.
 */
static option_t chap_option_list[] = {
    { "chap-restart", o_int, &chap_timeout_time,
      "Set timeout for CHAP", OPT_PRIO },
    { "chap-max-challenge", o_int, &pcb->settings.chap_max_transmits,
      "Set max #xmits for challenge", OPT_PRIO },
    { "chap-interval", o_int, &pcb->settings.chap_rechallenge_time,
      "Set interval for rechallenge", OPT_PRIO },
    { NULL }
};
#endif /* PPP_OPTIONS */


/* Values for flags in chap_client_state and chap_server_state */
#define LOWERUP         1
#define AUTH_STARTED        2
#define AUTH_DONE       4
#define AUTH_FAILED     8
#define TIMEOUT_PENDING     0x10
#define CHALLENGE_VALID     0x20

/*
 * Prototypes.
 */
static void chap_init(ppp_pcb *pcb);
static void chap_lowerup(ppp_pcb *pcb);
static void chap_lowerdown(ppp_pcb *pcb);
#if PPP_SERVER
static void chap_timeout(void *arg);
static void chap_generate_challenge(ppp_pcb *pcb);
static void chap_handle_response(ppp_pcb *pcb, int code,
        unsigned char *pkt, int len);
static int chap_verify_response(ppp_pcb *pcb, const char *name, const char *ourname, int id,
        const struct chap_digest_type *digest,
        const unsigned char *challenge, const unsigned char *response,
        char *message, int message_space);
#endif /* PPP_SERVER */
static void chap_respond(ppp_pcb *pcb, int id,
        unsigned char *pkt, int len);
static void chap_handle_status(ppp_pcb *pcb, int code, int id,
        unsigned char *pkt, int len);
static void chap_protrej(ppp_pcb *pcb);
static void chap_input(ppp_pcb *pcb, unsigned char *pkt, int pktlen);
#if PRINTPKT_SUPPORT
static int chap_print_pkt(const unsigned char *p, int plen,
        void (*printer) (void *, const char *, ...), void *arg);
#endif /* PRINTPKT_SUPPORT */

/* List of digest types that we know about */
static const struct chap_digest_type* const chap_digests[] = {
    &md5_digest,
#if MSCHAP_SUPPORT
    &chapms_digest,
    &chapms2_digest,
#endif /* MSCHAP_SUPPORT */
    NULL
};

/*
 * chap_init - reset to initial state.
 */
static void chap_init(ppp_pcb *pcb) {
    LWIP_UNUSED_ARG(pcb);

#if 0 /* Not necessary, everything is cleared in ppp_new() */
    memset(&pcb->chap_client, 0, sizeof(chap_client_state));
#if PPP_SERVER
    memset(&pcb->chap_server, 0, sizeof(chap_server_state));
#endif /* PPP_SERVER */
#endif /* 0 */
}

/*
 * chap_lowerup - we can start doing stuff now.
 */
static void chap_lowerup(ppp_pcb *pcb) {

    pcb->chap_client.flags |= LOWERUP;
#if PPP_SERVER
    pcb->chap_server.flags |= LOWERUP;
    if (pcb->chap_server.flags & AUTH_STARTED)
        chap_timeout(pcb);
#endif /* PPP_SERVER */
}

static void chap_lowerdown(ppp_pcb *pcb) {

    pcb->chap_client.flags = 0;
#if PPP_SERVER
    if (pcb->chap_server.flags & TIMEOUT_PENDING)
        UNTIMEOUT(chap_timeout, pcb);
    pcb->chap_server.flags = 0;
#endif /* PPP_SERVER */
}

#if PPP_SERVER
/*
 * chap_auth_peer - Start authenticating the peer.
 * If the lower layer is already up, we start sending challenges,
 * otherwise we wait for the lower layer to come up.
 */
void chap_auth_peer(ppp_pcb *pcb, const char *our_name, int digest_code) {
    const struct chap_digest_type *dp;
    int i;

    if (pcb->chap_server.flags & AUTH_STARTED) {
        ppp_error("CHAP: peer authentication already started!");
        return;
    }
    for (i = 0; (dp = chap_digests[i]) != NULL; ++i)
        if (dp->code == digest_code)
            break;
    if (dp == NULL)
        ppp_fatal("CHAP digest 0x%x requested but not available",
              digest_code);

    pcb->chap_server.digest = dp;
    pcb->chap_server.name = our_name;
    /* Start with a random ID value */
    pcb->chap_server.id = magic();
    pcb->chap_server.flags |= AUTH_STARTED;
    if (pcb->chap_server.flags & LOWERUP)
        chap_timeout(pcb);
}
#endif /* PPP_SERVER */

/*
 * chap_auth_with_peer - Prepare to authenticate ourselves to the peer.
 * There isn't much to do until we receive a challenge.
 */
void chap_auth_with_peer(ppp_pcb *pcb, const char *our_name, int digest_code) {
    const struct chap_digest_type *dp;
    int i;

    if(NULL == our_name)
        return;

    if (pcb->chap_client.flags & AUTH_STARTED) {
        ppp_error("CHAP: authentication with peer already started!");
        return;
    }
    for (i = 0; (dp = chap_digests[i]) != NULL; ++i)
        if (dp->code == digest_code)
            break;

    if (dp == NULL)
        ppp_fatal("CHAP digest 0x%x requested but not available",
              digest_code);

    pcb->chap_client.digest = dp;
    pcb->chap_client.name = our_name;
    pcb->chap_client.flags |= AUTH_STARTED;
}

#if PPP_SERVER
/*
 * chap_timeout - It's time to send another challenge to the peer.
 * This could be either a retransmission of a previous challenge,
 * or a new challenge to start re-authentication.
 */
static void chap_timeout(void *arg) {
    ppp_pcb *pcb = (ppp_pcb*)arg;
    struct pbuf *p;

    pcb->chap_server.flags &= ~TIMEOUT_PENDING;
    if ((pcb->chap_server.flags & CHALLENGE_VALID) == 0) {
        pcb->chap_server.challenge_xmits = 0;
        chap_generate_challenge(pcb);
        pcb->chap_server.flags |= CHALLENGE_VALID;
    } else if (pcb->chap_server.challenge_xmits >= pcb->settings.chap_max_transmits) {
        pcb->chap_server.flags &= ~CHALLENGE_VALID;
        pcb->chap_server.flags |= AUTH_DONE | AUTH_FAILED;
        auth_peer_fail(pcb, PPP_CHAP);
        return;
    }

    p = pbuf_alloc(PBUF_RAW, (u16_t)(pcb->chap_server.challenge_pktlen), PPP_CTRL_PBUF_TYPE);
    if(NULL == p)
        return;
    if(p->tot_len != p->len) {
        pbuf_free(p);
        return;
    }
    MEMCPY(p->payload, pcb->chap_server.challenge, pcb->chap_server.challenge_pktlen);
    ppp_write(pcb, p);
    ++pcb->chap_server.challenge_xmits;
    pcb->chap_server.flags |= TIMEOUT_PENDING;
    TIMEOUT(chap_timeout, arg, pcb->settings.chap_timeout_time);
}

/*
 * chap_generate_challenge - generate a challenge string and format
 * the challenge packet in pcb->chap_server.challenge_pkt.
 */
static void chap_generate_challenge(ppp_pcb *pcb) {
    int clen = 1, nlen, len;
    unsigned char *p;

    p = pcb->chap_server.challenge;
    MAKEHEADER(p, PPP_CHAP);
    p += CHAP_HDRLEN;
    pcb->chap_server.digest->generate_challenge(pcb, p);
    clen = *p;
    nlen = strlen(pcb->chap_server.name);
    memcpy(p + 1 + clen, pcb->chap_server.name, nlen);

    len = CHAP_HDRLEN + 1 + clen + nlen;
    pcb->chap_server.challenge_pktlen = PPP_HDRLEN + len;

    p = pcb->chap_server.challenge + PPP_HDRLEN;
    p[0] = CHAP_CHALLENGE;
    p[1] = ++pcb->chap_server.id;
    p[2] = len >> 8;
    p[3] = len;
}

/*
 * chap_handle_response - check the response to our challenge.
 */
static void  chap_handle_response(ppp_pcb *pcb, int id,
             unsigned char *pkt, int len) {
    int response_len, ok, mlen;
    const unsigned char *response;
    unsigned char *outp;
    struct pbuf *p;
    const char *name = NULL;    /* initialized to shut gcc up */
#if 0 /* UNUSED */
    int (*verifier)(const char *, const char *, int, const struct chap_digest_type *,
        const unsigned char *, const unsigned char *, char *, int);
#endif /* UNUSED */
    char rname[MAXNAMELEN+1];
    char message[256];

    if ((pcb->chap_server.flags & LOWERUP) == 0)
        return;
    if (id != pcb->chap_server.challenge[PPP_HDRLEN+1] || len < 2)
        return;
    if (pcb->chap_server.flags & CHALLENGE_VALID) {
        response = pkt;
        GETCHAR(response_len, pkt);
        len -= response_len + 1;    /* length of name */
        name = (char *)pkt + response_len;
        if (len < 0)
            return;

        if (pcb->chap_server.flags & TIMEOUT_PENDING) {
            pcb->chap_server.flags &= ~TIMEOUT_PENDING;
            UNTIMEOUT(chap_timeout, pcb);
        }
#if PPP_REMOTENAME
        if (pcb->settings.explicit_remote) {
            name = pcb->remote_name;
        } else
#endif /* PPP_REMOTENAME */
        {
            /* Null terminate and clean remote name. */
            ppp_slprintf(rname, sizeof(rname), "%.*v", len, name);
            name = rname;
        }

#if 0 /* UNUSED */
        if (chap_verify_hook)
            verifier = chap_verify_hook;
        else
            verifier = chap_verify_response;
        ok = (*verifier)(name, pcb->chap_server.name, id, pcb->chap_server.digest,
                 pcb->chap_server.challenge + PPP_HDRLEN + CHAP_HDRLEN,
                 response, pcb->chap_server.message, sizeof(pcb->chap_server.message));
#endif /* UNUSED */
        ok = chap_verify_response(pcb, name, pcb->chap_server.name, id, pcb->chap_server.digest,
                    pcb->chap_server.challenge + PPP_HDRLEN + CHAP_HDRLEN,
                    response, message, sizeof(message));
#if 0 /* UNUSED */
        if (!ok || !auth_number()) {
#endif /* UNUSED */
        if (!ok) {
            pcb->chap_server.flags |= AUTH_FAILED;
            ppp_warn("Peer %q failed CHAP authentication", name);
        }
    } else if ((pcb->chap_server.flags & AUTH_DONE) == 0)
        return;

    /* send the response */
    mlen = strlen(message);
    len = CHAP_HDRLEN + mlen;
    p = pbuf_alloc(PBUF_RAW, (u16_t)(PPP_HDRLEN +len), PPP_CTRL_PBUF_TYPE);
    if(NULL == p)
        return;
    if(p->tot_len != p->len) {
        pbuf_free(p);
        return;
    }

    outp = (unsigned char *)p->payload;
    MAKEHEADER(outp, PPP_CHAP);

    outp[0] = (pcb->chap_server.flags & AUTH_FAILED)? CHAP_FAILURE: CHAP_SUCCESS;
    outp[1] = id;
    outp[2] = len >> 8;
    outp[3] = len;
    if (mlen > 0)
        memcpy(outp + CHAP_HDRLEN, message, mlen);
    ppp_write(pcb, p);

    if (pcb->chap_server.flags & CHALLENGE_VALID) {
        pcb->chap_server.flags &= ~CHALLENGE_VALID;
        if (!(pcb->chap_server.flags & AUTH_DONE) && !(pcb->chap_server.flags & AUTH_FAILED)) {

#if 0 /* UNUSED */
            /*
             * Auth is OK, so now we need to check session restrictions
             * to ensure everything is OK, but only if we used a
             * plugin, and only if we're configured to check.  This
             * allows us to do PAM checks on PPP servers that
             * authenticate against ActiveDirectory, and use AD for
             * account info (like when using Winbind integrated with
             * PAM).
             */
            if (session_mgmt &&
            session_check(name, NULL, devnam, NULL) == 0) {
            pcb->chap_server.flags |= AUTH_FAILED;
            ppp_warn("Peer %q failed CHAP Session verification", name);
            }
#endif /* UNUSED */

        }
        if (pcb->chap_server.flags & AUTH_FAILED) {
            auth_peer_fail(pcb, PPP_CHAP);
        } else {
            if ((pcb->chap_server.flags & AUTH_DONE) == 0)
                auth_peer_success(pcb, PPP_CHAP,
                          pcb->chap_server.digest->code,
                          name, strlen(name));
            if (pcb->settings.chap_rechallenge_time) {
                pcb->chap_server.flags |= TIMEOUT_PENDING;
                TIMEOUT(chap_timeout, pcb,
                    pcb->settings.chap_rechallenge_time);
            }
        }
        pcb->chap_server.flags |= AUTH_DONE;
    }
}

/*
 * chap_verify_response - check whether the peer's response matches
 * what we think it should be.  Returns 1 if it does (authentication
 * succeeded), or 0 if it doesn't.
 */
static int chap_verify_response(ppp_pcb *pcb, const char *name, const char *ourname, int id,
             const struct chap_digest_type *digest,
             const unsigned char *challenge, const unsigned char *response,
             char *message, int message_space) {
    int ok;
    unsigned char secret[MAXSECRETLEN];
    int secret_len;

    /* Get the secret that the peer is supposed to know */
    if (!get_secret(pcb, name, ourname, (char *)secret, &secret_len, 1)) {
        ppp_error("No CHAP secret found for authenticating %q", name);
        return 0;
    }
    ok = digest->verify_response(pcb, id, name, secret, secret_len, challenge,
                     response, message, message_space);
    memset(secret, 0, sizeof(secret));

    return ok;
}
#endif /* PPP_SERVER */

/*
 * chap_respond - Generate and send a response to a challenge.
 */
static void chap_respond(ppp_pcb *pcb, int id,
         unsigned char *pkt, int len) {
    int clen, nlen;
    int secret_len;
    struct pbuf *p;
    u_char *outp;
    char rname[MAXNAMELEN+1];
    char secret[MAXSECRETLEN+1];

    p = pbuf_alloc(PBUF_RAW, (u16_t)(RESP_MAX_PKTLEN), PPP_CTRL_PBUF_TYPE);
    if(NULL == p)
        return;
    if(p->tot_len != p->len) {
        pbuf_free(p);
        return;
    }

    if ((pcb->chap_client.flags & (LOWERUP | AUTH_STARTED)) != (LOWERUP | AUTH_STARTED))
        return;     /* not ready */
    if (len < 2 || len < pkt[0] + 1)
        return;     /* too short */
    clen = pkt[0];
    nlen = len - (clen + 1);

    /* Null terminate and clean remote name. */
    ppp_slprintf(rname, sizeof(rname), "%.*v", nlen, pkt + clen + 1);

#if PPP_REMOTENAME
    /* Microsoft doesn't send their name back in the PPP packet */
    if (pcb->settings.explicit_remote || (pcb->settings.remote_name[0] != 0 && rname[0] == 0))
        strlcpy(rname, pcb->settings.remote_name, sizeof(rname));
#endif /* PPP_REMOTENAME */

    /* get secret for authenticating ourselves with the specified host */
    if (!get_secret(pcb, pcb->chap_client.name, rname, secret, &secret_len, 0)) {
        secret_len = 0; /* assume null secret if can't find one */
        ppp_warn("No CHAP secret found for authenticating us to %q", rname);
    }

    outp = (u_char*)p->payload;
    MAKEHEADER(outp, PPP_CHAP);
    outp += CHAP_HDRLEN;

    pcb->chap_client.digest->make_response(pcb, outp, id, pcb->chap_client.name, pkt,
                  secret, secret_len, pcb->chap_client.priv);
    memset(secret, 0, secret_len);

    clen = *outp;
    nlen = strlen(pcb->chap_client.name);
    memcpy(outp + clen + 1, pcb->chap_client.name, nlen);

    outp = (u_char*)p->payload + PPP_HDRLEN;
    len = CHAP_HDRLEN + clen + 1 + nlen;
    outp[0] = CHAP_RESPONSE;
    outp[1] = id;
    outp[2] = len >> 8;
    outp[3] = len;

    pbuf_realloc(p, PPP_HDRLEN + len);
    ppp_write(pcb, p);
}

static void chap_handle_status(ppp_pcb *pcb, int code, int id,
           unsigned char *pkt, int len) {
    const char *msg = NULL;
    LWIP_UNUSED_ARG(id);

    if ((pcb->chap_client.flags & (AUTH_DONE|AUTH_STARTED|LOWERUP))
        != (AUTH_STARTED|LOWERUP))
        return;
    pcb->chap_client.flags |= AUTH_DONE;

    if (code == CHAP_SUCCESS) {
        /* used for MS-CHAP v2 mutual auth, yuck */
        if (pcb->chap_client.digest->check_success != NULL) {
            if (!(*pcb->chap_client.digest->check_success)(pcb, pkt, len, pcb->chap_client.priv))
                code = CHAP_FAILURE;
        } else
            msg = "CHAP authentication succeeded";
    } else {
        if (pcb->chap_client.digest->handle_failure != NULL)
            (*pcb->chap_client.digest->handle_failure)(pcb, pkt, len);
        else
            msg = "CHAP authentication failed";
    }
    if (msg) {
        if (len > 0)
            ppp_info("%s: %.*v", msg, len, pkt);
        else
            ppp_info("%s", msg);
    }
    if (code == CHAP_SUCCESS)
        auth_withpeer_success(pcb, PPP_CHAP, pcb->chap_client.digest->code);
    else {
        pcb->chap_client.flags |= AUTH_FAILED;
        ppp_error("CHAP authentication failed");
        auth_withpeer_fail(pcb, PPP_CHAP);
    }
}

static void chap_input(ppp_pcb *pcb, unsigned char *pkt, int pktlen) {
    unsigned char code, id;
    int len;

    if (pktlen < CHAP_HDRLEN)
        return;
    GETCHAR(code, pkt);
    GETCHAR(id, pkt);
    GETSHORT(len, pkt);
    if (len < CHAP_HDRLEN || len > pktlen)
        return;
    len -= CHAP_HDRLEN;

    switch (code) {
    case CHAP_CHALLENGE:
        chap_respond(pcb, id, pkt, len);
        break;
#if PPP_SERVER
    case CHAP_RESPONSE:
        chap_handle_response(pcb, id, pkt, len);
        break;
#endif /* PPP_SERVER */
    case CHAP_FAILURE:
    case CHAP_SUCCESS:
        chap_handle_status(pcb, code, id, pkt, len);
        break;
    default:
        break;
    }
}

static void chap_protrej(ppp_pcb *pcb) {

#if PPP_SERVER
    if (pcb->chap_server.flags & TIMEOUT_PENDING) {
        pcb->chap_server.flags &= ~TIMEOUT_PENDING;
        UNTIMEOUT(chap_timeout, pcb);
    }
    if (pcb->chap_server.flags & AUTH_STARTED) {
        pcb->chap_server.flags = 0;
        auth_peer_fail(pcb, PPP_CHAP);
    }
#endif /* PPP_SERVER */
    if ((pcb->chap_client.flags & (AUTH_STARTED|AUTH_DONE)) == AUTH_STARTED) {
        pcb->chap_client.flags &= ~AUTH_STARTED;
        ppp_error("CHAP authentication failed due to protocol-reject");
        auth_withpeer_fail(pcb, PPP_CHAP);
    }
}

#if PRINTPKT_SUPPORT
/*
 * chap_print_pkt - print the contents of a CHAP packet.
 */
static const char* const chap_code_names[] = {
    "Challenge", "Response", "Success", "Failure"
};

static int chap_print_pkt(const unsigned char *p, int plen,
           void (*printer) (void *, const char *, ...), void *arg) {
    int code, id, len;
    int clen, nlen;
    unsigned char x;

    if (plen < CHAP_HDRLEN)
        return 0;
    GETCHAR(code, p);
    GETCHAR(id, p);
    GETSHORT(len, p);
    if (len < CHAP_HDRLEN || len > plen)
        return 0;

    if (code >= 1 && code <= (int)LWIP_ARRAYSIZE(chap_code_names))
        printer(arg, " %s", chap_code_names[code-1]);
    else
        printer(arg, " code=0x%x", code);
    printer(arg, " id=0x%x", id);
    len -= CHAP_HDRLEN;
    switch (code) {
    case CHAP_CHALLENGE:
    case CHAP_RESPONSE:
        if (len < 1)
            break;
        clen = p[0];
        if (len < clen + 1)
            break;
        ++p;
        nlen = len - clen - 1;
        printer(arg, " <");
        for (; clen > 0; --clen) {
            GETCHAR(x, p);
            printer(arg, "%.2x", x);
        }
        printer(arg, ">, name = ");
        ppp_print_string(p, nlen, printer, arg);
        break;
    case CHAP_FAILURE:
    case CHAP_SUCCESS:
        printer(arg, " ");
        ppp_print_string(p, len, printer, arg);
        break;
    default:
        for (clen = len; clen > 0; --clen) {
            GETCHAR(x, p);
            printer(arg, " %.2x", x);
        }
        /* no break */
    }

    return len + CHAP_HDRLEN;
}
#endif /* PRINTPKT_SUPPORT */

const struct protent chap_protent = {
    PPP_CHAP,
    chap_init,
    chap_input,
    chap_protrej,
    chap_lowerup,
    chap_lowerdown,
    NULL,       /* open */
    NULL,       /* close */
#if PRINTPKT_SUPPORT
    chap_print_pkt,
#endif /* PRINTPKT_SUPPORT */
#if PPP_DATAINPUT
    NULL,       /* datainput */
#endif /* PPP_DATAINPUT */
#if PRINTPKT_SUPPORT
    "CHAP",     /* name */
    NULL,       /* data_name */
#endif /* PRINTPKT_SUPPORT */
#if PPP_OPTIONS
    chap_option_list,
    NULL,       /* check_options */
#endif /* PPP_OPTIONS */
#if DEMAND_SUPPORT
    NULL,
    NULL
#endif /* DEMAND_SUPPORT */
};

#endif /* PPP_SUPPORT && CHAP_SUPPORT */