svc_auth_des.c

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/*
 * Copyright (c) 1988 by Sun Microsystems, Inc.
 */

/*
 * Copyright (c) 2009, Sun Microsystems, 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:
 * - Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 * - 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.
 * - Neither the name of Sun Microsystems, Inc. nor the names of its
 *   contributors may be used to endorse or promote products derived
 *   from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT HOLDER 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.
 */

/*
 * svcauth_des.c, server-side des authentication
 *
 * We insure for the service the following:
 * (1) The timestamp microseconds do not exceed 1 million.
 * (2) The timestamp plus the window is less than the current time.
 * (3) The timestamp is not less than the one previously
 *     seen in the current session.
 *
 * It is up to the server to determine if the window size is
 * too small .
 *
 */
#include <wintirpc.h>
//#include <pthread.h>
#include <reentrant.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
//#include <unistd.h>
#include <rpc/des_crypt.h>
//#include <sys/param.h>
//#include <netinet/in.h>
#include <rpc/types.h>
#include <rpc/xdr.h>
#include <rpc/auth.h>
#include <rpc/auth_des.h>
#include <rpc/svc.h>
#include <rpc/rpc_msg.h>
#include <rpc/svc_auth.h>
#include <libc_private.h>

extern int key_decryptsession_pk(const char *, netobj *, des_block *);

#define debug(msg)   printf("svcauth_des: %s\n", msg) 

#define USEC_PER_SEC ((u_long) 1000000L)
#define BEFORE(t1, t2) timercmp(t1, t2, <)

/*
 * LRU cache of conversation keys and some other useful items.
 */
#define AUTHDES_CACHESZ 64
struct cache_entry {
    des_block key;      /* conversation key */
    char *rname;        /* client's name */
    u_int window;       /* credential lifetime window */
    struct timeval laststamp;   /* detect replays of creds */
    char *localcred;    /* generic local credential */
};
static struct cache_entry *authdes_cache/* [AUTHDES_CACHESZ] */;
static short *authdes_lru/* [AUTHDES_CACHESZ] */;

static void cache_init();   /* initialize the cache */
static short cache_spot();  /* find an entry in the cache */
static void cache_ref(/*short sid*/);   /* note that sid was ref'd */

static void invalidate();   /* invalidate entry in cache */

/*
 * cache statistics 
 */
static struct {
    u_long ncachehits;  /* times cache hit, and is not replay */
    u_long ncachereplays;   /* times cache hit, and is replay */
    u_long ncachemisses;    /* times cache missed */
} svcauthdes_stats;

/*
 * Service side authenticator for AUTH_DES
 */
enum auth_stat
_svcauth_des(rqst, msg)
    struct svc_req *rqst;
    struct rpc_msg *msg;
{

    long *ixdr;
    des_block cryptbuf[2];
    struct authdes_cred *cred;
    struct authdes_verf verf;
    int status;
    struct cache_entry *entry;
    short sid = 0;
    des_block *sessionkey;
    des_block ivec;
    u_int window;
    struct timeval timestamp;
    u_long namelen;
    struct area {
        struct authdes_cred area_cred;
        char area_netname[MAXNETNAMELEN+1];
    } *area;

    if (authdes_cache == NULL) {
        cache_init();
    }

    area = (struct area *)rqst->rq_clntcred;
    cred = (struct authdes_cred *)&area->area_cred;

    /*
     * Get the credential
     */
    ixdr = (long *)msg->rm_call.cb_cred.oa_base;
    cred->adc_namekind = IXDR_GET_ENUM(ixdr, enum authdes_namekind);
    switch (cred->adc_namekind) {
    case ADN_FULLNAME:
        namelen = IXDR_GET_U_LONG(ixdr);
        if (namelen > MAXNETNAMELEN) {
            return (AUTH_BADCRED);
        }
        cred->adc_fullname.name = area->area_netname;
        bcopy((char *)ixdr, cred->adc_fullname.name, 
            (u_int)namelen);
        cred->adc_fullname.name[namelen] = 0;
        ixdr += (RNDUP(namelen) / BYTES_PER_XDR_UNIT);
        cred->adc_fullname.key.key.high = (u_long)*ixdr++;
        cred->adc_fullname.key.key.low = (u_long)*ixdr++;
        cred->adc_fullname.window = (u_long)*ixdr++;
        break;
    case ADN_NICKNAME:
        cred->adc_nickname = (u_long)*ixdr++;
        break;
    default:
        return (AUTH_BADCRED);  
    }

    /*
     * Get the verifier
     */
    ixdr = (long *)msg->rm_call.cb_verf.oa_base;
    verf.adv_xtimestamp.key.high = (u_long)*ixdr++;
    verf.adv_xtimestamp.key.low =  (u_long)*ixdr++;
    verf.adv_int_u = (u_long)*ixdr++;


    /*
     * Get the conversation key
     */
    if (cred->adc_namekind == ADN_FULLNAME) {
        netobj pkey;
        char pkey_data[1024];

        sessionkey = &cred->adc_fullname.key;
        if (! getpublickey(cred->adc_fullname.name, pkey_data)) {
            debug("getpublickey");
            return(AUTH_BADCRED);
        }
        pkey.n_bytes = pkey_data;
        pkey.n_len = strlen(pkey_data) + 1;
        if (key_decryptsession_pk(cred->adc_fullname.name, &pkey,
                       sessionkey) < 0) {
            debug("decryptsessionkey");
            return (AUTH_BADCRED); /* key not found */
        }
    } else { /* ADN_NICKNAME */ 
        sid = (short)cred->adc_nickname;
        if (sid < 0 || sid >= AUTHDES_CACHESZ) {
            debug("bad nickname");
            return (AUTH_BADCRED);  /* garbled credential */
        }
        sessionkey = &authdes_cache[sid].key;
    }


    /*
     * Decrypt the timestamp
     */
    cryptbuf[0] = verf.adv_xtimestamp; 
    if (cred->adc_namekind == ADN_FULLNAME) {
        cryptbuf[1].key.high = cred->adc_fullname.window;
        cryptbuf[1].key.low = verf.adv_winverf;
        ivec.key.high = ivec.key.low = 0;   
        status = cbc_crypt((char *)sessionkey, (char *)cryptbuf,
            2*sizeof(des_block), DES_DECRYPT | DES_HW, 
            (char *)&ivec);
    } else {
        status = ecb_crypt((char *)sessionkey, (char *)cryptbuf,
            sizeof(des_block), DES_DECRYPT | DES_HW);
    }
    if (DES_FAILED(status)) {
        debug("decryption failure");
        return (AUTH_FAILED);   /* system error */
    }

    /*
     * XDR the decrypted timestamp
     */
    ixdr = (long *)cryptbuf;
    timestamp.tv_sec = IXDR_GET_LONG(ixdr);
    timestamp.tv_usec = IXDR_GET_LONG(ixdr);

    /*
     * Check for valid credentials and verifiers.
     * They could be invalid because the key was flushed
     * out of the cache, and so a new session should begin.
     * Be sure and send AUTH_REJECTED{CRED, VERF} if this is the case.
     */
    {
        struct timeval current;
        int nick;
        int winverf;

        if (cred->adc_namekind == ADN_FULLNAME) {
            window = IXDR_GET_U_LONG(ixdr);
            winverf = IXDR_GET_U_LONG(ixdr);
            if (winverf != window - 1) {
                debug("window verifier mismatch");
                return (AUTH_BADCRED);  /* garbled credential */
            }
            sid = cache_spot(sessionkey, cred->adc_fullname.name, 
                &timestamp);
            if (sid < 0) {
                debug("replayed credential");
                return (AUTH_REJECTEDCRED); /* replay */
            }
            nick = 0;
        } else {    /* ADN_NICKNAME */
            window = authdes_cache[sid].window;
            nick = 1;
        }

        if ((u_long)timestamp.tv_usec >= USEC_PER_SEC) {
            debug("invalid usecs");
            /* cached out (bad key), or garbled verifier */
            return (nick ? AUTH_REJECTEDVERF : AUTH_BADVERF);
        }
        if (nick && BEFORE(&timestamp, 
                   &authdes_cache[sid].laststamp)) {
            debug("timestamp before last seen");
            return (AUTH_REJECTEDVERF); /* replay */
        }
        (void) gettimeofday(&current, (struct timezone *)NULL);
        current.tv_sec -= window;   /* allow for expiration */
        if (!BEFORE(&current, &timestamp)) {
            debug("timestamp expired");
            /* replay, or garbled credential */
            return (nick ? AUTH_REJECTEDVERF : AUTH_BADCRED);
        }
    }

    /*
     * Set up the reply verifier
     */
    verf.adv_nickname = (u_long)sid;

    /*
     * xdr the timestamp before encrypting
     */
    ixdr = (long *)cryptbuf;
    IXDR_PUT_LONG(ixdr, timestamp.tv_sec - 1);
    IXDR_PUT_LONG(ixdr, timestamp.tv_usec);

    /*   
     * encrypt the timestamp
     */
    status = ecb_crypt((char *)sessionkey, (char *)cryptbuf,
        sizeof(des_block), DES_ENCRYPT | DES_HW);
    if (DES_FAILED(status)) {
        debug("encryption failure");
        return (AUTH_FAILED);   /* system error */
    }
    verf.adv_xtimestamp = cryptbuf[0];

    /*
     * Serialize the reply verifier, and update rqst
     */
    ixdr = (long *)msg->rm_call.cb_verf.oa_base;
    *ixdr++ = (long)verf.adv_xtimestamp.key.high;
    *ixdr++ = (long)verf.adv_xtimestamp.key.low;
    *ixdr++ = (long)verf.adv_int_u;

    rqst->rq_xprt->xp_verf.oa_flavor = AUTH_DES;
    rqst->rq_xprt->xp_verf.oa_base = msg->rm_call.cb_verf.oa_base;
    rqst->rq_xprt->xp_verf.oa_length = 
        (char *)ixdr - msg->rm_call.cb_verf.oa_base;

    /*
     * We succeeded, commit the data to the cache now and
     * finish cooking the credential.
     */
    entry = &authdes_cache[sid];
    entry->laststamp = timestamp;
    cache_ref(sid);
    if (cred->adc_namekind == ADN_FULLNAME) {
        cred->adc_fullname.window = window;
        cred->adc_nickname = (u_long)sid;   /* save nickname */
        if (entry->rname != NULL) {
            mem_free(entry->rname, strlen(entry->rname) + 1);
        }
        entry->rname = (char *)mem_alloc((u_int)strlen(cred->adc_fullname.name)
                     + 1);
        if (entry->rname != NULL) {
            (void) strcpy(entry->rname, cred->adc_fullname.name);
        } else {
            debug("out of memory");
        }
        entry->key = *sessionkey;
        entry->window = window;
        invalidate(entry->localcred); /* mark any cached cred invalid */
    } else { /* ADN_NICKNAME */
        /*
         * nicknames are cooked into fullnames
         */ 
        cred->adc_namekind = ADN_FULLNAME;
        cred->adc_fullname.name = entry->rname;
        cred->adc_fullname.key = entry->key;
        cred->adc_fullname.window = entry->window;
    }
    return (AUTH_OK);   /* we made it!*/
}


/*
 * Initialize the cache
 */
static void
cache_init()
{
    int i;

    authdes_cache = (struct cache_entry *)
        mem_alloc(sizeof(struct cache_entry) * AUTHDES_CACHESZ);    
    bzero((char *)authdes_cache, 
        sizeof(struct cache_entry) * AUTHDES_CACHESZ);

    authdes_lru = (short *)mem_alloc(sizeof(short) * AUTHDES_CACHESZ);
    /*
     * Initialize the lru list
     */
    for (i = 0; i < AUTHDES_CACHESZ; i++) {
        authdes_lru[i] = i;
    }
}


/*
 * Find the lru victim
 */
static short
cache_victim()
{
    return (authdes_lru[AUTHDES_CACHESZ-1]);
}

/*
 * Note that sid was referenced
 */
static void
cache_ref(sid)
    short sid;
{
    int i;
    short curr;
    short prev;

    prev = authdes_lru[0];
    authdes_lru[0] = sid;
    for (i = 1; prev != sid; i++) {
        curr = authdes_lru[i];
        authdes_lru[i] = prev;
        prev = curr;
    }
}


/*
 * Find a spot in the cache for a credential containing
 * the items given.  Return -1 if a replay is detected, otherwise
 * return the spot in the cache.
 */
static short
cache_spot(key, name, timestamp)
    des_block *key;
    char *name;
    struct timeval *timestamp;
{
    struct cache_entry *cp;
    int i;
    u_long hi;

    hi = key->key.high;
    for (cp = authdes_cache, i = 0; i < AUTHDES_CACHESZ; i++, cp++) {
        if (cp->key.key.high == hi && 
            cp->key.key.low == key->key.low &&
            cp->rname != NULL &&
            bcmp(cp->rname, name, strlen(name) + 1) == 0) {
            if (BEFORE(timestamp, &cp->laststamp)) {
                svcauthdes_stats.ncachereplays++;
                return (-1); /* replay */
            }
            svcauthdes_stats.ncachehits++;
            return (i); /* refresh */
        }
    }
    svcauthdes_stats.ncachemisses++;
    return (cache_victim());    /* new credential */
}


#if (defined(sun) || defined(vax) || defined(__FreeBSD__))
/*
 * Local credential handling stuff.
 * NOTE: bsd unix dependent.
 * Other operating systems should put something else here.
 */
#define UNKNOWN     -2  /* grouplen, if cached cred is unknown user */
#define INVALID     -1  /* grouplen, if cache entry is invalid */

struct bsdcred {
    short uid;      /* cached uid */
    short gid;      /* cached gid */
    short grouplen; /* length of cached groups */
    short groups[NGROUPS];  /* cached groups */
};

/*
 * Map a des credential into a unix cred.
 * We cache the credential here so the application does
 * not have to make an rpc call every time to interpret
 * the credential.
 */
int
authdes_getucred(adc, uid, gid, grouplen, groups)
    struct authdes_cred *adc;
    uid_t *uid;
    gid_t *gid;
    int *grouplen;
    gid_t *groups;
{
    unsigned sid;
    int i;
    uid_t i_uid;    
    gid_t i_gid;
    int i_grouplen;
    struct bsdcred *cred;

    sid = adc->adc_nickname;
    if (sid >= AUTHDES_CACHESZ) {
        debug("invalid nickname");
        return (0);
    }
    cred = (struct bsdcred *)authdes_cache[sid].localcred;
    if (cred == NULL) {
        cred = (struct bsdcred *)mem_alloc(sizeof(struct bsdcred));
        authdes_cache[sid].localcred = (char *)cred;
        cred->grouplen = INVALID;
    }
    if (cred->grouplen == INVALID) {
        /*
         * not in cache: lookup
         */
        if (!netname2user(adc->adc_fullname.name, &i_uid, &i_gid, 
            &i_grouplen, groups))
        {
            debug("unknown netname");
            cred->grouplen = UNKNOWN;   /* mark as lookup up, but not found */
            return (0);
        }
        debug("missed ucred cache");
        *uid = cred->uid = i_uid;
        *gid = cred->gid = i_gid;
        *grouplen = cred->grouplen = i_grouplen;
        for (i = i_grouplen - 1; i >= 0; i--) {
            cred->groups[i] = groups[i]; /* int to short */
        }
        return (1);
    } else if (cred->grouplen == UNKNOWN) {
        /*
         * Already lookup up, but no match found
         */ 
        return (0);
    }

    /*
     * cached credentials
     */
    *uid = cred->uid;
    *gid = cred->gid;
    *grouplen = cred->grouplen;
    for (i = cred->grouplen - 1; i >= 0; i--) {
        groups[i] = cred->groups[i];    /* short to int */
    }
    return (1);
}

static void
invalidate(cred)
    char *cred;
{
    if (cred == NULL) {
        return;
    }
    ((struct bsdcred *)cred)->grouplen = INVALID;
}
#endif