pam_modules/dhkeys/dhkeys.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#include <stdlib.h>
#include <syslog.h>
#include <errno.h>
#include <string.h>
#include <rpc/rpc.h>
#include <unistd.h>
#include <assert.h>
#include <stdarg.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <limits.h>
#include <signal.h>
#include <pthread.h>
#include <synch.h>

#include <rpcsvc/nis.h>
#include <rpcsvc/yppasswd.h>
#include <rpcsvc/ypclnt.h>
#include <rpc/key_prot.h>
#include <rpc/rpc.h>
#include <nfs/nfs.h>
#include <nfs/nfssys.h>
#include <nss_dbdefs.h>
#include <nsswitch.h>
#include <rpcsvc/nis_dhext.h>

#include <security/pam_appl.h>
#include <security/pam_modules.h>
#include <security/pam_impl.h>

#include <libintl.h>

#include <sys/mman.h>

#include <passwdutil.h>

#include "key_call_uid.h"
#include <shadow.h>

extern  int _nfssys(int, void *);

/*
 * int msg(pamh, ...)
 *
 * display message to the user
 */
/*PRINTFLIKE2*/
static int
msg(pam_handle_t *pamh, char *fmt, ...)
{
    va_list ap;
    char    messages[PAM_MAX_NUM_MSG][PAM_MAX_MSG_SIZE];

    va_start(ap, fmt);
    (void) vsnprintf(messages[0], sizeof (messages[0]), fmt, ap);
    va_end(ap);

    return (__pam_display_msg(pamh, PAM_ERROR_MSG, 1, messages, NULL));
}


/*
 * Get the secret key for the given netname, key length, and algorithm
 * type and send it to keyserv if the given pw decrypts it.  Update the
 * following counter args as necessary: get_seckey_cnt, good_pw_cnt, and
 * set_seckey_cnt.
 *
 * Returns 0 on malloc failure, else 1.
 */
static int
get_and_set_seckey(
    pam_handle_t    *pamh,          /* in */
    const char  *netname,       /* in */
    keylen_t    keylen,         /* in */
    algtype_t   algtype,        /* in */
    const char  *pw,            /* in */
    uid_t       uid,            /* in */
    gid_t       gid,            /* in */
    int     *get_seckey_cnt,    /* out */
    int     *good_pw_cnt,       /* out */
    int     *set_seckey_cnt,    /* out */
    int     flags,          /* in */
    int     debug)          /* in */
{
    char    *skey;
    int skeylen;
    char    messages[PAM_MAX_NUM_MSG][PAM_MAX_MSG_SIZE];

    skeylen = BITS2NIBBLES(keylen) + 1;

    if ((skey = malloc(skeylen)) == NULL) {
        return (0);
    }

    if (getsecretkey_g(netname, keylen, algtype, skey, skeylen, pw)) {
        (*get_seckey_cnt)++;

        if (skey[0]) {
            /* password does decrypt secret key */
            (*good_pw_cnt)++;
            if (key_setnet_g_uid(netname, skey, keylen, NULL, 0,
                algtype, uid, gid) >= 0) {
                (*set_seckey_cnt)++;
            } else {
                if (debug)
                    syslog(LOG_DEBUG, "pam_dhkeys: "
                        "get_and_set_seckey: could not "
                        "set secret key for keytype "
                        "%d-%d", keylen, algtype);
            }
        } else {
            if (pamh && !(flags & PAM_SILENT)) {
                (void) snprintf(messages[0],
                    sizeof (messages[0]),
                    dgettext(TEXT_DOMAIN,
                    "Password does not "
                    "decrypt secret key (type = %d-%d) "
                    "for '%s'."), keylen, algtype, netname);
                (void) __pam_display_msg(pamh, PAM_ERROR_MSG, 1,
                    messages, NULL);
            }
        }
    } else {
        if (debug)
            syslog(LOG_DEBUG, "pam_dhkeys: get_and_set_seckey: "
                "could not get secret key for keytype %d-%d",
                keylen, algtype);
    }

    free(skey);

    return (1);
}

/*
 * int establish_key(pamh, flags, debug, netname)
 *
 * This routine establishes the Secure RPC Credentials for the
 * user specified in PAM_USER, using the password in PAM_AUTHTOK.
 *
 * Establishing RPC credentials is considered a "helper" function for the PAM
 * stack so we should only return failures or PAM_IGNORE. Returning PAM_SUCCESS
 * may short circuit the stack and circumvent later critical checks.
 *
 * we are called from pam_sm_setcred:
 *  1. if we are root (uid == 0), we do nothing and return
 *     PAM_IGNORE.
 *  2. else, we try to establish credentials.
 *
 * We return framework errors as appropriate such as PAM_USER_UNKNOWN,
 * PAM_BUF_ERR, PAM_PERM_DENIED.
 *
 * If we succeed in establishing credentials we return PAM_IGNORE.
 *
 * If we fail to establish credentials then we return:
 *    - PAM_SERVICE_ERR (credentials needed) or PAM_SYSTEM_ERR
 *      (credentials not needed) if netname could not be created;
 *    - PAM_AUTH_ERR (credentials needed) or PAM_IGNORE (credentials
 *      not needed) if no credentials were retrieved;
 *    - PAM_AUTH_ERR if the password didn't decrypt the cred;
 *    - PAM_SYSTEM_ERR if the cred's could not be stored.
 *
 * This routine returns the user's netname in "netname".
 *
 * All tools--but the PAM stack--currently use getpass() to obtain
 * the user's secure RPC password. We must make sure we don't use more than
 * the first des_block (eight) characters of whatever is handed down to us.
 * Therefore, we use a local variable "short_pass" to hold those 8 char's.
 */
static int
establish_key(pam_handle_t *pamh, int flags, int debug, char *netname)
{
    char    *user;
    char    *passwd;
    char    short_pass[sizeof (des_block)+1], *short_passp;
    int result;
    uid_t   uid;
    gid_t   gid;
    int err;

    struct passwd pw;   /* Needed to obtain uid */
    char    *scratch;
    int scratchlen;

    mechanism_t **mechs;
    mechanism_t **mpp;
    int get_seckey_cnt = 0;
    int set_seckey_cnt = 0;
    int good_pw_cnt = 0;
    int valid_mech_cnt = 0;

    (void) pam_get_item(pamh, PAM_USER, (void **)&user);

    if (user == NULL || *user == '\0') {
        if (debug)
            syslog(LOG_DEBUG, "pam_dhkeys: user NULL or empty");
        return (PAM_USER_UNKNOWN);
    }

    (void) pam_get_item(pamh, PAM_AUTHTOK, (void **)&passwd);

    scratchlen = sysconf(_SC_GETPW_R_SIZE_MAX);
    if ((scratch = malloc(scratchlen)) == NULL)
        return (PAM_BUF_ERR);

    if (getpwnam_r(user, &pw, scratch, scratchlen) == NULL) {
        result = PAM_USER_UNKNOWN;
        goto out;
    }

    uid = pw.pw_uid;
    gid = pw.pw_gid;

    /*
     * We don't set credentials when root logs in.
     */
    if (uid == 0) {
        result = PAM_IGNORE;
        goto out;
    }

    err = user2netname(netname, uid, NULL);

    if (err != 1) {
        if (debug)
            syslog(LOG_DEBUG, "pam_dhkeys: user2netname failed");
            result = PAM_SYSTEM_ERR;
        goto out;
    }

    /* passwd can be NULL (no passwd or su as root) */
    if (passwd) {
        (void) strlcpy(short_pass, passwd, sizeof (short_pass));
        short_passp = short_pass;
    } else
        short_passp = NULL;

    if (mechs = __nis_get_mechanisms(FALSE)) {

        for (mpp = mechs; *mpp; mpp++) {
            mechanism_t *mp = *mpp;

            if (AUTH_DES_COMPAT_CHK(mp))
                break;  /* fall through to AUTH_DES below */

            if (!VALID_MECH_ENTRY(mp))
                continue;

            if (debug)
                syslog(LOG_DEBUG, "pam_dhkeys: trying "
                    "key type = %d-%d", mp->keylen,
                    mp->algtype);
            valid_mech_cnt++;
            if (!get_and_set_seckey(pamh, netname, mp->keylen,
                mp->algtype, short_passp, uid, gid,
                &get_seckey_cnt, &good_pw_cnt, &set_seckey_cnt,
                flags, debug)) {
                result = PAM_BUF_ERR;
                goto out;
            }
        }
        __nis_release_mechanisms(mechs);
        /* fall through to AUTH_DES below */
    } else {
        /*
         * No usable mechs found in security congifuration file thus
         * fallback to AUTH_DES compat.
         */
        if (debug)
            syslog(LOG_DEBUG, "pam_dhkeys: no valid mechs "
                "found. Trying AUTH_DES.");
    }

    /*
     * We always perform AUTH_DES for the benefit of services like NFS
     * that may depend on the classic des 192bit key being set.
     */
    if (!get_and_set_seckey(pamh, netname, AUTH_DES_KEYLEN,
        AUTH_DES_ALGTYPE, short_passp, uid, gid, &get_seckey_cnt,
        &good_pw_cnt, &set_seckey_cnt, flags, debug)) {
        result = PAM_BUF_ERR;
        goto out;
    }

    if (debug) {
        syslog(LOG_DEBUG, "pam_dhkeys: mech key totals:\n");
        syslog(LOG_DEBUG, "pam_dhkeys: %d valid mechanism(s)",
            valid_mech_cnt);
        syslog(LOG_DEBUG, "pam_dhkeys: %d secret key(s) retrieved",
            get_seckey_cnt);
        syslog(LOG_DEBUG, "pam_dhkeys: %d passwd decrypt successes",
            good_pw_cnt);
        syslog(LOG_DEBUG, "pam_dhkeys: %d secret key(s) set",
            set_seckey_cnt);
    }

    if (get_seckey_cnt == 0) {      /* No credentials */
        result = PAM_IGNORE;
        goto out;
    }

    if (good_pw_cnt == 0) {         /* wrong password */
        result = PAM_AUTH_ERR;
        goto out;
    }

    if (set_seckey_cnt == 0) {
        result = PAM_SYSTEM_ERR;
        goto out;
    }
    /* Credentials have been successfully established, return PAM_IGNORE */
    result = PAM_IGNORE;
out:
    /*
     * If we are authenticating we attempt to establish credentials
     * where appropriate. Failure to do so is only an error if we
     * definitely needed them. Thus always return PAM_IGNORE
     * if we are authenticating and credentials were not needed.
     */
    free(scratch);

    (void) memset(short_pass, '\0', sizeof (short_pass));

    return (result);
}

/*ARGSUSED*/
int
pam_sm_authenticate(pam_handle_t *pamh, int flags, int argc, const char **argv)
{
    return (PAM_IGNORE);
}


typedef struct argres {
    uid_t uid;
    int result;
} argres_t;

/*
 * Revoke NFS DES credentials.
 * NFS may not be installed so we need to deal with SIGSYS
 * when we call _nfssys(); we thus call _nfssys() in a seperate thread that
 * is created specifically for this call. The thread specific signalmask
 * is set to ignore SIGSYS. After the call to _nfssys(), the thread
 * ceases to exist.
 */
static void *
revoke_nfs_cred(void *ap)
{
    struct nfs_revauth_args nra;
    sigset_t isigset;
    argres_t *argres = (argres_t *)ap;

    nra.authtype = AUTH_DES;
    nra.uid = argres->uid;

    (void) sigemptyset(&isigset);
    (void) sigaddset(&isigset, SIGSYS);

    if (pthread_sigmask(SIG_BLOCK, &isigset, NULL) == 0) {
        argres->result = _nfssys(NFS_REVAUTH, &nra);
        if (argres->result < 0 && errno == ENOSYS) {
            argres->result = 0;
        }
    } else {
        argres->result = -1;
    }
    return (NULL);
}

static int
remove_key(pam_handle_t *pamh, int flags, int debug)
{
    int result;
    char *uname;
    attrlist attr_pw[2];
    struct pam_repository *auth_rep = NULL;
    pwu_repository_t *pwu_rep;
    uid_t uid;
    gid_t gid;
    argres_t argres;
    pthread_t tid;

    (void) pam_get_item(pamh, PAM_USER, (void **)&uname);
    if (uname == NULL || *uname == NULL) {
        if (debug)
            syslog(LOG_DEBUG,
                "pam_dhkeys: user NULL or empty in remove_key()");
        return (PAM_USER_UNKNOWN);
    }

    if (strcmp(uname, "root") == 0) {
        if ((flags & PAM_SILENT) == 0) {
            char msg[3][PAM_MAX_MSG_SIZE];
            (void) snprintf(msg[0], sizeof (msg[0]),
                dgettext(TEXT_DOMAIN,
                "removing root credentials would"
                " break the rpc services that"));
            (void) snprintf(msg[1], sizeof (msg[1]),
                dgettext(TEXT_DOMAIN,
                "use secure rpc on this host!"));
            (void) snprintf(msg[2], sizeof (msg[2]),
                dgettext(TEXT_DOMAIN,
                "root may use keylogout -f to do"
                " this (at your own risk)!"));
            (void) __pam_display_msg(pamh, PAM_ERROR_MSG, 3,
                msg, NULL);
        }
        return (PAM_PERM_DENIED);
    }

    (void) pam_get_item(pamh, PAM_REPOSITORY, (void **)&auth_rep);
    if (auth_rep != NULL) {
        if ((pwu_rep = calloc(1, sizeof (*pwu_rep))) == NULL)
            return (PAM_BUF_ERR);
        pwu_rep->type = auth_rep->type;
        pwu_rep->scope = auth_rep->scope;
        pwu_rep->scope_len = auth_rep->scope_len;
    } else
        pwu_rep = PWU_DEFAULT_REP;

    /* Retrieve user's uid/gid from the password repository */
    attr_pw[0].type = ATTR_UID; attr_pw[0].next = &attr_pw[1];
    attr_pw[1].type = ATTR_GID; attr_pw[1].next = NULL;

    result = __get_authtoken_attr(uname, pwu_rep, attr_pw);

    if (pwu_rep != PWU_DEFAULT_REP)
        free(pwu_rep);

    if (result == PWU_NOT_FOUND)
        return (PAM_USER_UNKNOWN);
    if (result == PWU_DENIED)
        return (PAM_PERM_DENIED);
    if (result != PWU_SUCCESS)
        return (PAM_SYSTEM_ERR);

    uid = (uid_t)attr_pw[0].data.val_i;
    gid = (gid_t)attr_pw[1].data.val_i;

    (void) key_removesecret_g_uid(uid, gid);

    argres.uid = uid;
    argres.result = -1;

    if (pthread_create(&tid, NULL, revoke_nfs_cred, (void *)&argres) == 0)
        (void) pthread_join(tid, NULL);

    if (argres.result < 0) {
        if ((flags & PAM_SILENT) == 0) {
            (void) msg(pamh, dgettext(TEXT_DOMAIN,
                "Warning: NFS credentials not destroyed"));
        }
        return (PAM_AUTH_ERR);
    }

    return (PAM_IGNORE);
}

int
pam_sm_setcred(pam_handle_t *pamh, int flags, int argc, const char **argv)
{
    int i;
    int debug = 0;
    int result;
    char    netname[MAXNETNAMELEN + 1];

    for (i = 0; i < argc; i++) {
        if (strcmp(argv[i], "debug") == 0)
            debug = 1;
        else if (strcmp(argv[i], "nowarn") == 0)
            flags |= PAM_SILENT;
    }

    /* Check for invalid flags */
    if (flags && (flags & PAM_ESTABLISH_CRED) == 0 &&
        (flags & PAM_REINITIALIZE_CRED) == 0 &&
        (flags & PAM_REFRESH_CRED) == 0 &&
        (flags & PAM_DELETE_CRED) == 0 &&
        (flags & PAM_SILENT) == 0) {
        syslog(LOG_ERR, "pam_dhkeys: pam_setcred: illegal flags %d",
            flags);
        return (PAM_SYSTEM_ERR);
    }


    if ((flags & PAM_REINITIALIZE_CRED) || (flags & PAM_REFRESH_CRED)) {
        /* doesn't apply to UNIX */
        if (debug)
            syslog(LOG_DEBUG, "pam_dhkeys: cred reinit/refresh "
                "ignored\n");
        return (PAM_IGNORE);
    }

    if (flags & PAM_DELETE_CRED) {
        if (debug)
            syslog(LOG_DEBUG, "pam_dhkeys: removing creds\n");
        result = remove_key(pamh, flags, debug);
    } else {
        result = establish_key(pamh, flags, debug, netname);
        /* Some diagnostics */
        if ((flags & PAM_SILENT) == 0) {
            if (result == PAM_AUTH_ERR)
                (void) msg(pamh, dgettext(TEXT_DOMAIN,
                    "Password does not decrypt any secret "
                    "keys for %s."), netname);
            else if (result == PAM_SYSTEM_ERR && netname[0])
                (void) msg(pamh, dgettext(TEXT_DOMAIN,
                    "Could not set secret key(s) for %s. "
                    "The key server may be down."), netname);
        }

        /* Not having credentials set is not an error... */
        result = PAM_IGNORE;
    }

    return (result);
}

/*ARGSUSED*/
void
rpc_cleanup(pam_handle_t *pamh, void *data, int pam_status)
{
    if (data) {
        (void) memset(data, 0, strlen(data));
        free(data);
    }
}

/*ARGSUSED*/
int
pam_sm_chauthtok(pam_handle_t *pamh, int flags, int argc, const char **argv)
{
    return (PAM_IGNORE);
}