/* auth_unix.c -- Unix passwd file authorization
 *
 * Copyright (c) 1994-2008 Carnegie Mellon University.  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.
 *
 * 3. The name "Carnegie Mellon University" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For permission or any legal
 *    details, please contact
 *      Carnegie Mellon University
 *      Center for Technology Transfer and Enterprise Creation
 *      4615 Forbes Avenue
 *      Suite 302
 *      Pittsburgh, PA  15213
 *      (412) 268-7393, fax: (412) 268-7395
 *      innovation@andrew.cmu.edu
 *
 * 4. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by Computing Services
 *     at Carnegie Mellon University (http://www.cmu.edu/computing/)."
 *
 * CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY 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 <config.h>
#include <stdlib.h>
#include <pwd.h>
#include <grp.h>
#include <ctype.h>
#include <string.h>

#include "auth.h"
#include "libcyr_cfg.h"
#include "xmalloc.h"
#include "strarray.h"
#include "util.h"

struct auth_state {
    char userid[81];
    strarray_t groups;
};

static struct auth_state auth_anonymous = {
    "anonymous", STRARRAY_INITIALIZER
};

/*
 * Determine if the user is a member of 'identifier'
 * Returns one of:
 *      0       User does not match identifier
 *      1       identifier matches everybody
 *      2       User is in the group that is identifier
 *      3       User is identifer
 */
static int mymemberof(const struct auth_state *auth_state, const char *identifier)
{
    int i;

    if (!auth_state) auth_state = &auth_anonymous;

    if (strcmp(identifier, "anyone") == 0) return 1;

    if (strcmp(identifier, auth_state->userid) == 0) return 3;

    if (strncmp(identifier, "group:", 6) != 0) return 0;

    for (i=0; i<auth_state->groups.count ; i++) {
        if (strcmp(identifier+6, auth_state->groups.data[i]) == 0) return 2;
    }
    return 0;
}

/* Map of which characters are allowed by auth_canonifyid.
 * Key: 0 -> not allowed (special, ctrl, or would confuse Unix or imapd)
 *      1 -> allowed, but requires an alpha somewhere else in the string
 *      2 -> allowed, and is an alpha
 *
 * At least one character must be an alpha.
 *
 * This may not be restrictive enough.
 * Here are the reasons for the restrictions:
 *
 * &    forbidden because of MUTF-7.  (This could be fixed.)
 * :    forbidden because it's special in /etc/passwd
 * /    forbidden because it can't be used in a mailbox name
 * * %  forbidden because they're IMAP magic in the LIST/LSUB commands
 * ?    it just scares me
 * ctrl chars, DEL
 *      can't send them as IMAP characters in plain folder names, I think
 * 80-FF forbidden because you can't send them in IMAP anyway
 *       (and they're forbidden as folder names). (This could be fixed.)
 *
 * + and - are *allowed* although '+' is probably used for userid+detail
 * subaddressing and qmail users use '-' for subaddressing.
 *
 * Identifiers don't require a digit, really, so that should probably be
 * relaxed, too.
 */
static const char allowedchars[256] = {
 /* 0  1  2  3  4  5  6  7  8  9  A  B  C  D  E  F */
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* 00-0F */
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* 10-1F */
    1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 0, 1, 1, 1, 1, 0, /* 20-2F */
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 0, /* 30-3F */

    1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, /* 40-4F */
    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, /* 50-5F */
    1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, /* 60-6F */
    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 0, /* 70-7F */

    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};

/*
 * Convert 'identifier' into canonical form.
 * Returns a pointer to a static buffer containing the canonical form
 * or NULL if 'identifier' is invalid.
 *
 * XXX If any of the characters marked with 0 are valid and are cropping up,
 * the right thing to do is probably to canonicalize the identifier to two
 * representations: one for getpwent calls and one for folder names.  The
 * latter canonicalizes to a MUTF7 representation.
 */
static const char *mycanonifyid(const char *identifier, size_t len)
{
    static char retbuf[81];
    struct group *grp;
    char *p;
    int username_tolower = 0;

    if (!len) len = strlen(identifier);
    if (len >= sizeof(retbuf)) return NULL;

    memmove(retbuf, identifier, len);
    retbuf[len] = '\0';

    /* This used to be far more restrictive, but many sites seem to ignore the
     * ye olde Unix conventions of username.  Specifically, we used to
     * - drop case on the buffer
     * - disallow lots of non-alpha characters ('-', '_', others)
     * Now we do neither of these, but impose a very different policy based on
     * the character map above.
     */

    if (!strncmp(retbuf, "group:", 6)) {
        grp = getgrnam(retbuf+6);
        if (!grp) return NULL;
        if (strlen(grp->gr_name) >= sizeof(retbuf)-6)
                return NULL;
        strcpy(retbuf+6, grp->gr_name);
        return retbuf;
    }

    /* Copy the string and look up values in the allowedchars array above.
     * If we see any we don't like, reject the string.
     * Lowercase usernames if requested.
     */
    username_tolower = libcyrus_config_getswitch(CYRUSOPT_USERNAME_TOLOWER);
    for (p = retbuf; *p; p++) {
        if (username_tolower && Uisupper(*p))
            *p = tolower((unsigned char)*p);

        switch (allowedchars[*(unsigned char*) p]) {
        case 0:
            return NULL;
        default:
            break;
        }
    }

    return retbuf;
}

/*
 * Set the current user to 'identifier'.  'cacheid', if non-null,
 * points to a 16-byte binary key to cache identifier's information
 * with.
 */
static struct auth_state *mynewstate(const char *identifier)
{
    struct auth_state *newstate;
    struct passwd *pwd;
    struct group *grp;
#if defined(HAVE_GETGROUPLIST) && defined(__GLIBC__)
    gid_t gid, *groupids = NULL;
    int ret, ngroups = 10, oldngroups;
#else
    char **mem;
#endif

    identifier = mycanonifyid(identifier, 0);
    if (!identifier) return 0;
    if (!strncmp(identifier, "group:", 6)) return 0;

    newstate = (struct auth_state *)xmalloc(sizeof(struct auth_state));

    strcpy(newstate->userid, identifier);
    strarray_init(&newstate->groups);

    if(!libcyrus_config_getswitch(CYRUSOPT_AUTH_UNIX_GROUP_ENABLE))
        return newstate;

    pwd = getpwnam(identifier);

#if defined(HAVE_GETGROUPLIST) && defined(__GLIBC__)
    gid = pwd ? pwd->pw_gid : (gid_t) -1;

    /* get the group ids */
    do {
        groupids = (gid_t *)xrealloc((gid_t *)groupids,
                                     ngroups * sizeof(gid_t));

        oldngroups = ngroups; /* copy of ngroups for comparison */
        ret = getgrouplist(identifier, gid, groupids, &ngroups);
        /*
         * This is tricky. We do this as long as getgrouplist tells us to
         * realloc _and_ the number of groups changes. It tells us to realloc
         * also in the case of failure...
         */
    } while (ret == -1 && ngroups != oldngroups);

    if (ret == -1)
        goto err;

    while (ngroups--) {
        if (pwd || groupids[ngroups] != gid) {
            if ((grp = getgrgid(groupids[ngroups])))
                strarray_append(&newstate->groups, grp->gr_name);
        }
    }

err:
    if (groupids) free(groupids);

#else /* !HAVE_GETGROUPLIST */
    setgrent();
    while ((grp = getgrent())) {
        for (mem = grp->gr_mem; *mem; mem++) {
            if (!strcmp(*mem, identifier)) break;
        }

        if (*mem || (pwd && pwd->pw_gid == grp->gr_gid))
            strarray_append(&newstate->groups, grp->gr_name);
    }
    endgrent();
#endif /* HAVE_GETGROUPLIST */

    return newstate;
}

static void myfreestate(struct auth_state *auth_state)
{
    strarray_fini(&auth_state->groups);
    free(auth_state);
}

static strarray_t *mygroups(const struct auth_state *auth_state)
{
    return strarray_dup(&auth_state->groups);
}

HIDDEN struct auth_mech auth_unix =
{
    "unix",             /* name */

    &mycanonifyid,
    &mymemberof,
    &mynewstate,
    &myfreestate,
    &mygroups,
};
