files/common/files_common.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 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */
/*
 * Copyright 2014 Nexenta Systems, Inc.  All rights reserved.
 */

/*
 * Common code and structures used by name-service-switch "files" backends.
 */

/*
 * An implementation that used mmap() sensibly would be a wonderful thing,
 *   but this here is just yer standard fgets() thang.
 */

#include "files_common.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <fcntl.h>
#include <poll.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/mman.h>

/*ARGSUSED*/
nss_status_t
_nss_files_setent(be, dummy)
    files_backend_ptr_t be;
    void            *dummy;
{
    if (be->f == 0) {
        if (be->filename == 0) {
            /* Backend isn't initialized properly? */
            return (NSS_UNAVAIL);
        }
        if ((be->f = fopen(be->filename, "rF")) == 0) {
            return (NSS_UNAVAIL);
        }
    } else {
        rewind(be->f);
    }
    return (NSS_SUCCESS);
}

/*ARGSUSED*/
nss_status_t
_nss_files_endent(be, dummy)
    files_backend_ptr_t be;
    void            *dummy;
{
    if (be->f != 0) {
        (void) fclose(be->f);
        be->f = 0;
    }
    if (be->buf != 0) {
        free(be->buf);
        be->buf = 0;
    }
    return (NSS_SUCCESS);
}

/*
 * This routine reads a line, including the processing of continuation
 * characters.  It always leaves (or inserts) \n\0 at the end of the line.
 * It returns the length of the line read, excluding the \n\0.  Who's idea
 * was this?
 * Returns -1 on EOF.
 *
 * Note that since each concurrent call to _nss_files_read_line has
 * it's own FILE pointer, we can use getc_unlocked w/o difficulties,
 * a substantial performance win.
 */
int
_nss_files_read_line(f, buffer, buflen)
    FILE            *f;
    char            *buffer;
    int         buflen;
{
    int         linelen;    /* 1st unused slot in buffer */
    int         c;

    /*CONSTCOND*/
    while (1) {
        linelen = 0;
        while (linelen < buflen - 1) {  /* "- 1" saves room for \n\0 */
            switch (c = getc_unlocked(f)) {
            case EOF:
                if (linelen == 0 ||
                    buffer[linelen - 1] == '\\') {
                    return (-1);
                } else {
                    buffer[linelen    ] = '\n';
                    buffer[linelen + 1] = '\0';
                    return (linelen);
                }
            case '\n':
                if (linelen > 0 &&
                    buffer[linelen - 1] == '\\') {
                    --linelen;  /* remove the '\\' */
                } else {
                    buffer[linelen    ] = '\n';
                    buffer[linelen + 1] = '\0';
                    return (linelen);
                }
                break;
            default:
                buffer[linelen++] = c;
            }
        }
        /* Buffer overflow -- eat rest of line and loop again */
        /* ===> Should syslog() */
        do {
            c = getc_unlocked(f);
            if (c == EOF) {
                return (-1);
            }
        } while (c != '\n');
    }
    /*NOTREACHED*/
}

/*
 * used only for getgroupbymem() now.
 */
nss_status_t
_nss_files_do_all(be, args, filter, func)
    files_backend_ptr_t be;
    void            *args;
    const char      *filter;
    files_do_all_func_t func;
{
    long            grlen;
    char            *buffer;
    int         buflen;
    nss_status_t        res;

    if (be->buf == 0) {
        if ((grlen = sysconf(_SC_GETGR_R_SIZE_MAX)) > 0)
            be->minbuf = grlen;
        if ((be->buf = malloc(be->minbuf)) == 0)
            return (NSS_UNAVAIL);
    }
    buffer = be->buf;
    buflen = be->minbuf;

    if ((res = _nss_files_setent(be, 0)) != NSS_SUCCESS) {
        return (res);
    }

    res = NSS_NOTFOUND;

    do {
        int     linelen;

        if ((linelen = _nss_files_read_line(be->f, buffer,
            buflen)) < 0) {
            /* End of file */
            break;
        }
        if (filter != 0 && strstr(buffer, filter) == 0) {
            /*
             * Optimization:  if the entry doesn't contain the
             *   filter string then it can't be the entry we want,
             *   so don't bother looking more closely at it.
             */
            continue;
        }
        res = (*func)(buffer, linelen, args);

    } while (res == NSS_NOTFOUND);

    (void) _nss_files_endent(be, 0);
    return (res);
}

/*
 * Could implement this as an iterator function on top of _nss_files_do_all(),
 *   but the shared code is small enough that it'd be pretty silly.
 */
nss_status_t
_nss_files_XY_all(be, args, netdb, filter, check)
    files_backend_ptr_t be;
    nss_XbyY_args_t     *args;
    int         netdb;      /* whether it uses netdb */
                        /* format or not */
    const char      *filter;    /* advisory, to speed up */
                        /* string search */
    files_XY_check_func check;  /* NULL means one-shot, for getXXent */
{
    char            *r;
    nss_status_t        res;
    int parsestat;
    int (*func)();

    if (filter != NULL && *filter == '\0')
        return (NSS_NOTFOUND);
    if (be->buf == 0 || (be->minbuf < args->buf.buflen)) {
        if (be->minbuf < args->buf.buflen) {
            if (be->buf == 0) {
                be->minbuf = args->buf.buflen;
            } else if (
                (r = realloc(be->buf, args->buf.buflen)) != NULL) {
                be->buf = r;
                be->minbuf = args->buf.buflen;
            }
        }
        if (be->buf == 0 &&
            (be->buf = malloc(be->minbuf)) == 0)
                return (NSS_UNAVAIL);
    }

    if (check != 0 || be->f == 0) {
        if ((res = _nss_files_setent(be, 0)) != NSS_SUCCESS) {
            return (res);
        }
    }

    res = NSS_NOTFOUND;

    /*CONSTCOND*/
    while (1) {
        char        *instr  = be->buf;
        int     linelen;

        if ((linelen = _nss_files_read_line(be->f, instr,
            be->minbuf)) < 0) {
            /* End of file */
            args->returnval = 0;
            args->returnlen = 0;
            break;
        }
        if (filter != 0 && strstr(instr, filter) == 0) {
            /*
             * Optimization:  if the entry doesn't contain the
             *   filter string then it can't be the entry we want,
             *   so don't bother looking more closely at it.
             */
            continue;
        }
        if (netdb) {
            char        *first;
            char        *last;

            if ((last = strchr(instr, '#')) == 0) {
                last = instr + linelen;
            }
            *last-- = '\0';     /* Nuke '\n' or #comment */

            /*
             * Skip leading whitespace.  Normally there isn't
             *   any, so it's not worth calling strspn().
             */
            for (first = instr;  isspace(*first);  first++) {
                ;
            }
            if (*first == '\0') {
                continue;
            }
            /*
             * Found something non-blank on the line.  Skip back
             * over any trailing whitespace;  since we know
             * there's non-whitespace earlier in the line,
             * checking for termination is easy.
             */
            while (isspace(*last)) {
                --last;
            }

            linelen = last - first + 1;
            if (first != instr) {
                    instr = first;
            }
        }

        args->returnval = 0;
        args->returnlen = 0;

        if (check != NULL && (*check)(args, instr, linelen) == 0)
            continue;

        parsestat = NSS_STR_PARSE_SUCCESS;
        if (be->filename != NULL) {
            /*
             * Special case for passwd and group wherein we
             * replace uids/gids > MAXUID by ID_NOBODY
             * because files backend does not support
             * ephemeral ids.
             */
            if (strcmp(be->filename, PF_PATH) == 0)
                parsestat = validate_passwd_ids(instr,
                    &linelen, be->minbuf, 2);
            else if (strcmp(be->filename, GF_PATH) == 0)
                parsestat = validate_group_ids(instr,
                    &linelen, be->minbuf, 2, check);
        }

        if (parsestat == NSS_STR_PARSE_SUCCESS) {
            func = args->str2ent;
            parsestat = (*func)(instr, linelen, args->buf.result,
                args->buf.buffer, args->buf.buflen);
        }

        if (parsestat == NSS_STR_PARSE_SUCCESS) {
            args->returnval = (args->buf.result != NULL)?
                    args->buf.result : args->buf.buffer;
            args->returnlen = linelen;
            res = NSS_SUCCESS;
            break;
        } else if (parsestat == NSS_STR_PARSE_ERANGE) {
            args->erange = 1;
            break;
        } /* else if (parsestat == NSS_STR_PARSE_PARSE) don't care ! */
    }

    /*
     * stayopen is set to 0 by default in order to close the opened
     * file.  Some applications may break if it is set to 1.
     */
    if (check != 0 && !args->stayopen) {
        (void) _nss_files_endent(be, 0);
    }

    return (res);
}

/*
 * File hashing support.  Critical for sites with large (e.g. 1000+ lines)
 * /etc/passwd or /etc/group files.  Currently only used by getpw*() and
 * getgr*() routines, but any files backend can use this stuff.
 */
static void
_nss_files_hash_destroy(files_hash_t *fhp)
{
    free(fhp->fh_table);
    fhp->fh_table = NULL;
    free(fhp->fh_line);
    fhp->fh_line = NULL;
    free(fhp->fh_file_start);
    fhp->fh_file_start = NULL;
}
#ifdef PIC
/*
 * It turns out the hashing stuff really needs to be disabled for processes
 * other than the nscd; the consumption of swap space and memory is otherwise
 * unacceptable when the nscd is killed w/ a large passwd file (4M) active.
 * See 4031930 for details.
 * So we just use this psuedo function to enable the hashing feature.  Since
 * this function name is private, we just create a function w/ the name
 *  __nss_use_files_hash in the nscd itself and everyone else uses the old
 * interface.
 * We also disable hashing for .a executables to avoid problems with large
 * files....
 */

#pragma weak __nss_use_files_hash

extern void  __nss_use_files_hash(void);
#endif /* pic */

/*ARGSUSED*/
nss_status_t
_nss_files_XY_hash(files_backend_ptr_t be, nss_XbyY_args_t *args,
    int netdb, files_hash_t *fhp, int hashop, files_XY_check_func check)
{
    /* LINTED E_FUNC_VAR_UNUSED */
    int fd, retries, ht, stat;
    /* LINTED E_FUNC_VAR_UNUSED */
    uint_t hash, line, f;
    /* LINTED E_FUNC_VAR_UNUSED */
    files_hashent_t *hp, *htab;
    /* LINTED E_FUNC_VAR_UNUSED */
    char *cp, *first, *last;
    /* LINTED E_FUNC_VAR_UNUSED */
    nss_XbyY_args_t xargs;
    /* LINTED E_FUNC_VAR_UNUSED */
    struct stat64 st;

#ifndef PIC
    return (_nss_files_XY_all(be, args, netdb, 0, check));
}
#else
    if (__nss_use_files_hash == 0)
        return (_nss_files_XY_all(be, args, netdb, 0, check));

    mutex_lock(&fhp->fh_lock);
retry:
    retries = 100;
    while (stat64(be->filename, &st) < 0) {
        /*
         * This can happen only in two cases: Either the file is
         * completely missing and we were not able to read it yet
         * (fh_table is NULL), or there is some brief period when the
         * file is being modified/renamed.  Keep trying until things
         * settle down, but eventually give up.
         */
        if (fhp->fh_table == NULL || --retries == 0)
            goto unavail;
        poll(0, 0, 100);
    }

    if (st.st_mtim.tv_sec == fhp->fh_mtime.tv_sec &&
        st.st_mtim.tv_nsec == fhp->fh_mtime.tv_nsec &&
        fhp->fh_table != NULL) {
        htab = &fhp->fh_table[hashop * fhp->fh_size];
        hash = fhp->fh_hash_func[hashop](args, 1, NULL, 0);
        for (hp = htab[hash % fhp->fh_size].h_first; hp != NULL;
            hp = hp->h_next) {
            if (hp->h_hash != hash)
                continue;
            line = hp - htab;
            if ((*check)(args, fhp->fh_line[line].l_start,
                    fhp->fh_line[line].l_len) == 0)
                continue;

            if (be->filename != NULL) {
                stat = NSS_STR_PARSE_SUCCESS;
                if (strcmp(be->filename, PF_PATH) == 0)
                    stat = validate_passwd_ids(
                        fhp->fh_line[line].l_start,
                        &fhp->fh_line[line].l_len,
                        fhp->fh_line[line].l_len + 1,
                        1);
                else if (strcmp(be->filename, GF_PATH) == 0)
                    stat = validate_group_ids(
                        fhp->fh_line[line].l_start,
                        &fhp->fh_line[line].l_len,
                        fhp->fh_line[line].l_len + 1,
                        1, check);
                if (stat != NSS_STR_PARSE_SUCCESS) {
                    if (stat == NSS_STR_PARSE_ERANGE)
                        args->erange = 1;
                    continue;
                }
            }

            if ((*args->str2ent)(fhp->fh_line[line].l_start,
                fhp->fh_line[line].l_len, args->buf.result,
                args->buf.buffer, args->buf.buflen) ==
                NSS_STR_PARSE_SUCCESS) {
                args->returnval = (args->buf.result)?
                    args->buf.result:args->buf.buffer;
                args->returnlen = fhp->fh_line[line].l_len;
                mutex_unlock(&fhp->fh_lock);
                return (NSS_SUCCESS);
            } else {
                args->erange = 1;
            }
        }
        args->returnval = 0;
        args->returnlen = 0;
        mutex_unlock(&fhp->fh_lock);
        return (NSS_NOTFOUND);
    }

    _nss_files_hash_destroy(fhp);

    if (st.st_size > SSIZE_MAX)
        goto unavail;

    if ((fhp->fh_file_start = malloc((ssize_t)st.st_size + 1)) == NULL)
        goto unavail;

    if ((fd = open(be->filename, O_RDONLY)) < 0)
        goto unavail;

    if (read(fd, fhp->fh_file_start, (ssize_t)st.st_size) !=
        (ssize_t)st.st_size) {
        close(fd);
        goto retry;
    }

    close(fd);

    fhp->fh_file_end = fhp->fh_file_start + (off_t)st.st_size;
    *fhp->fh_file_end = '\n';
    fhp->fh_mtime = st.st_mtim;

    /*
     * If the file changed since we read it, or if it's less than
     * 1-2 seconds old, don't trust it; its modification may still
     * be in progress.  The latter is a heuristic hack to minimize
     * the likelihood of damage if someone modifies /etc/mumble
     * directly (as opposed to editing and renaming a temp file).
     *
     * Note: the cast to u_int is there in case (1) someone rdated
     * the system backwards since the last modification of /etc/mumble
     * or (2) this is a diskless client whose time is badly out of sync
     * with its server.  The 1-2 second age hack doesn't cover these
     * cases -- oh well.
     */
    if (stat64(be->filename, &st) < 0 ||
        st.st_mtim.tv_sec != fhp->fh_mtime.tv_sec ||
        st.st_mtim.tv_nsec != fhp->fh_mtime.tv_nsec ||
        (uint_t)(time(0) - st.st_mtim.tv_sec + 2) < 4) {
        poll(0, 0, 1000);
        goto retry;
    }

    line = 1;
    for (cp = fhp->fh_file_start; cp < fhp->fh_file_end; cp++)
        if (*cp == '\n')
            line++;

    for (f = 2; f * f <= line; f++) {   /* find next largest prime */
        if (line % f == 0) {
            f = 1;
            line++;
        }
    }

    fhp->fh_size = line;
    fhp->fh_line = malloc(line * sizeof (files_linetab_t));
    fhp->fh_table = calloc(line * fhp->fh_nhtab, sizeof (files_hashent_t));
    if (fhp->fh_line == NULL || fhp->fh_table == NULL)
        goto unavail;

    line = 0;
    cp = fhp->fh_file_start;
    while (cp < fhp->fh_file_end) {
        first = cp;
        while (*cp != '\n')
            cp++;
        if (cp > first && *(cp - 1) == '\\') {
            memmove(first + 2, first, cp - first - 1);
            cp = first + 2;
            continue;
        }
        last = cp;
        *cp++ = '\0';
        if (netdb) {
            if ((last = strchr(first, '#')) == 0)
                last = cp - 1;
            *last-- = '\0';     /* nuke '\n' or #comment */
            while (isspace(*first)) /* nuke leading whitespace */
                first++;
            if (*first == '\0') /* skip content-free lines */
                continue;
            while (isspace(*last))  /* nuke trailing whitespace */
                --last;
            *++last = '\0';
        }
        for (ht = 0; ht < fhp->fh_nhtab; ht++) {
            hp = &fhp->fh_table[ht * fhp->fh_size + line];
            hp->h_hash = fhp->fh_hash_func[ht](&xargs, 0, first,
                    last - first);
        }
        fhp->fh_line[line].l_start = first;
        fhp->fh_line[line++].l_len = last - first;
    }

    /*
     * Populate the hash tables in reverse order so that the hash chains
     * end up in forward order.  This ensures that hashed lookups find
     * things in the same order that a linear search of the file would.
     * This is essential in cases where there could be multiple matches.
     * For example: until 2.7, root and smtp both had uid 0; but we
     * certainly wouldn't want getpwuid(0) to return smtp.
     */
    for (ht = 0; ht < fhp->fh_nhtab; ht++) {
        htab = &fhp->fh_table[ht * fhp->fh_size];
        for (hp = &htab[line - 1]; hp >= htab; hp--) {
            uint_t bucket = hp->h_hash % fhp->fh_size;
            hp->h_next = htab[bucket].h_first;
            htab[bucket].h_first = hp;
        }
    }

    goto retry;

unavail:
    _nss_files_hash_destroy(fhp);
    mutex_unlock(&fhp->fh_lock);
    return (NSS_UNAVAIL);
}
#endif /* PIC */

nss_status_t
_nss_files_getent_rigid(be, a)
    files_backend_ptr_t be;
    void            *a;
{
    nss_XbyY_args_t     *args = (nss_XbyY_args_t *)a;

    return (_nss_files_XY_all(be, args, 0, 0, 0));
}

nss_status_t
_nss_files_getent_netdb(be, a)
    files_backend_ptr_t be;
    void            *a;
{
    nss_XbyY_args_t     *args = (nss_XbyY_args_t *)a;

    return (_nss_files_XY_all(be, args, 1, 0, 0));
}

/*ARGSUSED*/
nss_status_t
_nss_files_destr(be, dummy)
    files_backend_ptr_t be;
    void            *dummy;
{
    if (be != 0) {
        if (be->f != 0) {
            (void) _nss_files_endent(be, 0);
        }
        if (be->hashinfo != NULL) {
            (void) mutex_lock(&be->hashinfo->fh_lock);
            if (--be->hashinfo->fh_refcnt == 0)
                _nss_files_hash_destroy(be->hashinfo);
            (void) mutex_unlock(&be->hashinfo->fh_lock);
        }
        free(be);
    }
    return (NSS_SUCCESS);   /* In case anyone is dumb enough to check */
}

nss_backend_t *
_nss_files_constr(ops, n_ops, filename, min_bufsize, fhp)
    files_backend_op_t  ops[];
    int         n_ops;
    const char      *filename;
    int         min_bufsize;
    files_hash_t        *fhp;
{
    files_backend_ptr_t be;

    if ((be = (files_backend_ptr_t)malloc(sizeof (*be))) == 0) {
        return (0);
    }
    be->ops     = ops;
    be->n_ops   = n_ops;
    be->filename    = filename;
    be->minbuf  = min_bufsize;
    be->f       = 0;
    be->buf     = 0;
    be->hashinfo    = fhp;

    if (fhp != NULL) {
        (void) mutex_lock(&fhp->fh_lock);
        fhp->fh_refcnt++;
        (void) mutex_unlock(&fhp->fh_lock);
    }

    return ((nss_backend_t *)be);
}

int
_nss_files_check_name_colon(nss_XbyY_args_t *argp, const char *line,
    int linelen)
{
    const char  *linep, *limit;
    const char  *keyp = argp->key.name;

    linep = line;
    limit = line + linelen;
    while (*keyp && linep < limit && *keyp == *linep) {
        keyp++;
        linep++;
    }
    return (linep < limit && *keyp == '\0' && *linep == ':');
}

/*
 * This routine is used to parse lines of the form:
 *  name number aliases
 * It returns 1 if the key in argp matches any one of the
 * names in the line, otherwise 0
 * Used by rpc, networks, protocols
 */
int
_nss_files_check_name_aliases(nss_XbyY_args_t *argp, const char *line,
    int linelen)
{
    const char  *limit, *linep, *keyp;

    linep = line;
    limit = line + linelen;
    keyp = argp->key.name;

    /* compare name */
    while (*keyp && linep < limit && !isspace(*linep) && *keyp == *linep) {
        keyp++;
        linep++;
    }
    if (*keyp == '\0' && linep < limit && isspace(*linep))
        return (1);
    /* skip remainder of the name, if any */
    while (linep < limit && !isspace(*linep))
        linep++;
    /* skip the delimiting spaces */
    while (linep < limit && isspace(*linep))
        linep++;
    /* compare with the aliases */
    while (linep < limit) {
        /*
         * 1st pass: skip number
         * Other passes: skip remainder of the alias name, if any
         */
        while (linep < limit && !isspace(*linep))
            linep++;
        /* skip the delimiting spaces */
        while (linep < limit && isspace(*linep))
            linep++;
        /* compare with the alias name */
        keyp = argp->key.name;
        while (*keyp && linep < limit && !isspace(*linep) &&
            *keyp == *linep) {
            keyp++;
            linep++;
        }
        if (*keyp == '\0' && (linep == limit || isspace(*linep)))
            return (1);
    }
    return (0);
}