/*
 * 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.
 * Copyright (c) 2017, Joyent, Inc.
 */

/*
 * 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);
}

/*
 * A few NSS modules hold onto data for the duration of their module. In this
 * case, when that module goes away, we must free that data. This is a place
 * that allows for modules to register items to take care of.
 */
#pragma fini(_nss_files_fini)
static void
_nss_files_fini(void)
{
        getexecattr_fini();
}