/*      $NetBSD: wordexp.c,v 1.4 2024/01/20 14:52:47 christos Exp $     */

/*-
 * Copyright (c) 2002 Tim J. Robbins.
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 */

#include "namespace.h"
#include <sys/cdefs.h>
#include <sys/types.h>
#include <assert.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <paths.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <wordexp.h>
#include "extern.h"

#if defined(LIBC_SCCS) && !defined(lint)
#if 0
__FBSDID("$FreeBSD: /repoman/r/ncvs/src/lib/libc/gen/wordexp.c,v 1.5 2004/04/09 11:32:32 tjr Exp $");
#else
__RCSID("$NetBSD: wordexp.c,v 1.4 2024/01/20 14:52:47 christos Exp $");
#endif
#endif /* LIBC_SCCS and not lint */

static int      we_askshell(const char *, wordexp_t *, int);
static int      we_check(const char *, int);

/*
 * wordexp --
 *      Perform shell word expansion on `words' and place the resulting list
 *      of words in `we'. See wordexp(3).
 *
 */
int
wordexp(const char * __restrict words, wordexp_t * __restrict we, int flags)
{
        int error;

        _DIAGASSERT(we != NULL);
        _DIAGASSERT(words != NULL);
        if (flags & WRDE_REUSE)
                wordfree(we);
        if ((flags & WRDE_APPEND) == 0) {
                we->we_wordc = 0;
                we->we_wordv = NULL;
                we->we_strings = NULL;
                we->we_nbytes = 0;
        }
        if ((error = we_check(words, flags)) != 0) {
                wordfree(we);
                return (error);
        }
        if ((error = we_askshell(words, we, flags)) != 0) {
                wordfree(we);
                return (error);
        }
        return (0);
}

/*
 * we_askshell --
 *      Use the `wordexp' /bin/sh builtin function to do most of the work
 *      in expanding the word string. This function is complicated by
 *      memory management.
 */
static int
we_askshell(const char *words, wordexp_t *we, int flags)
{
        int pdes[2];                    /* Pipe to child */
        size_t nwords, nbytes;          /* Number of words, bytes from child */
        int i;                          /* Handy integer */
        unsigned int ui;                /* For array iteration */
        size_t sofs;                    /* Offset into we->we_strings */
        size_t vofs;                    /* Offset into we->we_wordv */
        pid_t pid;                      /* Process ID of child */
        int status;                     /* Child exit status */
        const char *ifs;                /* IFS env. var. */
        char *np, *p;                   /* Handy pointers */
        char *nstrings;                 /* Temporary for realloc() */
        char **nwv;                     /* Temporary for realloc() */
        FILE *fp;                       /* Stream to read pipe */
        char *cmd;

        if ((ifs = getenv("IFS")) == NULL)
                ifs = " \t\n";
        if (asprintf(&cmd, "wordexp%c%s\n", *ifs, words) < 0)
                return (WRDE_NOSPACE);
        if (pipe(pdes) < 0) {
                free(cmd);
                return (WRDE_ERRNO);
        }
        if ((fp = fdopen(pdes[0], "r")) == NULL) {
                free(cmd);
                return (WRDE_ERRNO);
        }
        if ((pid = fork()) < 0) {
                free(cmd);
                fclose(fp);
                close(pdes[1]);
                return (WRDE_ERRNO);
        }
        else if (pid == 0) {
                /*
                 * We are the child; just get /bin/sh to run the wordexp
                 * builtin on `words'.
                 */
                int devnull;

                close(pdes[0]);
                if (pdes[1] != STDOUT_FILENO) {
                        if (dup2(pdes[1], STDOUT_FILENO) < 0)
                                _exit(1);
                        close(pdes[1]);
                }
                if ((flags & WRDE_SHOWERR) == 0) {
                        if ((devnull = open(_PATH_DEVNULL, O_RDWR, 0666)) < 0)
                                _exit(1);
                        if (dup2(devnull, STDERR_FILENO) < 0)
                                _exit(1);
                        close(devnull);
                }
                execle(_PATH_BSHELL, "sh", flags & WRDE_UNDEF ? "-u" : "+u",
                    "-c", cmd, (char *)NULL, environ);
                _exit(1);
        }

        /*
         * We are the parent; read the output of the shell wordexp function,
         * which is a decimal word count, an null, a decimal byte count,
         * (not including terminating null bytes), a null and then followed
         * by the expanded words separated by nulls.
         */
        free(cmd);
        close(pdes[1]);
        /* read the word count */       
        nwords = 0;
        while ((i = getc(fp)) != EOF) {
                if (i == '\0')
                        break;
                nwords *= 10;
                nwords += (i - '0');
        }
        /* read the byte count */
        nbytes = 0;
        while ((i = getc(fp)) != EOF) {
                if (i == '\0')
                        break;
                nbytes *= 10;
                nbytes += (i - '0');
        }
        if (i == EOF) {
                fclose(fp);
                waitpid(pid, &status, 0);
                return (flags & WRDE_UNDEF ? WRDE_BADVAL : WRDE_SYNTAX);
        }
        nbytes += nwords;

        /*
         * Allocate or reallocate (when flags & WRDE_APPEND) the word vector
         * and string storage buffers for the expanded words we're about to
         * read from the child.
         */
        sofs = we->we_nbytes;
        vofs = we->we_wordc;
        if ((flags & (WRDE_DOOFFS|WRDE_APPEND)) == (WRDE_DOOFFS|WRDE_APPEND))
                vofs += we->we_offs;
        we->we_wordc += nwords;
        we->we_nbytes += nbytes;
        if ((nwv = realloc(we->we_wordv, (we->we_wordc + 1 +
            (flags & WRDE_DOOFFS ?  we->we_offs : 0)) *
            sizeof(char *))) == NULL) {
                fclose(fp);
                waitpid(pid, &status, 0);
                return (WRDE_NOSPACE);
        }
        we->we_wordv = nwv;
        if ((nstrings = realloc(we->we_strings, we->we_nbytes)) == NULL) {
                fclose(fp);
                waitpid(pid, &status, 0);
                return (WRDE_NOSPACE);
        }
        for (ui = 0; ui < vofs; ui++)
                if (we->we_wordv[ui] != NULL)
                        we->we_wordv[ui] += nstrings - we->we_strings;
        we->we_strings = nstrings;

        if (fread(we->we_strings + sofs, sizeof(char), nbytes, fp) != nbytes) {
                fclose(fp);
                waitpid(pid, &status, 0);
                return (flags & WRDE_UNDEF ? WRDE_BADVAL : WRDE_SYNTAX);
        }

        if (waitpid(pid, &status, 0) < 0 || !WIFEXITED(status) ||
            WEXITSTATUS(status) != 0) {
                fclose(fp);
                return (flags & WRDE_UNDEF ? WRDE_BADVAL : WRDE_SYNTAX);
        }
        fclose(fp);

        /*
         * Break the null-terminated expanded word strings out into
         * the vector.
         */
        if (vofs == 0 && flags & WRDE_DOOFFS)
                while (vofs < we->we_offs)
                        we->we_wordv[vofs++] = NULL;
        p = we->we_strings + sofs;
        while (nwords-- != 0) {
                we->we_wordv[vofs++] = p;
                if ((np = memchr(p, '\0', nbytes)) == NULL)
                        return (WRDE_NOSPACE);  /* XXX */
                nbytes -= np - p + 1;
                p = np + 1;
        }
        we->we_wordv[vofs] = NULL;

        return (0);
}

/*
 * we_check --
 *      Check that the string contains none of the following unquoted
 *      special characters: <newline> |&;<>(){}
 *      or command substitutions when WRDE_NOCMD is set in flags.
 */
static int
we_check(const char *words, int flags)
{
        char c;
        int dquote, level, quote, squote;

        quote = squote = dquote = 0;
        while ((c = *words++) != '\0') {
                switch (c) {
                case '\\':
                        quote ^= 1;
                        continue;
                case '\'':
                        if (quote + dquote == 0)
                                squote ^= 1;
                        break;
                case '"':
                        if (quote + squote == 0)
                                dquote ^= 1;
                        break;
                case '`':
                        if (quote + squote == 0 && flags & WRDE_NOCMD)
                                return (WRDE_CMDSUB);
                        while ((c = *words++) != '\0' && c != '`')
                                if (c == '\\' && (c = *words++) == '\0')
                                        break;
                        if (c == '\0')
                                return (WRDE_SYNTAX);
                        break;
                case '|': case '&': case ';': case '<': case '>':
                case '{': case '}': case '(': case ')': case '\n':
                        if (quote + squote + dquote == 0)
                                return (WRDE_BADCHAR);
                        break;
                case '$':
                        if ((c = *words++) == '\0')
                                break;
                        else if (quote + squote == 0 && c == '(') {
                                if (flags & WRDE_NOCMD && *words != '(')
                                        return (WRDE_CMDSUB);
                                level = 1;
                                while ((c = *words++) != '\0') {
                                        if (c == '\\') {
                                                if ((c = *words++) == '\0')
                                                        break;
                                        } else if (c == '(')
                                                level++;
                                        else if (c == ')' && --level == 0)
                                                break;
                                }
                                if (c == '\0' || level != 0)
                                        return (WRDE_SYNTAX);
                        } else if (quote + squote == 0 && c == '{') {
                                level = 1;
                                while ((c = *words++) != '\0') {
                                        if (c == '\\') {
                                                if ((c = *words++) == '\0')
                                                        break;
                                        } else if (c == '{')
                                                level++;
                                        else if (c == '}' && --level == 0)
                                                break;
                                }
                                if (c == '\0' || level != 0)
                                        return (WRDE_SYNTAX);
                        } else
                                c = *--words;
                        break;
                default:
                        break;
                }
                quote = 0;
        }
        if (quote + squote + dquote != 0)
                return (WRDE_SYNTAX);

        return (0);
}

/*
 * wordfree --
 *      Free the result of wordexp(). See wordexp(3).
 *
 */
void
wordfree(wordexp_t *we)
{
        _DIAGASSERT(we != NULL);
        free(we->we_wordv);
        free(we->we_strings);
        we->we_wordv = NULL;
        we->we_strings = NULL;
        we->we_nbytes = 0;
        we->we_wordc = 0;
}