sys/kern/imgact_shell.c

   1 /*
   2  * Copyright (c) 1993, David Greenman
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  24  * SUCH DAMAGE.
  25  *
  26  * $FreeBSD: src/sys/kern/imgact_shell.c,v 1.21.2.2 2001/12/22 01:21:39 jwd Exp $
  27  * $DragonFly: src/sys/kern/imgact_shell.c,v 1.6 2005/02/28 05:44:52 dillon Exp $
  28  */
  29
  30 #include <sys/param.h>
  31 #include <sys/systm.h>
  32 #include <sys/sysproto.h>
  33 #include <sys/exec.h>
  34 #include <sys/imgact.h>
  35 #include <sys/kernel.h>
  36
  37 #if BYTE_ORDER == LITTLE_ENDIAN
  38 #define SHELLMAGIC      0x2123 /* #! */
  39 #else
  40 #define SHELLMAGIC      0x2321
  41 #endif
  42
  43 /*
  44  * Shell interpreter image activator. A interpreter name beginning
  45  *      at imgp->args->begin_argv is the minimal successful exit requirement.
  46  */
  47 int
  48 exec_shell_imgact(struct image_params *imgp)
  49 {
  50         const char *image_header = imgp->image_header;
  51         const char *ihp;
  52         size_t length, offset;
  53         int error;
  54
  55         /* a shell script? */
  56         if (((const short *) image_header)[0] != SHELLMAGIC)
  57                 return(-1);
  58
  59         /*
  60          * Don't allow a shell script to be the shell for a shell
  61          *      script. :-)
  62          */
  63         if (imgp->interpreted)
  64                 return(ENOEXEC);
  65
  66         imgp->interpreted = 1;
  67
  68         /*
  69          * Figure out the number of bytes that need to be reserved in the
  70          * argument string to copy the contents of the interpreter's command
  71          * line into the argument string.
  72          */
  73         ihp = &image_header[2];
  74         offset = 0;
  75         while (ihp < &image_header[PAGE_SIZE]) {
  76                 /* Skip any whitespace */
  77                 if (*ihp == ' ' || *ihp == '\t') {
  78                         ++ihp;
  79                         continue;
  80                 }
  81
  82                 /* End of line? */
  83                 if (*ihp == '\n' || *ihp == '#' || *ihp == '\0')
  84                         break;
  85
  86                 /* Found a token */
  87                 do {
  88                         ++offset;
  89                         ++ihp;
  90                 } while (ihp < &image_header[PAGE_SIZE] &&
  91                          *ihp != ' ' && *ihp != '\t' &&
  92                          *ihp != '\n' && *ihp != '#' && *ihp != '\0');
  93
  94                 /* Take into account the \0 that will terminate the token */
  95                 ++offset;
  96         }
  97
  98         /* If the script gives a null line as the interpreter, we bail */
  99         if (offset == 0)
 100                 return (ENOEXEC);
 101
 102         /* It should not be possible for offset to exceed PAGE_SIZE */
 103         KKASSERT(offset <= PAGE_SIZE);
 104
 105         /* Check that we aren't too big */
 106         if (ihp == &image_header[PAGE_SIZE])
 107                 return (ENAMETOOLONG);
 108
 109         /*
 110          * The full path name of the original script file must be tagged
 111          * onto the end, adjust the offset to deal with it.
 112          *
 113          * The original argv0 is being replaced, set 'length' to the number
 114          * of bytes being removed.  So 'offset' is the number of bytes being
 115          * added and 'length' is the number of bytes being removed.
 116          */
 117         offset += strlen(imgp->args->fname) + 1;        /* add fname */
 118         length = strlen(imgp->args->begin_argv) + 1;    /* bytes to delete */
 119
 120         if (offset > imgp->args->space + length)
 121                 return (E2BIG);
 122
 123         bcopy(imgp->args->begin_argv + length, imgp->args->begin_argv + offset,
 124                 imgp->args->endp - (imgp->args->begin_argv + length));
 125
 126         offset -= length;               /* calculate actual adjustment */
 127         imgp->args->begin_envv += offset;
 128         imgp->args->endp += offset;
 129         imgp->args->space -= offset;
 130         /* decr argc remove old argv[0], incr argc for fname add, net 0 */
 131
 132         /*
 133          * Loop through the interpreter name yet again, copying as
 134          * we go.
 135          */
 136         ihp = &image_header[2];
 137         offset = 0;
 138         while (ihp < &image_header[PAGE_SIZE]) {
 139                 /* Skip whitespace */
 140                 if (*ihp == ' ' || *ihp == '\t') {
 141                         ++ihp;
 142                         continue;
 143                 }
 144
 145                 /* End of line? */
 146                 if (*ihp == '\n' || *ihp == '#' || *ihp == '\0')
 147                         break;
 148
 149                 /* Found a token, copy it */
 150                 do {
 151                         imgp->args->begin_argv[offset] = *ihp;
 152                         ++ihp;
 153                         ++offset;
 154                 } while (ihp < &image_header[PAGE_SIZE] &&
 155                          *ihp != ' ' && *ihp != '\t' &&
 156                          *ihp != '\n' && *ihp != '#' && *ihp != '\0');
 157
 158                 /* And terminate the argument */
 159                 imgp->args->begin_argv[offset] = '\0';
 160                 imgp->args->argc++;
 161                 ++offset;
 162         }
 163
 164         /*
 165          * Finally, add the filename onto the end for the interpreter to
 166          * use and copy the interpreter's name to imgp->interpreter_name
 167          * for exec to use.
 168          */
 169         error = copystr(imgp->args->fname, imgp->args->buf + offset,
 170                         imgp->args->space, &length);
 171
 172         if (error == 0) {
 173                 error = copystr(imgp->args->begin_argv, imgp->interpreter_name,
 174                                 MAXSHELLCMDLEN, &length);
 175         }
 176         return (error);
 177 }
 178
 179 /*
 180  * Tell kern_execve.c about it, with a little help from the linker.
 181  */
 182 static struct execsw shell_execsw = { exec_shell_imgact, "#!" };
 183 EXEC_SET(shell, shell_execsw);