1/*- 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright (c) 1993, David Greenman 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29#include <sys/param.h> 30#include <sys/vnode.h> 31#include <sys/proc.h> 32#include <sys/sbuf.h> 33#include <sys/systm.h> 34#include <sys/sysproto.h> 35#include <sys/exec.h> 36#include <sys/imgact.h> 37#include <sys/kernel.h> 38 39#if BYTE_ORDER == LITTLE_ENDIAN 40#define SHELLMAGIC 0x2123 /* #! */ 41#else 42#define SHELLMAGIC 0x2321 43#endif 44 45/* 46 * At the time of this writing, MAXSHELLCMDLEN == PAGE_SIZE. This is 47 * significant because the caller has only mapped in one page of the 48 * file we're reading. 49 */ 50#if MAXSHELLCMDLEN > PAGE_SIZE 51#error "MAXSHELLCMDLEN is larger than a single page!" 52#endif 53 54/* 55 * MAXSHELLCMDLEN must be at least MAXINTERP plus the size of the `#!' 56 * prefix and terminating newline. 57 */ 58CTASSERT(MAXSHELLCMDLEN >= MAXINTERP + 3); 59 60/** 61 * Shell interpreter image activator. An interpreter name beginning at 62 * imgp->args->begin_argv is the minimal successful exit requirement. 63 * 64 * If the given file is a shell-script, then the first line will start 65 * with the two characters `#!' (aka SHELLMAGIC), followed by the name 66 * of the shell-interpreter to run, followed by zero or more tokens. 67 * 68 * The interpreter is then started up such that it will see: 69 * arg[0] -> The name of interpreter as specified after `#!' in the 70 * first line of the script. The interpreter name must 71 * not be longer than MAXSHELLCMDLEN bytes. 72 * arg[1] -> *If* there are any additional tokens on the first line, 73 * then we add a new arg[1], which is a copy of the rest of 74 * that line. The copy starts at the first token after the 75 * interpreter name. We leave it to the interpreter to 76 * parse the tokens in that value. 77 * arg[x] -> the full pathname of the script. This will either be 78 * arg[2] or arg[1], depending on whether or not tokens 79 * were found after the interpreter name. 80 * arg[x+1] -> all the arguments that were specified on the original 81 * command line. 82 * 83 * This processing is described in the execve(2) man page. 84 */ 85 86/* 87 * HISTORICAL NOTE: From 1993 to mid-2005, FreeBSD parsed out the tokens as 88 * found on the first line of the script, and setup each token as a separate 89 * value in arg[]. This extra processing did not match the behavior of other 90 * OS's, and caused a few subtle problems. For one, it meant the kernel was 91 * deciding how those values should be parsed (wrt characters for quoting or 92 * comments, etc), while the interpreter might have other rules for parsing. 93 * It also meant the interpreter had no way of knowing which arguments came 94 * from the first line of the shell script, and which arguments were specified 95 * by the user on the command line. That extra processing was dropped in the 96 * 6.x branch on May 28, 2005 (matching __FreeBSD_version 600029). 97 */ 98int 99exec_shell_imgact(struct image_params *imgp) 100{ 101 const char *image_header = imgp->image_header; 102 const char *ihp, *interpb, *interpe, *maxp, *optb, *opte, *fname; 103 int error, offset; 104 size_t length; 105 struct vattr vattr; 106 struct sbuf *sname; 107 108 /* a shell script? */ 109 if (((const short *)image_header)[0] != SHELLMAGIC) 110 return (-1); 111 112 /* 113 * Don't allow a shell script to be the shell for a shell 114 * script. :-) 115 */ 116 if (imgp->interpreted & IMGACT_SHELL) 117 return (ENOEXEC); 118 119 imgp->interpreted |= IMGACT_SHELL; 120 121 /* 122 * At this point we have the first page of the file mapped. 123 * However, we don't know how far into the page the contents are 124 * valid -- the actual file might be much shorter than the page. 125 * So find out the file size. 126 */ 127 error = VOP_GETATTR(imgp->vp, &vattr, imgp->proc->p_ucred); 128 if (error) 129 return (error); 130 131 /* 132 * Copy shell name and arguments from image_header into a string 133 * buffer. 134 */ 135 maxp = &image_header[MIN(vattr.va_size, MAXSHELLCMDLEN)]; 136 ihp = &image_header[2]; 137 138 /* 139 * Find the beginning and end of the interpreter_name. If the 140 * line does not include any interpreter, or if the name which 141 * was found is too long, we bail out. 142 */ 143 while (ihp < maxp && ((*ihp == ' ') || (*ihp == '\t'))) 144 ihp++; 145 interpb = ihp; 146 while (ihp < maxp && ((*ihp != ' ') && (*ihp != '\t') && (*ihp != '\n') 147 && (*ihp != '\0'))) 148 ihp++; 149 interpe = ihp; 150 if (interpb == interpe) 151 return (ENOEXEC); 152 if (interpe - interpb >= MAXINTERP) 153 return (ENAMETOOLONG); 154 155 /* 156 * Find the beginning of the options (if any), and the end-of-line. 157 * Then trim the trailing blanks off the value. Note that some 158 * other operating systems do *not* trim the trailing whitespace... 159 */ 160 while (ihp < maxp && ((*ihp == ' ') || (*ihp == '\t'))) 161 ihp++; 162 optb = ihp; 163 while (ihp < maxp && ((*ihp != '\n') && (*ihp != '\0'))) 164 ihp++; 165 opte = ihp; 166 if (opte == maxp) 167 return (ENOEXEC); 168 while (--ihp > optb && ((*ihp == ' ') || (*ihp == '\t'))) 169 opte = ihp; 170 171 if (imgp->args->fname != NULL) { 172 fname = imgp->args->fname; 173 sname = NULL; 174 } else { 175 sname = sbuf_new_auto(); 176 sbuf_printf(sname, "/dev/fd/%d", imgp->args->fd); 177 sbuf_finish(sname); 178 fname = sbuf_data(sname); 179 } 180 181 /* 182 * We need to "pop" (remove) the present value of arg[0], and "push" 183 * either two or three new values in the arg[] list. To do this, 184 * we first shift all the other values in the `begin_argv' area to 185 * provide the exact amount of room for the values added. Set up 186 * `offset' as the number of bytes to be added to the `begin_argv' 187 * area, and 'length' as the number of bytes being removed. 188 */ 189 offset = interpe - interpb + 1; /* interpreter */ 190 if (opte > optb) /* options (if any) */ 191 offset += opte - optb + 1; 192 offset += strlen(fname) + 1; /* fname of script */ 193 length = (imgp->args->argc == 0) ? 0 : 194 strlen(imgp->args->begin_argv) + 1; /* bytes to delete */ 195 196 error = exec_args_adjust_args(imgp->args, length, offset); 197 if (error != 0) { 198 if (sname != NULL) 199 sbuf_delete(sname); 200 return (error); 201 } 202 203 /* 204 * If there was no arg[0] when we started, then the interpreter_name 205 * is adding an argument (instead of replacing the arg[0] we started 206 * with). And we're always adding an argument when we include the 207 * full pathname of the original script. 208 */ 209 if (imgp->args->argc == 0) 210 imgp->args->argc = 1; 211 imgp->args->argc++; 212 213 /* 214 * The original arg[] list has been shifted appropriately. Copy in 215 * the interpreter name and options-string. 216 */ 217 length = interpe - interpb; 218 bcopy(interpb, imgp->args->begin_argv, length); 219 *(imgp->args->begin_argv + length) = '\0'; 220 offset = length + 1; 221 if (opte > optb) { 222 length = opte - optb; 223 bcopy(optb, imgp->args->begin_argv + offset, length); 224 *(imgp->args->begin_argv + offset + length) = '\0'; 225 offset += length + 1; 226 imgp->args->argc++; 227 } 228 229 /* 230 * Finally, add the filename onto the end for the interpreter to 231 * use and copy the interpreter's name to imgp->interpreter_name 232 * for exec to use. 233 */ 234 error = copystr(fname, imgp->args->begin_argv + offset, 235 imgp->args->stringspace, NULL); 236 237 if (error == 0) 238 imgp->interpreter_name = imgp->args->begin_argv; 239 240 if (sname != NULL) 241 sbuf_delete(sname); 242 return (error); 243} 244 245/* 246 * Tell kern_execve.c about it, with a little help from the linker. 247 */ 248static struct execsw shell_execsw = { 249 .ex_imgact = exec_shell_imgact, 250 .ex_name = "#!" 251}; 252EXEC_SET(shell, shell_execsw); 253