1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 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/cdefs.h> 30 __FBSDID("$FreeBSD$"); 31 32 #include <sys/param.h> 33 #include <sys/vnode.h> 34 #include <sys/proc.h> 35 #include <sys/sbuf.h> 36 #include <sys/systm.h> 37 #include <sys/sysproto.h> 38 #include <sys/exec.h> 39 #include <sys/imgact.h> 40 #include <sys/kernel.h> 41 42 #if BYTE_ORDER == LITTLE_ENDIAN 43 #define SHELLMAGIC 0x2123 /* #! */ 44 #else 45 #define SHELLMAGIC 0x2321 46 #endif 47 48 /* 49 * At the time of this writing, MAXSHELLCMDLEN == PAGE_SIZE. This is 50 * significant because the caller has only mapped in one page of the 51 * file we're reading. 52 */ 53 #if MAXSHELLCMDLEN > PAGE_SIZE 54 #error "MAXSHELLCMDLEN is larger than a single page!" 55 #endif 56 57 /* 58 * MAXSHELLCMDLEN must be at least MAXINTERP plus the size of the `#!' 59 * prefix and terminating newline. 60 */ 61 CTASSERT(MAXSHELLCMDLEN >= MAXINTERP + 3); 62 63 /** 64 * Shell interpreter image activator. An interpreter name beginning at 65 * imgp->args->begin_argv is the minimal successful exit requirement. 66 * 67 * If the given file is a shell-script, then the first line will start 68 * with the two characters `#!' (aka SHELLMAGIC), followed by the name 69 * of the shell-interpreter to run, followed by zero or more tokens. 70 * 71 * The interpreter is then started up such that it will see: 72 * arg[0] -> The name of interpreter as specified after `#!' in the 73 * first line of the script. The interpreter name must 74 * not be longer than MAXSHELLCMDLEN bytes. 75 * arg[1] -> *If* there are any additional tokens on the first line, 76 * then we add a new arg[1], which is a copy of the rest of 77 * that line. The copy starts at the first token after the 78 * interpreter name. We leave it to the interpreter to 79 * parse the tokens in that value. 80 * arg[x] -> the full pathname of the script. This will either be 81 * arg[2] or arg[1], depending on whether or not tokens 82 * were found after the interpreter name. 83 * arg[x+1] -> all the arguments that were specified on the original 84 * command line. 85 * 86 * This processing is described in the execve(2) man page. 87 */ 88 89 /* 90 * HISTORICAL NOTE: From 1993 to mid-2005, FreeBSD parsed out the tokens as 91 * found on the first line of the script, and setup each token as a separate 92 * value in arg[]. This extra processing did not match the behavior of other 93 * OS's, and caused a few subtle problems. For one, it meant the kernel was 94 * deciding how those values should be parsed (wrt characters for quoting or 95 * comments, etc), while the interpreter might have other rules for parsing. 96 * It also meant the interpreter had no way of knowing which arguments came 97 * from the first line of the shell script, and which arguments were specified 98 * by the user on the command line. That extra processing was dropped in the 99 * 6.x branch on May 28, 2005 (matching __FreeBSD_version 600029). 100 */ 101 int 102 exec_shell_imgact(struct image_params *imgp) 103 { 104 const char *image_header = imgp->image_header; 105 const char *ihp, *interpb, *interpe, *maxp, *optb, *opte, *fname; 106 int error, offset; 107 size_t length; 108 struct vattr vattr; 109 struct sbuf *sname; 110 111 /* a shell script? */ 112 if (((const short *)image_header)[0] != SHELLMAGIC) 113 return (-1); 114 115 /* 116 * Don't allow a shell script to be the shell for a shell 117 * script. :-) 118 */ 119 if (imgp->interpreted & IMGACT_SHELL) 120 return (ENOEXEC); 121 122 imgp->interpreted |= IMGACT_SHELL; 123 124 /* 125 * At this point we have the first page of the file mapped. 126 * However, we don't know how far into the page the contents are 127 * valid -- the actual file might be much shorter than the page. 128 * So find out the file size. 129 */ 130 error = VOP_GETATTR(imgp->vp, &vattr, imgp->proc->p_ucred); 131 if (error) 132 return (error); 133 134 /* 135 * Copy shell name and arguments from image_header into a string 136 * buffer. 137 */ 138 maxp = &image_header[MIN(vattr.va_size, MAXSHELLCMDLEN)]; 139 ihp = &image_header[2]; 140 141 /* 142 * Find the beginning and end of the interpreter_name. If the 143 * line does not include any interpreter, or if the name which 144 * was found is too long, we bail out. 145 */ 146 while (ihp < maxp && ((*ihp == ' ') || (*ihp == '\t'))) 147 ihp++; 148 interpb = ihp; 149 while (ihp < maxp && ((*ihp != ' ') && (*ihp != '\t') && (*ihp != '\n') 150 && (*ihp != '\0'))) 151 ihp++; 152 interpe = ihp; 153 if (interpb == interpe) 154 return (ENOEXEC); 155 if (interpe - interpb >= MAXINTERP) 156 return (ENAMETOOLONG); 157 158 /* 159 * Find the beginning of the options (if any), and the end-of-line. 160 * Then trim the trailing blanks off the value. Note that some 161 * other operating systems do *not* trim the trailing whitespace... 162 */ 163 while (ihp < maxp && ((*ihp == ' ') || (*ihp == '\t'))) 164 ihp++; 165 optb = ihp; 166 while (ihp < maxp && ((*ihp != '\n') && (*ihp != '\0'))) 167 ihp++; 168 opte = ihp; 169 if (opte == maxp) 170 return (ENOEXEC); 171 while (--ihp > optb && ((*ihp == ' ') || (*ihp == '\t'))) 172 opte = ihp; 173 174 if (imgp->args->fname != NULL) { 175 fname = imgp->args->fname; 176 sname = NULL; 177 } else { 178 sname = sbuf_new_auto(); 179 sbuf_printf(sname, "/dev/fd/%d", imgp->args->fd); 180 sbuf_finish(sname); 181 fname = sbuf_data(sname); 182 } 183 184 /* 185 * We need to "pop" (remove) the present value of arg[0], and "push" 186 * either two or three new values in the arg[] list. To do this, 187 * we first shift all the other values in the `begin_argv' area to 188 * provide the exact amount of room for the values added. Set up 189 * `offset' as the number of bytes to be added to the `begin_argv' 190 * area, and 'length' as the number of bytes being removed. 191 */ 192 offset = interpe - interpb + 1; /* interpreter */ 193 if (opte > optb) /* options (if any) */ 194 offset += opte - optb + 1; 195 offset += strlen(fname) + 1; /* fname of script */ 196 length = (imgp->args->argc == 0) ? 0 : 197 strlen(imgp->args->begin_argv) + 1; /* bytes to delete */ 198 199 error = exec_args_adjust_args(imgp->args, length, offset); 200 if (error != 0) { 201 if (sname != NULL) 202 sbuf_delete(sname); 203 return (error); 204 } 205 206 /* 207 * If there was no arg[0] when we started, then the interpreter_name 208 * is adding an argument (instead of replacing the arg[0] we started 209 * with). And we're always adding an argument when we include the 210 * full pathname of the original script. 211 */ 212 if (imgp->args->argc == 0) 213 imgp->args->argc = 1; 214 imgp->args->argc++; 215 216 /* 217 * The original arg[] list has been shifted appropriately. Copy in 218 * the interpreter name and options-string. 219 */ 220 length = interpe - interpb; 221 bcopy(interpb, imgp->args->begin_argv, length); 222 *(imgp->args->begin_argv + length) = '\0'; 223 offset = length + 1; 224 if (opte > optb) { 225 length = opte - optb; 226 bcopy(optb, imgp->args->begin_argv + offset, length); 227 *(imgp->args->begin_argv + offset + length) = '\0'; 228 offset += length + 1; 229 imgp->args->argc++; 230 } 231 232 /* 233 * Finally, add the filename onto the end for the interpreter to 234 * use and copy the interpreter's name to imgp->interpreter_name 235 * for exec to use. 236 */ 237 error = copystr(fname, imgp->args->begin_argv + offset, 238 imgp->args->stringspace, NULL); 239 240 if (error == 0) 241 imgp->interpreter_name = imgp->args->begin_argv; 242 243 if (sname != NULL) 244 sbuf_delete(sname); 245 return (error); 246 } 247 248 /* 249 * Tell kern_execve.c about it, with a little help from the linker. 250 */ 251 static struct execsw shell_execsw = { 252 .ex_imgact = exec_shell_imgact, 253 .ex_name = "#!" 254 }; 255 EXEC_SET(shell, shell_execsw); 256