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 27 #include <sys/cdefs.h> 28 __FBSDID("$FreeBSD$"); 29 30 #include <sys/param.h> 31 #include <sys/vnode.h> 32 #include <sys/proc.h> 33 #include <sys/sbuf.h> 34 #include <sys/systm.h> 35 #include <sys/sysproto.h> 36 #include <sys/exec.h> 37 #include <sys/imgact.h> 38 #include <sys/kernel.h> 39 40 #if BYTE_ORDER == LITTLE_ENDIAN 41 #define SHELLMAGIC 0x2123 /* #! */ 42 #else 43 #define SHELLMAGIC 0x2321 44 #endif 45 46 /* 47 * At the time of this writing, MAXSHELLCMDLEN == PAGE_SIZE. This is 48 * significant because the caller has only mapped in one page of the 49 * file we're reading. 50 */ 51 #if MAXSHELLCMDLEN > PAGE_SIZE 52 #error "MAXSHELLCMDLEN is larger than a single page!" 53 #endif 54 55 /* 56 * MAXSHELLCMDLEN must be at least MAXINTERP plus the size of the `#!' 57 * prefix and terminating newline. 58 */ 59 CTASSERT(MAXSHELLCMDLEN >= MAXINTERP + 3); 60 61 /** 62 * Shell interpreter image activator. An interpreter name beginning at 63 * imgp->args->begin_argv is the minimal successful exit requirement. 64 * 65 * If the given file is a shell-script, then the first line will start 66 * with the two characters `#!' (aka SHELLMAGIC), followed by the name 67 * of the shell-interpreter to run, followed by zero or more tokens. 68 * 69 * The interpreter is then started up such that it will see: 70 * arg[0] -> The name of interpreter as specified after `#!' in the 71 * first line of the script. The interpreter name must 72 * not be longer than MAXSHELLCMDLEN bytes. 73 * arg[1] -> *If* there are any additional tokens on the first line, 74 * then we add a new arg[1], which is a copy of the rest of 75 * that line. The copy starts at the first token after the 76 * interpreter name. We leave it to the interpreter to 77 * parse the tokens in that value. 78 * arg[x] -> the full pathname of the script. This will either be 79 * arg[2] or arg[1], depending on whether or not tokens 80 * were found after the interpreter name. 81 * arg[x+1] -> all the arguments that were specified on the original 82 * command line. 83 * 84 * This processing is described in the execve(2) man page. 85 */ 86 87 /* 88 * HISTORICAL NOTE: From 1993 to mid-2005, FreeBSD parsed out the tokens as 89 * found on the first line of the script, and setup each token as a separate 90 * value in arg[]. This extra processing did not match the behavior of other 91 * OS's, and caused a few subtle problems. For one, it meant the kernel was 92 * deciding how those values should be parsed (wrt characters for quoting or 93 * comments, etc), while the interpreter might have other rules for parsing. 94 * It also meant the interpreter had no way of knowing which arguments came 95 * from the first line of the shell script, and which arguments were specified 96 * by the user on the command line. That extra processing was dropped in the 97 * 6.x branch on May 28, 2005 (matching __FreeBSD_version 600029). 98 */ 99 int 100 exec_shell_imgact(imgp) 101 struct image_params *imgp; 102 { 103 const char *image_header = imgp->image_header; 104 const char *ihp, *interpb, *interpe, *maxp, *optb, *opte, *fname; 105 int error, offset; 106 size_t length; 107 struct vattr vattr; 108 struct sbuf *sname; 109 110 /* a shell script? */ 111 if (((const short *)image_header)[0] != SHELLMAGIC) 112 return (-1); 113 114 /* 115 * Don't allow a shell script to be the shell for a shell 116 * script. :-) 117 */ 118 if (imgp->interpreted) 119 return (ENOEXEC); 120 121 imgp->interpreted = 1; 122 123 /* 124 * At this point we have the first page of the file mapped. 125 * However, we don't know how far into the page the contents are 126 * valid -- the actual file might be much shorter than the page. 127 * So find out the file size. 128 */ 129 error = VOP_GETATTR(imgp->vp, &vattr, imgp->proc->p_ucred); 130 if (error) 131 return (error); 132 133 /* 134 * Copy shell name and arguments from image_header into a string 135 * buffer. 136 */ 137 maxp = &image_header[MIN(vattr.va_size, MAXSHELLCMDLEN)]; 138 ihp = &image_header[2]; 139 140 /* 141 * Find the beginning and end of the interpreter_name. If the 142 * line does not include any interpreter, or if the name which 143 * was found is too long, we bail out. 144 */ 145 while (ihp < maxp && ((*ihp == ' ') || (*ihp == '\t'))) 146 ihp++; 147 interpb = ihp; 148 while (ihp < maxp && ((*ihp != ' ') && (*ihp != '\t') && (*ihp != '\n') 149 && (*ihp != '\0'))) 150 ihp++; 151 interpe = ihp; 152 if (interpb == interpe) 153 return (ENOEXEC); 154 if (interpe - interpb >= MAXINTERP) 155 return (ENAMETOOLONG); 156 157 /* 158 * Find the beginning of the options (if any), and the end-of-line. 159 * Then trim the trailing blanks off the value. Note that some 160 * other operating systems do *not* trim the trailing whitespace... 161 */ 162 while (ihp < maxp && ((*ihp == ' ') || (*ihp == '\t'))) 163 ihp++; 164 optb = ihp; 165 while (ihp < maxp && ((*ihp != '\n') && (*ihp != '\0'))) 166 ihp++; 167 opte = ihp; 168 if (opte == maxp) 169 return (ENOEXEC); 170 while (--ihp > optb && ((*ihp == ' ') || (*ihp == '\t'))) 171 opte = ihp; 172 173 if (imgp->args->fname != NULL) { 174 fname = imgp->args->fname; 175 sname = NULL; 176 } else { 177 sname = sbuf_new_auto(); 178 sbuf_printf(sname, "/dev/fd/%d", imgp->args->fd); 179 sbuf_finish(sname); 180 fname = sbuf_data(sname); 181 } 182 183 /* 184 * We need to "pop" (remove) the present value of arg[0], and "push" 185 * either two or three new values in the arg[] list. To do this, 186 * we first shift all the other values in the `begin_argv' area to 187 * provide the exact amount of room for the values added. Set up 188 * `offset' as the number of bytes to be added to the `begin_argv' 189 * area, and 'length' as the number of bytes being removed. 190 */ 191 offset = interpe - interpb + 1; /* interpreter */ 192 if (opte > optb) /* options (if any) */ 193 offset += opte - optb + 1; 194 offset += strlen(fname) + 1; /* fname of script */ 195 length = (imgp->args->argc == 0) ? 0 : 196 strlen(imgp->args->begin_argv) + 1; /* bytes to delete */ 197 198 if (offset > imgp->args->stringspace + length) { 199 if (sname != NULL) 200 sbuf_delete(sname); 201 return (E2BIG); 202 } 203 204 bcopy(imgp->args->begin_argv + length, imgp->args->begin_argv + offset, 205 imgp->args->endp - (imgp->args->begin_argv + length)); 206 207 offset -= length; /* calculate actual adjustment */ 208 imgp->args->begin_envv += offset; 209 imgp->args->endp += offset; 210 imgp->args->stringspace -= offset; 211 212 /* 213 * If there was no arg[0] when we started, then the interpreter_name 214 * is adding an argument (instead of replacing the arg[0] we started 215 * with). And we're always adding an argument when we include the 216 * full pathname of the original script. 217 */ 218 if (imgp->args->argc == 0) 219 imgp->args->argc = 1; 220 imgp->args->argc++; 221 222 /* 223 * The original arg[] list has been shifted appropriately. Copy in 224 * the interpreter name and options-string. 225 */ 226 length = interpe - interpb; 227 bcopy(interpb, imgp->args->begin_argv, length); 228 *(imgp->args->begin_argv + length) = '\0'; 229 offset = length + 1; 230 if (opte > optb) { 231 length = opte - optb; 232 bcopy(optb, imgp->args->begin_argv + offset, length); 233 *(imgp->args->begin_argv + offset + length) = '\0'; 234 offset += length + 1; 235 imgp->args->argc++; 236 } 237 238 /* 239 * Finally, add the filename onto the end for the interpreter to 240 * use and copy the interpreter's name to imgp->interpreter_name 241 * for exec to use. 242 */ 243 error = copystr(fname, imgp->args->begin_argv + offset, 244 imgp->args->stringspace, NULL); 245 246 if (error == 0) 247 imgp->interpreter_name = imgp->args->begin_argv; 248 249 if (sname != NULL) 250 sbuf_delete(sname); 251 return (error); 252 } 253 254 /* 255 * Tell kern_execve.c about it, with a little help from the linker. 256 */ 257 static struct execsw shell_execsw = { exec_shell_imgact, "#!" }; 258 EXEC_SET(shell, shell_execsw); 259