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