/*- * SPDX-License-Identifier: BSD-2-Clause * * Copyright (c) 1993, David Greenman * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #include <sys/param.h> #include <sys/vnode.h> #include <sys/proc.h> #include <sys/sbuf.h> #include <sys/systm.h> #include <sys/sysproto.h> #include <sys/exec.h> #include <sys/imgact.h> #include <sys/kernel.h> #if BYTE_ORDER == LITTLE_ENDIAN #define SHELLMAGIC 0x2123 /* #! */ #else #define SHELLMAGIC 0x2321 #endif /* * At the time of this writing, MAXSHELLCMDLEN == PAGE_SIZE. This is * significant because the caller has only mapped in one page of the * file we're reading. */ #if MAXSHELLCMDLEN > PAGE_SIZE #error "MAXSHELLCMDLEN is larger than a single page!" #endif /* * MAXSHELLCMDLEN must be at least MAXINTERP plus the size of the `#!' * prefix and terminating newline. */ CTASSERT(MAXSHELLCMDLEN >= MAXINTERP + 3); /** * Shell interpreter image activator. An interpreter name beginning at * imgp->args->begin_argv is the minimal successful exit requirement. * * If the given file is a shell-script, then the first line will start * with the two characters `#!' (aka SHELLMAGIC), followed by the name * of the shell-interpreter to run, followed by zero or more tokens. * * The interpreter is then started up such that it will see: * arg[0] -> The name of interpreter as specified after `#!' in the * first line of the script. The interpreter name must * not be longer than MAXSHELLCMDLEN bytes. * arg[1] -> *If* there are any additional tokens on the first line, * then we add a new arg[1], which is a copy of the rest of * that line. The copy starts at the first token after the * interpreter name. We leave it to the interpreter to * parse the tokens in that value. * arg[x] -> the full pathname of the script. This will either be * arg[2] or arg[1], depending on whether or not tokens * were found after the interpreter name. * arg[x+1] -> all the arguments that were specified on the original * command line. * * This processing is described in the execve(2) man page. */ /* * HISTORICAL NOTE: From 1993 to mid-2005, FreeBSD parsed out the tokens as * found on the first line of the script, and setup each token as a separate * value in arg[]. This extra processing did not match the behavior of other * OS's, and caused a few subtle problems. For one, it meant the kernel was * deciding how those values should be parsed (wrt characters for quoting or * comments, etc), while the interpreter might have other rules for parsing. * It also meant the interpreter had no way of knowing which arguments came * from the first line of the shell script, and which arguments were specified * by the user on the command line. That extra processing was dropped in the * 6.x branch on May 28, 2005 (matching __FreeBSD_version 600029). */ int exec_shell_imgact(struct image_params *imgp) { const char *image_header = imgp->image_header; const char *ihp, *interpb, *interpe, *maxp, *optb, *opte, *fname; int error, offset; size_t length; struct vattr vattr; struct sbuf *sname; /* a shell script? */ if (((const short *)image_header)[0] != SHELLMAGIC) return (-1); /* * Don't allow a shell script to be the shell for a shell * script. :-) */ if (imgp->interpreted & IMGACT_SHELL) return (ENOEXEC); imgp->interpreted |= IMGACT_SHELL; /* * At this point we have the first page of the file mapped. * However, we don't know how far into the page the contents are * valid -- the actual file might be much shorter than the page. * So find out the file size. */ error = VOP_GETATTR(imgp->vp, &vattr, imgp->proc->p_ucred); if (error) return (error); /* * Copy shell name and arguments from image_header into a string * buffer. */ maxp = &image_header[MIN(vattr.va_size, MAXSHELLCMDLEN)]; ihp = &image_header[2]; /* * Find the beginning and end of the interpreter_name. If the * line does not include any interpreter, or if the name which * was found is too long, we bail out. */ while (ihp < maxp && ((*ihp == ' ') || (*ihp == '\t'))) ihp++; interpb = ihp; while (ihp < maxp && ((*ihp != ' ') && (*ihp != '\t') && (*ihp != '\n') && (*ihp != '\0'))) ihp++; interpe = ihp; if (interpb == interpe) return (ENOEXEC); if (interpe - interpb >= MAXINTERP) return (ENAMETOOLONG); /* * Find the beginning of the options (if any), and the end-of-line. * Then trim the trailing blanks off the value. Note that some * other operating systems do *not* trim the trailing whitespace... */ while (ihp < maxp && ((*ihp == ' ') || (*ihp == '\t'))) ihp++; optb = ihp; while (ihp < maxp && ((*ihp != '\n') && (*ihp != '\0'))) ihp++; opte = ihp; if (opte == maxp) return (ENOEXEC); while (--ihp > optb && ((*ihp == ' ') || (*ihp == '\t'))) opte = ihp; if (imgp->args->fname != NULL) { fname = imgp->args->fname; sname = NULL; } else { sname = sbuf_new_auto(); sbuf_printf(sname, "/dev/fd/%d", imgp->args->fd); sbuf_finish(sname); fname = sbuf_data(sname); } /* * We need to "pop" (remove) the present value of arg[0], and "push" * either two or three new values in the arg[] list. To do this, * we first shift all the other values in the `begin_argv' area to * provide the exact amount of room for the values added. Set up * `offset' as the number of bytes to be added to the `begin_argv' * area, and 'length' as the number of bytes being removed. */ offset = interpe - interpb + 1; /* interpreter */ if (opte > optb) /* options (if any) */ offset += opte - optb + 1; offset += strlen(fname) + 1; /* fname of script */ length = (imgp->args->argc == 0) ? 0 : strlen(imgp->args->begin_argv) + 1; /* bytes to delete */ error = exec_args_adjust_args(imgp->args, length, offset); if (error != 0) { if (sname != NULL) sbuf_delete(sname); return (error); } /* * If there was no arg[0] when we started, then the interpreter_name * is adding an argument (instead of replacing the arg[0] we started * with). And we're always adding an argument when we include the * full pathname of the original script. */ if (imgp->args->argc == 0) imgp->args->argc = 1; imgp->args->argc++; /* * The original arg[] list has been shifted appropriately. Copy in * the interpreter name and options-string. */ length = interpe - interpb; bcopy(interpb, imgp->args->begin_argv, length); *(imgp->args->begin_argv + length) = '\0'; offset = length + 1; if (opte > optb) { length = opte - optb; bcopy(optb, imgp->args->begin_argv + offset, length); *(imgp->args->begin_argv + offset + length) = '\0'; offset += length + 1; imgp->args->argc++; } /* * Finally, add the filename onto the end for the interpreter to * use and copy the interpreter's name to imgp->interpreter_name * for exec to use. */ error = copystr(fname, imgp->args->begin_argv + offset, imgp->args->stringspace, NULL); if (error == 0) imgp->interpreter_name = imgp->args->begin_argv; if (sname != NULL) sbuf_delete(sname); return (error); } /* * Tell kern_execve.c about it, with a little help from the linker. */ static struct execsw shell_execsw = { .ex_imgact = exec_shell_imgact, .ex_name = "#!" }; EXEC_SET(shell, shell_execsw);
