diff options
Diffstat (limited to 'sys/kern/imgact_shell.c')
| -rw-r--r-- | sys/kern/imgact_shell.c | 258 |
1 files changed, 258 insertions, 0 deletions
diff --git a/sys/kern/imgact_shell.c b/sys/kern/imgact_shell.c new file mode 100644 index 0000000..d9884f5 --- /dev/null +++ b/sys/kern/imgact_shell.c @@ -0,0 +1,258 @@ +/*- + * 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/cdefs.h> +__FBSDID("$FreeBSD$"); + +#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(imgp) + 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) + return (ENOEXEC); + + imgp->interpreted = 1; + + /* + * 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 */ + + if (offset > imgp->args->stringspace + length) { + if (sname != NULL) + sbuf_delete(sname); + return (E2BIG); + } + + bcopy(imgp->args->begin_argv + length, imgp->args->begin_argv + offset, + imgp->args->endp - (imgp->args->begin_argv + length)); + + offset -= length; /* calculate actual adjustment */ + imgp->args->begin_envv += offset; + imgp->args->endp += offset; + imgp->args->stringspace -= offset; + + /* + * 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 = { exec_shell_imgact, "#!" }; +EXEC_SET(shell, shell_execsw); |
