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123 lines
3.8 KiB
C
123 lines
3.8 KiB
C
// Copyright (c) 2012-2015, Matt Godbolt
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are met:
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//
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// * Redistributions of source code must retain the above copyright notice,
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// this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above copyright
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// notice, this list of conditions and the following disclaimer in the
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// documentation and/or other materials provided with the distribution.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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// POSSIBILITY OF SUCH DAMAGE.
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#define _GNU_SOURCE
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#include <dlfcn.h>
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#include <stdio.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <errno.h>
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#include <limits.h>
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#include <stdlib.h>
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#include <string.h>
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#include <libgen.h>
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#ifndef O_CREAT
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#define O_CREAT 0100
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#endif
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static int allowed_match(const char* path, const char* okpath) {
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char resolvedBuf[PATH_MAX];
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const char* resolved = path;
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if (!strncmp(resolved, "/proc/self", 10)) {
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// Leave references to /proc/self.* alone as its real path is different
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// each time.
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} else {
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resolved = realpath(path, resolvedBuf);
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if (resolved == NULL) {
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return 0;
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}
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}
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while (*okpath) {
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const char* end = strchrnul(okpath, ':');
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if (strncmp(okpath, resolved, end - okpath) == 0) return 1;
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okpath = end;
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while (*okpath == ':') ++okpath;
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}
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fprintf(stderr, "Access to \"%s\" denied by gcc-explorer policy\n", path);
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errno = EACCES;
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return 0;
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}
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static int allowed_env(const char* pathname, const char* envvar) {
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const char* okpath = getenv(envvar);
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if (okpath == NULL) {
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errno = EINVAL;
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return 0;
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}
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// Check file name first
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if (allowed_match(pathname, okpath)) return 1;
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// Check directory name
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char* dirpathbuf = strdup(pathname);
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char* dirpath = dirname(dirpathbuf);
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int dir_ok = allowed_match(dirpath, okpath);
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free(dirpathbuf);
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return dir_ok;
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}
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static int allowed(const char* pathname, int flags) {
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if (flags & O_CREAT)
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return allowed_env(pathname, "ALLOWED_FOR_CREATE");
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else
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return allowed_env(pathname, "ALLOWED_FOR_READ");
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}
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int open(const char *pathname, int flags, mode_t mode) {
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static int (*real_open)(const char*, int, mode_t) = NULL;
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if (!real_open) real_open = dlsym(RTLD_NEXT, "open");
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if (!allowed(pathname, flags)) {
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return -1;
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}
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return real_open(pathname, flags, mode);
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}
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int creat(const char *pathname, mode_t mode) {
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static int (*real_creat)(const char*, mode_t) = NULL;
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if (!real_creat) real_creat = dlsym(RTLD_NEXT, "creat");
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if (!allowed(pathname, O_CREAT)) {
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return -1;
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}
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return real_creat(pathname, mode);
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}
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FILE* fopen(const char* name, const char* mode) {
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static FILE* (*real_fopen)(const char*, const char*) = NULL;
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if (!real_fopen) real_fopen = dlsym(RTLD_NEXT, "fopen");
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if (!allowed(name, (mode[0] == 'r') ? 0 : O_CREAT)) {
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return NULL;
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}
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return real_fopen(name, mode);
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}
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