checkpath: use O_PATH when available
This avoids opening directories/files with read permission, which is sometimes rejected by selinux policy. Bug: https://bugs.gentoo.org/667122
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@ -16,9 +16,11 @@
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* except according to the terms contained in the LICENSE file.
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*/
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#define _GNU_SOURCE
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <assert.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <getopt.h>
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@ -69,6 +71,37 @@ const char * const longopts_help[] = {
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};
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const char *usagestring = NULL;
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/* On Linux, fchmod() returns EBADF when passed a file descriptor opened
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* with O_PATH. Use chmod() on /proc/self/fd as a workaround. */
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static int fchmod_opath(int fd, mode_t mode)
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{
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#ifdef O_PATH
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/* A 64-bit int will result in a maximum path length of 35 characters. */
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char path[35];
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/* Maybe we will have 128-bit ints someday. */
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assert(sizeof(int) <= 8);
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if (sprintf(path, "/proc/self/fd/%d", fd) < 0)
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return -1;
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return chmod(path, mode);
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#else
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return fchmod(fd, mode);
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#endif
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}
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/* On Linux, fchown() returns EBADF when passed a file descriptor opened
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* with O_PATH. fchownat() does not exhibit this flaw. */
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static int fchown_opath(int fd, uid_t uid, gid_t gid)
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{
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#ifdef O_PATH
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return fchownat(fd, "", uid, gid, AT_EMPTY_PATH);
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#else
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return fchown(fd, uid, gid);
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#endif
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}
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static int do_check(char *path, uid_t uid, gid_t gid, mode_t mode,
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inode_t type, bool trunc, bool chowner, bool selinux_on)
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{
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@ -82,7 +115,7 @@ static int do_check(char *path, uid_t uid, gid_t gid, mode_t mode,
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memset(&st, 0, sizeof(st));
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flags = O_CREAT|O_NDELAY|O_WRONLY|O_NOCTTY;
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readflags = O_NDELAY|O_NOCTTY|O_RDONLY;
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readflags = O_NDELAY|O_NOCTTY;
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#ifdef O_CLOEXEC
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flags |= O_CLOEXEC;
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readflags |= O_CLOEXEC;
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@ -90,6 +123,11 @@ static int do_check(char *path, uid_t uid, gid_t gid, mode_t mode,
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#ifdef O_NOFOLLOW
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flags |= O_NOFOLLOW;
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readflags |= O_NOFOLLOW;
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#endif
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#ifdef O_PATH
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readflags |= O_PATH;
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#else
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readflags |= O_RDONLY;
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#endif
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if (trunc)
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flags |= O_TRUNC;
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@ -177,7 +215,7 @@ static int do_check(char *path, uid_t uid, gid_t gid, mode_t mode,
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return -1;
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}
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einfo("%s: correcting mode", path);
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if (fchmod(readfd, mode)) {
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if (fchmod_opath(readfd, mode)) {
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eerror("%s: chmod: %s", applet, strerror(errno));
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close(readfd);
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return -1;
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@ -196,7 +234,7 @@ static int do_check(char *path, uid_t uid, gid_t gid, mode_t mode,
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return -1;
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}
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einfo("%s: correcting owner", path);
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if (fchown(readfd, uid, gid)) {
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if (fchown_opath(readfd, uid, gid)) {
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eerror("%s: chown: %s", applet, strerror(errno));
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close(readfd);
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return -1;
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