# Regenerate the junk that autotools wants to have around.
-aclocal
-automake --foreign --add-missing -Wall -Werror
-autoconf
+autoreconf --force --install
AC_PREREQ([2.68])
AC_INIT([apply-default-acl], [0.0.6], [michael@orlitzky.com])
-AM_INIT_AUTOMAKE
+AM_INIT_AUTOMAKE([foreign]) # don't bug me a bout README, NEWS, etc.
AC_CONFIG_SRCDIR([src/apply-default-acl.c])
AC_CONFIG_FILES([Makefile src/Makefile])
# Checks for programs.
AC_PROG_CC
+AM_PROG_AR
# Predefined header checks.
AC_HEADER_STAT # sys/stat.h
AC_CHECK_HEADERS([ fcntl.h ftw.h getopt.h libgen.h sys/acl.h sys/libacl.h ])
AC_CHECK_HEADERS([ sys/types.h unistd.h ])
+LT_INIT
+
AC_OUTPUT
# If we call apply-default-acl on a single file that does not exist,
# we get the expected error.
TESTNUM=25
-ACTUAL=$( ${BIN} test/nonexistent 2>&1 )
-EXPECTED="${BIN}: test/nonexistent: No such file or directory"
+ACTUAL=$( "${BIN}" test/nonexistent 2>&1 )
+ACTUAL="${ACTUAL#*: }"
+EXPECTED="test/nonexistent: No such file or directory"
compare
# Same as the previous test, but with --recursive.
TESTNUM=26
-ACTUAL=$( ${BIN} --recursive test/nonexistent 2>&1 )
-EXPECTED="${BIN}: test/nonexistent: No such file or directory"
+ACTUAL=$( "${BIN}" --recursive test/nonexistent 2>&1 )
+ACTUAL="${ACTUAL#*: }"
+EXPECTED="test/nonexistent: No such file or directory"
compare
# If we call apply-default-acl on more than one file, it should report any
DUMMY1="${TESTDIR}/dummy1"
DUMMY2="${TESTDIR}/dummy2"
touch "${DUMMY1}" "${DUMMY2}"
-ACTUAL=$( ${BIN} "${DUMMY1}" test/nonexistent "${DUMMY2}" 2>&1 )
-EXPECTED="${BIN}: test/nonexistent: No such file or directory"
+ACTUAL=$( "${BIN}" "${DUMMY1}" test/nonexistent "${DUMMY2}" 2>&1 )
+ACTUAL="${ACTUAL#*: }"
+EXPECTED="test/nonexistent: No such file or directory"
compare
+lib_LTLIBRARIES = libadacl.la
+libadacl_la_SOURCES = libadacl.c libadacl.h
+libadacl_la_LIBADD = -lacl
+include_HEADERS = libadacl.h
+
bin_PROGRAMS = apply-default-acl
-apply_default_acl_LDFLAGS = -lacl
+apply_default_acl_LDADD = libadacl.la
/**
* @file apply-default-acl.c
*
- * @brief The entire implementation.
+ * @brief The command-line interface.
*
*/
#include <fcntl.h> /* AT_FOO constants */
#include <ftw.h> /* nftw() et al. */
#include <getopt.h>
-#include <libgen.h> /* basename(), dirname() */
-#include <limits.h> /* PATH_MAX */
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
-#include <string.h>
-#include <sys/stat.h>
#include <unistd.h>
-/* ACLs */
-#include <acl/libacl.h> /* acl_get_perm, not portable */
-#include <sys/types.h>
-#include <sys/acl.h>
-
-/* Most of the libacl functions return 1 for success, 0 for failure,
- and -1 on error */
-#define ACL_ERROR -1
-#define ACL_FAILURE 0
-#define ACL_SUCCESS 1
-
-/* Even though most other library functions reliably return -1 for
- * error, it feels a little wrong to re-use the ACL_ERROR constant.
- */
-#define CLOSE_ERROR -1
-#define NFTW_ERROR -1
-#define OPEN_ERROR -1
-#define SNPRINTF_ERROR -1
-#define STAT_ERROR -1
-
-
-/**
- * @brief The recursive portion of the @c safe_open function, used to
- * open a file descriptor in a symlink-safe way when combined with
- * the @c O_NOFOLLOW flag.
- *
- * @param at_fd
- * A file descriptor relative to which @c pathname will be opened.
- *
- * @param pathname
- * The path to the file/directory/whatever whose descriptor you want.
- *
- * @return a file descriptor for @c pathname if everything goes well,
- * and @c OPEN_ERROR if not.
- */
-int safe_open_ex(int at_fd, char* pathname, int flags) {
- if (pathname != NULL && strlen(pathname) == 0) {
- /* Oops, went one level to deep with nothing to do. */
- return at_fd;
- }
-
- char* firstslash = strchr(pathname, '/');
- if (firstslash == NULL) {
- /* No more slashes, this is the base case. */
- int r = openat(at_fd, pathname, flags);
- return r;
- }
-
- /* Temporarily disable the slash, so that the subsequent call to
- openat() opens only the next directory (and doesn't recurse). */
- *firstslash = '\0';
- int fd = safe_open_ex(at_fd, pathname, flags);
- if (fd == OPEN_ERROR) {
- if (errno != ELOOP) {
- /* Don't output anything if we ignore a symlink */
- perror("safe_open_ex (safe_open_ex)");
- }
- return OPEN_ERROR;
- }
-
- /* The ++ is safe because there needs to be at least a null byte
- after the first slash, even if it's the last real character in
- the string. */
- int result = safe_open_ex(fd, firstslash+1, flags);
- if (close(fd) == CLOSE_ERROR) {
- perror("safe_open_ex (close)");
- return OPEN_ERROR;
- }
- return result;
-}
-
-
-/**
- * @brief A version of @c open that is completely symlink-safe when
- * used with the @c O_NOFOLLOW flag.
- *
- * The @c openat function exists to ensure that you can anchor one
- * path to a particular directory while opening it; however, if you
- * open "b/c/d" relative to "/a", then even the @c openat function will
- * still follow symlinks in the "b" component. This can be exploited
- * by an attacker to make you open the wrong path.
- *
- * To avoid that problem, this function uses a recursive
- * implementation that opens every path from the root, one level at a
- * time. So "a" is opened relative to "/", and then "b" is opened
- * relative to "/a", and then "c" is opened relative to "/a/b",
- * etc. When the @c O_NOFOLLOW flag is used, this approach ensures
- * that no symlinks in any component are followed.
- *
- * @param pathname
- * The path to the file/directory/whatever whose descriptor you want.
- *
- * @return a file descriptor for @c pathname if everything goes well,
- * and @c OPEN_ERROR if not.
- */
-int safe_open(const char* pathname, int flags) {
- if (pathname == NULL || strlen(pathname) == 0 || pathname[0] == '\0') {
- /* error? */
- return OPEN_ERROR;
- }
-
- char abspath[PATH_MAX];
- int snprintf_result = 0;
- if (strchr(pathname, '/') == pathname) {
- /* pathname is already absolute; just copy it. */
- snprintf_result = snprintf(abspath, PATH_MAX, "%s", pathname);
- }
- else {
- /* Concatenate the current working directory and pathname into an
- * absolute path. We use realpath() ONLY on the cwd part, and not
- * on the pathname part, because realpath() resolves symlinks. And
- * the whole point of all this crap is to avoid following symlinks
- * in the pathname.
- *
- * Using realpath() on the cwd lets us operate on relative paths
- * while we're sitting in a directory that happens to have a
- * symlink in it; for example: cd /var/run && apply-default-acl foo.
- */
- char* cwd = get_current_dir_name();
- if (cwd == NULL) {
- perror("safe_open (get_current_dir_name)");
- return OPEN_ERROR;
- }
-
- char abs_cwd[PATH_MAX];
- if (realpath(cwd, abs_cwd) == NULL) {
- perror("safe_open (realpath)");
- free(cwd);
- return OPEN_ERROR;
- }
- snprintf_result = snprintf(abspath, PATH_MAX, "%s/%s", abs_cwd, pathname);
- free(cwd);
- }
- if (snprintf_result == SNPRINTF_ERROR || snprintf_result > PATH_MAX) {
- perror("safe_open (snprintf)");
- return OPEN_ERROR;
- }
-
- int fd = open("/", flags);
- if (strcmp(abspath, "/") == 0) {
- return fd;
- }
-
- int result = safe_open_ex(fd, abspath+1, flags);
- if (close(fd) == CLOSE_ERROR) {
- perror("safe_open (close)");
- return OPEN_ERROR;
- }
- return result;
-}
+#include "libadacl.h"
}
-
-/**
- * @brief Update (or create) an entry in an @b minimal ACL.
- *
- * This function will not work if @c aclp contains extended
- * entries. This is fine for our purposes, since we call @c wipe_acls
- * on each path before applying the default to it.
- *
- * The assumption that there are no extended entries makes things much
- * simpler. For example, we only have to update the @c ACL_USER_OBJ,
- * @c ACL_GROUP_OBJ, and @c ACL_OTHER entries -- all others can simply
- * be created anew. This means we don't have to fool around comparing
- * named-user/group entries.
- *
- * @param aclp
- * A pointer to the acl_t structure whose entry we want to modify.
- *
- * @param entry
- * The new entry. If @c entry contains a user/group/other entry, we
- * update the existing one. Otherwise we create a new entry.
- *
- * @return If there is an unexpected library error, @c ACL_ERROR is
- * returned. Otherwise, @c ACL_SUCCESS.
- *
- */
-int acl_set_entry(acl_t* aclp, acl_entry_t entry) {
-
- acl_tag_t entry_tag;
- if (acl_get_tag_type(entry, &entry_tag) == ACL_ERROR) {
- perror("acl_set_entry (acl_get_tag_type)");
- return ACL_ERROR;
- }
-
- acl_permset_t entry_permset;
- if (acl_get_permset(entry, &entry_permset) == ACL_ERROR) {
- perror("acl_set_entry (acl_get_permset)");
- return ACL_ERROR;
- }
-
- acl_entry_t existing_entry;
- /* Loop through the given ACL looking for matching entries. */
- int result = acl_get_entry(*aclp, ACL_FIRST_ENTRY, &existing_entry);
-
- while (result == ACL_SUCCESS) {
- acl_tag_t existing_tag = ACL_UNDEFINED_TAG;
-
- if (acl_get_tag_type(existing_entry, &existing_tag) == ACL_ERROR) {
- perror("set_acl_tag_permset (acl_get_tag_type)");
- return ACL_ERROR;
- }
-
- if (existing_tag == entry_tag) {
- if (entry_tag == ACL_USER_OBJ ||
- entry_tag == ACL_GROUP_OBJ ||
- entry_tag == ACL_OTHER) {
- /* Only update for these three since all other tags will have
- been wiped. These three are guaranteed to exist, so if we
- match one of them, we're allowed to return ACL_SUCCESS
- below and bypass the rest of the function. */
- acl_permset_t existing_permset;
- if (acl_get_permset(existing_entry, &existing_permset) == ACL_ERROR) {
- perror("acl_set_entry (acl_get_permset)");
- return ACL_ERROR;
- }
-
- if (acl_set_permset(existing_entry, entry_permset) == ACL_ERROR) {
- perror("acl_set_entry (acl_set_permset)");
- return ACL_ERROR;
- }
-
- return ACL_SUCCESS;
- }
-
- }
-
- result = acl_get_entry(*aclp, ACL_NEXT_ENTRY, &existing_entry);
- }
-
- /* This catches both the initial acl_get_entry and the ones at the
- end of the loop. */
- if (result == ACL_ERROR) {
- perror("acl_set_entry (acl_get_entry)");
- return ACL_ERROR;
- }
-
- /* If we've made it this far, we need to add a new entry to the
- ACL. */
- acl_entry_t new_entry;
-
- /* The acl_create_entry() function can allocate new memory and/or
- * change the location of the ACL structure entirely. When that
- * happens, the value pointed to by aclp is updated, which means
- * that a new acl_t gets "passed out" to our caller, eventually to
- * be fed to acl_free(). In other words, we should still be freeing
- * the right thing, even if the value pointed to by aclp changes.
- */
- if (acl_create_entry(aclp, &new_entry) == ACL_ERROR) {
- perror("acl_set_entry (acl_create_entry)");
- return ACL_ERROR;
- }
-
- if (acl_set_tag_type(new_entry, entry_tag) == ACL_ERROR) {
- perror("acl_set_entry (acl_set_tag_type)");
- return ACL_ERROR;
- }
-
- if (acl_set_permset(new_entry, entry_permset) == ACL_ERROR) {
- perror("acl_set_entry (acl_set_permset)");
- return ACL_ERROR;
- }
-
- if (entry_tag == ACL_USER || entry_tag == ACL_GROUP) {
- /* We need to set the qualifier too. */
- void* entry_qual = acl_get_qualifier(entry);
- if (entry_qual == (void*)NULL) {
- perror("acl_set_entry (acl_get_qualifier)");
- return ACL_ERROR;
- }
-
- if (acl_set_qualifier(new_entry, entry_qual) == ACL_ERROR) {
- perror("acl_set_entry (acl_set_qualifier)");
- return ACL_ERROR;
- }
- }
-
- return ACL_SUCCESS;
-}
-
-
-
-/**
- * @brief Determine the number of entries in the given ACL.
- *
- * @param acl
- * The ACL to inspect.
- *
- * @return Either the non-negative number of entries in @c acl, or
- * @c ACL_ERROR on error.
- */
-int acl_entry_count(acl_t acl) {
-
- acl_entry_t entry;
- int entry_count = 0;
- int result = acl_get_entry(acl, ACL_FIRST_ENTRY, &entry);
-
- while (result == ACL_SUCCESS) {
- entry_count++;
- result = acl_get_entry(acl, ACL_NEXT_ENTRY, &entry);
- }
-
- if (result == ACL_ERROR) {
- perror("acl_entry_count (acl_get_entry)");
- return ACL_ERROR;
- }
-
- return entry_count;
-}
-
-
-
-/**
- * @brief Determine whether or not the given ACL is minimal.
- *
- * An ACL is minimal if it has fewer than four entries.
- *
- * @param acl
- * The ACL whose minimality is in question.
- *
- * @return
- * - @c ACL_SUCCESS - @c acl is minimal
- * - @c ACL_FAILURE - @c acl is not minimal
- * - @c ACL_ERROR - Unexpected library error
- */
-int acl_is_minimal(acl_t acl) {
-
- int ec = acl_entry_count(acl);
-
- if (ec == ACL_ERROR) {
- perror("acl_is_minimal (acl_entry_count)");
- return ACL_ERROR;
- }
-
- if (ec < 4) {
- return ACL_SUCCESS;
- }
- else {
- return ACL_FAILURE;
- }
-}
-
-
-
-/**
- * @brief Determine whether the given ACL's mask denies execute.
- *
- * @param acl
- * The ACL whose mask we want to check.
- *
- * @return
- * - @c ACL_SUCCESS - The @c acl has a mask which denies execute.
- * - @c ACL_FAILURE - The @c acl has a mask which does not deny execute.
- * - @c ACL_ERROR - Unexpected library error.
- */
-int acl_execute_masked(acl_t acl) {
-
- acl_entry_t entry;
- int ge_result = acl_get_entry(acl, ACL_FIRST_ENTRY, &entry);
-
- while (ge_result == ACL_SUCCESS) {
- acl_tag_t tag = ACL_UNDEFINED_TAG;
-
- if (acl_get_tag_type(entry, &tag) == ACL_ERROR) {
- perror("acl_execute_masked (acl_get_tag_type)");
- return ACL_ERROR;
- }
-
- if (tag == ACL_MASK) {
- /* This is the mask entry, get its permissions, and see if
- execute is specified. */
- acl_permset_t permset;
-
- if (acl_get_permset(entry, &permset) == ACL_ERROR) {
- perror("acl_execute_masked (acl_get_permset)");
- return ACL_ERROR;
- }
-
- int gp_result = acl_get_perm(permset, ACL_EXECUTE);
- if (gp_result == ACL_ERROR) {
- perror("acl_execute_masked (acl_get_perm)");
- return ACL_ERROR;
- }
-
- if (gp_result == ACL_FAILURE) {
- /* No execute bit set in the mask; execute not allowed. */
- return ACL_SUCCESS;
- }
- }
-
- ge_result = acl_get_entry(acl, ACL_NEXT_ENTRY, &entry);
- }
-
- return ACL_FAILURE;
-}
-
-
-
-/**
- * @brief Determine whether @c fd is executable by anyone.
- *
- *
- * This is used as part of the heuristic to determine whether or not
- * we should mask the execute bit when inheriting an ACL. If @c fd
- * describes a file, we check the @a effective permissions, contrary
- * to what setfacl does.
- *
- * @param fd
- * The file descriptor to check.
- *
- * @param sp
- * A pointer to a stat structure for @c fd.
- *
- * @return
- * - @c ACL_SUCCESS - Someone has effective execute permissions on @c fd.
- * - @c ACL_FAILURE - Nobody can execute @c fd.
- * - @c ACL_ERROR - Unexpected library error.
- */
-int any_can_execute(int fd, const struct stat* sp) {
- acl_t acl = acl_get_fd(fd);
-
- if (acl == (acl_t)NULL) {
- perror("any_can_execute (acl_get_file)");
- return ACL_ERROR;
- }
-
- /* Our return value. */
- int result = ACL_FAILURE;
-
- if (acl_is_minimal(acl)) {
- if (sp->st_mode & (S_IXUSR | S_IXOTH | S_IXGRP)) {
- result = ACL_SUCCESS;
- goto cleanup;
- }
- else {
- result = ACL_FAILURE;
- goto cleanup;
- }
- }
-
- acl_entry_t entry;
- int ge_result = acl_get_entry(acl, ACL_FIRST_ENTRY, &entry);
-
- while (ge_result == ACL_SUCCESS) {
- /* The first thing we do is check to see if this is a mask
- entry. If it is, we skip it entirely. */
- acl_tag_t tag = ACL_UNDEFINED_TAG;
-
- if (acl_get_tag_type(entry, &tag) == ACL_ERROR) {
- perror("any_can_execute_or (acl_get_tag_type)");
- result = ACL_ERROR;
- goto cleanup;
- }
-
- if (tag == ACL_MASK) {
- ge_result = acl_get_entry(acl, ACL_NEXT_ENTRY, &entry);
- continue;
- }
-
- /* Ok, so it's not a mask entry. Check the execute perms. */
- acl_permset_t permset;
-
- if (acl_get_permset(entry, &permset) == ACL_ERROR) {
- perror("any_can_execute_or (acl_get_permset)");
- result = ACL_ERROR;
- goto cleanup;
- }
-
- int gp_result = acl_get_perm(permset, ACL_EXECUTE);
- if (gp_result == ACL_ERROR) {
- perror("any_can_execute (acl_get_perm)");
- result = ACL_ERROR;
- goto cleanup;
- }
-
- if (gp_result == ACL_SUCCESS) {
- /* Only return ACL_SUCCESS if this execute bit is not masked. */
- if (acl_execute_masked(acl) != ACL_SUCCESS) {
- result = ACL_SUCCESS;
- goto cleanup;
- }
- }
-
- ge_result = acl_get_entry(acl, ACL_NEXT_ENTRY, &entry);
- }
-
- if (ge_result == ACL_ERROR) {
- perror("any_can_execute (acl_get_entry)");
- result = ACL_ERROR;
- goto cleanup;
- }
-
- cleanup:
- acl_free(acl);
- return result;
-}
-
-
-
-/**
- * @brief Set @c acl as the default ACL on @c path.
- *
- * This overwrites any existing default ACL on @c path. If @c path is
- * not a directory, we return ACL_ERROR and @c errno is set.
- *
- * @param path
- * The target directory whose ACL we wish to replace or create.
- *
- * @param acl
- * The ACL to set as default on @c path.
- *
- * @return
- * - @c ACL_SUCCESS - The default ACL was assigned successfully.
- * - @c ACL_ERROR - Unexpected library error.
- */
-int assign_default_acl(const char* path, acl_t acl) {
-
- if (path == NULL) {
- errno = EINVAL;
- perror("assign_default_acl (args)");
- return ACL_ERROR;
- }
-
- /* Our return value; success unless something bad happens. */
- int result = ACL_SUCCESS;
- acl_t path_acl = acl_dup(acl);
-
- if (path_acl == (acl_t)NULL) {
- perror("assign_default_acl (acl_dup)");
- return ACL_ERROR; /* Nothing to clean up in this case. */
- }
-
- if (acl_set_file(path, ACL_TYPE_DEFAULT, path_acl) == ACL_ERROR) {
- perror("assign_default_acl (acl_set_file)");
- result = ACL_ERROR;
- }
-
- acl_free(path_acl);
- return result;
-}
-
-
-
-/**
- * @brief Remove all @c ACL_TYPE_ACCESS entries from the given file
- * descriptor, leaving the UNIX permission bits.
- *
- * @param fd
- * The file descriptor whose ACLs we want to wipe.
- *
- * @return
- * - @c ACL_SUCCESS - The ACLs were wiped successfully, or none
- * existed in the first place.
- * - @c ACL_ERROR - Unexpected library error.
- */
-int wipe_acls(int fd) {
- /* Initialize an empty ACL, and then overwrite the one on "fd" with it. */
- acl_t empty_acl = acl_init(0);
-
- if (empty_acl == (acl_t)NULL) {
- perror("wipe_acls (acl_init)");
- return ACL_ERROR;
- }
-
- if (acl_set_fd(fd, empty_acl) == ACL_ERROR) {
- perror("wipe_acls (acl_set_fd)");
- acl_free(empty_acl);
- return ACL_ERROR;
- }
-
- acl_free(empty_acl);
- return ACL_SUCCESS;
-}
-
-
-
-/**
- * @brief Apply parent default ACL to a path.
- *
- * This overwrites any existing ACLs on @c path.
- *
- * @param path
- * The path whose ACL we would like to reset to its default.
- *
- * @param sp
- * A pointer to a stat structure for @c path, or @c NULL if you don't
- * have one handy.
- *
- * @param no_exec_mask
- * The value (either true or false) of the --no-exec-mask flag.
- *
- * @return
- * - @c ACL_SUCCESS - The parent default ACL was inherited successfully.
- * - @c ACL_FAILURE - The target path is not a regular file/directory,
- * or the parent of @c path is not a directory.
- * - @c ACL_ERROR - Unexpected library error.
- */
-int apply_default_acl(const char* path,
- const struct stat* sp,
- bool no_exec_mask) {
-
- if (path == NULL) {
- errno = EINVAL;
- perror("apply_default_acl (args)");
- return ACL_ERROR;
- }
-
- /* Define these next three variables here because we may have to
- * jump to the cleanup routine which expects them to exist.
- */
-
- /* Our return value. */
- int result = ACL_SUCCESS;
-
- /* The default ACL on path's parent directory */
- acl_t defacl = (acl_t)NULL;
-
- /* The file descriptor corresponding to "path" */
- int fd = 0;
-
- /* Get the parent directory of "path" with dirname(), which happens
- * to murder its argument and necessitates a path_copy.
- */
- char* path_copy = strdup(path);
- if (path_copy == NULL) {
- perror("apply_default_acl (strdup)");
- return ACL_ERROR;
- }
- char* parent = dirname(path_copy);
-
- fd = safe_open(path, O_NOFOLLOW);
- if (fd == OPEN_ERROR) {
- if (errno == ELOOP) {
- result = ACL_FAILURE; /* hit a symlink */
- goto cleanup;
- }
- else {
- perror("apply_default_acl (open fd)");
- result = ACL_ERROR;
- goto cleanup;
- }
- }
-
-
- /* Refuse to operate on hard links, which can be abused by an
- * attacker to trick us into changing the ACL on a file we didn't
- * intend to; namely the "target" of the hard link. There is TOCTOU
- * race condition here, but the window is as small as possible
- * between when we open the file descriptor (look above) and when we
- * fstat it.
- *
- * Note: we only need to call fstat ourselves if we weren't passed a
- * valid pointer to a stat structure (nftw does that).
- */
- if (sp == NULL) {
- struct stat s;
- if (fstat(fd, &s) == STAT_ERROR) {
- perror("apply_default_acl (fstat)");
- goto cleanup;
- }
-
- sp = &s;
- }
-
- if (!S_ISDIR(sp->st_mode)) {
- /* If it's not a directory, make sure it's a regular,
- non-hard-linked file. */
- if (!S_ISREG(sp->st_mode) || sp->st_nlink != 1) {
- result = ACL_FAILURE;
- goto cleanup;
- }
- }
-
-
- /* Default to not masking the exec bit; i.e. applying the default
- ACL literally. If --no-exec-mask was not specified, then we try
- to "guess" whether or not to mask the exec bit. This behavior
- is modeled after the capital 'X' perms of setfacl. */
- bool allow_exec = true;
-
- if (!no_exec_mask) {
- /* Never mask the execute bit on directories. */
- int ace_result = any_can_execute(fd,sp) || S_ISDIR(sp->st_mode);
-
- if (ace_result == ACL_ERROR) {
- perror("apply_default_acl (any_can_execute)");
- result = ACL_ERROR;
- goto cleanup;
- }
-
- allow_exec = (bool)ace_result;
- }
-
- defacl = acl_get_file(parent, ACL_TYPE_DEFAULT);
-
- if (defacl == (acl_t)NULL) {
- perror("apply_default_acl (acl_get_file)");
- result = ACL_ERROR;
- goto cleanup;
- }
-
- if (wipe_acls(fd) == ACL_ERROR) {
- perror("apply_default_acl (wipe_acls)");
- result = ACL_ERROR;
- goto cleanup;
- }
-
- /* Do this after wipe_acls(), otherwise we'll overwrite the wiped
- ACL with this one. */
- acl_t acl = acl_get_fd(fd);
- if (acl == (acl_t)NULL) {
- perror("apply_default_acl (acl_get_fd)");
- result = ACL_ERROR;
- goto cleanup;
- }
-
- /* If it's a directory, inherit the parent's default. We sure hope
- * that "path" still points to the same thing that "fd" and this
- * "sp" describe. If not, we may wind up trying to set a default ACL
- * on a file, and this will throw an error. I guess that's what we
- * want to do?
- */
- if (S_ISDIR(sp->st_mode) && assign_default_acl(path, defacl) == ACL_ERROR) {
- perror("apply_default_acl (assign_default_acl)");
- result = ACL_ERROR;
- goto cleanup;
- }
-
- acl_entry_t entry;
- int ge_result = acl_get_entry(defacl, ACL_FIRST_ENTRY, &entry);
-
- while (ge_result == ACL_SUCCESS) {
- acl_tag_t tag = ACL_UNDEFINED_TAG;
-
- if (acl_get_tag_type(entry, &tag) == ACL_ERROR) {
- perror("apply_default_acl (acl_get_tag_type)");
- result = ACL_ERROR;
- goto cleanup;
- }
-
-
- /* We've got an entry/tag from the default ACL. Get its permset. */
- acl_permset_t permset;
- if (acl_get_permset(entry, &permset) == ACL_ERROR) {
- perror("apply_default_acl (acl_get_permset)");
- result = ACL_ERROR;
- goto cleanup;
- }
-
- /* If this is a default mask, fix it up. */
- if (tag == ACL_MASK ||
- tag == ACL_USER_OBJ ||
- tag == ACL_GROUP_OBJ ||
- tag == ACL_OTHER) {
-
- if (!allow_exec) {
- /* The mask doesn't affect acl_user_obj, acl_group_obj (in
- minimal ACLs) or acl_other entries, so if execute should be
- masked, we have to do it manually. */
- if (acl_delete_perm(permset, ACL_EXECUTE) == ACL_ERROR) {
- perror("apply_default_acl (acl_delete_perm)");
- result = ACL_ERROR;
- goto cleanup;
- }
-
- if (acl_set_permset(entry, permset) == ACL_ERROR) {
- perror("apply_default_acl (acl_set_permset)");
- result = ACL_ERROR;
- goto cleanup;
- }
- }
- }
-
- /* Finally, add the permset to the access ACL. It's actually
- * important that we pass in the address of "acl" here, and not
- * "acl" itself. Why? The call to acl_create_entry() within
- * acl_set_entry() can allocate new memory for the entry.
- * Sometimes that can be done in-place, in which case everything
- * is cool and the new memory gets released when we call
- * acl_free(acl).
- *
- * But occasionally, the whole ACL structure will have to be moved
- * in order to allocate the extra space. When that happens,
- * acl_create_entry() modifies the pointer it was passed (in this
- * case, &acl) to point to the new location. We want to call
- * acl_free() on the new location, and since acl_free() gets
- * called right here, we need acl_create_entry() to update the
- * value of "acl". To do that, it needs the address of "acl".
- */
- if (acl_set_entry(&acl, entry) == ACL_ERROR) {
- perror("apply_default_acl (acl_set_entry)");
- result = ACL_ERROR;
- goto cleanup;
- }
-
- ge_result = acl_get_entry(defacl, ACL_NEXT_ENTRY, &entry);
- }
-
- /* Catches the first acl_get_entry as well as the ones at the end of
- the loop. */
- if (ge_result == ACL_ERROR) {
- perror("apply_default_acl (acl_get_entry)");
- result = ACL_ERROR;
- goto cleanup;
- }
-
- if (acl_set_fd(fd, acl) == ACL_ERROR) {
- perror("apply_default_acl (acl_set_fd)");
- result = ACL_ERROR;
- goto cleanup;
- }
-
- cleanup:
- free(path_copy);
- if (defacl != (acl_t)NULL) {
- acl_free(defacl);
- }
- if (fd >= 0 && close(fd) == CLOSE_ERROR) {
- perror("apply_default_acl (close)");
- result = ACL_ERROR;
- }
- return result;
-}
-
-
-
/**
* @brief Display program usage information.
*
--- /dev/null
+/**
+ * @file libadacl.c
+ *
+ * @brief The adacl (apply default acl) shared library.
+ *
+ */
+
+/* Enables get_current_dir_name() in unistd.h */
+#define _GNU_SOURCE
+
+#include <errno.h>
+#include <fcntl.h>
+#include <libgen.h> /* basename(), dirname() */
+#include <limits.h> /* PATH_MAX */
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <unistd.h> /* get_current_dir_name() */
+
+/* ACLs */
+#include <acl/libacl.h> /* acl_get_perm, not portable */
+#include <sys/types.h>
+#include <sys/acl.h>
+
+#include "libadacl.h"
+
+
+/**
+ * @brief The recursive portion of the @c safe_open function, used to
+ * open a file descriptor in a symlink-safe way when combined with
+ * the @c O_NOFOLLOW flag.
+ *
+ * @param at_fd
+ * A file descriptor relative to which @c pathname will be opened.
+ *
+ * @param pathname
+ * The path to the file/directory/whatever whose descriptor you want.
+ *
+ * @return a file descriptor for @c pathname if everything goes well,
+ * and @c OPEN_ERROR if not.
+ */
+int safe_open_ex(int at_fd, char* pathname, int flags) {
+ if (pathname != NULL && strlen(pathname) == 0) {
+ /* Oops, went one level to deep with nothing to do. */
+ return at_fd;
+ }
+
+ char* firstslash = strchr(pathname, '/');
+ if (firstslash == NULL) {
+ /* No more slashes, this is the base case. */
+ int r = openat(at_fd, pathname, flags);
+ return r;
+ }
+
+ /* Temporarily disable the slash, so that the subsequent call to
+ openat() opens only the next directory (and doesn't recurse). */
+ *firstslash = '\0';
+ int fd = safe_open_ex(at_fd, pathname, flags);
+ if (fd == OPEN_ERROR) {
+ if (errno != ELOOP) {
+ /* Don't output anything if we ignore a symlink */
+ perror("safe_open_ex (safe_open_ex)");
+ }
+ return OPEN_ERROR;
+ }
+
+ /* The ++ is safe because there needs to be at least a null byte
+ after the first slash, even if it's the last real character in
+ the string. */
+ int result = safe_open_ex(fd, firstslash+1, flags);
+ if (close(fd) == CLOSE_ERROR) {
+ perror("safe_open_ex (close)");
+ return OPEN_ERROR;
+ }
+ return result;
+}
+
+
+/**
+ * @brief A version of @c open that is completely symlink-safe when
+ * used with the @c O_NOFOLLOW flag.
+ *
+ * The @c openat function exists to ensure that you can anchor one
+ * path to a particular directory while opening it; however, if you
+ * open "b/c/d" relative to "/a", then even the @c openat function will
+ * still follow symlinks in the "b" component. This can be exploited
+ * by an attacker to make you open the wrong path.
+ *
+ * To avoid that problem, this function uses a recursive
+ * implementation that opens every path from the root, one level at a
+ * time. So "a" is opened relative to "/", and then "b" is opened
+ * relative to "/a", and then "c" is opened relative to "/a/b",
+ * etc. When the @c O_NOFOLLOW flag is used, this approach ensures
+ * that no symlinks in any component are followed.
+ *
+ * @param pathname
+ * The path to the file/directory/whatever whose descriptor you want.
+ *
+ * @return a file descriptor for @c pathname if everything goes well,
+ * and @c OPEN_ERROR if not.
+ */
+int safe_open(const char* pathname, int flags) {
+ if (pathname == NULL || strlen(pathname) == 0 || pathname[0] == '\0') {
+ /* error? */
+ return OPEN_ERROR;
+ }
+
+ char abspath[PATH_MAX];
+ int snprintf_result = 0;
+ if (strchr(pathname, '/') == pathname) {
+ /* pathname is already absolute; just copy it. */
+ snprintf_result = snprintf(abspath, PATH_MAX, "%s", pathname);
+ }
+ else {
+ /* Concatenate the current working directory and pathname into an
+ * absolute path. We use realpath() ONLY on the cwd part, and not
+ * on the pathname part, because realpath() resolves symlinks. And
+ * the whole point of all this crap is to avoid following symlinks
+ * in the pathname.
+ *
+ * Using realpath() on the cwd lets us operate on relative paths
+ * while we're sitting in a directory that happens to have a
+ * symlink in it; for example: cd /var/run && apply-default-acl foo.
+ */
+ char* cwd = get_current_dir_name();
+ if (cwd == NULL) {
+ perror("safe_open (get_current_dir_name)");
+ return OPEN_ERROR;
+ }
+
+ char abs_cwd[PATH_MAX];
+ if (realpath(cwd, abs_cwd) == NULL) {
+ perror("safe_open (realpath)");
+ free(cwd);
+ return OPEN_ERROR;
+ }
+ snprintf_result = snprintf(abspath, PATH_MAX, "%s/%s", abs_cwd, pathname);
+ free(cwd);
+ }
+ if (snprintf_result == SNPRINTF_ERROR || snprintf_result > PATH_MAX) {
+ perror("safe_open (snprintf)");
+ return OPEN_ERROR;
+ }
+
+ int fd = open("/", flags);
+ if (strcmp(abspath, "/") == 0) {
+ return fd;
+ }
+
+ int result = safe_open_ex(fd, abspath+1, flags);
+ if (close(fd) == CLOSE_ERROR) {
+ perror("safe_open (close)");
+ return OPEN_ERROR;
+ }
+ return result;
+}
+
+
+
+
+/**
+ * @brief Update (or create) an entry in an @b minimal ACL.
+ *
+ * This function will not work if @c aclp contains extended
+ * entries. This is fine for our purposes, since we call @c wipe_acls
+ * on each path before applying the default to it.
+ *
+ * The assumption that there are no extended entries makes things much
+ * simpler. For example, we only have to update the @c ACL_USER_OBJ,
+ * @c ACL_GROUP_OBJ, and @c ACL_OTHER entries -- all others can simply
+ * be created anew. This means we don't have to fool around comparing
+ * named-user/group entries.
+ *
+ * @param aclp
+ * A pointer to the acl_t structure whose entry we want to modify.
+ *
+ * @param entry
+ * The new entry. If @c entry contains a user/group/other entry, we
+ * update the existing one. Otherwise we create a new entry.
+ *
+ * @return If there is an unexpected library error, @c ACL_ERROR is
+ * returned. Otherwise, @c ACL_SUCCESS.
+ *
+ */
+int acl_set_entry(acl_t* aclp, acl_entry_t entry) {
+
+ acl_tag_t entry_tag;
+ if (acl_get_tag_type(entry, &entry_tag) == ACL_ERROR) {
+ perror("acl_set_entry (acl_get_tag_type)");
+ return ACL_ERROR;
+ }
+
+ acl_permset_t entry_permset;
+ if (acl_get_permset(entry, &entry_permset) == ACL_ERROR) {
+ perror("acl_set_entry (acl_get_permset)");
+ return ACL_ERROR;
+ }
+
+ acl_entry_t existing_entry;
+ /* Loop through the given ACL looking for matching entries. */
+ int result = acl_get_entry(*aclp, ACL_FIRST_ENTRY, &existing_entry);
+
+ while (result == ACL_SUCCESS) {
+ acl_tag_t existing_tag = ACL_UNDEFINED_TAG;
+
+ if (acl_get_tag_type(existing_entry, &existing_tag) == ACL_ERROR) {
+ perror("set_acl_tag_permset (acl_get_tag_type)");
+ return ACL_ERROR;
+ }
+
+ if (existing_tag == entry_tag) {
+ if (entry_tag == ACL_USER_OBJ ||
+ entry_tag == ACL_GROUP_OBJ ||
+ entry_tag == ACL_OTHER) {
+ /* Only update for these three since all other tags will have
+ been wiped. These three are guaranteed to exist, so if we
+ match one of them, we're allowed to return ACL_SUCCESS
+ below and bypass the rest of the function. */
+ acl_permset_t existing_permset;
+ if (acl_get_permset(existing_entry, &existing_permset) == ACL_ERROR) {
+ perror("acl_set_entry (acl_get_permset)");
+ return ACL_ERROR;
+ }
+
+ if (acl_set_permset(existing_entry, entry_permset) == ACL_ERROR) {
+ perror("acl_set_entry (acl_set_permset)");
+ return ACL_ERROR;
+ }
+
+ return ACL_SUCCESS;
+ }
+
+ }
+
+ result = acl_get_entry(*aclp, ACL_NEXT_ENTRY, &existing_entry);
+ }
+
+ /* This catches both the initial acl_get_entry and the ones at the
+ end of the loop. */
+ if (result == ACL_ERROR) {
+ perror("acl_set_entry (acl_get_entry)");
+ return ACL_ERROR;
+ }
+
+ /* If we've made it this far, we need to add a new entry to the
+ ACL. */
+ acl_entry_t new_entry;
+
+ /* The acl_create_entry() function can allocate new memory and/or
+ * change the location of the ACL structure entirely. When that
+ * happens, the value pointed to by aclp is updated, which means
+ * that a new acl_t gets "passed out" to our caller, eventually to
+ * be fed to acl_free(). In other words, we should still be freeing
+ * the right thing, even if the value pointed to by aclp changes.
+ */
+ if (acl_create_entry(aclp, &new_entry) == ACL_ERROR) {
+ perror("acl_set_entry (acl_create_entry)");
+ return ACL_ERROR;
+ }
+
+ if (acl_set_tag_type(new_entry, entry_tag) == ACL_ERROR) {
+ perror("acl_set_entry (acl_set_tag_type)");
+ return ACL_ERROR;
+ }
+
+ if (acl_set_permset(new_entry, entry_permset) == ACL_ERROR) {
+ perror("acl_set_entry (acl_set_permset)");
+ return ACL_ERROR;
+ }
+
+ if (entry_tag == ACL_USER || entry_tag == ACL_GROUP) {
+ /* We need to set the qualifier too. */
+ void* entry_qual = acl_get_qualifier(entry);
+ if (entry_qual == (void*)NULL) {
+ perror("acl_set_entry (acl_get_qualifier)");
+ return ACL_ERROR;
+ }
+
+ if (acl_set_qualifier(new_entry, entry_qual) == ACL_ERROR) {
+ perror("acl_set_entry (acl_set_qualifier)");
+ return ACL_ERROR;
+ }
+ }
+
+ return ACL_SUCCESS;
+}
+
+
+
+/**
+ * @brief Determine the number of entries in the given ACL.
+ *
+ * @param acl
+ * The ACL to inspect.
+ *
+ * @return Either the non-negative number of entries in @c acl, or
+ * @c ACL_ERROR on error.
+ */
+int acl_entry_count(acl_t acl) {
+
+ acl_entry_t entry;
+ int entry_count = 0;
+ int result = acl_get_entry(acl, ACL_FIRST_ENTRY, &entry);
+
+ while (result == ACL_SUCCESS) {
+ entry_count++;
+ result = acl_get_entry(acl, ACL_NEXT_ENTRY, &entry);
+ }
+
+ if (result == ACL_ERROR) {
+ perror("acl_entry_count (acl_get_entry)");
+ return ACL_ERROR;
+ }
+
+ return entry_count;
+}
+
+
+
+/**
+ * @brief Determine whether or not the given ACL is minimal.
+ *
+ * An ACL is minimal if it has fewer than four entries.
+ *
+ * @param acl
+ * The ACL whose minimality is in question.
+ *
+ * @return
+ * - @c ACL_SUCCESS - @c acl is minimal
+ * - @c ACL_FAILURE - @c acl is not minimal
+ * - @c ACL_ERROR - Unexpected library error
+ */
+int acl_is_minimal(acl_t acl) {
+
+ int ec = acl_entry_count(acl);
+
+ if (ec == ACL_ERROR) {
+ perror("acl_is_minimal (acl_entry_count)");
+ return ACL_ERROR;
+ }
+
+ if (ec < 4) {
+ return ACL_SUCCESS;
+ }
+ else {
+ return ACL_FAILURE;
+ }
+}
+
+
+
+/**
+ * @brief Determine whether the given ACL's mask denies execute.
+ *
+ * @param acl
+ * The ACL whose mask we want to check.
+ *
+ * @return
+ * - @c ACL_SUCCESS - The @c acl has a mask which denies execute.
+ * - @c ACL_FAILURE - The @c acl has a mask which does not deny execute.
+ * - @c ACL_ERROR - Unexpected library error.
+ */
+int acl_execute_masked(acl_t acl) {
+
+ acl_entry_t entry;
+ int ge_result = acl_get_entry(acl, ACL_FIRST_ENTRY, &entry);
+
+ while (ge_result == ACL_SUCCESS) {
+ acl_tag_t tag = ACL_UNDEFINED_TAG;
+
+ if (acl_get_tag_type(entry, &tag) == ACL_ERROR) {
+ perror("acl_execute_masked (acl_get_tag_type)");
+ return ACL_ERROR;
+ }
+
+ if (tag == ACL_MASK) {
+ /* This is the mask entry, get its permissions, and see if
+ execute is specified. */
+ acl_permset_t permset;
+
+ if (acl_get_permset(entry, &permset) == ACL_ERROR) {
+ perror("acl_execute_masked (acl_get_permset)");
+ return ACL_ERROR;
+ }
+
+ int gp_result = acl_get_perm(permset, ACL_EXECUTE);
+ if (gp_result == ACL_ERROR) {
+ perror("acl_execute_masked (acl_get_perm)");
+ return ACL_ERROR;
+ }
+
+ if (gp_result == ACL_FAILURE) {
+ /* No execute bit set in the mask; execute not allowed. */
+ return ACL_SUCCESS;
+ }
+ }
+
+ ge_result = acl_get_entry(acl, ACL_NEXT_ENTRY, &entry);
+ }
+
+ return ACL_FAILURE;
+}
+
+
+
+/**
+ * @brief Determine whether @c fd is executable by anyone.
+ *
+ *
+ * This is used as part of the heuristic to determine whether or not
+ * we should mask the execute bit when inheriting an ACL. If @c fd
+ * describes a file, we check the @a effective permissions, contrary
+ * to what setfacl does.
+ *
+ * @param fd
+ * The file descriptor to check.
+ *
+ * @param sp
+ * A pointer to a stat structure for @c fd.
+ *
+ * @return
+ * - @c ACL_SUCCESS - Someone has effective execute permissions on @c fd.
+ * - @c ACL_FAILURE - Nobody can execute @c fd.
+ * - @c ACL_ERROR - Unexpected library error.
+ */
+int any_can_execute(int fd, const struct stat* sp) {
+ acl_t acl = acl_get_fd(fd);
+
+ if (acl == (acl_t)NULL) {
+ perror("any_can_execute (acl_get_file)");
+ return ACL_ERROR;
+ }
+
+ /* Our return value. */
+ int result = ACL_FAILURE;
+
+ if (acl_is_minimal(acl)) {
+ if (sp->st_mode & (S_IXUSR | S_IXOTH | S_IXGRP)) {
+ result = ACL_SUCCESS;
+ goto cleanup;
+ }
+ else {
+ result = ACL_FAILURE;
+ goto cleanup;
+ }
+ }
+
+ acl_entry_t entry;
+ int ge_result = acl_get_entry(acl, ACL_FIRST_ENTRY, &entry);
+
+ while (ge_result == ACL_SUCCESS) {
+ /* The first thing we do is check to see if this is a mask
+ entry. If it is, we skip it entirely. */
+ acl_tag_t tag = ACL_UNDEFINED_TAG;
+
+ if (acl_get_tag_type(entry, &tag) == ACL_ERROR) {
+ perror("any_can_execute_or (acl_get_tag_type)");
+ result = ACL_ERROR;
+ goto cleanup;
+ }
+
+ if (tag == ACL_MASK) {
+ ge_result = acl_get_entry(acl, ACL_NEXT_ENTRY, &entry);
+ continue;
+ }
+
+ /* Ok, so it's not a mask entry. Check the execute perms. */
+ acl_permset_t permset;
+
+ if (acl_get_permset(entry, &permset) == ACL_ERROR) {
+ perror("any_can_execute_or (acl_get_permset)");
+ result = ACL_ERROR;
+ goto cleanup;
+ }
+
+ int gp_result = acl_get_perm(permset, ACL_EXECUTE);
+ if (gp_result == ACL_ERROR) {
+ perror("any_can_execute (acl_get_perm)");
+ result = ACL_ERROR;
+ goto cleanup;
+ }
+
+ if (gp_result == ACL_SUCCESS) {
+ /* Only return ACL_SUCCESS if this execute bit is not masked. */
+ if (acl_execute_masked(acl) != ACL_SUCCESS) {
+ result = ACL_SUCCESS;
+ goto cleanup;
+ }
+ }
+
+ ge_result = acl_get_entry(acl, ACL_NEXT_ENTRY, &entry);
+ }
+
+ if (ge_result == ACL_ERROR) {
+ perror("any_can_execute (acl_get_entry)");
+ result = ACL_ERROR;
+ goto cleanup;
+ }
+
+ cleanup:
+ acl_free(acl);
+ return result;
+}
+
+
+
+/**
+ * @brief Set @c acl as the default ACL on @c path.
+ *
+ * This overwrites any existing default ACL on @c path. If @c path is
+ * not a directory, we return ACL_ERROR and @c errno is set.
+ *
+ * @param path
+ * The target directory whose ACL we wish to replace or create.
+ *
+ * @param acl
+ * The ACL to set as default on @c path.
+ *
+ * @return
+ * - @c ACL_SUCCESS - The default ACL was assigned successfully.
+ * - @c ACL_ERROR - Unexpected library error.
+ */
+int assign_default_acl(const char* path, acl_t acl) {
+
+ if (path == NULL) {
+ errno = EINVAL;
+ perror("assign_default_acl (args)");
+ return ACL_ERROR;
+ }
+
+ /* Our return value; success unless something bad happens. */
+ int result = ACL_SUCCESS;
+ acl_t path_acl = acl_dup(acl);
+
+ if (path_acl == (acl_t)NULL) {
+ perror("assign_default_acl (acl_dup)");
+ return ACL_ERROR; /* Nothing to clean up in this case. */
+ }
+
+ if (acl_set_file(path, ACL_TYPE_DEFAULT, path_acl) == ACL_ERROR) {
+ perror("assign_default_acl (acl_set_file)");
+ result = ACL_ERROR;
+ }
+
+ acl_free(path_acl);
+ return result;
+}
+
+
+
+/**
+ * @brief Remove all @c ACL_TYPE_ACCESS entries from the given file
+ * descriptor, leaving the UNIX permission bits.
+ *
+ * @param fd
+ * The file descriptor whose ACLs we want to wipe.
+ *
+ * @return
+ * - @c ACL_SUCCESS - The ACLs were wiped successfully, or none
+ * existed in the first place.
+ * - @c ACL_ERROR - Unexpected library error.
+ */
+int wipe_acls(int fd) {
+ /* Initialize an empty ACL, and then overwrite the one on "fd" with it. */
+ acl_t empty_acl = acl_init(0);
+
+ if (empty_acl == (acl_t)NULL) {
+ perror("wipe_acls (acl_init)");
+ return ACL_ERROR;
+ }
+
+ if (acl_set_fd(fd, empty_acl) == ACL_ERROR) {
+ perror("wipe_acls (acl_set_fd)");
+ acl_free(empty_acl);
+ return ACL_ERROR;
+ }
+
+ acl_free(empty_acl);
+ return ACL_SUCCESS;
+}
+
+
+
+/**
+ * @brief Apply parent default ACL to a path.
+ *
+ * This overwrites any existing ACLs on @c path.
+ *
+ * @param path
+ * The path whose ACL we would like to reset to its default.
+ *
+ * @param sp
+ * A pointer to a stat structure for @c path, or @c NULL if you don't
+ * have one handy.
+ *
+ * @param no_exec_mask
+ * The value (either true or false) of the --no-exec-mask flag.
+ *
+ * @return
+ * - @c ACL_SUCCESS - The parent default ACL was inherited successfully.
+ * - @c ACL_FAILURE - The target path is not a regular file/directory,
+ * or the parent of @c path is not a directory.
+ * - @c ACL_ERROR - Unexpected library error.
+ */
+int apply_default_acl(const char* path,
+ const struct stat* sp,
+ bool no_exec_mask) {
+
+ if (path == NULL) {
+ errno = EINVAL;
+ perror("apply_default_acl (args)");
+ return ACL_ERROR;
+ }
+
+ /* Define these next three variables here because we may have to
+ * jump to the cleanup routine which expects them to exist.
+ */
+
+ /* Our return value. */
+ int result = ACL_SUCCESS;
+
+ /* The default ACL on path's parent directory */
+ acl_t defacl = (acl_t)NULL;
+
+ /* The file descriptor corresponding to "path" */
+ int fd = 0;
+
+ /* Get the parent directory of "path" with dirname(), which happens
+ * to murder its argument and necessitates a path_copy.
+ */
+ char* path_copy = strdup(path);
+ if (path_copy == NULL) {
+ perror("apply_default_acl (strdup)");
+ return ACL_ERROR;
+ }
+ char* parent = dirname(path_copy);
+
+ fd = safe_open(path, O_NOFOLLOW);
+ if (fd == OPEN_ERROR) {
+ if (errno == ELOOP) {
+ result = ACL_FAILURE; /* hit a symlink */
+ goto cleanup;
+ }
+ else {
+ perror("apply_default_acl (open fd)");
+ result = ACL_ERROR;
+ goto cleanup;
+ }
+ }
+
+
+ /* Refuse to operate on hard links, which can be abused by an
+ * attacker to trick us into changing the ACL on a file we didn't
+ * intend to; namely the "target" of the hard link. There is TOCTOU
+ * race condition here, but the window is as small as possible
+ * between when we open the file descriptor (look above) and when we
+ * fstat it.
+ *
+ * Note: we only need to call fstat ourselves if we weren't passed a
+ * valid pointer to a stat structure (nftw does that).
+ */
+ if (sp == NULL) {
+ struct stat s;
+ if (fstat(fd, &s) == STAT_ERROR) {
+ perror("apply_default_acl (fstat)");
+ goto cleanup;
+ }
+
+ sp = &s;
+ }
+
+ if (!S_ISDIR(sp->st_mode)) {
+ /* If it's not a directory, make sure it's a regular,
+ non-hard-linked file. */
+ if (!S_ISREG(sp->st_mode) || sp->st_nlink != 1) {
+ result = ACL_FAILURE;
+ goto cleanup;
+ }
+ }
+
+
+ /* Default to not masking the exec bit; i.e. applying the default
+ ACL literally. If --no-exec-mask was not specified, then we try
+ to "guess" whether or not to mask the exec bit. This behavior
+ is modeled after the capital 'X' perms of setfacl. */
+ bool allow_exec = true;
+
+ if (!no_exec_mask) {
+ /* Never mask the execute bit on directories. */
+ int ace_result = any_can_execute(fd,sp) || S_ISDIR(sp->st_mode);
+
+ if (ace_result == ACL_ERROR) {
+ perror("apply_default_acl (any_can_execute)");
+ result = ACL_ERROR;
+ goto cleanup;
+ }
+
+ allow_exec = (bool)ace_result;
+ }
+
+ defacl = acl_get_file(parent, ACL_TYPE_DEFAULT);
+
+ if (defacl == (acl_t)NULL) {
+ perror("apply_default_acl (acl_get_file)");
+ result = ACL_ERROR;
+ goto cleanup;
+ }
+
+ if (wipe_acls(fd) == ACL_ERROR) {
+ perror("apply_default_acl (wipe_acls)");
+ result = ACL_ERROR;
+ goto cleanup;
+ }
+
+ /* Do this after wipe_acls(), otherwise we'll overwrite the wiped
+ ACL with this one. */
+ acl_t acl = acl_get_fd(fd);
+ if (acl == (acl_t)NULL) {
+ perror("apply_default_acl (acl_get_fd)");
+ result = ACL_ERROR;
+ goto cleanup;
+ }
+
+ /* If it's a directory, inherit the parent's default. We sure hope
+ * that "path" still points to the same thing that "fd" and this
+ * "sp" describe. If not, we may wind up trying to set a default ACL
+ * on a file, and this will throw an error. I guess that's what we
+ * want to do?
+ */
+ if (S_ISDIR(sp->st_mode) && assign_default_acl(path, defacl) == ACL_ERROR) {
+ perror("apply_default_acl (assign_default_acl)");
+ result = ACL_ERROR;
+ goto cleanup;
+ }
+
+ acl_entry_t entry;
+ int ge_result = acl_get_entry(defacl, ACL_FIRST_ENTRY, &entry);
+
+ while (ge_result == ACL_SUCCESS) {
+ acl_tag_t tag = ACL_UNDEFINED_TAG;
+
+ if (acl_get_tag_type(entry, &tag) == ACL_ERROR) {
+ perror("apply_default_acl (acl_get_tag_type)");
+ result = ACL_ERROR;
+ goto cleanup;
+ }
+
+
+ /* We've got an entry/tag from the default ACL. Get its permset. */
+ acl_permset_t permset;
+ if (acl_get_permset(entry, &permset) == ACL_ERROR) {
+ perror("apply_default_acl (acl_get_permset)");
+ result = ACL_ERROR;
+ goto cleanup;
+ }
+
+ /* If this is a default mask, fix it up. */
+ if (tag == ACL_MASK ||
+ tag == ACL_USER_OBJ ||
+ tag == ACL_GROUP_OBJ ||
+ tag == ACL_OTHER) {
+
+ if (!allow_exec) {
+ /* The mask doesn't affect acl_user_obj, acl_group_obj (in
+ minimal ACLs) or acl_other entries, so if execute should be
+ masked, we have to do it manually. */
+ if (acl_delete_perm(permset, ACL_EXECUTE) == ACL_ERROR) {
+ perror("apply_default_acl (acl_delete_perm)");
+ result = ACL_ERROR;
+ goto cleanup;
+ }
+
+ if (acl_set_permset(entry, permset) == ACL_ERROR) {
+ perror("apply_default_acl (acl_set_permset)");
+ result = ACL_ERROR;
+ goto cleanup;
+ }
+ }
+ }
+
+ /* Finally, add the permset to the access ACL. It's actually
+ * important that we pass in the address of "acl" here, and not
+ * "acl" itself. Why? The call to acl_create_entry() within
+ * acl_set_entry() can allocate new memory for the entry.
+ * Sometimes that can be done in-place, in which case everything
+ * is cool and the new memory gets released when we call
+ * acl_free(acl).
+ *
+ * But occasionally, the whole ACL structure will have to be moved
+ * in order to allocate the extra space. When that happens,
+ * acl_create_entry() modifies the pointer it was passed (in this
+ * case, &acl) to point to the new location. We want to call
+ * acl_free() on the new location, and since acl_free() gets
+ * called right here, we need acl_create_entry() to update the
+ * value of "acl". To do that, it needs the address of "acl".
+ */
+ if (acl_set_entry(&acl, entry) == ACL_ERROR) {
+ perror("apply_default_acl (acl_set_entry)");
+ result = ACL_ERROR;
+ goto cleanup;
+ }
+
+ ge_result = acl_get_entry(defacl, ACL_NEXT_ENTRY, &entry);
+ }
+
+ /* Catches the first acl_get_entry as well as the ones at the end of
+ the loop. */
+ if (ge_result == ACL_ERROR) {
+ perror("apply_default_acl (acl_get_entry)");
+ result = ACL_ERROR;
+ goto cleanup;
+ }
+
+ if (acl_set_fd(fd, acl) == ACL_ERROR) {
+ perror("apply_default_acl (acl_set_fd)");
+ result = ACL_ERROR;
+ goto cleanup;
+ }
+
+ cleanup:
+ free(path_copy);
+ if (defacl != (acl_t)NULL) {
+ acl_free(defacl);
+ }
+ if (fd >= 0 && close(fd) == CLOSE_ERROR) {
+ perror("apply_default_acl (close)");
+ result = ACL_ERROR;
+ }
+ return result;
+}
--- /dev/null
+/**
+ * @file libadacl.h
+ *
+ * @brief The public API for libadacl.
+ *
+ */
+
+/* Most of the libacl functions return 1 for success, 0 for failure,
+ and -1 on error */
+#define ACL_ERROR -1
+#define ACL_FAILURE 0
+#define ACL_SUCCESS 1
+
+/* Even though most other library functions reliably return -1 for
+ * error, it feels a little wrong to re-use the ACL_ERROR constant.
+ */
+#define CLOSE_ERROR -1
+#define NFTW_ERROR -1
+#define OPEN_ERROR -1
+#define SNPRINTF_ERROR -1
+#define STAT_ERROR -1
+
+int apply_default_acl(const char* path,
+ const struct stat* sp,
+ bool no_exec_mask);
projects / apply-default-acl.git / commitdiff