From 7ce092ba47607098bb57695396357b8eab90e81b Mon Sep 17 00:00:00 2001 From: Michael Orlitzky Date: Mon, 26 Feb 2018 09:40:18 -0500 Subject: [PATCH] Split most functions off into a separate shared library. --- autogen.sh | 4 +- configure.ac | 5 +- run-tests.sh | 15 +- src/Makefile.am | 7 +- src/apply-default-acl.c | 831 +-------------------------------------- src/libadacl.c | 832 ++++++++++++++++++++++++++++++++++++++++ src/libadacl.h | 25 ++ 7 files changed, 879 insertions(+), 840 deletions(-) create mode 100644 src/libadacl.c create mode 100644 src/libadacl.h diff --git a/autogen.sh b/autogen.sh index cabc6bd..e7ae7a0 100755 --- a/autogen.sh +++ b/autogen.sh @@ -1,4 +1,2 @@ # Regenerate the junk that autotools wants to have around. -aclocal -automake --foreign --add-missing -Wall -Werror -autoconf +autoreconf --force --install diff --git a/configure.ac b/configure.ac index c279015..b3afe4a 100644 --- a/configure.ac +++ b/configure.ac @@ -3,12 +3,13 @@ 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 @@ -20,4 +21,6 @@ AC_TYPE_MODE_T 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 diff --git a/run-tests.sh b/run-tests.sh index d75e91e..e4ca376 100755 --- a/run-tests.sh +++ b/run-tests.sh @@ -671,14 +671,16 @@ compare # 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="${ACTUAL#*: }" +EXPECTED="test/nonexistent: No such file or directory" compare # If we call apply-default-acl on more than one file, it should report any @@ -687,8 +689,9 @@ TESTNUM=27 DUMMY1="${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 diff --git a/src/Makefile.am b/src/Makefile.am index f2d86ec..dd95ec1 100644 --- a/src/Makefile.am +++ b/src/Makefile.am @@ -1,2 +1,7 @@ +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 diff --git a/src/apply-default-acl.c b/src/apply-default-acl.c index 3cf3060..c075059 100644 --- a/src/apply-default-acl.c +++ b/src/apply-default-acl.c @@ -1,7 +1,7 @@ /** * @file apply-default-acl.c * - * @brief The entire implementation. + * @brief The command-line interface. * */ @@ -13,165 +13,12 @@ #include /* AT_FOO constants */ #include /* nftw() et al. */ #include -#include /* basename(), dirname() */ -#include /* PATH_MAX */ #include #include #include -#include -#include #include -/* ACLs */ -#include /* acl_get_perm, not portable */ -#include -#include - -/* 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" @@ -208,680 +55,6 @@ bool path_accessible(const char* path) { } - -/** - * @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. * diff --git a/src/libadacl.c b/src/libadacl.c new file mode 100644 index 0000000..28d5782 --- /dev/null +++ b/src/libadacl.c @@ -0,0 +1,832 @@ +/** + * @file libadacl.c + * + * @brief The adacl (apply default acl) shared library. + * + */ + +/* Enables get_current_dir_name() in unistd.h */ +#define _GNU_SOURCE + +#include +#include +#include /* basename(), dirname() */ +#include /* PATH_MAX */ +#include +#include +#include +#include +#include +#include /* get_current_dir_name() */ + +/* ACLs */ +#include /* acl_get_perm, not portable */ +#include +#include + +#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; +} diff --git a/src/libadacl.h b/src/libadacl.h new file mode 100644 index 0000000..d2c9785 --- /dev/null +++ b/src/libadacl.h @@ -0,0 +1,25 @@ +/** + * @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); -- 2.43.2