+/**
+ * @file apply-default-acl.c
+ *
+ * @brief The entire implementation.
+ *
+ */
+
/* On Linux, ftw.h needs this special voodoo to work. */
#define _XOPEN_SOURCE 500
+#define _GNU_SOURCE
#include <errno.h>
+#include <fcntl.h> /* AT_FOO constants */
#include <ftw.h> /* nftw() et al. */
#include <getopt.h>
-#include <libgen.h> /* dirname() */
-#include <limits.h> /* PATH_MAX */
+#include <libgen.h> /* basename(), dirname() */
+#include <limits.h> /* PATH_MAX */
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#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
-mode_t get_mode(const char* path) {
- /*
- * Get the mode bits from path.
- */
- if (path == NULL) {
- errno = ENOENT;
- return -1;
- }
-
- struct stat s;
- int result = stat(path, &s);
- if (result == 0) {
- return s.st_mode;
+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;
}
- else {
- /* errno will be set already by stat() */
- return result;
+
+ 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 == -1) {
+ if (errno != ELOOP) {
+ /* Don't output anything if we ignore a symlink */
+ perror("safe_open_ex (safe_open_ex)");
+ }
+ return -1;
+ }
+
+ /* 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) == -1) {
+ perror("safe_open_ex (close)");
+ return -1;
+ }
+ return result;
}
-bool is_regular_file(const char* path) {
- /*
- * Returns true if path is a regular file, false otherwise.
- */
- if (path == NULL) {
- return false;
+int safe_open(const char* pathname, int flags) {
+ if (pathname == NULL || strlen(pathname) == 0 || pathname[0] == '\0') {
+ /* error? */
+ return -1;
}
- struct stat s;
- int result = stat(path, &s);
- if (result == 0) {
- return S_ISREG(s.st_mode);
+ 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 {
- return false;
+ /* 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 -1;
+ }
+
+ char abs_cwd[PATH_MAX];
+ if (realpath(cwd, abs_cwd) == NULL) {
+ perror("safe_open (realpath)");
+ free(cwd);
+ return -1;
+ }
+ snprintf_result = snprintf(abspath, PATH_MAX, "%s/%s", abs_cwd, pathname);
+ free(cwd);
+ }
+ if (snprintf_result == -1 || snprintf_result > PATH_MAX) {
+ perror("safe_open (snprintf)");
+ return -1;
}
+
+ int fd = open("/", flags);
+ if (strcmp(abspath, "/") == 0) {
+ return fd;
+ }
+
+ int result = safe_open_ex(fd, abspath+1, flags);
+ if (close(fd) == -1) {
+ perror("safe_open (close)");
+ return -1;
+ }
+ return result;
}
-bool is_directory(const char* path) {
- /*
- * Returns true if path is a directory, false otherwise.
- */
+
+
+/**
+ * @brief Determine whether or not the given path is accessible.
+ *
+ * @param path
+ * The path to test.
+ *
+ * @return true if @c path is accessible to the current effective
+ * user/group, false otherwise.
+ */
+bool path_accessible(const char* path) {
if (path == NULL) {
return false;
}
- struct stat s;
- int result = stat(path, &s);
- if (result == 0) {
- return S_ISDIR(s.st_mode);
+ /* Test for access using the effective user and group rather than
+ the real one. */
+ int flags = AT_EACCESS;
+
+ /* Don't follow symlinks when checking for a path's existence,
+ since we won't follow them to set its ACLs either. */
+ flags |= AT_SYMLINK_NOFOLLOW;
+
+ /* If the path is relative, interpret it relative to the current
+ working directory (just like the access() system call). */
+ if (faccessat(AT_FDCWD, path, F_OK, flags) == 0) {
+ return true;
}
else {
return false;
-int acl_set_entry(acl_t* aclp,
- acl_entry_t entry) {
- /*
- * Update or create the given entry.
- */
+/**
+ * @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;
- int gt_result = acl_get_tag_type(entry, &entry_tag);
- if (gt_result == -1) {
+ if (acl_get_tag_type(entry, &entry_tag) == ACL_ERROR) {
perror("acl_set_entry (acl_get_tag_type)");
- return -1;
+ return ACL_ERROR;
}
acl_permset_t entry_permset;
- int ps_result = acl_get_permset(entry, &entry_permset);
- if (ps_result == -1) {
+ if (acl_get_permset(entry, &entry_permset) == ACL_ERROR) {
perror("acl_set_entry (acl_get_permset)");
- return -1;
+ 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 == 1) {
+ while (result == ACL_SUCCESS) {
acl_tag_t existing_tag = ACL_UNDEFINED_TAG;
- int tag_result = acl_get_tag_type(existing_entry, &existing_tag);
- if (tag_result == -1) {
+ if (acl_get_tag_type(existing_entry, &existing_tag) == ACL_ERROR) {
perror("set_acl_tag_permset (acl_get_tag_type)");
- return -1;
+ return ACL_ERROR;
}
if (existing_tag == entry_tag) {
entry_tag == ACL_GROUP_OBJ ||
entry_tag == ACL_OTHER) {
/* Only update for these three since all other tags will have
- been wiped. */
+ 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;
- int gep_result = acl_get_permset(existing_entry, &existing_permset);
- if (gep_result == -1) {
+ if (acl_get_permset(existing_entry, &existing_permset) == ACL_ERROR) {
perror("acl_set_entry (acl_get_permset)");
- return -1;
+ return ACL_ERROR;
}
- int s_result = acl_set_permset(existing_entry, entry_permset);
- if (s_result == -1) {
+ if (acl_set_permset(existing_entry, entry_permset) == ACL_ERROR) {
perror("acl_set_entry (acl_set_permset)");
- return -1;
+ return ACL_ERROR;
}
- return 1;
+ return ACL_SUCCESS;
}
}
/* This catches both the initial acl_get_entry and the ones at the
end of the loop. */
- if (result == -1) {
+ if (result == ACL_ERROR) {
perror("acl_set_entry (acl_get_entry)");
- return -1;
+ 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;
- /* We allocate memory here that we should release! */
- int c_result = acl_create_entry(aclp, &new_entry);
- if (c_result == -1) {
+ /* 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 -1;
+ return ACL_ERROR;
}
- int st_result = acl_set_tag_type(new_entry, entry_tag);
- if (st_result == -1) {
+ if (acl_set_tag_type(new_entry, entry_tag) == ACL_ERROR) {
perror("acl_set_entry (acl_set_tag_type)");
- return -1;
+ return ACL_ERROR;
}
- int s_result = acl_set_permset(new_entry, entry_permset);
- if (s_result == -1) {
+ if (acl_set_permset(new_entry, entry_permset) == ACL_ERROR) {
perror("acl_set_entry (acl_set_permset)");
- return -1;
+ return ACL_ERROR;
}
if (entry_tag == ACL_USER || entry_tag == ACL_GROUP) {
void* entry_qual = acl_get_qualifier(entry);
if (entry_qual == (void*)NULL) {
perror("acl_set_entry (acl_get_qualifier)");
- return -1;
+ return ACL_ERROR;
}
- int sq_result = acl_set_qualifier(new_entry, entry_qual);
- if (sq_result == -1) {
+ if (acl_set_qualifier(new_entry, entry_qual) == ACL_ERROR) {
perror("acl_set_entry (acl_set_qualifier)");
- return -1;
+ return ACL_ERROR;
}
}
- return 1;
+ return ACL_SUCCESS;
}
-int acl_entry_count(acl_t* acl) {
- /*
- * Return the number of entries in acl, or -1 on error.
- */
+/**
+ * @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);
+ int result = acl_get_entry(acl, ACL_FIRST_ENTRY, &entry);
- while (result == 1) {
+ while (result == ACL_SUCCESS) {
entry_count++;
- result = acl_get_entry(*acl, ACL_NEXT_ENTRY, &entry);
+ result = acl_get_entry(acl, ACL_NEXT_ENTRY, &entry);
}
- if (result == -1) {
- perror("acl_is_minimal (acl_get_entry)");
- return -1;
+ if (result == ACL_ERROR) {
+ perror("acl_entry_count (acl_get_entry)");
+ return ACL_ERROR;
}
return entry_count;
}
-int acl_is_minimal(acl_t* acl) {
- /* An ACL is minimal if it has fewer than four entries. Return 0 for
- * false, 1 for true, and -1 on error.
- */
+
+/**
+ * @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 == -1) {
+
+ if (ec == ACL_ERROR) {
perror("acl_is_minimal (acl_entry_count)");
- return -1;
+ return ACL_ERROR;
}
if (ec < 4) {
- return 1;
+ return ACL_SUCCESS;
}
else {
- return 0;
+ return ACL_FAILURE;
}
}
-int any_can_execute(const char* path) {
- /* Returns 1 if any ACL entry has execute access, 0 if none do, and
- * -1 on error.
- */
- acl_t acl = acl_get_file(path, ACL_TYPE_ACCESS);
+
+/**
+ * @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) {
- return 0;
+ perror("any_can_execute (acl_get_file)");
+ return ACL_ERROR;
}
/* Our return value. */
- int result = 0;
+ int result = ACL_FAILURE;
- if (acl_is_minimal(&acl)) {
- mode_t mode = get_mode(path);
- if (mode & (S_IXUSR | S_IXOTH | S_IXGRP)) {
- result = 1;
+ if (acl_is_minimal(acl)) {
+ if (sp->st_mode & (S_IXUSR | S_IXOTH | S_IXGRP)) {
+ result = ACL_SUCCESS;
goto cleanup;
}
else {
- result = 0;
+ result = ACL_FAILURE;
goto cleanup;
}
}
acl_entry_t entry;
int ge_result = acl_get_entry(acl, ACL_FIRST_ENTRY, &entry);
- while (ge_result == 1) {
+ 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;
- int ps_result = acl_get_permset(entry, &permset);
- if (ps_result == -1) {
- perror("any_can_execute (acl_get_permset)");
- result = -1;
+ 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 == -1) {
+ if (gp_result == ACL_ERROR) {
perror("any_can_execute (acl_get_perm)");
- result = -1;
+ result = ACL_ERROR;
goto cleanup;
}
- if (gp_result == 1) {
- result = 1;
- 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 == -1) {
+ if (ge_result == ACL_ERROR) {
perror("any_can_execute (acl_get_entry)");
- result = -1;
+ result = ACL_ERROR;
goto cleanup;
}
}
-int inherit_default_acl(const char* path, const char* parent) {
- /* Inherit the default ACL from parent to path. This overwrites any
- * existing default ACL. Returns 1 for success, 0 for failure, and
- * -1 on error.
- */
- /* Our return value. */
- int result = 1;
+/**
+ * @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 = ENOENT;
- return -1;
- }
-
- if (!is_directory(path) || !is_directory(parent)) {
- return 0;
- }
-
- acl_t parent_acl = acl_get_file(parent, ACL_TYPE_DEFAULT);
- if (parent_acl == (acl_t)NULL) {
- return 0;
+ errno = EINVAL;
+ perror("assign_default_acl (args)");
+ return ACL_ERROR;
}
- acl_t path_acl = acl_dup(parent_acl);
+ /* 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("inherit_default_acl (acl_dup)");
- acl_free(parent_acl);
- return -1;
+ perror("assign_default_acl (acl_dup)");
+ return ACL_ERROR; /* Nothing to clean up in this case. */
}
- int sf_result = acl_set_file(path, ACL_TYPE_DEFAULT, path_acl);
- if (sf_result == -1) {
- perror("inherit_default_acl (acl_set_file)");
- result = -1;
- goto cleanup;
+ if (acl_set_file(path, ACL_TYPE_DEFAULT, path_acl) == ACL_ERROR) {
+ perror("assign_default_acl (acl_set_file)");
+ result = ACL_ERROR;
}
- cleanup:
acl_free(path_acl);
return result;
}
-int wipe_acls(const char* path) {
- /* Remove ACL_USER, ACL_GROUP, and ACL_MASK entries from
- path. Returns 1 for success, 0 for failure, and -1 on error. */
- if (path == NULL) {
- errno = ENOENT;
- return -1;
+/**
+ * @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;
}
- /* Finally, remove individual named/mask entries. */
- acl_t acl = acl_get_file(path, ACL_TYPE_ACCESS);
- if (acl == (acl_t)NULL) {
- perror("wipe_acls (acl_get_file)");
- return -1;
+ if (acl_set_fd(fd, empty_acl) == ACL_ERROR) {
+ perror("wipe_acls (acl_set_fd)");
+ acl_free(empty_acl);
+ return ACL_ERROR;
}
- /* Our return value. */
- int result = 1;
+ acl_free(empty_acl);
+ return ACL_SUCCESS;
+}
- acl_entry_t entry;
- int ge_result = acl_get_entry(acl, ACL_FIRST_ENTRY, &entry);
- while (ge_result == 1) {
- int d_result = acl_delete_entry(acl, entry);
- if (d_result == -1) {
- perror("wipe_acls (acl_delete_entry)");
- result = -1;
- goto cleanup;
- }
- ge_result = acl_get_entry(acl, ACL_NEXT_ENTRY, &entry);
- }
+/**
+ * @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) {
- /* Catches the first acl_get_entry as well as the ones at the end of
- the loop. */
- if (ge_result == -1) {
- perror("wipe_acls (acl_get_entry)");
- result = -1;
- goto cleanup;
+ if (path == NULL) {
+ errno = EINVAL;
+ perror("apply_default_acl (args)");
+ return ACL_ERROR;
}
- int sf_result = acl_set_file(path, ACL_TYPE_ACCESS, acl);
- if (sf_result == -1) {
- perror("wipe_acls (acl_set_file)");
- result = -1;
- goto cleanup;
- }
+ /* Define these next three variables here because we may have to
+ * jump to the cleanup routine which expects them to exist.
+ */
- cleanup:
- acl_free(acl);
- return result;
-}
+ /* 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;
-int apply_default_acl(const char* path) {
- /* Really apply the default ACL by looping through it. Returns one
- * for success, zero for failure (i.e. no ACL), and -1 on unexpected
- * errors.
+ /* Get the parent directory of "path" with dirname(), which happens
+ * to murder its argument and necessitates a path_copy.
*/
- if (path == NULL) {
- return 0;
+ char* path_copy = strdup(path);
+ if (path_copy == NULL) {
+ perror("apply_default_acl (strdup)");
+ return ACL_ERROR;
}
+ char* parent = dirname(path_copy);
- if (!is_regular_file(path) && !is_directory(path)) {
- return 0;
+ fd = safe_open(path, O_NOFOLLOW);
+ if (fd == -1) {
+ if (errno == ELOOP) {
+ result = ACL_FAILURE; /* hit a symlink */
+ goto cleanup;
+ }
+ else {
+ perror("apply_default_acl (open fd)");
+ result = ACL_ERROR;
+ goto cleanup;
+ }
}
- /* dirname mangles its argument */
- char path_copy[PATH_MAX];
- strncpy(path_copy, path, PATH_MAX-1);
- path_copy[PATH_MAX-1] = 0;
- char* parent = dirname(path_copy);
- if (!is_directory(parent)) {
- /* Make sure dirname() did what we think it did. */
- return 0;
+ /* 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) == -1) {
+ perror("apply_default_acl (fstat)");
+ goto cleanup;
+ }
+
+ sp = &s;
}
- int ace_result = any_can_execute(path);
- if (ace_result == -1) {
- perror("apply_default_acl (any_can_execute)");
- return -1;
+ 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;
+ }
}
- bool allow_exec = (bool)ace_result;
- acl_t defacl = acl_get_file(parent, ACL_TYPE_DEFAULT);
+ /* 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)");
- return -1;
+ result = ACL_ERROR;
+ goto cleanup;
}
- /* Our return value. */
- int result = 1;
-
- int wipe_result = wipe_acls(path);
- if (wipe_result == -1) {
+ if (wipe_acls(fd) == ACL_ERROR) {
perror("apply_default_acl (wipe_acls)");
- result = -1;
+ 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_file(path, ACL_TYPE_ACCESS);
+ acl_t acl = acl_get_fd(fd);
if (acl == (acl_t)NULL) {
- perror("apply_default_acl (acl_get_file)");
- return -1;
+ perror("apply_default_acl (acl_get_fd)");
+ result = ACL_ERROR;
+ goto cleanup;
}
- /* If it's a directory, inherit the parent's default. */
- int inherit_result = inherit_default_acl(path, parent);
- if (inherit_result == -1) {
- perror("apply_default_acl (inherit_acls)");
- result = -1;
+ /* 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 == 1) {
+ while (ge_result == ACL_SUCCESS) {
acl_tag_t tag = ACL_UNDEFINED_TAG;
- int tag_result = acl_get_tag_type(entry, &tag);
- if (tag_result == -1) {
- perror("has_default_tag_acl (acl_get_tag_type)");
- result = -1;
+ 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;
- int ps_result = acl_get_permset(entry, &permset);
- if (ps_result == -1) {
+ if (acl_get_permset(entry, &permset) == ACL_ERROR) {
perror("apply_default_acl (acl_get_permset)");
- result = -1;
+ result = ACL_ERROR;
goto cleanup;
}
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. */
- int d_result = acl_delete_perm(permset, ACL_EXECUTE);
- if (d_result == -1) {
+ if (acl_delete_perm(permset, ACL_EXECUTE) == ACL_ERROR) {
perror("apply_default_acl (acl_delete_perm)");
- result = -1;
+ result = ACL_ERROR;
goto cleanup;
}
- int sp_result = acl_set_permset(entry, permset);
- if (sp_result == -1) {
+ if (acl_set_permset(entry, permset) == ACL_ERROR) {
perror("apply_default_acl (acl_set_permset)");
- result = -1;
+ result = ACL_ERROR;
goto cleanup;
}
}
}
- /* Finally, add the permset to the access ACL. */
- int set_result = acl_set_entry(&acl, entry);
- if (set_result == -1) {
+ /* 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 = -1;
+ result = ACL_ERROR;
goto cleanup;
}
/* Catches the first acl_get_entry as well as the ones at the end of
the loop. */
- if (ge_result == -1) {
+ if (ge_result == ACL_ERROR) {
perror("apply_default_acl (acl_get_entry)");
- result = -1;
+ result = ACL_ERROR;
goto cleanup;
}
- int sf_result = acl_set_file(path, ACL_TYPE_ACCESS, acl);
- if (sf_result == -1) {
- perror("apply_default_acl (acl_set_file)");
- result = -1;
+ if (acl_set_fd(fd, acl) == ACL_ERROR) {
+ perror("apply_default_acl (acl_set_fd)");
+ result = ACL_ERROR;
goto cleanup;
}
cleanup:
- acl_free(defacl);
+ free(path_copy);
+ if (defacl != (acl_t)NULL) {
+ acl_free(defacl);
+ }
+ if (fd >= 0 && close(fd) == -1) {
+ perror("apply_default_acl (close)");
+ result = ACL_ERROR;
+ }
return result;
}
-void usage(char* program_name) {
- /*
- * Print usage information.
- */
+
+/**
+ * @brief Display program usage information.
+ *
+ * @param program_name
+ * The program name to use in the output.
+ *
+ */
+void usage(const char* program_name) {
printf("Apply any applicable default ACLs to the given files or "
"directories.\n\n");
printf("Usage: %s [flags] <target1> [<target2> [ <target3>...]]\n\n",
printf("Flags:\n");
printf(" -h, --help Print this help message\n");
printf(" -r, --recursive Act on any given directories recursively\n");
+ printf(" -x, --no-exec-mask Apply execute permissions unconditionally\n");
+
+ return;
}
+/**
+ * @brief Wrapper around @c apply_default_acl() for use with @c nftw().
+ *
+ * For parameter information, see the @c nftw man page.
+ *
+ * @return If the ACL was applied to @c target successfully, we return
+ * @c FTW_CONTINUE to signal to @ nftw() that we should proceed onto
+ * the next file or directory. Otherwise, we return @c FTW_STOP to
+ * signal failure.
+ *
+ */
int apply_default_acl_nftw(const char *target,
- const struct stat *s,
+ const struct stat *sp,
+ int info,
+ struct FTW *ftw) {
+
+ if (apply_default_acl(target, sp, false)) {
+ return FTW_CONTINUE;
+ }
+ else {
+ return FTW_STOP;
+ }
+}
+
+
+
+/**
+ * @brief Wrapper around @c apply_default_acl() for use with @c nftw().
+ *
+ * This is identical to @c apply_default_acl_nftw(), except it passes
+ * @c true to @c apply_default_acl() as its no_exec_mask argument.
+ *
+ */
+int apply_default_acl_nftw_x(const char *target,
+ const struct stat *sp,
int info,
struct FTW *ftw) {
- /* A wrapper around the apply_default_acl() function for use with
- * nftw(). We need to adjust the return value so that nftw() doesn't
- * think we've failed.
- */
- bool reapp_result = apply_default_acl(target);
- if (reapp_result) {
- return 0;
+
+ if (apply_default_acl(target, sp, true)) {
+ return FTW_CONTINUE;
}
else {
- return 1;
+ return FTW_STOP;
}
}
-bool apply_default_acl_recursive(const char *target) {
- /* Attempt to apply default ACLs recursively. If target is a
- * directory, we recurse through its entries. If not, we just
- * apply the default ACL to target.
- *
- * We ignore symlinks for consistency with chmod -r.
- *
- */
- if (!is_directory(target)) {
- return apply_default_acl(target);
- }
+/**
+ * @brief Recursive version of @c apply_default_acl().
+ *
+ * If @c target is a directory, we use @c nftw() to call @c
+ * apply_default_acl() recursively on all of its children. Otherwise,
+ * we just delegate to @c apply_default_acl().
+ *
+ * We ignore symlinks for consistency with chmod -r.
+ *
+ * @param target
+ * The root (path) of the recursive application.
+ *
+ * @param no_exec_mask
+ * The value (either true or false) of the --no-exec-mask flag.
+ *
+ * @return
+ * If @c target is not a directory, we return the result of
+ * calling @c apply_default_acl() on @c target. Otherwise, we convert
+ * the return value of @c nftw(). If @c nftw() succeeds (returns 0),
+ * then we return @c true. Otherwise, we return @c false.
+ * \n\n
+ * If there is an error, it will be reported via @c perror, but
+ * we still return @c false.
+ */
+bool apply_default_acl_recursive(const char *target, bool no_exec_mask) {
int max_levels = 256;
int flags = FTW_PHYS; /* Don't follow links. */
- int nftw_result = nftw(target,
- apply_default_acl_nftw,
- max_levels,
- flags);
+ /* There are two separate functions that could be passed to
+ nftw(). One passes no_exec_mask = true to apply_default_acl(),
+ and the other passes no_exec_mask = false. Since the function we
+ pass to nftw() cannot have parameters, we have to create separate
+ options and make the decision here. */
+ int (*fn)(const char *, const struct stat *, int, struct FTW *) = NULL;
+ fn = no_exec_mask ? apply_default_acl_nftw_x : apply_default_acl_nftw;
+
+ int nftw_result = nftw(target, fn, max_levels, flags);
if (nftw_result == 0) {
/* Success */
}
+
+/**
+ * @brief Call apply_default_acl (possibly recursively) on each
+ * command-line argument.
+ *
+ * @return Either @c EXIT_FAILURE or @c EXIT_SUCCESS. If everything
+ * goes as expected, we return @c EXIT_SUCCESS. Otherwise, we return
+ * @c EXIT_FAILURE.
+ */
int main(int argc, char* argv[]) {
- /*
- * Call apply_default_acl on each command-line argument.
- */
+
if (argc < 2) {
usage(argv[0]);
return EXIT_FAILURE;
}
-
bool recursive = false;
+ bool no_exec_mask = false;
struct option long_options[] = {
/* These options set a flag. */
{"help", no_argument, NULL, 'h'},
{"recursive", no_argument, NULL, 'r'},
+ {"no-exec-mask", no_argument, NULL, 'x'},
{NULL, 0, NULL, 0}
};
int opt = 0;
- while ((opt = getopt_long(argc, argv, "hr", long_options, NULL)) != -1) {
+ while ((opt = getopt_long(argc, argv, "hrx", long_options, NULL)) != -1) {
switch (opt) {
case 'h':
usage(argv[0]);
case 'r':
recursive = true;
break;
+ case 'x':
+ no_exec_mask = true;
+ break;
default:
usage(argv[0]);
return EXIT_FAILURE;
const char* target = argv[arg_index];
bool reapp_result = false;
+ /* Make sure we can access the given path before we go out of our
+ * way to please it. Doing this check outside of
+ * apply_default_acl() lets us spit out a better error message for
+ * typos, too.
+ */
+ if (!path_accessible(target)) {
+ fprintf(stderr, "%s: %s: No such file or directory\n", argv[0], target);
+ result = EXIT_FAILURE;
+ continue;
+ }
+
if (recursive) {
- reapp_result = apply_default_acl_recursive(target);
+ reapp_result = apply_default_acl_recursive(target, no_exec_mask);
}
else {
- /* It's either normal file, or we're not operating recursively. */
- reapp_result = apply_default_acl(target);
+ /* It's either a normal file, or we're not operating recursively. */
+ reapp_result = apply_default_acl(target, NULL, no_exec_mask);
}
if (!reapp_result) {
projects / apply-default-acl.git / blobdiff