X-Git-Url: http://gitweb.michael.orlitzky.com/?p=apply-default-acl.git;a=blobdiff_plain;f=src%2Flibadacl.c;h=a21aa709ba842bc7bd21aa672b99b4e3cb750cf0;hp=38e362e5066fdeb4f086ba19774fd65faae78c99;hb=HEAD;hpb=8373437e3e99e776f99ae592f2a0f2560317cc0a diff --git a/src/libadacl.c b/src/libadacl.c index 38e362e..a21aa70 100644 --- a/src/libadacl.c +++ b/src/libadacl.c @@ -5,7 +5,9 @@ * */ -/* Enables get_current_dir_name() in unistd.h and the O_PATH flag. */ +/* Enables get_current_dir_name() in unistd.h, the O_PATH flag, and + * the asprintf() function. +*/ #define _GNU_SOURCE #include /* readdir(), etc. */ @@ -14,7 +16,7 @@ #include /* basename(), dirname() */ #include /* PATH_MAX */ #include /* the "bool" type */ -#include /* perror(), snprintf() */ +#include /* perror(), asprintf() */ #include /* free() */ #include /* strdup() */ #include /* fstat() */ @@ -36,11 +38,29 @@ */ #define CLOSE_ERROR -1 #define OPEN_ERROR -1 -#define SNPRINTF_ERROR -1 +#define ASPRINTF_ERROR -1 #define STAT_ERROR -1 #define XATTR_ERROR -1 +/* Prototypes */ +int safe_open_ex(int at_fd, char* pathname, int flags); +int safe_open(const char* pathname, int flags); +int acl_update_entry(acl_t aclp, acl_entry_t updated_entry); +int acl_entry_count(acl_t acl); +int acl_is_minimal(acl_t acl); +int acl_execute_masked(acl_t acl); +int any_can_execute(int fd, const struct stat* sp); +int acl_copy_xattr(int src_fd, + acl_type_t src_type, + int dst_fd, + acl_type_t dst_type); +int has_default_acl_fd(int fd); +int apply_default_acl_fds(int parent_fd, int fd, bool recursive); +int apply_default_acl(const char* path, bool recursive); + + + /** * @brief The recursive portion of the @c safe_open function, used to * open a file descriptor in a symlink-safe way when combined with @@ -134,11 +154,11 @@ int safe_open(const char* pathname, int flags) { return OPEN_ERROR; } - char abspath[PATH_MAX]; - int snprintf_result = 0; + char* abspath = NULL; + int asprintf_result = 0; if (strchr(pathname, '/') == pathname) { /* pathname is already absolute; just copy it. */ - snprintf_result = snprintf(abspath, PATH_MAX, "%s", pathname); + asprintf_result = asprintf(&abspath, "%s", pathname); } else { /* Concatenate the current working directory and pathname into an @@ -163,14 +183,17 @@ int safe_open(const char* pathname, int flags) { free(cwd); return OPEN_ERROR; } - snprintf_result = snprintf(abspath, PATH_MAX, "%s/%s", abs_cwd, pathname); + asprintf_result = asprintf(&abspath, "%s/%s", abs_cwd, pathname); free(cwd); } - if (snprintf_result == SNPRINTF_ERROR || snprintf_result > PATH_MAX) { - perror("safe_open (snprintf)"); + if (asprintf_result == ASPRINTF_ERROR) { + perror("safe_open (asprintf)"); return OPEN_ERROR; } + /* Beyond here, asprintf() worked, and we need to free abspath. */ + int result = OPEN_ERROR; + bool abspath_is_root = (strcmp(abspath, "/") == 0); int rootflags = flags | O_DIRECTORY; if (!abspath_is_root) { @@ -180,18 +203,24 @@ int safe_open(const char* pathname, int flags) { int rootfd = open("/", rootflags); if (rootfd == OPEN_ERROR) { perror("safe_open (open)"); - return OPEN_ERROR; + result = OPEN_ERROR; + goto cleanup; } if (abspath_is_root) { - return rootfd; + result = rootfd; + goto cleanup; } - int result = safe_open_ex(rootfd, abspath+1, flags); + result = safe_open_ex(rootfd, abspath+1, flags); if (close(rootfd) == CLOSE_ERROR) { perror("safe_open (close)"); - return OPEN_ERROR; + result = OPEN_ERROR; + goto cleanup; } + + cleanup: + free(abspath); return result; } @@ -204,66 +233,131 @@ int safe_open(const char* pathname, int flags) { * @param aclp * A pointer to the acl_t structure whose entry we want to update. * - * @param entry - * The new entry. + * @param updated_entry + * An updated copy of an existing entry in @c aclp. * * @return * - @c ACL_SUCCESS - If we update an existing entry. * - @c ACL_FAILURE - If we don't find an entry to update. * - @c ACL_ERROR - Unexpected library error. */ -int acl_update_entry(acl_t aclp, acl_entry_t entry) { - if (aclp == NULL || entry == NULL) { +int acl_update_entry(acl_t aclp, acl_entry_t updated_entry) { + if (aclp == NULL || updated_entry == NULL) { errno = EINVAL; perror("acl_update_entry (args)"); return ACL_ERROR; } - acl_tag_t entry_tag; - if (acl_get_tag_type(entry, &entry_tag) == ACL_ERROR) { + acl_tag_t updated_tag; + if (acl_get_tag_type(updated_entry, &updated_tag) == ACL_ERROR) { perror("acl_update_entry (acl_get_tag_type)"); return ACL_ERROR; } - acl_permset_t entry_permset; - if (acl_get_permset(entry, &entry_permset) == ACL_ERROR) { + acl_permset_t updated_permset; + if (acl_get_permset(updated_entry, &updated_permset) == ACL_ERROR) { perror("acl_update_entry (acl_get_permset)"); return ACL_ERROR; } + /* This can allocate memory, so from here on out we have to jump to + the "cleanup" label to exit. */ + void* updated_qualifier = acl_get_qualifier(updated_entry); + if (updated_qualifier == NULL && + (updated_tag == ACL_USER || updated_tag == ACL_GROUP)) { + /* acl_get_qualifier() can return NULL, but it shouldn't for + ACL_USER or ACL_GROUP entries. */ + perror("acl_update_entry (acl_get_qualifier)"); + return ACL_ERROR; + } + + /* Our return value. Default to failure, and change to success if we + actually update something. */ + int result = ACL_FAILURE; + 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); + int get_entry_result = acl_get_entry(aclp, ACL_FIRST_ENTRY, &existing_entry); - while (result == ACL_SUCCESS) { + while (get_entry_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; + result = ACL_ERROR; + goto cleanup; } - if (existing_tag == entry_tag) { - /* If we update something, we're done and return ACL_SUCCESS */ - if (acl_set_permset(existing_entry, entry_permset) == ACL_ERROR) { - perror("acl_update_entry (acl_set_permset)"); - return ACL_ERROR; + if (existing_tag == updated_tag) { + /* Our tag types match, but if we have a named user or group + entry, then we need to check that the user/group (that is, + the qualifier) matches too. */ + bool qualifiers_match = false; + + /* There are three ways the qualifiers can match... */ + void* existing_qualifier = acl_get_qualifier(existing_entry); + if (existing_qualifier == NULL) { + if (existing_tag == ACL_USER || existing_tag == ACL_GROUP) { + perror("acl_update_entry (acl_get_qualifier)"); + result = ACL_ERROR; + goto cleanup; + } + else { + /* First, we could be dealing with an entry that isn't a + named user or group, in which case they "match + vacuously." */ + qualifiers_match = true; + } } - return ACL_SUCCESS; + /* Second, they could have matching UIDs. We don't really need to + check both tags here, since we know that they're equal. However, + clang-tidy can't figure that out, and the redundant equality + check prevents it from complaining about a potential null pointer + dereference. */ + if (updated_tag == ACL_USER && existing_tag == ACL_USER) { + qualifiers_match = ( *((uid_t*)existing_qualifier) + == + *((uid_t*)updated_qualifier) ); + } + + /* Third, they could have matching GIDs. See above for why + we check the redundant condition existing_tag == ACL_GROUP. */ + if (updated_tag == ACL_GROUP && existing_tag == ACL_GROUP) { + qualifiers_match = ( *((gid_t*)existing_qualifier) + == + *((gid_t*)updated_qualifier) ); + } + + /* Be sure to free this inside the loop, where memory is allocated. */ + acl_free(existing_qualifier); + + if (qualifiers_match) { + /* If we update something, we're done and return ACL_SUCCESS */ + if (acl_set_permset(existing_entry, updated_permset) == ACL_ERROR) { + perror("acl_update_entry (acl_set_permset)"); + result = ACL_ERROR; + goto cleanup; + } + + result = ACL_SUCCESS; + goto cleanup; + } } - result = acl_get_entry(aclp, ACL_NEXT_ENTRY, &existing_entry); + get_entry_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) { + if (get_entry_result == ACL_ERROR) { perror("acl_update_entry (acl_get_entry)"); - return ACL_ERROR; + result = ACL_ERROR; } - return ACL_FAILURE; + cleanup: + acl_free(updated_qualifier); + return result; } @@ -579,8 +673,14 @@ int acl_copy_xattr(int src_fd, return ACL_ERROR; } char* src_acl_p = alloca(src_size_guess); - /* The actual size may be smaller than our guess? I don't know. */ - ssize_t src_size = fgetxattr(src_fd, src_name, src_acl_p, src_size_guess); + /* The actual size may be smaller than our guess? I don't know. The + return value from fgetxattr() will either be nonnegative, or + XATTR_ERROR (which we've already ruled out), so it's safe to cast + it to an unsigned size_t here to avoid a compiler warning. */ + ssize_t src_size = fgetxattr(src_fd, + src_name, + src_acl_p, + (size_t)src_size_guess); if (src_size == XATTR_ERROR) { if (errno == ENODATA) { /* A missing ACL isn't an error. */ @@ -590,7 +690,14 @@ int acl_copy_xattr(int src_fd, return ACL_ERROR; } - if (fsetxattr(dst_fd, dst_name, src_acl_p, src_size, 0) == XATTR_ERROR) { + /* See above: src_size must be nonnegative at this point,so we cast + it to size_t to avoid a compiler warning. */ + if (fsetxattr(dst_fd, + dst_name, + src_acl_p, + (size_t)src_size, + 0) + == XATTR_ERROR) { perror("acl_copy_xattr (fsetxattr)"); return ACL_ERROR; } @@ -644,9 +751,6 @@ int has_default_acl_fd(int fd) { * @param fd * The file descriptor that should inherit its parent's default ACL. * - * @param no_exec_mask - * The value (either true or false) of the --no-exec-mask flag. - * * @param recursive * Should we recurse into subdirectories? * @@ -655,10 +759,7 @@ int has_default_acl_fd(int fd) { * - @c ACL_FAILURE - If symlinks or hard links are encountered. * - @c ACL_ERROR - Unexpected library error. */ -int apply_default_acl_fds(int parent_fd, - int fd, - bool no_exec_mask, - bool recursive) { +int apply_default_acl_fds(int parent_fd, int fd, bool recursive) { int result = ACL_SUCCESS; /* The new ACL for this path */ @@ -708,24 +809,20 @@ int apply_default_acl_fds(int parent_fd, } - /* 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; + /* Next We try to guess whether or not to strip the execute bits. + * This behavior is modeled after the capital 'X' perms of setfacl. + */ + int ace_result = any_can_execute(fd, &s); - if (!no_exec_mask) { - /* Never mask the execute bit on directories. */ - int ace_result = any_can_execute(fd,&s) || S_ISDIR(s.st_mode); + if (ace_result == ACL_ERROR) { + perror("apply_default_acl_fds (any_can_execute)"); + result = ACL_ERROR; + goto cleanup; + } - if (ace_result == ACL_ERROR) { - perror("apply_default_acl_fds (any_can_execute)"); - result = ACL_ERROR; - goto cleanup; - } + /* Never mask the execute bit on directories. */ + bool allow_exec = (bool)ace_result || S_ISDIR(s.st_mode); - allow_exec = (bool)ace_result; - } /* If it's a directory, inherit the parent's default. */ if (S_ISDIR(s.st_mode)) { @@ -807,6 +904,8 @@ int apply_default_acl_fds(int parent_fd, goto cleanup; } + /* To mimic what the kernel does, I think we could drop + ACL_GROUP_OBJ from the list below? */ if (tag == ACL_MASK || tag == ACL_USER_OBJ || tag == ACL_GROUP_OBJ || @@ -893,12 +992,13 @@ int apply_default_acl_fds(int parent_fd, continue; } } - switch (apply_default_acl_fds(fd, new_fd, no_exec_mask, recursive)) { + switch (apply_default_acl_fds(fd, new_fd, recursive)) { /* Don't overwrite an error result with success/failure. */ case ACL_FAILURE: if (result == ACL_SUCCESS) { result = ACL_FAILURE; } + break; case ACL_ERROR: result = ACL_ERROR; default: @@ -927,9 +1027,6 @@ int apply_default_acl_fds(int parent_fd, * @param path * The path whose ACL we would like to reset to its default. * - * @param no_exec_mask - * The value (either true or false) of the --no-exec-mask flag. - * * @param recursive * Should we recurse into subdirectories? * @@ -938,7 +1035,7 @@ int apply_default_acl_fds(int parent_fd, * - @c ACL_FAILURE - If symlinks or hard links are encountered. * - @c ACL_ERROR - Unexpected library error. */ -int apply_default_acl(const char* path, bool no_exec_mask, bool recursive) { +int apply_default_acl(const char* path, bool recursive) { if (path == NULL) { errno = EINVAL; @@ -972,7 +1069,30 @@ int apply_default_acl(const char* path, bool no_exec_mask, bool recursive) { return ACL_ERROR; } char* parent = dirname(dirname_path_copy); + + basename_path_copy = strdup(path); + if (basename_path_copy == NULL) { + perror("apply_default_acl (strdup)"); + result = ACL_ERROR; + goto cleanup; + } + char* child = basename(basename_path_copy); + + /* Just kidding, if the path is "." or "..", then dirname will do + * the wrong thing and give us "." as its parent, too. So, we handle + * those as special cases. We use "child" instead of "path" here to + * catch things like "./" and "../" + */ + bool path_is_dots = strcmp(child, ".") == 0 || strcmp(child, "..") == 0; + char dots_parent[6] = "../"; + if (path_is_dots) { + /* We know that "child" contains no more than two characters here, and + using strncat to enforce that belief keeps clang-tidy happy. */ + parent = strncat(dots_parent, child, 2); + } + parent_fd = safe_open(parent, O_DIRECTORY | O_NOFOLLOW); + if (parent_fd == OPEN_ERROR) { if (errno == ELOOP || errno == ENOTDIR) { /* We hit a symlink, either in the last path component (ELOOP) @@ -988,15 +1108,20 @@ int apply_default_acl(const char* path, bool no_exec_mask, bool recursive) { } /* We already obtained the parent fd safely, so if we use the - basename of path here instead of the full thing, then we can get - away with using openat() and spare ourselves the slowness of - another safe_open(). */ - basename_path_copy = strdup(path); - if (basename_path_copy == NULL) { - perror("apply_default_acl (strdup)"); - return ACL_ERROR; + * basename of path here instead of the full thing, then we can get + * away with using openat() and spare ourselves the slowness of + * another safe_open(). + * + * Note that if the basename is "." or "..", then we don't want to + * open it relative to the parent_fd, so we need another special + * case for those paths here. + */ + if (path_is_dots) { + fd = open(child, O_NOFOLLOW); + } + else { + fd = openat(parent_fd, child, O_NOFOLLOW); } - fd = openat(parent_fd, basename(basename_path_copy), O_NOFOLLOW); if (fd == OPEN_ERROR) { if (errno == ELOOP || errno == ENOTDIR) { /* We hit a symlink, either in the last path component (ELOOP) @@ -1011,7 +1136,7 @@ int apply_default_acl(const char* path, bool no_exec_mask, bool recursive) { } } - result = apply_default_acl_fds(parent_fd, fd, no_exec_mask, recursive); + result = apply_default_acl_fds(parent_fd, fd, recursive); cleanup: free(dirname_path_copy);