X-Git-Url: http://gitweb.michael.orlitzky.com/?p=apply-default-acl.git;a=blobdiff_plain;f=src%2Flibadacl.c;h=a21aa709ba842bc7bd21aa672b99b4e3cb750cf0;hp=8ff0c17de6a8a91812469880af2003fbb6e6644f;hb=HEAD;hpb=cb2ef6b2386de44200124904c7a03ce8512f3585 diff --git a/src/libadacl.c b/src/libadacl.c index 8ff0c17..a21aa70 100644 --- a/src/libadacl.c +++ b/src/libadacl.c @@ -14,6 +14,7 @@ #include /* EINVAL, ELOOP, ENOTDIR, etc. */ #include /* openat() */ #include /* basename(), dirname() */ +#include /* PATH_MAX */ #include /* the "bool" type */ #include /* perror(), asprintf() */ #include /* free() */ @@ -45,7 +46,7 @@ /* 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 entry); +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); @@ -232,66 +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; + } + } + + /* 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) ); } - return ACL_SUCCESS; + /* 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; } @@ -1004,14 +1070,25 @@ int apply_default_acl(const char* path, bool recursive) { } 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. + * those as special cases. We use "child" instead of "path" here to + * catch things like "./" and "../" */ - bool path_is_dots = strcmp(path, ".") == 0 || strcmp(path, "..") == 0; + bool path_is_dots = strcmp(child, ".") == 0 || strcmp(child, "..") == 0; char dots_parent[6] = "../"; if (path_is_dots) { - parent = strcat(dots_parent, path); + /* 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); @@ -1031,24 +1108,19 @@ int apply_default_acl(const char* path, 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)"); - result = ACL_ERROR; - goto cleanup; - } - - /* 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. */ + * 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(path, O_NOFOLLOW); + fd = open(child, O_NOFOLLOW); } else { - fd = openat(parent_fd, basename(basename_path_copy), O_NOFOLLOW); + fd = openat(parent_fd, child, O_NOFOLLOW); } if (fd == OPEN_ERROR) { if (errno == ELOOP || errno == ENOTDIR) {