shared/acl-util: add mask only when needed, always add base ACLs

For ACLs to be valid, a set of entries for user, group, and other
must be always present. Always add those entries.

While at it, only add the mask ACL if it is actually required, i.e.
when at least on ACL for non-owner group or user exists.

4 files changed, 112 insertions, 36 deletions

diff --git a/man/tmpfiles.d.xml b/man/tmpfiles.d.xml
index 957910dd6d..8815bf9970 100644
--- a/man/tmpfiles.d.xml
+++ b/man/tmpfiles.d.xml
@@ -306,16 +306,16 @@
           <term><varname>a</varname></term>
           <term><varname>a+</varname></term>
           <listitem><para>Set POSIX ACLs (access control lists). If
-          suffixed with <varname>+</varname>, specified mask will be
-          added to existing
-          entries. <command>systemd-tmpfiles</command> does not
-          automatically add the required base entries for user and
-          group to the specified mask, so they must be specified
-          explicitly if <varname>+</varname> is not used. The
-          mask will be added if not specified explicitly.
-          Lines of this type accept shell-style globs in place
-          of normal path names. This can be useful for allowing
-          additional access to certain files.  </para></listitem>
+          suffixed with <varname>+</varname>, specified entries will
+          be added to the existing set.
+          <command>systemd-tmpfiles</command> will automatically add
+          the required base entries for user and group based on the
+          access mode of the file, unless base entries already exist
+          or are explictly specified. The mask will be added if not
+          specified explicitly or already present. Lines of this type
+          accept shell-style globs in place of normal path names. This
+          can be useful for allowing additional access to certain
+          files.</para></listitem>
         </varlistentry>
 
         <varlistentry>
diff --git a/src/shared/acl-util.c b/src/shared/acl-util.c
index 950f472ddd..a4ff1ab878 100644
--- a/src/shared/acl-util.c
+++ b/src/shared/acl-util.c
@@ -29,14 +29,14 @@
 
 int acl_find_uid(acl_t acl, uid_t uid, acl_entry_t *entry) {
         acl_entry_t i;
-        int found;
+        int r;
 
         assert(acl);
         assert(entry);
 
-        for (found = acl_get_entry(acl, ACL_FIRST_ENTRY, &i);
-             found > 0;
-             found = acl_get_entry(acl, ACL_NEXT_ENTRY, &i)) {
+        for (r = acl_get_entry(acl, ACL_FIRST_ENTRY, &i);
+             r > 0;
+             r = acl_get_entry(acl, ACL_NEXT_ENTRY, &i)) {
 
                 acl_tag_t tag;
                 uid_t *u;
@@ -60,8 +60,7 @@ int acl_find_uid(acl_t acl, uid_t uid, acl_entry_t *entry) {
                         return 1;
                 }
         }
-
-        if (found < 0)
+        if (r < 0)
                 return -errno;
 
         return 0;
@@ -69,14 +68,13 @@ int acl_find_uid(acl_t acl, uid_t uid, acl_entry_t *entry) {
 
 int calc_acl_mask_if_needed(acl_t *acl_p) {
         acl_entry_t i;
-        int found;
+        int r;
 
         assert(acl_p);
 
-        for (found = acl_get_entry(*acl_p, ACL_FIRST_ENTRY, &i);
-             found > 0;
-             found = acl_get_entry(*acl_p, ACL_NEXT_ENTRY, &i)) {
-
+        for (r = acl_get_entry(*acl_p, ACL_FIRST_ENTRY, &i);
+             r > 0;
+             r = acl_get_entry(*acl_p, ACL_NEXT_ENTRY, &i)) {
                 acl_tag_t tag;
 
                 if (acl_get_tag_type(i, &tag) < 0)
@@ -84,14 +82,80 @@ int calc_acl_mask_if_needed(acl_t *acl_p) {
 
                 if (tag == ACL_MASK)
                         return 0;
+                if (IN_SET(tag, ACL_USER, ACL_GROUP))
+                        goto calc;
         }
-
-        if (found < 0)
+        if (r < 0)
                 return -errno;
+        return 0;
 
+calc:
         if (acl_calc_mask(acl_p) < 0)
                 return -errno;
+        return 1;
+}
+
+int add_base_acls_if_needed(acl_t *acl_p, const char *path) {
+        acl_entry_t i;
+        int r;
+        bool have_user_obj = false, have_group_obj = false, have_other = false;
+        struct stat st;
+        _cleanup_(acl_freep) acl_t basic = NULL;
+
+        assert(acl_p);
+
+        for (r = acl_get_entry(*acl_p, ACL_FIRST_ENTRY, &i);
+             r > 0;
+             r = acl_get_entry(*acl_p, ACL_NEXT_ENTRY, &i)) {
+                acl_tag_t tag;
+
+                if (acl_get_tag_type(i, &tag) < 0)
+                        return -errno;
+
+                if (tag == ACL_USER_OBJ)
+                        have_user_obj = true;
+                else if (tag == ACL_GROUP_OBJ)
+                        have_group_obj = true;
+                else if (tag == ACL_OTHER)
+                        have_other = true;
+                if (have_user_obj && have_group_obj && have_other)
+                        return 0;
+        }
+        if (r < 0)
+                return -errno;
 
+        r = stat(path, &st);
+        if (r < 0)
+                return -errno;
+
+        basic = acl_from_mode(st.st_mode);
+        if (!basic)
+                return -errno;
+
+        for (r = acl_get_entry(basic, ACL_FIRST_ENTRY, &i);
+             r > 0;
+             r = acl_get_entry(basic, ACL_NEXT_ENTRY, &i)) {
+                acl_tag_t tag;
+                acl_entry_t dst;
+
+                if (acl_get_tag_type(i, &tag) < 0)
+                        return -errno;
+
+                if ((tag == ACL_USER_OBJ && have_user_obj) ||
+                    (tag == ACL_GROUP_OBJ && have_group_obj) ||
+                    (tag == ACL_OTHER && have_other))
+                        continue;
+
+                r = acl_create_entry(acl_p, &dst);
+                if (r < 0)
+                        return -errno;
+
+                r = acl_copy_entry(dst, i);
+                if (r < 0)
+                        return -errno;
+        }
+        if (r < 0)
+                return -errno;
         return 0;
 }
 
@@ -221,15 +285,15 @@ int parse_acl(char *text, acl_t *acl_access, acl_t *acl_default, bool want_mask)
 int acls_for_file(const char *path, acl_type_t type, acl_t new, acl_t *acl) {
         _cleanup_(acl_freep) acl_t old;
         acl_entry_t i;
-        int found, r;
+        int r;
 
         old = acl_get_file(path, type);
         if (!old)
                 return -errno;
 
-        for (found = acl_get_entry(new, ACL_FIRST_ENTRY, &i);
-             found > 0;
-             found = acl_get_entry(new, ACL_NEXT_ENTRY, &i)) {
+        for (r = acl_get_entry(new, ACL_FIRST_ENTRY, &i);
+             r > 0;
+             r = acl_get_entry(new, ACL_NEXT_ENTRY, &i)) {
 
                 acl_entry_t j;
 
@@ -239,10 +303,8 @@ int acls_for_file(const char *path, acl_type_t type, acl_t new, acl_t *acl) {
                 if (acl_copy_entry(j, i) < 0)
                         return -errno;
         }
-
-        r = calc_acl_mask_if_needed(&old);
         if (r < 0)
-                return r;
+                return -errno;
 
         *acl = old;
         old = NULL;
diff --git a/src/shared/acl-util.h b/src/shared/acl-util.h
index 1ad4a2ebc7..90e88ffa26 100644
--- a/src/shared/acl-util.h
+++ b/src/shared/acl-util.h
@@ -31,6 +31,7 @@
 
 int acl_find_uid(acl_t acl, uid_t uid, acl_entry_t *entry);
 int calc_acl_mask_if_needed(acl_t *acl_p);
+int add_base_acls_if_needed(acl_t *acl_p, const char *path);
 int search_acl_groups(char*** dst, const char* path, bool* belong);
 int parse_acl(char *text, acl_t *acl_access, acl_t *acl_default, bool want_mask);
 int acls_for_file(const char *path, acl_type_t type, acl_t new, acl_t *acl);
diff --git a/src/tmpfiles/tmpfiles.c b/src/tmpfiles/tmpfiles.c
index 3c8993e894..7edeeb7428 100644
--- a/src/tmpfiles/tmpfiles.c
+++ b/src/tmpfiles/tmpfiles.c
@@ -614,22 +614,35 @@ static int get_acls_from_arg(Item *item) {
 }
 
 static int path_set_acl(const char *path, acl_type_t type, acl_t acl, bool modify) {
-        _cleanup_(acl_freep) acl_t cleanme = NULL;
+        _cleanup_(acl_freep) acl_t dup = NULL;
         int r;
 
         if (modify) {
-                r = acls_for_file(path, type, acl, &cleanme);
+                r = acls_for_file(path, type, acl, &dup);
                 if (r < 0)
                         return r;
-                acl = cleanme;
-        };
 
-        r = acl_set_file(path, type, acl);
+                r = calc_acl_mask_if_needed(&dup);
+                if (r < 0)
+                        return r;
+        } else {
+                dup = acl_dup(acl);
+                if (!dup)
+                        return -errno;
+
+                /* the mask was already added earlier if needed */
+        }
+
+        r = add_base_acls_if_needed(&dup, path);
+        if (r < 0)
+                return r;
+
+        r = acl_set_file(path, type, dup);
         if (r < 0) {
                 _cleanup_(acl_free_charpp) char *t;
 
                 r = -errno;
-                t = acl_to_any_text(acl, NULL, ',', TEXT_ABBREVIATE);
+                t = acl_to_any_text(dup, NULL, ',', TEXT_ABBREVIATE);
                 log_error_errno(r,
                                 "Setting %s ACL \"%s\" on %s failed: %m",
                                 type == ACL_TYPE_ACCESS ? "access" : "default",