Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > linux.kernel > #1171710
| From | Andreas Gruenbacher <andreas.gruenbacher@gmail.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [RFC v4 25/31] richacl: Isolate the owner and group classes |
| Date | 2015-06-25 00:10 +0200 |
| Message-ID | <pF11N-5Zy-29@gated-at.bofh.it> (permalink) |
| References | <pF0S5-5yK-3@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
When applying the file masks to an acl, we need to ensure that no
process gets more permissions than allowed by its file mask.
This may require inserting an owner@ deny ace to ensure this if the
owner mask contains fewer permissions than the group or other mask. For
example, when applying mode 0466 to the following acl:
everyone@:rw::allow
A deny ace needs to be inserted so that the owner won't get elevated
write access:
owner@:w::deny
everyone@:rw::allow
Likewise, we may need to insert group class deny aces if the group mask
contains fewer permissions than the other mask. For example, when
applying mode 0646 to the following acl:
owner@:rw::allow
everyone@:rw::allow
A deny ace needs to be inserted so that the owning group won't get
elevated write access:
owner@:rw::allow
group@:w::deny
everyone@:rw::allow
Signed-off-by: Andreas Gruenbacher <agruen@kernel.org>
---
fs/richacl_compat.c | 228 ++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 228 insertions(+)
diff --git a/fs/richacl_compat.c b/fs/richacl_compat.c
index b699cd3..ae10fa6 100644
--- a/fs/richacl_compat.c
+++ b/fs/richacl_compat.c
@@ -480,3 +480,231 @@ richacl_set_other_permissions(struct richacl_alloc *alloc)
richace_change_mask(alloc, &ace, other_mask);
return 0;
}
+
+/**
+ * richacl_max_allowed - maximum permissions that anybody is allowed
+ */
+static unsigned int
+richacl_max_allowed(struct richacl *acl)
+{
+ struct richace *ace;
+ unsigned int allowed = 0;
+
+ richacl_for_each_entry_reverse(ace, acl) {
+ if (richace_is_inherit_only(ace))
+ continue;
+ if (richace_is_allow(ace))
+ allowed |= ace->e_mask;
+ else if (richace_is_deny(ace)) {
+ if (richace_is_everyone(ace))
+ allowed &= ~ace->e_mask;
+ }
+ }
+ return allowed;
+}
+
+/**
+ * richacl_isolate_owner_class - limit the owner class to the owner file mask
+ * @alloc: acl and number of allocated entries
+ *
+ * POSIX requires that after a chmod, the owner class is granted no more
+ * permissions than the owner file permission bits. For richacls, this
+ * means that the owner class must not be granted any permissions that the
+ * owner mask does not include.
+ *
+ * When we apply file masks to an acl which grant more permissions to the group
+ * or other class than to the owner class, we may end up in a situation where
+ * the owner is granted additional permissions from other aces. For example,
+ * given this acl:
+ *
+ * everyone:rwx::allow
+ *
+ * when file masks corresponding to mode 0466 are applied, after
+ * richacl_propagate_everyone() and __richacl_apply_masks(), we end up with:
+ *
+ * owner@:r::allow
+ * everyone@:rw::allow
+ *
+ * This acl still grants the owner rw access through the everyone@ allow ace.
+ * To fix this, we must deny the owner w access:
+ *
+ * owner@:w::deny
+ * owner@:r::allow
+ * everyone@:rw::allow
+ */
+static int
+richacl_isolate_owner_class(struct richacl_alloc *alloc)
+{
+ struct richace *ace;
+ unsigned int allowed = 0;
+
+ allowed = richacl_max_allowed(alloc->acl);
+ if (allowed & ~alloc->acl->a_owner_mask) {
+ /*
+ * Figure out if we can update an existig OWNER@ DENY entry.
+ */
+ richacl_for_each_entry(ace, alloc->acl) {
+ if (richace_is_inherit_only(ace))
+ continue;
+ if (richace_is_deny(ace)) {
+ if (richace_is_owner(ace))
+ break;
+ } else if (richace_is_allow(ace)) {
+ ace = alloc->acl->a_entries + alloc->acl->a_count;
+ break;
+ }
+ }
+ if (ace != alloc->acl->a_entries + alloc->acl->a_count) {
+ if (richace_change_mask(alloc, &ace, ace->e_mask |
+ (allowed & ~alloc->acl->a_owner_mask)))
+ return -1;
+ } else {
+ /* Insert an owner@ deny entry at the front. */
+ ace = alloc->acl->a_entries;
+ if (richacl_insert_entry(alloc, &ace))
+ return -1;
+ ace->e_type = RICHACE_ACCESS_DENIED_ACE_TYPE;
+ ace->e_flags = RICHACE_SPECIAL_WHO;
+ ace->e_mask = allowed & ~alloc->acl->a_owner_mask;
+ ace->e_id.special = RICHACE_OWNER_SPECIAL_ID;
+ }
+ }
+ return 0;
+}
+
+/**
+ * __richacl_isolate_who - isolate entry from everyone@ allow entry
+ * @alloc: acl and number of allocated entries
+ * @who: identifier to isolate
+ * @deny: permissions this identifier should not be allowed
+ *
+ * See richacl_isolate_group_class().
+ */
+static int
+__richacl_isolate_who(struct richacl_alloc *alloc, struct richace *who,
+ unsigned int deny)
+{
+ struct richace *ace;
+ unsigned int n;
+ /*
+ * Compute the permissions already denied to @who.
+ */
+ richacl_for_each_entry(ace, alloc->acl) {
+ if (richace_is_inherit_only(ace))
+ continue;
+ if (richace_is_same_identifier(ace, who) &&
+ richace_is_deny(ace))
+ deny &= ~ace->e_mask;
+ }
+ if (!deny)
+ return 0;
+
+ /*
+ * Figure out if we can update an existig deny entry. Start from the
+ * entry before the trailing everyone@ allow entry. We will not hit
+ * everyone@ entries in the loop.
+ */
+ for (n = alloc->acl->a_count - 2; n != -1; n--) {
+ ace = alloc->acl->a_entries + n;
+ if (richace_is_inherit_only(ace))
+ continue;
+ if (richace_is_deny(ace)) {
+ if (richace_is_same_identifier(ace, who))
+ break;
+ } else if (richace_is_allow(ace) &&
+ (ace->e_mask & deny)) {
+ n = -1;
+ break;
+ }
+ }
+ if (n != -1) {
+ if (richace_change_mask(alloc, &ace, ace->e_mask | deny))
+ return -1;
+ } else {
+ /*
+ * Insert a new entry before the trailing everyone@ deny entry.
+ */
+ struct richace who_copy;
+
+ ace = alloc->acl->a_entries + alloc->acl->a_count - 1;
+ memcpy(&who_copy, who, sizeof(struct richace));
+ if (richacl_insert_entry(alloc, &ace))
+ return -1;
+ memcpy(ace, &who_copy, sizeof(struct richace));
+ ace->e_type = RICHACE_ACCESS_DENIED_ACE_TYPE;
+ richace_clear_inheritance_flags(ace);
+ ace->e_mask = deny;
+ }
+ return 0;
+}
+
+/**
+ * richacl_isolate_group_class - limit the group class to the group file mask
+ * @alloc: acl and number of allocated entries
+ *
+ * POSIX requires that after a chmod, the group class is granted no more
+ * permissions than the group file permission bits. For richacls, this
+ * means that the group class must not be granted any permissions that the
+ * group mask does not include.
+ *
+ * When we apply file masks to an acl which grant more permissions to the other
+ * class than to the group class, we may end up in a situation where processes
+ * in the group class are granted additional permission from other aces. For
+ * example, given this acl:
+ *
+ * joe:rwx::allow
+ * everyone:rwx::allow
+ *
+ * when file masks corresponding to mode 0646 are applied, after
+ * richacl_propagate_everyone() and __richacl_apply_masks(), we end up with:
+ *
+ * joe:r::allow
+ * owner@:rw::allow
+ * group@:r::allow
+ * everyone@:rw::allow
+ *
+ * This acl still grants joe and group@ rw access through the everyone@ allow
+ * ace. To fix this, we must deny w access to group class aces before the
+ * everyone@ allow ace at the end of the acl:
+ *
+ * joe:r::allow
+ * owner@:rw::allow
+ * group@:r::allow
+ * joe:w::deny
+ * group@:w::deny
+ * everyone@:rw::allow
+ */
+static int
+richacl_isolate_group_class(struct richacl_alloc *alloc)
+{
+ struct richace who = {
+ .e_flags = RICHACE_SPECIAL_WHO,
+ .e_id.special = RICHACE_GROUP_SPECIAL_ID,
+ };
+ unsigned int deny;
+
+ deny = alloc->acl->a_other_mask & ~alloc->acl->a_group_mask;
+
+ if (deny) {
+ unsigned int n;
+
+ if (__richacl_isolate_who(alloc, &who, deny))
+ return -1;
+ /*
+ * Start from the entry before the trailing everyone@ allow
+ * entry. We will not hit everyone@ entries in the loop.
+ */
+ for (n = alloc->acl->a_count - 1; n != -1; n--) {
+ struct richace *ace = alloc->acl->a_entries + n;
+
+ if (richace_is_inherit_only(ace) ||
+ richace_is_owner(ace) ||
+ richace_is_group(ace) ||
+ richace_is_everyone(ace))
+ continue;
+ if (__richacl_isolate_who(alloc, ace, deny))
+ return -1;
+ }
+ }
+ return 0;
+}
--
2.4.2
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
[RFC v4 00/31] Richacls Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:00 +0200
[RFC v4 20/31] richacl: acl editing helper functions Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:00 +0200
[RFC v4 22/31] richacl: Propagate everyone@ permissions to other aces Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:00 +0200
[RFC v4 23/31] richacl: Set the owner permissions to the owner mask Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:00 +0200
[RFC v4 04/31] vfs: Make the inode passed to inode_change_ok non-const Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:00 +0200
[RFC v4 26/31] richacl: Apply the file masks to a richacl Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:00 +0200
[RFC v4 19/31] ext4: Add richacl feature flag Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:10 +0200
[RFC v4 18/31] ext4: Add richacl support Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:10 +0200
[RFC v4 14/31] richacl: Create-time inheritance Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:10 +0200
[RFC v4 08/31] richacl: Compute maximum file masks from an acl Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:10 +0200
[RFC v4 25/31] richacl: Isolate the owner and group classes Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:10 +0200
[RFC v4 06/31] richacl: In-memory representation and helper functions Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:10 +0200
Re: [RFC v4 06/31] richacl: In-memory representation and helper functions "Stefan (metze) Metzmacher" <metze@samba.org> - 2015-06-25 23:50 +0200
[RFC v4 03/31] vfs: Add MAY_DELETE_SELF and MAY_DELETE_CHILD permission flags Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:10 +0200
[RFC v4 16/31] richacl: xattr mapping functions Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:10 +0200
[RFC v4 05/31] vfs: Add permission flags for setting file attributes Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:10 +0200
[RFC v4 31/31] nfsd: Add support for the v4.1 dacl attribute Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:10 +0200
[RFC v4 09/31] richacl: Update the file masks in chmod() Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:10 +0200
[RFC v4 12/31] vfs: Cache richacl in struct inode Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:10 +0200
[RFC v4 30/31] nfsd: Add richacl support Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:10 +0200
[RFC v4 11/31] vfs: Cache base_acl objects in inodes Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:10 +0200
[RFC v4 07/31] richacl: Permission mapping functions Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:10 +0200
[RFC v4 13/31] richacl: Check if an acl is equivalent to a file mode Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:10 +0200
[RFC v4 01/31] vfs: Add IS_ACL() and IS_RICHACL() tests Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:10 +0200
[RFC v4 17/31] vfs: Add richacl permission checking Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:10 +0200
[RFC v4 15/31] richacl: Automatic Inheritance Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-06-25 00:10 +0200
csiph-web