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131 lines
3.9 KiB
131 lines
3.9 KiB
From: Andreas Gruenbacher <agruen@suse.de>
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Date: Fri, 11 Jun 2010 16:12:48 +0530
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Subject: [PATCH 08/16] richacl: Permission check algorithm
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Patch-mainline: not yet
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As in the standard POSIX file permission model, each process is the
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owner, group, or other file class. A process is
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- in the owner file class if it owns the file,
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- in the group file class if it is in the file's owning group or it
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matches any of the user or group entries, and
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- in the other file class otherwise.
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Each file class is associated with a file mask.
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A richacl grants a requested access if the NFSv4 acl in the richacl
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grants the requested permissions (according to the NFSv4 permission
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check algorithm) and the file mask that applies to the process includes
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the requested permissions.
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Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
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Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
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---
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fs/richacl_base.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++++
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include/linux/richacl.h | 2 +
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2 files changed, 89 insertions(+)
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--- a/fs/richacl_base.c
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+++ b/fs/richacl_base.c
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@@ -367,3 +367,90 @@ richacl_chmod(struct richacl *acl, mode_
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return clone;
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}
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EXPORT_SYMBOL_GPL(richacl_chmod);
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+
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+/**
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+ * richacl_permission - richacl permission check algorithm
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+ * @inode: inode to check
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+ * @acl: rich acl of the inode
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+ * @mask: requested access (ACE4_* bitmask)
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+ *
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+ * Checks if the current process is granted @mask flags in @acl.
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+ */
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+int
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+richacl_permission(struct inode *inode, const struct richacl *acl,
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+ unsigned int mask)
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+{
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+ const struct richace *ace;
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+ unsigned int file_mask, requested = mask, denied = 0;
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+ int in_owning_group = in_group_p(inode->i_gid);
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+ int in_owner_or_group_class = in_owning_group;
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+
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+ /*
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+ * A process is
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+ * - in the owner file class if it owns the file,
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+ * - in the group file class if it is in the file's owning group or
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+ * it matches any of the user or group entries, and
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+ * - in the other file class otherwise.
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+ */
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+
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+ /*
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+ * Check if the acl grants the requested access and determine which
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+ * file class the process is in.
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+ */
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+ richacl_for_each_entry(ace, acl) {
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+ unsigned int ace_mask = ace->e_mask;
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+
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+ if (richace_is_inherit_only(ace))
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+ continue;
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+ if (richace_is_owner(ace)) {
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+ if (current_fsuid() != inode->i_uid)
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+ continue;
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+ goto is_owner;
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+ } else if (richace_is_group(ace)) {
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+ if (!in_owning_group)
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+ continue;
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+ } else if (richace_is_unix_id(ace)) {
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+ if (ace->e_flags & ACE4_IDENTIFIER_GROUP) {
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+ if (!in_group_p(ace->u.e_id))
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+ continue;
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+ } else {
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+ if (current_fsuid() != ace->u.e_id)
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+ continue;
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+ }
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+ } else
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+ goto is_everyone;
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+
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+is_owner:
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+ /* The process is in the owner or group file class. */
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+ in_owner_or_group_class = 1;
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+
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+is_everyone:
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+ /* Check which mask flags the ACE allows or denies. */
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+ if (richace_is_deny(ace))
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+ denied |= ace_mask & mask;
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+ mask &= ~ace_mask;
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+
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+ /*
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+ * Keep going until we know which file class
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+ * the process is in.
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+ */
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+ if (!mask && in_owner_or_group_class)
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+ break;
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+ }
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+ denied |= mask;
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+
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+ /*
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+ * The file class a process is in determines which file mask applies.
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+ * Check if that file mask also grants the requested access.
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+ */
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+ if (current_fsuid() == inode->i_uid)
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+ file_mask = acl->a_owner_mask;
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+ else if (in_owner_or_group_class)
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+ file_mask = acl->a_group_mask;
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+ else
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+ file_mask = acl->a_other_mask;
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+ denied |= requested & ~file_mask;
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+
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+ return denied ? -EACCES : 0;
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+}
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+EXPORT_SYMBOL_GPL(richacl_permission);
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--- a/include/linux/richacl.h
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+++ b/include/linux/richacl.h
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@@ -270,5 +270,7 @@ extern unsigned int richacl_mode_to_mask
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extern unsigned int richacl_want_to_mask(int);
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extern void richacl_compute_max_masks(struct richacl *);
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extern struct richacl *richacl_chmod(struct richacl *, mode_t);
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+extern int richacl_permission(struct inode *, const struct richacl *,
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+ unsigned int);
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#endif /* __RICHACL_H */
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