[PATCH] 7/11 Ext2/3 Updates: Extended attributes, ACL, etc.

tytso
2002-10-29T16:44:54Z

Port of 0.8.50 acl patch to 2.5

This patch (as well as the following two) implements core ACL support.
This set of convenience functions is used by the ext2/3 filesystem,
and may be useful to other filesystems that wish to use "struct posix_acl"
as their internal representation of acl's. User mode tools which
support this interface may be found at http://acl.bestbits.at

fs/Config.in | 5
fs/Makefile | 3
fs/posix_acl.c | 423 ++++++++++++++++++++++++++++++++++++++++++++++
include/linux/posix_acl.h | 87 +++++++++
4 files changed, 517 insertions(+), 1 deletion(-)

diff -Nru a/fs/Config.in b/fs/Config.in
--- a/fs/Config.in Tue Oct 29 09:55:28 2002
+++ b/fs/Config.in Tue Oct 29 09:55:28 2002
@@ -198,6 +198,11 @@
fi
fi

+# Posix ACL utility routines (for now, only ext2/ext3)
+if [ "$CONFIG_EXT2_FS_POSIX_ACL" = "y" -o "$CONFIG_EXT3_FS_POSIX_ACL" = "y" ]; then
+ define_bool CONFIG_FS_POSIX_ACL y
+fi
+
mainmenu_option next_comment
comment 'Partition Types'
source fs/partitions/Config.in
diff -Nru a/fs/Makefile b/fs/Makefile
--- a/fs/Makefile Tue Oct 29 09:55:28 2002
+++ b/fs/Makefile Tue Oct 29 09:55:28 2002
@@ -6,7 +6,7 @@
#

export-objs := open.o dcache.o buffer.o bio.o inode.o dquot.o mpage.o aio.o \
- fcntl.o read_write.o dcookies.o mbcache.o
+ fcntl.o read_write.o dcookies.o mbcache.o posix_acl.o

obj-y := open.o read_write.o devices.o file_table.o buffer.o \
bio.o super.o block_dev.o char_dev.o stat.o exec.o pipe.o \
@@ -31,6 +31,7 @@
obj-$(CONFIG_BINFMT_ELF) += binfmt_elf.o

obj-$(CONFIG_FS_MBCACHE) += mbcache.o
+obj-$(CONFIG_FS_POSIX_ACL) += posix_acl.o

obj-$(CONFIG_QUOTA) += dquot.o
obj-$(CONFIG_QFMT_V1) += quota_v1.o
diff -Nru a/fs/posix_acl.c b/fs/posix_acl.c
--- /dev/null Wed Dec 31 16:00:00 1969
+++ b/fs/posix_acl.c Tue Oct 29 09:55:28 2002
@@ -0,0 +1,423 @@
+/*
+ * linux/fs/posix_acl.c
+ *
+ * Copyright (C) 2002 by Andreas Gruenbacher <a.gruenbacher@computer.org>
+ *
+ * Fixes from William Schumacher incorporated on 15 March 2001.
+ * (Reported by Charles Bertsch, <CBertsch@microtest.com>).
+ */
+
+/*
+ * This file contains generic functions for manipulating
+ * POSIX 1003.1e draft standard 17 ACLs.
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <asm/atomic.h>
+#include <linux/fs.h>
+#include <linux/sched.h>
+#include <linux/posix_acl.h>
+#include <linux/module.h>
+
+#include <linux/errno.h>
+
+EXPORT_SYMBOL(posix_acl_alloc);
+EXPORT_SYMBOL(posix_acl_clone);
+EXPORT_SYMBOL(posix_acl_valid);
+EXPORT_SYMBOL(posix_acl_equiv_mode);
+EXPORT_SYMBOL(posix_acl_from_mode);
+EXPORT_SYMBOL(posix_acl_create_masq);
+EXPORT_SYMBOL(posix_acl_chmod_masq);
+EXPORT_SYMBOL(posix_acl_masq_nfs_mode);
+EXPORT_SYMBOL(posix_acl_permission);
+
+/*
+ * Allocate a new ACL with the specified number of entries.
+ */
+struct posix_acl *
+posix_acl_alloc(int count, int flags)
+{
+ const size_t size = sizeof(struct posix_acl) +
+ count * sizeof(struct posix_acl_entry);
+ struct posix_acl *acl = kmalloc(size, flags);
+ if (acl) {
+ atomic_set(&acl->a_refcount, 1);
+ acl->a_count = count;
+ }
+ return acl;
+}
+
+/*
+ * Clone an ACL.
+ */
+struct posix_acl *
+posix_acl_clone(const struct posix_acl *acl, int flags)
+{
+ struct posix_acl *clone = NULL;
+
+ if (acl) {
+ int size = sizeof(struct posix_acl) + acl->a_count *
+ sizeof(struct posix_acl_entry);
+ clone = kmalloc(size, flags);
+ if (clone) {
+ memcpy(clone, acl, size);
+ atomic_set(&clone->a_refcount, 1);
+ }
+ }
+ return clone;
+}
+
+/*
+ * Check if an acl is valid. Returns 0 if it is, or -E... otherwise.
+ */
+int
+posix_acl_valid(const struct posix_acl *acl)
+{
+ const struct posix_acl_entry *pa, *pe;
+ int state = ACL_USER_OBJ;
+ unsigned int id = 0; /* keep gcc happy */
+ int needs_mask = 0;
+
+ FOREACH_ACL_ENTRY(pa, acl, pe) {
+ if (pa->e_perm & ~(ACL_READ|ACL_WRITE|ACL_EXECUTE))
+ return -EINVAL;
+ switch (pa->e_tag) {
+ case ACL_USER_OBJ:
+ if (state == ACL_USER_OBJ) {
+ id = 0;
+ state = ACL_USER;
+ break;
+ }
+ return -EINVAL;
+
+ case ACL_USER:
+ if (state != ACL_USER)
+ return -EINVAL;
+ if (pa->e_id == ACL_UNDEFINED_ID ||
+ pa->e_id < id)
+ return -EINVAL;
+ id = pa->e_id + 1;
+ needs_mask = 1;
+ break;
+
+ case ACL_GROUP_OBJ:
+ if (state == ACL_USER) {
+ id = 0;
+ state = ACL_GROUP;
+ break;
+ }
+ return -EINVAL;
+
+ case ACL_GROUP:
+ if (state != ACL_GROUP)
+ return -EINVAL;
+ if (pa->e_id == ACL_UNDEFINED_ID ||
+ pa->e_id < id)
+ return -EINVAL;
+ id = pa->e_id + 1;
+ needs_mask = 1;
+ break;
+
+ case ACL_MASK:
+ if (state != ACL_GROUP)
+ return -EINVAL;
+ state = ACL_OTHER;
+ break;
+
+ case ACL_OTHER:
+ if (state == ACL_OTHER ||
+ (state == ACL_GROUP && !needs_mask)) {
+ state = 0;
+ break;
+ }
+ return -EINVAL;
+
+ default:
+ return -EINVAL;
+ }
+ }
+ if (state == 0)
+ return 0;
+ return -EINVAL;
+}
+
+/*
+ * Returns 0 if the acl can be exactly represented in the traditional
+ * file mode permission bits, or else 1. Returns -E... on error.
+ */
+int
+posix_acl_equiv_mode(const struct posix_acl *acl, mode_t *mode_p)
+{
+ const struct posix_acl_entry *pa, *pe;
+ mode_t mode = 0;
+ int not_equiv = 0;
+
+ FOREACH_ACL_ENTRY(pa, acl, pe) {
+ switch (pa->e_tag) {
+ case ACL_USER_OBJ:
+ mode |= (pa->e_perm & S_IRWXO) << 6;
+ break;
+ case ACL_GROUP_OBJ:
+ mode |= (pa->e_perm & S_IRWXO) << 3;
+ break;
+ case ACL_OTHER:
+ mode |= pa->e_perm & S_IRWXO;
+ break;
+ case ACL_MASK:
+ mode = (mode & ~S_IRWXG) |
+ ((pa->e_perm & S_IRWXO) << 3);
+ not_equiv = 1;
+ break;
+ case ACL_USER:
+ case ACL_GROUP:
+ not_equiv = 1;
+ break;
+ default:
+ return -EINVAL;
+ }
+ }
+ if (mode_p)
+ *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
+ return not_equiv;
+}
+
+/*
+ * Create an ACL representing the file mode permission bits of an inode.
+ */
+struct posix_acl *
+posix_acl_from_mode(mode_t mode, int flags)
+{
+ struct posix_acl *acl = posix_acl_alloc(3, flags);
+ if (!acl)
+ return ERR_PTR(-ENOMEM);
+
+ acl->a_entries[0].e_tag = ACL_USER_OBJ;
+ acl->a_entries[0].e_id = ACL_UNDEFINED_ID;
+ acl->a_entries[0].e_perm = (mode & S_IRWXU) >> 6;
+
+ acl->a_entries[1].e_tag = ACL_GROUP_OBJ;
+ acl->a_entries[1].e_id = ACL_UNDEFINED_ID;
+ acl->a_entries[1].e_perm = (mode & S_IRWXG) >> 3;
+
+ acl->a_entries[2].e_tag = ACL_OTHER;
+ acl->a_entries[2].e_id = ACL_UNDEFINED_ID;
+ acl->a_entries[2].e_perm = (mode & S_IRWXO);
+ return acl;
+}
+
+/*
+ * Return 0 if current is granted want access to the inode
+ * by the acl. Returns -E... otherwise.
+ */
+int
+posix_acl_permission(struct inode *inode, const struct posix_acl *acl, int want)
+{
+ const struct posix_acl_entry *pa, *pe, *mask_obj;
+ int found = 0;
+
+ FOREACH_ACL_ENTRY(pa, acl, pe) {
+ switch(pa->e_tag) {
+ case ACL_USER_OBJ:
+ /* (May have been checked already) */
+ if (inode->i_uid == current->fsuid)
+ goto check_perm;
+ break;
+ case ACL_USER:
+ if (pa->e_id == current->fsuid)
+ goto mask;
+ break;
+ case ACL_GROUP_OBJ:
+ if (in_group_p(inode->i_gid)) {
+ found = 1;
+ if ((pa->e_perm & want) == want)
+ goto mask;
+ }
+ break;
+ case ACL_GROUP:
+ if (in_group_p(pa->e_id)) {
+ found = 1;
+ if ((pa->e_perm & want) == want)
+ goto mask;
+ }
+ break;
+ case ACL_MASK:
+ break;
+ case ACL_OTHER:
+ if (found)
+ return -EACCES;
+ else
+ goto check_perm;
+ default:
+ return -EIO;
+ }
+ }
+ return -EIO;
+
+mask:
+ for (mask_obj = pa+1; mask_obj != pe; mask_obj++) {
+ if (mask_obj->e_tag == ACL_MASK) {
+ if ((pa->e_perm & mask_obj->e_perm & want) == want)
+ return 0;
+ return -EACCES;
+ }
+ }
+
+check_perm:
+ if ((pa->e_perm & want) == want)
+ return 0;
+ return -EACCES;
+}
+
+/*
+ * Modify acl when creating a new inode. The caller must ensure the acl is
+ * only referenced once.
+ *
+ * mode_p initially must contain the mode parameter to the open() / creat()
+ * system calls. All permissions that are not granted by the acl are removed.
+ * The permissions in the acl are changed to reflect the mode_p parameter.
+ */
+int
+posix_acl_create_masq(struct posix_acl *acl, mode_t *mode_p)
+{
+ struct posix_acl_entry *pa, *pe;
+ struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
+ mode_t mode = *mode_p;
+ int not_equiv = 0;
+
+ /* assert(atomic_read(acl->a_refcount) == 1); */
+
+ FOREACH_ACL_ENTRY(pa, acl, pe) {
+ switch(pa->e_tag) {
+ case ACL_USER_OBJ:
+ pa->e_perm &= (mode >> 6) | ~S_IRWXO;
+ mode &= (pa->e_perm << 6) | ~S_IRWXU;
+ break;
+
+ case ACL_USER:
+ case ACL_GROUP:
+ not_equiv = 1;
+ break;
+
+ case ACL_GROUP_OBJ:
+ group_obj = pa;
+ break;
+
+ case ACL_OTHER:
+ pa->e_perm &= mode | ~S_IRWXO;
+ mode &= pa->e_perm | ~S_IRWXO;
+ break;
+
+ case ACL_MASK:
+ mask_obj = pa;
+ not_equiv = 1;
+ break;
+
+ default:
+ return -EIO;
+ }
+ }
+
+ if (mask_obj) {
+ mask_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
+ mode &= (mask_obj->e_perm << 3) | ~S_IRWXG;
+ } else {
+ if (!group_obj)
+ return -EIO;
+ group_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
+ mode &= (group_obj->e_perm << 3) | ~S_IRWXG;
+ }
+
+ *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
+ return not_equiv;
+}
+
+/*
+ * Modify the ACL for the chmod syscall.
+ */
+int
+posix_acl_chmod_masq(struct posix_acl *acl, mode_t mode)
+{
+ struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
+ struct posix_acl_entry *pa, *pe;
+
+ /* assert(atomic_read(acl->a_refcount) == 1); */
+
+ FOREACH_ACL_ENTRY(pa, acl, pe) {
+ switch(pa->e_tag) {
+ case ACL_USER_OBJ:
+ pa->e_perm = (mode & S_IRWXU) >> 6;
+ break;
+
+ case ACL_USER:
+ case ACL_GROUP:
+ break;
+
+ case ACL_GROUP_OBJ:
+ group_obj = pa;
+ break;
+
+ case ACL_MASK:
+ mask_obj = pa;
+ break;
+
+ case ACL_OTHER:
+ pa->e_perm = (mode & S_IRWXO);
+ break;
+
+ default:
+ return -EIO;
+ }
+ }
+
+ if (mask_obj) {
+ mask_obj->e_perm = (mode & S_IRWXG) >> 3;
+ } else {
+ if (!group_obj)
+ return -EIO;
+ group_obj->e_perm = (mode & S_IRWXG) >> 3;
+ }
+
+ return 0;
+}
+
+/*
+ * Adjust the mode parameter so that NFSv2 grants nobody permissions
+ * that may not be granted by the ACL. This is necessary because NFSv2
+ * may compute access permissions on the client side, and may serve cached
+ * data whenever it assumes access would be granted. Since ACLs may also
+ * be used to deny access to specific users, the minimal permissions
+ * for secure operation over NFSv2 are very restrictive. Permissions
+ * granted to users via Access Control Lists will not be effective over
+ * NFSv2.
+ *
+ * Privilege escalation can only happen for read operations, as writes are
+ * always carried out on the NFS server, where the proper access checks are
+ * implemented.
+ */
+int
+posix_acl_masq_nfs_mode(struct posix_acl *acl, mode_t *mode_p)
+{
+ struct posix_acl_entry *pa, *pe; int min_perm = S_IRWXO;
+
+ FOREACH_ACL_ENTRY(pa, acl, pe) {
+ switch(pa->e_tag) {
+ case ACL_USER_OBJ:
+ break;
+
+ case ACL_USER:
+ case ACL_GROUP_OBJ:
+ case ACL_GROUP:
+ case ACL_MASK:
+ case ACL_OTHER:
+ min_perm &= pa->e_perm;
+ break;
+
+ default:
+ return -EIO;
+ }
+ }
+ *mode_p = (*mode_p & ~(S_IRWXG|S_IRWXO)) | (min_perm << 3) | min_perm;
+
+ return 0;
+}
diff -Nru a/include/linux/posix_acl.h b/include/linux/posix_acl.h
--- /dev/null Wed Dec 31 16:00:00 1969
+++ b/include/linux/posix_acl.h Tue Oct 29 09:55:28 2002
@@ -0,0 +1,87 @@
+/*
+ File: linux/posix_acl.h
+
+ (C) 2002 Andreas Gruenbacher, <a.gruenbacher@computer.org>
+*/
+
+
+#ifndef __LINUX_POSIX_ACL_H
+#define __LINUX_POSIX_ACL_H
+
+#include <linux/slab.h>
+
+#define ACL_UNDEFINED_ID (-1)
+
+/* a_type field in acl_user_posix_entry_t */
+#define ACL_TYPE_ACCESS (0x8000)
+#define ACL_TYPE_DEFAULT (0x4000)
+
+/* e_tag entry in struct posix_acl_entry */
+#define ACL_USER_OBJ (0x01)
+#define ACL_USER (0x02)
+#define ACL_GROUP_OBJ (0x04)
+#define ACL_GROUP (0x08)
+#define ACL_MASK (0x10)
+#define ACL_OTHER (0x20)
+
+/* permissions in the e_perm field */
+#define ACL_READ (0x04)
+#define ACL_WRITE (0x02)
+#define ACL_EXECUTE (0x01)
+//#define ACL_ADD (0x08)
+//#define ACL_DELETE (0x10)
+
+struct posix_acl_entry {
+ short e_tag;
+ unsigned short e_perm;
+ unsigned int e_id;
+};
+
+struct posix_acl {
+ atomic_t a_refcount;
+ unsigned int a_count;
+ struct posix_acl_entry a_entries[0];
+};
+
+#define FOREACH_ACL_ENTRY(pa, acl, pe) \
+ for(pa=(acl)->a_entries, pe=pa+(acl)->a_count; pa<pe; pa++)
+
+
+/*
+ * Duplicate an ACL handle.
+ */
+static inline struct posix_acl *
+posix_acl_dup(struct posix_acl *acl)
+{
+ if (acl)
+ atomic_inc(&acl->a_refcount);
+ return acl;
+}
+
+/*
+ * Free an ACL handle.
+ */
+static inline void
+posix_acl_release(struct posix_acl *acl)
+{
+ if (acl && atomic_dec_and_test(&acl->a_refcount))
+ kfree(acl);
+}
+
+
+/* posix_acl.c */
+
+extern struct posix_acl *posix_acl_alloc(int, int);
+extern struct posix_acl *posix_acl_clone(const struct posix_acl *, int);
+extern int posix_acl_valid(const struct posix_acl *);
+extern int posix_acl_permission(struct inode *, const struct posix_acl *, int);
+extern struct posix_acl *posix_acl_from_mode(mode_t, int);
+extern int posix_acl_equiv_mode(const struct posix_acl *, mode_t *);
+extern int posix_acl_create_masq(struct posix_acl *, mode_t *);
+extern int posix_acl_chmod_masq(struct posix_acl *, mode_t);
+extern int posix_acl_masq_nfs_mode(struct posix_acl *, mode_t *);
+
+extern struct posix_acl *get_posix_acl(struct inode *, int);
+extern int set_posix_acl(struct inode *, int, struct posix_acl *);
+
+#endif /* __LINUX_POSIX_ACL_H */