/*
   * fs/nfs_common/nfsacl.c
   *
   *  Copyright (C) 2002-2003 Andreas Gruenbacher <agruen@suse.de>
   */
  
  /*
   * The Solaris nfsacl protocol represents some ACLs slightly differently
   * than POSIX 1003.1e draft 17 does (and we do):
   *
   *  - Minimal ACLs always have an ACL_MASK entry, so they have
   *    four instead of three entries.
   *  - The ACL_MASK entry in such minimal ACLs always has the same
   *    permissions as the ACL_GROUP_OBJ entry. (In extended ACLs
   *    the ACL_MASK and ACL_GROUP_OBJ entries may differ.)
   *  - The identifier fields of the ACL_USER_OBJ and ACL_GROUP_OBJ
   *    entries contain the identifiers of the owner and owning group.
   *    (In POSIX ACLs we always set them to ACL_UNDEFINED_ID).
   *  - ACL entries in the kernel are kept sorted in ascending order
   *    of (e_tag, e_id). Solaris ACLs are unsorted.
   */
  
  #include <linux/module.h>
  #include <linux/fs.h>
  #include <linux/gfp.h>
  #include <linux/sunrpc/xdr.h>
  #include <linux/nfsacl.h>
  #include <linux/nfs3.h>
  #include <linux/sort.h>
  
  MODULE_LICENSE("GPL");
  
  EXPORT_SYMBOL_GPL(nfsacl_encode);
  EXPORT_SYMBOL_GPL(nfsacl_decode);
  
  struct nfsacl_encode_desc {
  	struct xdr_array2_desc desc;
  	unsigned int count;
  	struct posix_acl *acl;
  	int typeflag;
  	kuid_t uid;
  	kgid_t gid;
  };
  
  struct nfsacl_simple_acl {
  	struct posix_acl acl;
  	struct posix_acl_entry ace[4];
  };
  
  static int
  xdr_nfsace_encode(struct xdr_array2_desc *desc, void *elem)
  {
  	struct nfsacl_encode_desc *nfsacl_desc =
  		(struct nfsacl_encode_desc *) desc;
  	__be32 *p = elem;
  
  	struct posix_acl_entry *entry =
  		&nfsacl_desc->acl->a_entries[nfsacl_desc->count++];
  
  	*p++ = htonl(entry->e_tag | nfsacl_desc->typeflag);
  	switch(entry->e_tag) {
  		case ACL_USER_OBJ:
  			*p++ = htonl(from_kuid(&init_user_ns, nfsacl_desc->uid));
  			break;
  		case ACL_GROUP_OBJ:
  			*p++ = htonl(from_kgid(&init_user_ns, nfsacl_desc->gid));
  			break;
  		case ACL_USER:
  			*p++ = htonl(from_kuid(&init_user_ns, entry->e_uid));
  			break;
  		case ACL_GROUP:
  			*p++ = htonl(from_kgid(&init_user_ns, entry->e_gid));
  			break;
  		default:  /* Solaris depends on that! */
  			*p++ = 0;
  			break;
  	}
  	*p++ = htonl(entry->e_perm & S_IRWXO);
  	return 0;
  }
  
  /**
   * nfsacl_encode - Encode an NFSv3 ACL
   *
   * @buf: destination xdr_buf to contain XDR encoded ACL
   * @base: byte offset in xdr_buf where XDR'd ACL begins
   * @inode: inode of file whose ACL this is
   * @acl: posix_acl to encode
   * @encode_entries: whether to encode ACEs as well
   * @typeflag: ACL type: NFS_ACL_DEFAULT or zero
   *
   * Returns size of encoded ACL in bytes or a negative errno value.
   */
  int nfsacl_encode(struct xdr_buf *buf, unsigned int base, struct inode *inode,
  		  struct posix_acl *acl, int encode_entries, int typeflag)
  {
  	int entries = (acl && acl->a_count) ? max_t(int, acl->a_count, 4) : 0;
  	struct nfsacl_encode_desc nfsacl_desc = {
  		.desc = {
  			.elem_size = 12,
  			.array_len = encode_entries ? entries : 0,
  			.xcode = xdr_nfsace_encode,
  		},
  		.acl = acl,
  		.typeflag = typeflag,
  		.uid = inode->i_uid,
  		.gid = inode->i_gid,
  	};
  	struct nfsacl_simple_acl aclbuf;
  	int err;
  
  	if (entries > NFS_ACL_MAX_ENTRIES ||
  	    xdr_encode_word(buf, base, entries))
  		return -EINVAL;
  	if (encode_entries && acl && acl->a_count == 3) {
  		struct posix_acl *acl2 = &aclbuf.acl;
  
  		/* Avoid the use of posix_acl_alloc().  nfsacl_encode() is
  		 * invoked in contexts where a memory allocation failure is
  		 * fatal.  Fortunately this fake ACL is small enough to
  		 * construct on the stack. */
  		posix_acl_init(acl2, 4);
  
  		/* Insert entries in canonical order: other orders seem
  		 to confuse Solaris VxFS. */
  		acl2->a_entries[0] = acl->a_entries[0];  /* ACL_USER_OBJ */
  		acl2->a_entries[1] = acl->a_entries[1];  /* ACL_GROUP_OBJ */
  		acl2->a_entries[2] = acl->a_entries[1];  /* ACL_MASK */
  		acl2->a_entries[2].e_tag = ACL_MASK;
  		acl2->a_entries[3] = acl->a_entries[2];  /* ACL_OTHER */
  		nfsacl_desc.acl = acl2;
  	}
  	err = xdr_encode_array2(buf, base + 4, &nfsacl_desc.desc);
  	if (!err)
  		err = 8 + nfsacl_desc.desc.elem_size *
  			  nfsacl_desc.desc.array_len;
  	return err;
  }
  
  struct nfsacl_decode_desc {
  	struct xdr_array2_desc desc;
  	unsigned int count;
  	struct posix_acl *acl;
  };
  
  static int
  xdr_nfsace_decode(struct xdr_array2_desc *desc, void *elem)
  {
  	struct nfsacl_decode_desc *nfsacl_desc =
  		(struct nfsacl_decode_desc *) desc;
  	__be32 *p = elem;
  	struct posix_acl_entry *entry;
  	unsigned int id;
  
  	if (!nfsacl_desc->acl) {
  		if (desc->array_len > NFS_ACL_MAX_ENTRIES)
  			return -EINVAL;
  		nfsacl_desc->acl = posix_acl_alloc(desc->array_len, GFP_KERNEL);
  		if (!nfsacl_desc->acl)
  			return -ENOMEM;
  		nfsacl_desc->count = 0;
  	}
  
  	entry = &nfsacl_desc->acl->a_entries[nfsacl_desc->count++];
  	entry->e_tag = ntohl(*p++) & ~NFS_ACL_DEFAULT;
  	id = ntohl(*p++);
  	entry->e_perm = ntohl(*p++);
  
  	switch(entry->e_tag) {
  		case ACL_USER:
  			entry->e_uid = make_kuid(&init_user_ns, id);
  			if (!uid_valid(entry->e_uid))
  				return -EINVAL;
  			break;
  		case ACL_GROUP:
  			entry->e_gid = make_kgid(&init_user_ns, id);
  			if (!gid_valid(entry->e_gid))
  				return -EINVAL;
  			break;
  		case ACL_USER_OBJ:
  		case ACL_GROUP_OBJ:
  		case ACL_OTHER:
  			if (entry->e_perm & ~S_IRWXO)
  				return -EINVAL;
  			break;
  		case ACL_MASK:
  			/* Solaris sometimes sets additional bits in the mask */
  			entry->e_perm &= S_IRWXO;
  			break;
  		default:
  			return -EINVAL;
  	}
  
  	return 0;
  }
  
  static int
  cmp_acl_entry(const void *x, const void *y)
  {
  	const struct posix_acl_entry *a = x, *b = y;
  
  	if (a->e_tag != b->e_tag)
  		return a->e_tag - b->e_tag;
  	else if ((a->e_tag == ACL_USER) && uid_gt(a->e_uid, b->e_uid))
  		return 1;
  	else if ((a->e_tag == ACL_USER) && uid_lt(a->e_uid, b->e_uid))
  		return -1;
  	else if ((a->e_tag == ACL_GROUP) && gid_gt(a->e_gid, b->e_gid))
  		return 1;
  	else if ((a->e_tag == ACL_GROUP) && gid_lt(a->e_gid, b->e_gid))
  		return -1;
  	else
  		return 0;
  }
  
  /*
   * Convert from a Solaris ACL to a POSIX 1003.1e draft 17 ACL.
   */
  static int
  posix_acl_from_nfsacl(struct posix_acl *acl)
  {
  	struct posix_acl_entry *pa, *pe,
  	       *group_obj = NULL, *mask = NULL;
  
  	if (!acl)
  		return 0;
  
  	sort(acl->a_entries, acl->a_count, sizeof(struct posix_acl_entry),
  	     cmp_acl_entry, NULL);
  
  	/* Find the ACL_GROUP_OBJ and ACL_MASK entries. */
  	FOREACH_ACL_ENTRY(pa, acl, pe) {
  		switch(pa->e_tag) {
  			case ACL_USER_OBJ:
  				break;
  			case ACL_GROUP_OBJ:
  				group_obj = pa;
  				break;
  			case ACL_MASK:
  				mask = pa;
  				/* fall through */
  			case ACL_OTHER:
  				break;
  		}
  	}
  	if (acl->a_count == 4 && group_obj && mask &&
  	    mask->e_perm == group_obj->e_perm) {
  		/* remove bogus ACL_MASK entry */
  		memmove(mask, mask+1, (3 - (mask - acl->a_entries)) *
  				      sizeof(struct posix_acl_entry));
  		acl->a_count = 3;
  	}
  	return 0;
  }
  
  /**
   * nfsacl_decode - Decode an NFSv3 ACL
   *
   * @buf: xdr_buf containing XDR'd ACL data to decode
   * @base: byte offset in xdr_buf where XDR'd ACL begins
   * @aclcnt: count of ACEs in decoded posix_acl
   * @pacl: buffer in which to place decoded posix_acl
   *
   * Returns the length of the decoded ACL in bytes, or a negative errno value.
   */
  int nfsacl_decode(struct xdr_buf *buf, unsigned int base, unsigned int *aclcnt,
  		  struct posix_acl **pacl)
  {
  	struct nfsacl_decode_desc nfsacl_desc = {
  		.desc = {
  			.elem_size = 12,
  			.xcode = pacl ? xdr_nfsace_decode : NULL,
  		},
  	};
  	u32 entries;
  	int err;
  
  	if (xdr_decode_word(buf, base, &entries) ||
  	    entries > NFS_ACL_MAX_ENTRIES)
  		return -EINVAL;
  	nfsacl_desc.desc.array_maxlen = entries;
  	err = xdr_decode_array2(buf, base + 4, &nfsacl_desc.desc);
  	if (err)
  		return err;
  	if (pacl) {
  		if (entries != nfsacl_desc.desc.array_len ||
  		    posix_acl_from_nfsacl(nfsacl_desc.acl) != 0) {
  			posix_acl_release(nfsacl_desc.acl);
  			return -EINVAL;
  		}
  		*pacl = nfsacl_desc.acl;
  	}
  	if (aclcnt)
  		*aclcnt = entries;
  	return 8 + nfsacl_desc.desc.elem_size *
  		   nfsacl_desc.desc.array_len;
  }