/*
 * 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;
}