/*
 *  linux/net/sunrpc/gss_krb5_crypto.c
 *
 *  Copyright (c) 2000 The Regents of the University of Michigan.
 *  All rights reserved.
 *
 *  Andy Adamson   <andros@umich.edu>
 *  Bruce Fields   <bfields@umich.edu>
 */

/*
 * Copyright (C) 1998 by the FundsXpress, INC.
 *
 * All rights reserved.
 *
 * Export of this software from the United States of America may require
 * a specific license from the United States Government.  It is the
 * responsibility of any person or organization contemplating export to
 * obtain such a license before exporting.
 *
 * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
 * distribute this software and its documentation for any purpose and
 * without fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright notice and
 * this permission notice appear in supporting documentation, and that
 * the name of FundsXpress. not be used in advertising or publicity pertaining
 * to distribution of the software without specific, written prior
 * permission.  FundsXpress makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is" without express
 * or implied warranty.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#include <linux/err.h>
#include <linux/types.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/scatterlist.h>
#include <linux/crypto.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/sunrpc/gss_krb5.h>
#include <linux/sunrpc/xdr.h>

#ifdef RPC_DEBUG
# define RPCDBG_FACILITY        RPCDBG_AUTH
#endif

u32
krb5_encrypt(
        struct crypto_blkcipher *tfm,
        void * iv,
        void * in,
        void * out,
        int length)
{
        u32 ret = -EINVAL;
        struct scatterlist sg[1];
        u8 local_iv[16] = {0};
        struct blkcipher_desc desc = { .tfm = tfm, .info = local_iv };

        if (length % crypto_blkcipher_blocksize(tfm) != 0)
                goto out;

        if (crypto_blkcipher_ivsize(tfm) > 16) {
                dprintk("RPC:       gss_k5encrypt: tfm iv size too large %d\n",
                        crypto_blkcipher_ivsize(tfm));
                goto out;
        }

        if (iv)
                memcpy(local_iv, iv, crypto_blkcipher_ivsize(tfm));

        memcpy(out, in, length);
        sg_init_one(sg, out, length);

        ret = crypto_blkcipher_encrypt_iv(&desc, sg, sg, length);
out:
        dprintk("RPC:       krb5_encrypt returns %d\n", ret);
        return ret;
}

u32
krb5_decrypt(
     struct crypto_blkcipher *tfm,
     void * iv,
     void * in,
     void * out,
     int length)
{
        u32 ret = -EINVAL;
        struct scatterlist sg[1];
        u8 local_iv[16] = {0};
        struct blkcipher_desc desc = { .tfm = tfm, .info = local_iv };

        if (length % crypto_blkcipher_blocksize(tfm) != 0)
                goto out;

        if (crypto_blkcipher_ivsize(tfm) > 16) {
                dprintk("RPC:       gss_k5decrypt: tfm iv size too large %d\n",
                        crypto_blkcipher_ivsize(tfm));
                goto out;
        }
        if (iv)
                memcpy(local_iv,iv, crypto_blkcipher_ivsize(tfm));

        memcpy(out, in, length);
        sg_init_one(sg, out, length);

        ret = crypto_blkcipher_decrypt_iv(&desc, sg, sg, length);
out:
        dprintk("RPC:       gss_k5decrypt returns %d\n",ret);
        return ret;
}

static int
checksummer(struct scatterlist *sg, void *data)
{
        struct hash_desc *desc = data;

        return crypto_hash_update(desc, sg, sg->length);
}

/* checksum the plaintext data and hdrlen bytes of the token header */
s32
make_checksum(char *cksumname, char *header, int hdrlen, struct xdr_buf *body,
                   int body_offset, struct xdr_netobj *cksum)
{
        struct hash_desc                desc; /* XXX add to ctx? */
        struct scatterlist              sg[1];
        int err;

        desc.tfm = crypto_alloc_hash(cksumname, 0, CRYPTO_ALG_ASYNC);
        if (IS_ERR(desc.tfm))
                return GSS_S_FAILURE;
        cksum->len = crypto_hash_digestsize(desc.tfm);
        desc.flags = CRYPTO_TFM_REQ_MAY_SLEEP;

        err = crypto_hash_init(&desc);
        if (err)
                goto out;
        sg_init_one(sg, header, hdrlen);
        err = crypto_hash_update(&desc, sg, hdrlen);
        if (err)
                goto out;
        err = xdr_process_buf(body, body_offset, body->len - body_offset,
                              checksummer, &desc);
        if (err)
                goto out;
        err = crypto_hash_final(&desc, cksum->data);

out:
        crypto_free_hash(desc.tfm);
        return err ? GSS_S_FAILURE : 0;
}

struct encryptor_desc {
        u8 iv[8]; /* XXX hard-coded blocksize */
        struct blkcipher_desc desc;
        int pos;
        struct xdr_buf *outbuf;
        struct page **pages;
        struct scatterlist infrags[4];
        struct scatterlist outfrags[4];
        int fragno;
        int fraglen;
};

static int
encryptor(struct scatterlist *sg, void *data)
{
        struct encryptor_desc *desc = data;
        struct xdr_buf *outbuf = desc->outbuf;
        struct page *in_page;
        int thislen = desc->fraglen + sg->length;
        int fraglen, ret;
        int page_pos;

        /* Worst case is 4 fragments: head, end of page 1, start
         * of page 2, tail.  Anything more is a bug. */
        BUG_ON(desc->fragno > 3);

        page_pos = desc->pos - outbuf->head[0].iov_len;
        if (page_pos >= 0 && page_pos < outbuf->page_len) {
                /* pages are not in place: */
                int i = (page_pos + outbuf->page_base) >> PAGE_CACHE_SHIFT;
                in_page = desc->pages[i];
        } else {
                in_page = sg_page(sg);
        }
        sg_set_page(&desc->infrags[desc->fragno], in_page, sg->length,
                    sg->offset);
        sg_set_page(&desc->outfrags[desc->fragno], sg_page(sg), sg->length,
                    sg->offset);
        desc->fragno++;
        desc->fraglen += sg->length;
        desc->pos += sg->length;

        fraglen = thislen & 7; /* XXX hardcoded blocksize */
        thislen -= fraglen;

        if (thislen == 0)
                return 0;

        sg_mark_end(&desc->infrags[desc->fragno - 1]);
        sg_mark_end(&desc->outfrags[desc->fragno - 1]);

        ret = crypto_blkcipher_encrypt_iv(&desc->desc, desc->outfrags,
                                          desc->infrags, thislen);
        if (ret)
                return ret;

        sg_init_table(desc->infrags, 4);
        sg_init_table(desc->outfrags, 4);

        if (fraglen) {
                sg_set_page(&desc->outfrags[0], sg_page(sg), fraglen,
                                sg->offset + sg->length - fraglen);
                desc->infrags[0] = desc->outfrags[0];
                sg_assign_page(&desc->infrags[0], in_page);
                desc->fragno = 1;
                desc->fraglen = fraglen;
        } else {
                desc->fragno = 0;
                desc->fraglen = 0;
        }
        return 0;
}

int
gss_encrypt_xdr_buf(struct crypto_blkcipher *tfm, struct xdr_buf *buf,
                    int offset, struct page **pages)
{
        int ret;
        struct encryptor_desc desc;

        BUG_ON((buf->len - offset) % crypto_blkcipher_blocksize(tfm) != 0);

        memset(desc.iv, 0, sizeof(desc.iv));
        desc.desc.tfm = tfm;
        desc.desc.info = desc.iv;
        desc.desc.flags = 0;
        desc.pos = offset;
        desc.outbuf = buf;
        desc.pages = pages;
        desc.fragno = 0;
        desc.fraglen = 0;

        sg_init_table(desc.infrags, 4);
        sg_init_table(desc.outfrags, 4);

        ret = xdr_process_buf(buf, offset, buf->len - offset, encryptor, &desc);
        return ret;
}

struct decryptor_desc {
        u8 iv[8]; /* XXX hard-coded blocksize */
        struct blkcipher_desc desc;
        struct scatterlist frags[4];
        int fragno;
        int fraglen;
};

static int
decryptor(struct scatterlist *sg, void *data)
{
        struct decryptor_desc *desc = data;
        int thislen = desc->fraglen + sg->length;
        int fraglen, ret;

        /* Worst case is 4 fragments: head, end of page 1, start
         * of page 2, tail.  Anything more is a bug. */
        BUG_ON(desc->fragno > 3);
        sg_set_page(&desc->frags[desc->fragno], sg_page(sg), sg->length,
                    sg->offset);
        desc->fragno++;
        desc->fraglen += sg->length;

        fraglen = thislen & 7; /* XXX hardcoded blocksize */
        thislen -= fraglen;

        if (thislen == 0)
                return 0;

        sg_mark_end(&desc->frags[desc->fragno - 1]);

        ret = crypto_blkcipher_decrypt_iv(&desc->desc, desc->frags,
                                          desc->frags, thislen);
        if (ret)
                return ret;

        sg_init_table(desc->frags, 4);

        if (fraglen) {
                sg_set_page(&desc->frags[0], sg_page(sg), fraglen,
                                sg->offset + sg->length - fraglen);
                desc->fragno = 1;
                desc->fraglen = fraglen;
        } else {
                desc->fragno = 0;
                desc->fraglen = 0;
        }
        return 0;
}

int
gss_decrypt_xdr_buf(struct crypto_blkcipher *tfm, struct xdr_buf *buf,
                    int offset)
{
        struct decryptor_desc desc;

        /* XXXJBF: */
        BUG_ON((buf->len - offset) % crypto_blkcipher_blocksize(tfm) != 0);

        memset(desc.iv, 0, sizeof(desc.iv));
        desc.desc.tfm = tfm;
        desc.desc.info = desc.iv;
        desc.desc.flags = 0;
        desc.fragno = 0;
        desc.fraglen = 0;

        sg_init_table(desc.frags, 4);

        return xdr_process_buf(buf, offset, buf->len - offset, decryptor, &desc);
}