LXR linux/net/sunrpc/auth_gss/gss_krb5

   1#include <linux/types.h>
   2#include <linux/slab.h>
   3#include <linux/jiffies.h>
   4#include <linux/sunrpc/gss_krb5.h>
   5#include <linux/random.h>
   6#include <linux/pagemap.h>
   7#include <linux/crypto.h>
   8
   9#ifdef RPC_DEBUG
  10# define RPCDBG_FACILITY        RPCDBG_AUTH
  11#endif
  12
  13static inline int
  14gss_krb5_padding(int blocksize, int length)
  15{
  16        /* Most of the code is block-size independent but currently we
  17         * use only 8: */
  18        BUG_ON(blocksize != 8);
  19        return 8 - (length & 7);
  20}
  21
  22static inline void
  23gss_krb5_add_padding(struct xdr_buf *buf, int offset, int blocksize)
  24{
  25        int padding = gss_krb5_padding(blocksize, buf->len - offset);
  26        char *p;
  27        struct kvec *iov;
  28
  29        if (buf->page_len || buf->tail[0].iov_len)
  30                iov = &buf->tail[0];
  31        else
  32                iov = &buf->head[0];
  33        p = iov->iov_base + iov->iov_len;
  34        iov->iov_len += padding;
  35        buf->len += padding;
  36        memset(p, padding, padding);
  37}
  38
  39static inline int
  40gss_krb5_remove_padding(struct xdr_buf *buf, int blocksize)
  41{
  42        u8 *ptr;
  43        u8 pad;
  44        size_t len = buf->len;
  45
  46        if (len <= buf->head[0].iov_len) {
  47                pad = *(u8 *)(buf->head[0].iov_base + len - 1);
  48                if (pad > buf->head[0].iov_len)
  49                        return -EINVAL;
  50                buf->head[0].iov_len -= pad;
  51                goto out;
  52        } else
  53                len -= buf->head[0].iov_len;
  54        if (len <= buf->page_len) {
  55                unsigned int last = (buf->page_base + len - 1)
  56                                        >>PAGE_CACHE_SHIFT;
  57                unsigned int offset = (buf->page_base + len - 1)
  58                                        & (PAGE_CACHE_SIZE - 1);
  59                ptr = kmap_atomic(buf->pages[last], KM_USER0);
  60                pad = *(ptr + offset);
  61                kunmap_atomic(ptr, KM_USER0);
  62                goto out;
  63        } else
  64                len -= buf->page_len;
  65        BUG_ON(len > buf->tail[0].iov_len);
  66        pad = *(u8 *)(buf->tail[0].iov_base + len - 1);
  67out:
  68        /* XXX: NOTE: we do not adjust the page lengths--they represent
  69         * a range of data in the real filesystem page cache, and we need
  70         * to know that range so the xdr code can properly place read data.
  71         * However adjusting the head length, as we do above, is harmless.
  72         * In the case of a request that fits into a single page, the server
  73         * also uses length and head length together to determine the original
  74         * start of the request to copy the request for deferal; so it's
  75         * easier on the server if we adjust head and tail length in tandem.
  76         * It's not really a problem that we don't fool with the page and
  77         * tail lengths, though--at worst badly formed xdr might lead the
  78         * server to attempt to parse the padding.
  79         * XXX: Document all these weird requirements for gss mechanism
  80         * wrap/unwrap functions. */
  81        if (pad > blocksize)
  82                return -EINVAL;
  83        if (buf->len > pad)
  84                buf->len -= pad;
  85        else
  86                return -EINVAL;
  87        return 0;
  88}
  89
  90static inline void
  91make_confounder(char *p, int blocksize)
  92{
  93        static u64 i = 0;
  94        u64 *q = (u64 *)p;
  95
  96        /* rfc1964 claims this should be "random".  But all that's really
  97         * necessary is that it be unique.  And not even that is necessary in
  98         * our case since our "gssapi" implementation exists only to support
  99         * rpcsec_gss, so we know that the only buffers we will ever encrypt
 100         * already begin with a unique sequence number.  Just to hedge my bets
 101         * I'll make a half-hearted attempt at something unique, but ensuring
 102         * uniqueness would mean worrying about atomicity and rollover, and I
 103         * don't care enough. */
 104
 105        BUG_ON(blocksize != 8);
 106        *q = i++;
 107}
 108
 109/* Assumptions: the head and tail of inbuf are ours to play with.
 110 * The pages, however, may be real pages in the page cache and we replace
 111 * them with scratch pages from **pages before writing to them. */
 112/* XXX: obviously the above should be documentation of wrap interface,
 113 * and shouldn't be in this kerberos-specific file. */
 114
 115/* XXX factor out common code with seal/unseal. */
 116
 117u32
 118gss_wrap_kerberos(struct gss_ctx *ctx, int offset,
 119                struct xdr_buf *buf, struct page **pages)
 120{
 121        struct krb5_ctx         *kctx = ctx->internal_ctx_id;
 122        char                    cksumdata[16];
 123        struct xdr_netobj       md5cksum = {.len = 0, .data = cksumdata};
 124        int                     blocksize = 0, plainlen;
 125        unsigned char           *ptr, *krb5_hdr, *msg_start;
 126        s32                     now;
 127        int                     headlen;
 128        struct page             **tmp_pages;
 129        u32                     seq_send;
 130
 131        dprintk("RPC:       gss_wrap_kerberos\n");
 132
 133        now = get_seconds();
 134
 135        blocksize = crypto_blkcipher_blocksize(kctx->enc);
 136        gss_krb5_add_padding(buf, offset, blocksize);
 137        BUG_ON((buf->len - offset) % blocksize);
 138        plainlen = blocksize + buf->len - offset;
 139
 140        headlen = g_token_size(&kctx->mech_used, 22 + plainlen) -
 141                                                (buf->len - offset);
 142
 143        ptr = buf->head[0].iov_base + offset;
 144        /* shift data to make room for header. */
 145        /* XXX Would be cleverer to encrypt while copying. */
 146        /* XXX bounds checking, slack, etc. */
 147        memmove(ptr + headlen, ptr, buf->head[0].iov_len - offset);
 148        buf->head[0].iov_len += headlen;
 149        buf->len += headlen;
 150        BUG_ON((buf->len - offset - headlen) % blocksize);
 151
 152        g_make_token_header(&kctx->mech_used, 22 + plainlen, &ptr);
 153
 154
 155        *ptr++ = (unsigned char) ((KG_TOK_WRAP_MSG>>8)&0xff);
 156        *ptr++ = (unsigned char) (KG_TOK_WRAP_MSG&0xff);
 157
 158        /* ptr now at byte 2 of header described in rfc 1964, section 1.2.1: */
 159        krb5_hdr = ptr - 2;
 160        msg_start = krb5_hdr + 24;
 161
 162        *(__be16 *)(krb5_hdr + 2) = htons(SGN_ALG_DES_MAC_MD5);
 163        memset(krb5_hdr + 4, 0xff, 4);
 164        *(__be16 *)(krb5_hdr + 4) = htons(SEAL_ALG_DES);
 165
 166        make_confounder(msg_start, blocksize);
 167
 168        /* XXXJBF: UGH!: */
 169        tmp_pages = buf->pages;
 170        buf->pages = pages;
 171        if (make_checksum("md5", krb5_hdr, 8, buf,
 172                                offset + headlen - blocksize, &md5cksum))
 173                return GSS_S_FAILURE;
 174        buf->pages = tmp_pages;
 175
 176        if (krb5_encrypt(kctx->seq, NULL, md5cksum.data,
 177                          md5cksum.data, md5cksum.len))
 178                return GSS_S_FAILURE;
 179        memcpy(krb5_hdr + 16,
 180               md5cksum.data + md5cksum.len - KRB5_CKSUM_LENGTH,
 181               KRB5_CKSUM_LENGTH);
 182
 183        spin_lock(&krb5_seq_lock);
 184        seq_send = kctx->seq_send++;
 185        spin_unlock(&krb5_seq_lock);
 186
 187        /* XXX would probably be more efficient to compute checksum
 188         * and encrypt at the same time: */
 189        if ((krb5_make_seq_num(kctx->seq, kctx->initiate ? 0 : 0xff,
 190                               seq_send, krb5_hdr + 16, krb5_hdr + 8)))
 191                return GSS_S_FAILURE;
 192
 193        if (gss_encrypt_xdr_buf(kctx->enc, buf, offset + headlen - blocksize,
 194                                                                        pages))
 195                return GSS_S_FAILURE;
 196
 197        return (kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE;
 198}
 199
 200u32
 201gss_unwrap_kerberos(struct gss_ctx *ctx, int offset, struct xdr_buf *buf)
 202{
 203        struct krb5_ctx         *kctx = ctx->internal_ctx_id;
 204        int                     signalg;
 205        int                     sealalg;
 206        char                    cksumdata[16];
 207        struct xdr_netobj       md5cksum = {.len = 0, .data = cksumdata};
 208        s32                     now;
 209        int                     direction;
 210        s32                     seqnum;
 211        unsigned char           *ptr;
 212        int                     bodysize;
 213        void                    *data_start, *orig_start;
 214        int                     data_len;
 215        int                     blocksize;
 216
 217        dprintk("RPC:       gss_unwrap_kerberos\n");
 218
 219        ptr = (u8 *)buf->head[0].iov_base + offset;
 220        if (g_verify_token_header(&kctx->mech_used, &bodysize, &ptr,
 221                                        buf->len - offset))
 222                return GSS_S_DEFECTIVE_TOKEN;
 223
 224        if ((*ptr++ != ((KG_TOK_WRAP_MSG>>8)&0xff)) ||
 225            (*ptr++ !=  (KG_TOK_WRAP_MSG    &0xff))   )
 226                return GSS_S_DEFECTIVE_TOKEN;
 227
 228        /* XXX sanity-check bodysize?? */
 229
 230        /* get the sign and seal algorithms */
 231
 232        signalg = ptr[0] + (ptr[1] << 8);
 233        if (signalg != SGN_ALG_DES_MAC_MD5)
 234                return GSS_S_DEFECTIVE_TOKEN;
 235
 236        sealalg = ptr[2] + (ptr[3] << 8);
 237        if (sealalg != SEAL_ALG_DES)
 238                return GSS_S_DEFECTIVE_TOKEN;
 239
 240        if ((ptr[4] != 0xff) || (ptr[5] != 0xff))
 241                return GSS_S_DEFECTIVE_TOKEN;
 242
 243        if (gss_decrypt_xdr_buf(kctx->enc, buf,
 244                        ptr + 22 - (unsigned char *)buf->head[0].iov_base))
 245                return GSS_S_DEFECTIVE_TOKEN;
 246
 247        if (make_checksum("md5", ptr - 2, 8, buf,
 248                 ptr + 22 - (unsigned char *)buf->head[0].iov_base, &md5cksum))
 249                return GSS_S_FAILURE;
 250
 251        if (krb5_encrypt(kctx->seq, NULL, md5cksum.data,
 252                           md5cksum.data, md5cksum.len))
 253                return GSS_S_FAILURE;
 254
 255        if (memcmp(md5cksum.data + 8, ptr + 14, 8))
 256                return GSS_S_BAD_SIG;
 257
 258        /* it got through unscathed.  Make sure the context is unexpired */
 259
 260        now = get_seconds();
 261
 262        if (now > kctx->endtime)
 263                return GSS_S_CONTEXT_EXPIRED;
 264
 265        /* do sequencing checks */
 266
 267        if (krb5_get_seq_num(kctx->seq, ptr + 14, ptr + 6, &direction,
 268                                    &seqnum))
 269                return GSS_S_BAD_SIG;
 270
 271        if ((kctx->initiate && direction != 0xff) ||
 272            (!kctx->initiate && direction != 0))
 273                return GSS_S_BAD_SIG;
 274
 275        /* Copy the data back to the right position.  XXX: Would probably be
 276         * better to copy and encrypt at the same time. */
 277
 278        blocksize = crypto_blkcipher_blocksize(kctx->enc);
 279        data_start = ptr + 22 + blocksize;
 280        orig_start = buf->head[0].iov_base + offset;
 281        data_len = (buf->head[0].iov_base + buf->head[0].iov_len) - data_start;
 282        memmove(orig_start, data_start, data_len);
 283        buf->head[0].iov_len -= (data_start - orig_start);
 284        buf->len -= (data_start - orig_start);
 285
 286        if (gss_krb5_remove_padding(buf, blocksize))
 287                return GSS_S_DEFECTIVE_TOKEN;
 288
 289        return GSS_S_COMPLETE;
 290}
 291