net/sunrpc/auth_gss/gss_krb5_wrap.c

   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 <asm/scatterlist.h>
   8 #include <linux/crypto.h>
   9
  10 #ifdef RPC_DEBUG
  11 # define RPCDBG_FACILITY        RPCDBG_AUTH
  12 #endif
  13
  14 static inline int
  15 gss_krb5_padding(int blocksize, int length)
  16 {
  17         /* Most of the code is block-size independent but currently we
  18          * use only 8: */
  19         BUG_ON(blocksize != 8);
  20         return 8 - (length & 7);
  21 }
  22
  23 static inline void
  24 gss_krb5_add_padding(struct xdr_buf *buf, int offset, int blocksize)
  25 {
  26         int padding = gss_krb5_padding(blocksize, buf->len - offset);
  27         char *p;
  28         struct kvec *iov;
  29
  30         if (buf->page_len || buf->tail[0].iov_len)
  31                 iov = &buf->tail[0];
  32         else
  33                 iov = &buf->head[0];
  34         p = iov->iov_base + iov->iov_len;
  35         iov->iov_len += padding;
  36         buf->len += padding;
  37         memset(p, padding, padding);
  38 }
  39
  40 static inline int
  41 gss_krb5_remove_padding(struct xdr_buf *buf, int blocksize)
  42 {
  43         u8 *ptr;
  44         u8 pad;
  45         int len = buf->len;
  46
  47         if (len <= buf->head[0].iov_len) {
  48                 pad = *(u8 *)(buf->head[0].iov_base + len - 1);
  49                 if (pad > buf->head[0].iov_len)
  50                         return -EINVAL;
  51                 buf->head[0].iov_len -= pad;
  52                 goto out;
  53         } else
  54                 len -= buf->head[0].iov_len;
  55         if (len <= buf->page_len) {
  56                 int last = (buf->page_base + len - 1)
  57                                         >>PAGE_CACHE_SHIFT;
  58                 int offset = (buf->page_base + len - 1)
  59                                         & (PAGE_CACHE_SIZE - 1);
  60                 ptr = kmap_atomic(buf->pages[last], KM_SKB_SUNRPC_DATA);
  61                 pad = *(ptr + offset);
  62                 kunmap_atomic(ptr, KM_SKB_SUNRPC_DATA);
  63                 goto out;
  64         } else
  65                 len -= buf->page_len;
  66         BUG_ON(len > buf->tail[0].iov_len);
  67         pad = *(u8 *)(buf->tail[0].iov_base + len - 1);
  68 out:
  69         /* XXX: NOTE: we do not adjust the page lengths--they represent
  70          * a range of data in the real filesystem page cache, and we need
  71          * to know that range so the xdr code can properly place read data.
  72          * However adjusting the head length, as we do above, is harmless.
  73          * In the case of a request that fits into a single page, the server
  74          * also uses length and head length together to determine the original
  75          * start of the request to copy the request for deferal; so it's
  76          * easier on the server if we adjust head and tail length in tandem.
  77          * It's not really a problem that we don't fool with the page and
  78          * tail lengths, though--at worst badly formed xdr might lead the
  79          * server to attempt to parse the padding.
  80          * XXX: Document all these weird requirements for gss mechanism
  81          * wrap/unwrap functions. */
  82         if (pad > blocksize)
  83                 return -EINVAL;
  84         if (buf->len > pad)
  85                 buf->len -= pad;
  86         else
  87                 return -EINVAL;
  88         return 0;
  89 }
  90
  91 static inline void
  92 make_confounder(char *p, int blocksize)
  93 {
  94         static u64 i = 0;
  95         u64 *q = (u64 *)p;
  96
  97         /* rfc1964 claims this should be "random".  But all that's really
  98          * necessary is that it be unique.  And not even that is necessary in
  99          * our case since our "gssapi" implementation exists only to support
 100          * rpcsec_gss, so we know that the only buffers we will ever encrypt
 101          * already begin with a unique sequence number.  Just to hedge my bets
 102          * I'll make a half-hearted attempt at something unique, but ensuring
 103          * uniqueness would mean worrying about atomicity and rollover, and I
 104          * don't care enough. */
 105
 106         BUG_ON(blocksize != 8);
 107         *q = i++;
 108 }
 109
 110 /* Assumptions: the head and tail of inbuf are ours to play with.
 111  * The pages, however, may be real pages in the page cache and we replace
 112  * them with scratch pages from **pages before writing to them. */
 113 /* XXX: obviously the above should be documentation of wrap interface,
 114  * and shouldn't be in this kerberos-specific file. */
 115
 116 /* XXX factor out common code with seal/unseal. */
 117
 118 u32
 119 gss_wrap_kerberos(struct gss_ctx *ctx, int offset,
 120                 struct xdr_buf *buf, struct page **pages)
 121 {
 122         struct krb5_ctx         *kctx = ctx->internal_ctx_id;
 123         s32                     checksum_type;
 124         struct xdr_netobj       md5cksum = {.len = 0, .data = NULL};
 125         int                     blocksize = 0, plainlen;
 126         unsigned char           *ptr, *krb5_hdr, *msg_start;
 127         s32                     now;
 128         int                     headlen;
 129         struct page             **tmp_pages;
 130
 131         dprintk("RPC:     gss_wrap_kerberos\n");
 132
 133         now = get_seconds();
 134
 135         switch (kctx->signalg) {
 136                 case SGN_ALG_DES_MAC_MD5:
 137                         checksum_type = CKSUMTYPE_RSA_MD5;
 138                         break;
 139                 default:
 140                         dprintk("RPC:      gss_krb5_seal: kctx->signalg %d not"
 141                                 " supported\n", kctx->signalg);
 142                         goto out_err;
 143         }
 144         if (kctx->sealalg != SEAL_ALG_NONE && kctx->sealalg != SEAL_ALG_DES) {
 145                 dprintk("RPC:      gss_krb5_seal: kctx->sealalg %d not supported\n",
 146                         kctx->sealalg);
 147                 goto out_err;
 148         }
 149
 150         blocksize = crypto_tfm_alg_blocksize(kctx->enc);
 151         gss_krb5_add_padding(buf, offset, blocksize);
 152         BUG_ON((buf->len - offset) % blocksize);
 153         plainlen = blocksize + buf->len - offset;
 154
 155         headlen = g_token_size(&kctx->mech_used, 22 + plainlen) -
 156                                                 (buf->len - offset);
 157
 158         ptr = buf->head[0].iov_base + offset;
 159         /* shift data to make room for header. */
 160         /* XXX Would be cleverer to encrypt while copying. */
 161         /* XXX bounds checking, slack, etc. */
 162         memmove(ptr + headlen, ptr, buf->head[0].iov_len - offset);
 163         buf->head[0].iov_len += headlen;
 164         buf->len += headlen;
 165         BUG_ON((buf->len - offset - headlen) % blocksize);
 166
 167         g_make_token_header(&kctx->mech_used, 22 + plainlen, &ptr);
 168
 169
 170         *ptr++ = (unsigned char) ((KG_TOK_WRAP_MSG>>8)&0xff);
 171         *ptr++ = (unsigned char) (KG_TOK_WRAP_MSG&0xff);
 172
 173         /* ptr now at byte 2 of header described in rfc 1964, section 1.2.1: */
 174         krb5_hdr = ptr - 2;
 175         msg_start = krb5_hdr + 24;
 176         /* XXXJBF: */ BUG_ON(buf->head[0].iov_base + offset + headlen != msg_start + blocksize);
 177
 178         *(u16 *)(krb5_hdr + 2) = htons(kctx->signalg);
 179         memset(krb5_hdr + 4, 0xff, 4);
 180         *(u16 *)(krb5_hdr + 4) = htons(kctx->sealalg);
 181
 182         make_confounder(msg_start, blocksize);
 183
 184         /* XXXJBF: UGH!: */
 185         tmp_pages = buf->pages;
 186         buf->pages = pages;
 187         if (make_checksum(checksum_type, krb5_hdr, 8, buf,
 188                                 offset + headlen - blocksize, &md5cksum))
 189                 goto out_err;
 190         buf->pages = tmp_pages;
 191
 192         switch (kctx->signalg) {
 193         case SGN_ALG_DES_MAC_MD5:
 194                 if (krb5_encrypt(kctx->seq, NULL, md5cksum.data,
 195                                   md5cksum.data, md5cksum.len))
 196                         goto out_err;
 197                 memcpy(krb5_hdr + 16,
 198                        md5cksum.data + md5cksum.len - KRB5_CKSUM_LENGTH,
 199                        KRB5_CKSUM_LENGTH);
 200
 201                 dprintk("RPC:      make_seal_token: cksum data: \n");
 202                 print_hexl((u32 *) (krb5_hdr + 16), KRB5_CKSUM_LENGTH, 0);
 203                 break;
 204         default:
 205                 BUG();
 206         }
 207
 208         kfree(md5cksum.data);
 209
 210         /* XXX would probably be more efficient to compute checksum
 211          * and encrypt at the same time: */
 212         if ((krb5_make_seq_num(kctx->seq, kctx->initiate ? 0 : 0xff,
 213                                kctx->seq_send, krb5_hdr + 16, krb5_hdr + 8)))
 214                 goto out_err;
 215
 216         if (gss_encrypt_xdr_buf(kctx->enc, buf, offset + headlen - blocksize,
 217                                                                         pages))
 218                 goto out_err;
 219
 220         kctx->seq_send++;
 221
 222         return ((kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE);
 223 out_err:
 224         if (md5cksum.data) kfree(md5cksum.data);
 225         return GSS_S_FAILURE;
 226 }
 227
 228 u32
 229 gss_unwrap_kerberos(struct gss_ctx *ctx, int offset, struct xdr_buf *buf)
 230 {
 231         struct krb5_ctx         *kctx = ctx->internal_ctx_id;
 232         int                     signalg;
 233         int                     sealalg;
 234         s32                     checksum_type;
 235         struct xdr_netobj       md5cksum = {.len = 0, .data = NULL};
 236         s32                     now;
 237         int                     direction;
 238         s32                     seqnum;
 239         unsigned char           *ptr;
 240         int                     bodysize;
 241         u32                     ret = GSS_S_DEFECTIVE_TOKEN;
 242         void                    *data_start, *orig_start;
 243         int                     data_len;
 244         int                     blocksize;
 245
 246         dprintk("RPC:      gss_unwrap_kerberos\n");
 247
 248         ptr = (u8 *)buf->head[0].iov_base + offset;
 249         if (g_verify_token_header(&kctx->mech_used, &bodysize, &ptr,
 250                                         buf->len - offset))
 251                 goto out;
 252
 253         if ((*ptr++ != ((KG_TOK_WRAP_MSG>>8)&0xff)) ||
 254             (*ptr++ !=  (KG_TOK_WRAP_MSG    &0xff))   )
 255                 goto out;
 256
 257         /* XXX sanity-check bodysize?? */
 258
 259         /* get the sign and seal algorithms */
 260
 261         signalg = ptr[0] + (ptr[1] << 8);
 262         sealalg = ptr[2] + (ptr[3] << 8);
 263
 264         /* Sanity checks */
 265
 266         if ((ptr[4] != 0xff) || (ptr[5] != 0xff))
 267                 goto out;
 268
 269         if (sealalg == 0xffff)
 270                 goto out;
 271
 272         /* in the current spec, there is only one valid seal algorithm per
 273            key type, so a simple comparison is ok */
 274
 275         if (sealalg != kctx->sealalg)
 276                 goto out;
 277
 278         /* there are several mappings of seal algorithms to sign algorithms,
 279            but few enough that we can try them all. */
 280
 281         if ((kctx->sealalg == SEAL_ALG_NONE && signalg > 1) ||
 282             (kctx->sealalg == SEAL_ALG_1 && signalg != SGN_ALG_3) ||
 283             (kctx->sealalg == SEAL_ALG_DES3KD &&
 284              signalg != SGN_ALG_HMAC_SHA1_DES3_KD))
 285                 goto out;
 286
 287         if (gss_decrypt_xdr_buf(kctx->enc, buf,
 288                         ptr + 22 - (unsigned char *)buf->head[0].iov_base))
 289                 goto out;
 290
 291         /* compute the checksum of the message */
 292
 293         /* initialize the the cksum */
 294         switch (signalg) {
 295         case SGN_ALG_DES_MAC_MD5:
 296                 checksum_type = CKSUMTYPE_RSA_MD5;
 297                 break;
 298         default:
 299                 ret = GSS_S_DEFECTIVE_TOKEN;
 300                 goto out;
 301         }
 302
 303         switch (signalg) {
 304         case SGN_ALG_DES_MAC_MD5:
 305                 ret = make_checksum(checksum_type, ptr - 2, 8, buf,
 306                          ptr + 22 - (unsigned char *)buf->head[0].iov_base, &md5cksum);
 307                 if (ret)
 308                         goto out;
 309
 310                 ret = krb5_encrypt(kctx->seq, NULL, md5cksum.data,
 311                                    md5cksum.data, md5cksum.len);
 312                 if (ret)
 313                         goto out;
 314
 315                 if (memcmp(md5cksum.data + 8, ptr + 14, 8)) {
 316                         ret = GSS_S_BAD_SIG;
 317                         goto out;
 318                 }
 319                 break;
 320         default:
 321                 ret = GSS_S_DEFECTIVE_TOKEN;
 322                 goto out;
 323         }
 324
 325         /* it got through unscathed.  Make sure the context is unexpired */
 326
 327         now = get_seconds();
 328
 329         ret = GSS_S_CONTEXT_EXPIRED;
 330         if (now > kctx->endtime)
 331                 goto out;
 332
 333         /* do sequencing checks */
 334
 335         ret = GSS_S_BAD_SIG;
 336         if ((ret = krb5_get_seq_num(kctx->seq, ptr + 14, ptr + 6, &direction,
 337                                     &seqnum)))
 338                 goto out;
 339
 340         if ((kctx->initiate && direction != 0xff) ||
 341             (!kctx->initiate && direction != 0))
 342                 goto out;
 343
 344         /* Copy the data back to the right position.  XXX: Would probably be
 345          * better to copy and encrypt at the same time. */
 346
 347         blocksize = crypto_tfm_alg_blocksize(kctx->enc);
 348         data_start = ptr + 22 + blocksize;
 349         orig_start = buf->head[0].iov_base + offset;
 350         data_len = (buf->head[0].iov_base + buf->head[0].iov_len) - data_start;
 351         memmove(orig_start, data_start, data_len);
 352         buf->head[0].iov_len -= (data_start - orig_start);
 353         buf->len -= (data_start - orig_start);
 354
 355         ret = GSS_S_DEFECTIVE_TOKEN;
 356         if (gss_krb5_remove_padding(buf, blocksize))
 357                 goto out;
 358
 359         ret = GSS_S_COMPLETE;
 360 out:
 361         if (md5cksum.data) kfree(md5cksum.data);
 362         return ret;
 363 }