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         char                    cksumdata[16];
 125         struct xdr_netobj       md5cksum = {.len = 0, .data = cksumdata};
 126         int                     blocksize = 0, plainlen;
 127         unsigned char           *ptr, *krb5_hdr, *msg_start;
 128         s32                     now;
 129         int                     headlen;
 130         struct page             **tmp_pages;
 131         u32                     seq_send;
 132
 133         dprintk("RPC:     gss_wrap_kerberos\n");
 134
 135         now = get_seconds();
 136
 137         switch (kctx->signalg) {
 138                 case SGN_ALG_DES_MAC_MD5:
 139                         checksum_type = CKSUMTYPE_RSA_MD5;
 140                         break;
 141                 default:
 142                         dprintk("RPC:      gss_krb5_seal: kctx->signalg %d not"
 143                                 " supported\n", kctx->signalg);
 144                         goto out_err;
 145         }
 146         if (kctx->sealalg != SEAL_ALG_NONE && kctx->sealalg != SEAL_ALG_DES) {
 147                 dprintk("RPC:      gss_krb5_seal: kctx->sealalg %d not supported\n",
 148                         kctx->sealalg);
 149                 goto out_err;
 150         }
 151
 152         blocksize = crypto_tfm_alg_blocksize(kctx->enc);
 153         gss_krb5_add_padding(buf, offset, blocksize);
 154         BUG_ON((buf->len - offset) % blocksize);
 155         plainlen = blocksize + buf->len - offset;
 156
 157         headlen = g_token_size(&kctx->mech_used, 22 + plainlen) -
 158                                                 (buf->len - offset);
 159
 160         ptr = buf->head[0].iov_base + offset;
 161         /* shift data to make room for header. */
 162         /* XXX Would be cleverer to encrypt while copying. */
 163         /* XXX bounds checking, slack, etc. */
 164         memmove(ptr + headlen, ptr, buf->head[0].iov_len - offset);
 165         buf->head[0].iov_len += headlen;
 166         buf->len += headlen;
 167         BUG_ON((buf->len - offset - headlen) % blocksize);
 168
 169         g_make_token_header(&kctx->mech_used, 22 + plainlen, &ptr);
 170
 171
 172         *ptr++ = (unsigned char) ((KG_TOK_WRAP_MSG>>8)&0xff);
 173         *ptr++ = (unsigned char) (KG_TOK_WRAP_MSG&0xff);
 174
 175         /* ptr now at byte 2 of header described in rfc 1964, section 1.2.1: */
 176         krb5_hdr = ptr - 2;
 177         msg_start = krb5_hdr + 24;
 178         /* XXXJBF: */ BUG_ON(buf->head[0].iov_base + offset + headlen != msg_start + blocksize);
 179
 180         *(u16 *)(krb5_hdr + 2) = htons(kctx->signalg);
 181         memset(krb5_hdr + 4, 0xff, 4);
 182         *(u16 *)(krb5_hdr + 4) = htons(kctx->sealalg);
 183
 184         make_confounder(msg_start, blocksize);
 185
 186         /* XXXJBF: UGH!: */
 187         tmp_pages = buf->pages;
 188         buf->pages = pages;
 189         if (make_checksum(checksum_type, krb5_hdr, 8, buf,
 190                                 offset + headlen - blocksize, &md5cksum))
 191                 goto out_err;
 192         buf->pages = tmp_pages;
 193
 194         switch (kctx->signalg) {
 195         case SGN_ALG_DES_MAC_MD5:
 196                 if (krb5_encrypt(kctx->seq, NULL, md5cksum.data,
 197                                   md5cksum.data, md5cksum.len))
 198                         goto out_err;
 199                 memcpy(krb5_hdr + 16,
 200                        md5cksum.data + md5cksum.len - KRB5_CKSUM_LENGTH,
 201                        KRB5_CKSUM_LENGTH);
 202
 203                 dprintk("RPC:      make_seal_token: cksum data: \n");
 204                 print_hexl((u32 *) (krb5_hdr + 16), KRB5_CKSUM_LENGTH, 0);
 205                 break;
 206         default:
 207                 BUG();
 208         }
 209
 210         spin_lock(&krb5_seq_lock);
 211         seq_send = kctx->seq_send++;
 212         spin_unlock(&krb5_seq_lock);
 213
 214         /* XXX would probably be more efficient to compute checksum
 215          * and encrypt at the same time: */
 216         if ((krb5_make_seq_num(kctx->seq, kctx->initiate ? 0 : 0xff,
 217                                seq_send, krb5_hdr + 16, krb5_hdr + 8)))
 218                 goto out_err;
 219
 220         if (gss_encrypt_xdr_buf(kctx->enc, buf, offset + headlen - blocksize,
 221                                                                         pages))
 222                 goto out_err;
 223
 224         return ((kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE);
 225 out_err:
 226         return GSS_S_FAILURE;
 227 }
 228
 229 u32
 230 gss_unwrap_kerberos(struct gss_ctx *ctx, int offset, struct xdr_buf *buf)
 231 {
 232         struct krb5_ctx         *kctx = ctx->internal_ctx_id;
 233         int                     signalg;
 234         int                     sealalg;
 235         s32                     checksum_type;
 236         char                    cksumdata[16];
 237         struct xdr_netobj       md5cksum = {.len = 0, .data = cksumdata};
 238         s32                     now;
 239         int                     direction;
 240         s32                     seqnum;
 241         unsigned char           *ptr;
 242         int                     bodysize;
 243         u32                     ret = GSS_S_DEFECTIVE_TOKEN;
 244         void                    *data_start, *orig_start;
 245         int                     data_len;
 246         int                     blocksize;
 247
 248         dprintk("RPC:      gss_unwrap_kerberos\n");
 249
 250         ptr = (u8 *)buf->head[0].iov_base + offset;
 251         if (g_verify_token_header(&kctx->mech_used, &bodysize, &ptr,
 252                                         buf->len - offset))
 253                 goto out;
 254
 255         if ((*ptr++ != ((KG_TOK_WRAP_MSG>>8)&0xff)) ||
 256             (*ptr++ !=  (KG_TOK_WRAP_MSG    &0xff))   )
 257                 goto out;
 258
 259         /* XXX sanity-check bodysize?? */
 260
 261         /* get the sign and seal algorithms */
 262
 263         signalg = ptr[0] + (ptr[1] << 8);
 264         sealalg = ptr[2] + (ptr[3] << 8);
 265
 266         /* Sanity checks */
 267
 268         if ((ptr[4] != 0xff) || (ptr[5] != 0xff))
 269                 goto out;
 270
 271         if (sealalg == 0xffff)
 272                 goto out;
 273
 274         /* in the current spec, there is only one valid seal algorithm per
 275            key type, so a simple comparison is ok */
 276
 277         if (sealalg != kctx->sealalg)
 278                 goto out;
 279
 280         /* there are several mappings of seal algorithms to sign algorithms,
 281            but few enough that we can try them all. */
 282
 283         if ((kctx->sealalg == SEAL_ALG_NONE && signalg > 1) ||
 284             (kctx->sealalg == SEAL_ALG_1 && signalg != SGN_ALG_3) ||
 285             (kctx->sealalg == SEAL_ALG_DES3KD &&
 286              signalg != SGN_ALG_HMAC_SHA1_DES3_KD))
 287                 goto out;
 288
 289         if (gss_decrypt_xdr_buf(kctx->enc, buf,
 290                         ptr + 22 - (unsigned char *)buf->head[0].iov_base))
 291                 goto out;
 292
 293         /* compute the checksum of the message */
 294
 295         /* initialize the the cksum */
 296         switch (signalg) {
 297         case SGN_ALG_DES_MAC_MD5:
 298                 checksum_type = CKSUMTYPE_RSA_MD5;
 299                 break;
 300         default:
 301                 ret = GSS_S_DEFECTIVE_TOKEN;
 302                 goto out;
 303         }
 304
 305         switch (signalg) {
 306         case SGN_ALG_DES_MAC_MD5:
 307                 ret = make_checksum(checksum_type, ptr - 2, 8, buf,
 308                          ptr + 22 - (unsigned char *)buf->head[0].iov_base, &md5cksum);
 309                 if (ret)
 310                         goto out;
 311
 312                 ret = krb5_encrypt(kctx->seq, NULL, md5cksum.data,
 313                                    md5cksum.data, md5cksum.len);
 314                 if (ret)
 315                         goto out;
 316
 317                 if (memcmp(md5cksum.data + 8, ptr + 14, 8)) {
 318                         ret = GSS_S_BAD_SIG;
 319                         goto out;
 320                 }
 321                 break;
 322         default:
 323                 ret = GSS_S_DEFECTIVE_TOKEN;
 324                 goto out;
 325         }
 326
 327         /* it got through unscathed.  Make sure the context is unexpired */
 328
 329         now = get_seconds();
 330
 331         ret = GSS_S_CONTEXT_EXPIRED;
 332         if (now > kctx->endtime)
 333                 goto out;
 334
 335         /* do sequencing checks */
 336
 337         ret = GSS_S_BAD_SIG;
 338         if ((ret = krb5_get_seq_num(kctx->seq, ptr + 14, ptr + 6, &direction,
 339                                     &seqnum)))
 340                 goto out;
 341
 342         if ((kctx->initiate && direction != 0xff) ||
 343             (!kctx->initiate && direction != 0))
 344                 goto out;
 345
 346         /* Copy the data back to the right position.  XXX: Would probably be
 347          * better to copy and encrypt at the same time. */
 348
 349         blocksize = crypto_tfm_alg_blocksize(kctx->enc);
 350         data_start = ptr + 22 + blocksize;
 351         orig_start = buf->head[0].iov_base + offset;
 352         data_len = (buf->head[0].iov_base + buf->head[0].iov_len) - data_start;
 353         memmove(orig_start, data_start, data_len);
 354         buf->head[0].iov_len -= (data_start - orig_start);
 355         buf->len -= (data_start - orig_start);
 356
 357         ret = GSS_S_DEFECTIVE_TOKEN;
 358         if (gss_krb5_remove_padding(buf, blocksize))
 359                 goto out;
 360
 361         ret = GSS_S_COMPLETE;
 362 out:
 363         return ret;
 364 }