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