net/sunrpc/auth_gss/gss_krb5_wrap.c

   1 #include <linux/types.h>
   2 #include <linux/jiffies.h>
   3 #include <linux/sunrpc/gss_krb5.h>
   4 #include <linux/random.h>
   5 #include <linux/pagemap.h>
   6 #include <linux/crypto.h>
   7
   8 #ifdef RPC_DEBUG
   9 # define RPCDBG_FACILITY        RPCDBG_AUTH
  10 #endif
  11
  12 static inline int
  13 gss_krb5_padding(int blocksize, int length)
  14 {
  15         /* Most of the code is block-size independent but currently we
  16          * use only 8: */
  17         BUG_ON(blocksize != 8);
  18         return 8 - (length & 7);
  19 }
  20
  21 static inline void
  22 gss_krb5_add_padding(struct xdr_buf *buf, int offset, int blocksize)
  23 {
  24         int padding = gss_krb5_padding(blocksize, buf->len - offset);
  25         char *p;
  26         struct kvec *iov;
  27
  28         if (buf->page_len || buf->tail[0].iov_len)
  29                 iov = &buf->tail[0];
  30         else
  31                 iov = &buf->head[0];
  32         p = iov->iov_base + iov->iov_len;
  33         iov->iov_len += padding;
  34         buf->len += padding;
  35         memset(p, padding, padding);
  36 }
  37
  38 static inline int
  39 gss_krb5_remove_padding(struct xdr_buf *buf, int blocksize)
  40 {
  41         u8 *ptr;
  42         u8 pad;
  43         size_t len = buf->len;
  44
  45         if (len <= buf->head[0].iov_len) {
  46                 pad = *(u8 *)(buf->head[0].iov_base + len - 1);
  47                 if (pad > buf->head[0].iov_len)
  48                         return -EINVAL;
  49                 buf->head[0].iov_len -= pad;
  50                 goto out;
  51         } else
  52                 len -= buf->head[0].iov_len;
  53         if (len <= buf->page_len) {
  54                 unsigned int last = (buf->page_base + len - 1)
  55                                         >>PAGE_CACHE_SHIFT;
  56                 unsigned int offset = (buf->page_base + len - 1)
  57                                         & (PAGE_CACHE_SIZE - 1);
  58                 ptr = kmap_atomic(buf->pages[last], KM_USER0);
  59                 pad = *(ptr + offset);
  60                 kunmap_atomic(ptr, KM_USER0);
  61                 goto out;
  62         } else
  63                 len -= buf->page_len;
  64         BUG_ON(len > buf->tail[0].iov_len);
  65         pad = *(u8 *)(buf->tail[0].iov_base + len - 1);
  66 out:
  67         /* XXX: NOTE: we do not adjust the page lengths--they represent
  68          * a range of data in the real filesystem page cache, and we need
  69          * to know that range so the xdr code can properly place read data.
  70          * However adjusting the head length, as we do above, is harmless.
  71          * In the case of a request that fits into a single page, the server
  72          * also uses length and head length together to determine the original
  73          * start of the request to copy the request for deferal; so it's
  74          * easier on the server if we adjust head and tail length in tandem.
  75          * It's not really a problem that we don't fool with the page and
  76          * tail lengths, though--at worst badly formed xdr might lead the
  77          * server to attempt to parse the padding.
  78          * XXX: Document all these weird requirements for gss mechanism
  79          * wrap/unwrap functions. */
  80         if (pad > blocksize)
  81                 return -EINVAL;
  82         if (buf->len > pad)
  83                 buf->len -= pad;
  84         else
  85                 return -EINVAL;
  86         return 0;
  87 }
  88
  89 static void
  90 make_confounder(char *p, u32 conflen)
  91 {
  92         static u64 i = 0;
  93         u64 *q = (u64 *)p;
  94
  95         /* rfc1964 claims this should be "random".  But all that's really
  96          * necessary is that it be unique.  And not even that is necessary in
  97          * our case since our "gssapi" implementation exists only to support
  98          * rpcsec_gss, so we know that the only buffers we will ever encrypt
  99          * already begin with a unique sequence number.  Just to hedge my bets
 100          * I'll make a half-hearted attempt at something unique, but ensuring
 101          * uniqueness would mean worrying about atomicity and rollover, and I
 102          * don't care enough. */
 103
 104         /* initialize to random value */
 105         if (i == 0) {
 106                 i = random32();
 107                 i = (i << 32) | random32();
 108         }
 109
 110         switch (conflen) {
 111         case 16:
 112                 *q++ = i++;
 113                 /* fall through */
 114         case 8:
 115                 *q++ = i++;
 116                 break;
 117         default:
 118                 BUG();
 119         }
 120 }
 121
 122 /* Assumptions: the head and tail of inbuf are ours to play with.
 123  * The pages, however, may be real pages in the page cache and we replace
 124  * them with scratch pages from **pages before writing to them. */
 125 /* XXX: obviously the above should be documentation of wrap interface,
 126  * and shouldn't be in this kerberos-specific file. */
 127
 128 /* XXX factor out common code with seal/unseal. */
 129
 130 u32
 131 gss_wrap_kerberos(struct gss_ctx *ctx, int offset,
 132                 struct xdr_buf *buf, struct page **pages)
 133 {
 134         struct krb5_ctx         *kctx = ctx->internal_ctx_id;
 135         char                    cksumdata[16];
 136         struct xdr_netobj       md5cksum = {.len = 0, .data = cksumdata};
 137         int                     blocksize = 0, plainlen;
 138         unsigned char           *ptr, *msg_start;
 139         s32                     now;
 140         int                     headlen;
 141         struct page             **tmp_pages;
 142         u32                     seq_send;
 143
 144         dprintk("RPC:       gss_wrap_kerberos\n");
 145
 146         now = get_seconds();
 147
 148         blocksize = crypto_blkcipher_blocksize(kctx->enc);
 149         gss_krb5_add_padding(buf, offset, blocksize);
 150         BUG_ON((buf->len - offset) % blocksize);
 151         plainlen = blocksize + buf->len - offset;
 152
 153         headlen = g_token_size(&kctx->mech_used, 24 + plainlen) -
 154                                                 (buf->len - offset);
 155
 156         ptr = buf->head[0].iov_base + offset;
 157         /* shift data to make room for header. */
 158         /* XXX Would be cleverer to encrypt while copying. */
 159         /* XXX bounds checking, slack, etc. */
 160         memmove(ptr + headlen, ptr, buf->head[0].iov_len - offset);
 161         buf->head[0].iov_len += headlen;
 162         buf->len += headlen;
 163         BUG_ON((buf->len - offset - headlen) % blocksize);
 164
 165         g_make_token_header(&kctx->mech_used,
 166                                 GSS_KRB5_TOK_HDR_LEN + 8 + plainlen, &ptr);
 167
 168
 169         /* ptr now at header described in rfc 1964, section 1.2.1: */
 170         ptr[0] = (unsigned char) ((KG_TOK_WRAP_MSG >> 8) & 0xff);
 171         ptr[1] = (unsigned char) (KG_TOK_WRAP_MSG & 0xff);
 172
 173         msg_start = ptr + 24;
 174
 175         *(__be16 *)(ptr + 2) = htons(SGN_ALG_DES_MAC_MD5);
 176         memset(ptr + 4, 0xff, 4);
 177         *(__be16 *)(ptr + 4) = htons(SEAL_ALG_DES);
 178
 179         make_confounder(msg_start, blocksize);
 180
 181         /* XXXJBF: UGH!: */
 182         tmp_pages = buf->pages;
 183         buf->pages = pages;
 184         if (make_checksum("md5", ptr, 8, buf,
 185                                 offset + headlen - blocksize, &md5cksum))
 186                 return GSS_S_FAILURE;
 187         buf->pages = tmp_pages;
 188
 189         if (krb5_encrypt(kctx->seq, NULL, md5cksum.data,
 190                           md5cksum.data, md5cksum.len))
 191                 return GSS_S_FAILURE;
 192         memcpy(ptr + GSS_KRB5_TOK_HDR_LEN, md5cksum.data + md5cksum.len - 8, 8);
 193
 194         spin_lock(&krb5_seq_lock);
 195         seq_send = kctx->seq_send++;
 196         spin_unlock(&krb5_seq_lock);
 197
 198         /* XXX would probably be more efficient to compute checksum
 199          * and encrypt at the same time: */
 200         if ((krb5_make_seq_num(kctx->seq, kctx->initiate ? 0 : 0xff,
 201                                seq_send, ptr + GSS_KRB5_TOK_HDR_LEN, ptr + 8)))
 202                 return GSS_S_FAILURE;
 203
 204         if (gss_encrypt_xdr_buf(kctx->enc, buf, offset + headlen - blocksize,
 205                                                                         pages))
 206                 return GSS_S_FAILURE;
 207
 208         return (kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE;
 209 }
 210
 211 u32
 212 gss_unwrap_kerberos(struct gss_ctx *ctx, int offset, struct xdr_buf *buf)
 213 {
 214         struct krb5_ctx         *kctx = ctx->internal_ctx_id;
 215         int                     signalg;
 216         int                     sealalg;
 217         char                    cksumdata[16];
 218         struct xdr_netobj       md5cksum = {.len = 0, .data = cksumdata};
 219         s32                     now;
 220         int                     direction;
 221         s32                     seqnum;
 222         unsigned char           *ptr;
 223         int                     bodysize;
 224         void                    *data_start, *orig_start;
 225         int                     data_len;
 226         int                     blocksize;
 227
 228         dprintk("RPC:       gss_unwrap_kerberos\n");
 229
 230         ptr = (u8 *)buf->head[0].iov_base + offset;
 231         if (g_verify_token_header(&kctx->mech_used, &bodysize, &ptr,
 232                                         buf->len - offset))
 233                 return GSS_S_DEFECTIVE_TOKEN;
 234
 235         if ((ptr[0] != ((KG_TOK_WRAP_MSG >> 8) & 0xff)) ||
 236             (ptr[1] !=  (KG_TOK_WRAP_MSG & 0xff)))
 237                 return GSS_S_DEFECTIVE_TOKEN;
 238
 239         /* XXX sanity-check bodysize?? */
 240
 241         /* get the sign and seal algorithms */
 242
 243         signalg = ptr[2] + (ptr[3] << 8);
 244         if (signalg != SGN_ALG_DES_MAC_MD5)
 245                 return GSS_S_DEFECTIVE_TOKEN;
 246
 247         sealalg = ptr[4] + (ptr[5] << 8);
 248         if (sealalg != SEAL_ALG_DES)
 249                 return GSS_S_DEFECTIVE_TOKEN;
 250
 251         if ((ptr[6] != 0xff) || (ptr[7] != 0xff))
 252                 return GSS_S_DEFECTIVE_TOKEN;
 253
 254         if (gss_decrypt_xdr_buf(kctx->enc, buf,
 255                         ptr + GSS_KRB5_TOK_HDR_LEN + 8 - (unsigned char *)buf->head[0].iov_base))
 256                 return GSS_S_DEFECTIVE_TOKEN;
 257
 258         if (make_checksum("md5", ptr, 8, buf,
 259                  ptr + GSS_KRB5_TOK_HDR_LEN + 8 - (unsigned char *)buf->head[0].iov_base, &md5cksum))
 260                 return GSS_S_FAILURE;
 261
 262         if (krb5_encrypt(kctx->seq, NULL, md5cksum.data,
 263                            md5cksum.data, md5cksum.len))
 264                 return GSS_S_FAILURE;
 265
 266         if (memcmp(md5cksum.data + 8, ptr + GSS_KRB5_TOK_HDR_LEN, 8))
 267                 return GSS_S_BAD_SIG;
 268
 269         /* it got through unscathed.  Make sure the context is unexpired */
 270
 271         now = get_seconds();
 272
 273         if (now > kctx->endtime)
 274                 return GSS_S_CONTEXT_EXPIRED;
 275
 276         /* do sequencing checks */
 277
 278         if (krb5_get_seq_num(kctx->seq, ptr + GSS_KRB5_TOK_HDR_LEN, ptr + 8,
 279                                     &direction, &seqnum))
 280                 return GSS_S_BAD_SIG;
 281
 282         if ((kctx->initiate && direction != 0xff) ||
 283             (!kctx->initiate && direction != 0))
 284                 return GSS_S_BAD_SIG;
 285
 286         /* Copy the data back to the right position.  XXX: Would probably be
 287          * better to copy and encrypt at the same time. */
 288
 289         blocksize = crypto_blkcipher_blocksize(kctx->enc);
 290         data_start = ptr + GSS_KRB5_TOK_HDR_LEN + 8 + blocksize;
 291         orig_start = buf->head[0].iov_base + offset;
 292         data_len = (buf->head[0].iov_base + buf->head[0].iov_len) - data_start;
 293         memmove(orig_start, data_start, data_len);
 294         buf->head[0].iov_len -= (data_start - orig_start);
 295         buf->len -= (data_start - orig_start);
 296
 297         if (gss_krb5_remove_padding(buf, blocksize))
 298                 return GSS_S_DEFECTIVE_TOKEN;
 299
 300         return GSS_S_COMPLETE;
 301 }