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 <linux/crypto.h>
   8
   9 #ifdef RPC_DEBUG
  10 # define RPCDBG_FACILITY        RPCDBG_AUTH
  11 #endif
  12
  13 static inline int
  14 gss_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
  22 static inline void
  23 gss_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
  39 static inline int
  40 gss_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);
  67 out:
  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
  90 static void
  91 make_confounder(char *p, u32 conflen)
  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         /* initialize to random value */
 106         if (i == 0) {
 107                 i = random32();
 108                 i = (i << 32) | random32();
 109         }
 110
 111         switch (conflen) {
 112         case 16:
 113                 *q++ = i++;
 114                 /* fall through */
 115         case 8:
 116                 *q++ = i++;
 117                 break;
 118         default:
 119                 BUG();
 120         }
 121 }
 122
 123 /* Assumptions: the head and tail of inbuf are ours to play with.
 124  * The pages, however, may be real pages in the page cache and we replace
 125  * them with scratch pages from **pages before writing to them. */
 126 /* XXX: obviously the above should be documentation of wrap interface,
 127  * and shouldn't be in this kerberos-specific file. */
 128
 129 /* XXX factor out common code with seal/unseal. */
 130
 131 u32
 132 gss_wrap_kerberos(struct gss_ctx *ctx, int offset,
 133                 struct xdr_buf *buf, struct page **pages)
 134 {
 135         struct krb5_ctx         *kctx = ctx->internal_ctx_id;
 136         char                    cksumdata[16];
 137         struct xdr_netobj       md5cksum = {.len = 0, .data = cksumdata};
 138         int                     blocksize = 0, plainlen;
 139         unsigned char           *ptr, *msg_start;
 140         s32                     now;
 141         int                     headlen;
 142         struct page             **tmp_pages;
 143         u32                     seq_send;
 144
 145         dprintk("RPC:       gss_wrap_kerberos\n");
 146
 147         now = get_seconds();
 148
 149         blocksize = crypto_blkcipher_blocksize(kctx->enc);
 150         gss_krb5_add_padding(buf, offset, blocksize);
 151         BUG_ON((buf->len - offset) % blocksize);
 152         plainlen = blocksize + buf->len - offset;
 153
 154         headlen = g_token_size(&kctx->mech_used, 24 + plainlen) -
 155                                                 (buf->len - offset);
 156
 157         ptr = buf->head[0].iov_base + offset;
 158         /* shift data to make room for header. */
 159         /* XXX Would be cleverer to encrypt while copying. */
 160         /* XXX bounds checking, slack, etc. */
 161         memmove(ptr + headlen, ptr, buf->head[0].iov_len - offset);
 162         buf->head[0].iov_len += headlen;
 163         buf->len += headlen;
 164         BUG_ON((buf->len - offset - headlen) % blocksize);
 165
 166         g_make_token_header(&kctx->mech_used,
 167                                 GSS_KRB5_TOK_HDR_LEN + 8 + plainlen, &ptr);
 168
 169
 170         /* ptr now at header described in rfc 1964, section 1.2.1: */
 171         ptr[0] = (unsigned char) ((KG_TOK_WRAP_MSG >> 8) & 0xff);
 172         ptr[1] = (unsigned char) (KG_TOK_WRAP_MSG & 0xff);
 173
 174         msg_start = ptr + 24;
 175
 176         *(__be16 *)(ptr + 2) = htons(SGN_ALG_DES_MAC_MD5);
 177         memset(ptr + 4, 0xff, 4);
 178         *(__be16 *)(ptr + 4) = htons(SEAL_ALG_DES);
 179
 180         make_confounder(msg_start, blocksize);
 181
 182         /* XXXJBF: UGH!: */
 183         tmp_pages = buf->pages;
 184         buf->pages = pages;
 185         if (make_checksum("md5", ptr, 8, buf,
 186                                 offset + headlen - blocksize, &md5cksum))
 187                 return GSS_S_FAILURE;
 188         buf->pages = tmp_pages;
 189
 190         if (krb5_encrypt(kctx->seq, NULL, md5cksum.data,
 191                           md5cksum.data, md5cksum.len))
 192                 return GSS_S_FAILURE;
 193         memcpy(ptr + GSS_KRB5_TOK_HDR_LEN, md5cksum.data + md5cksum.len - 8, 8);
 194
 195         spin_lock(&krb5_seq_lock);
 196         seq_send = kctx->seq_send++;
 197         spin_unlock(&krb5_seq_lock);
 198
 199         /* XXX would probably be more efficient to compute checksum
 200          * and encrypt at the same time: */
 201         if ((krb5_make_seq_num(kctx->seq, kctx->initiate ? 0 : 0xff,
 202                                seq_send, ptr + GSS_KRB5_TOK_HDR_LEN, ptr + 8)))
 203                 return GSS_S_FAILURE;
 204
 205         if (gss_encrypt_xdr_buf(kctx->enc, buf, offset + headlen - blocksize,
 206                                                                         pages))
 207                 return GSS_S_FAILURE;
 208
 209         return (kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE;
 210 }
 211
 212 u32
 213 gss_unwrap_kerberos(struct gss_ctx *ctx, int offset, struct xdr_buf *buf)
 214 {
 215         struct krb5_ctx         *kctx = ctx->internal_ctx_id;
 216         int                     signalg;
 217         int                     sealalg;
 218         char                    cksumdata[16];
 219         struct xdr_netobj       md5cksum = {.len = 0, .data = cksumdata};
 220         s32                     now;
 221         int                     direction;
 222         s32                     seqnum;
 223         unsigned char           *ptr;
 224         int                     bodysize;
 225         void                    *data_start, *orig_start;
 226         int                     data_len;
 227         int                     blocksize;
 228
 229         dprintk("RPC:       gss_unwrap_kerberos\n");
 230
 231         ptr = (u8 *)buf->head[0].iov_base + offset;
 232         if (g_verify_token_header(&kctx->mech_used, &bodysize, &ptr,
 233                                         buf->len - offset))
 234                 return GSS_S_DEFECTIVE_TOKEN;
 235
 236         if ((ptr[0] != ((KG_TOK_WRAP_MSG >> 8) & 0xff)) ||
 237             (ptr[1] !=  (KG_TOK_WRAP_MSG & 0xff)))
 238                 return GSS_S_DEFECTIVE_TOKEN;
 239
 240         /* XXX sanity-check bodysize?? */
 241
 242         /* get the sign and seal algorithms */
 243
 244         signalg = ptr[2] + (ptr[3] << 8);
 245         if (signalg != SGN_ALG_DES_MAC_MD5)
 246                 return GSS_S_DEFECTIVE_TOKEN;
 247
 248         sealalg = ptr[4] + (ptr[5] << 8);
 249         if (sealalg != SEAL_ALG_DES)
 250                 return GSS_S_DEFECTIVE_TOKEN;
 251
 252         if ((ptr[6] != 0xff) || (ptr[7] != 0xff))
 253                 return GSS_S_DEFECTIVE_TOKEN;
 254
 255         if (gss_decrypt_xdr_buf(kctx->enc, buf,
 256                         ptr + GSS_KRB5_TOK_HDR_LEN + 8 - (unsigned char *)buf->head[0].iov_base))
 257                 return GSS_S_DEFECTIVE_TOKEN;
 258
 259         if (make_checksum("md5", ptr, 8, buf,
 260                  ptr + GSS_KRB5_TOK_HDR_LEN + 8 - (unsigned char *)buf->head[0].iov_base, &md5cksum))
 261                 return GSS_S_FAILURE;
 262
 263         if (krb5_encrypt(kctx->seq, NULL, md5cksum.data,
 264                            md5cksum.data, md5cksum.len))
 265                 return GSS_S_FAILURE;
 266
 267         if (memcmp(md5cksum.data + 8, ptr + GSS_KRB5_TOK_HDR_LEN, 8))
 268                 return GSS_S_BAD_SIG;
 269
 270         /* it got through unscathed.  Make sure the context is unexpired */
 271
 272         now = get_seconds();
 273
 274         if (now > kctx->endtime)
 275                 return GSS_S_CONTEXT_EXPIRED;
 276
 277         /* do sequencing checks */
 278
 279         if (krb5_get_seq_num(kctx->seq, ptr + GSS_KRB5_TOK_HDR_LEN, ptr + 8,
 280                                     &direction, &seqnum))
 281                 return GSS_S_BAD_SIG;
 282
 283         if ((kctx->initiate && direction != 0xff) ||
 284             (!kctx->initiate && direction != 0))
 285                 return GSS_S_BAD_SIG;
 286
 287         /* Copy the data back to the right position.  XXX: Would probably be
 288          * better to copy and encrypt at the same time. */
 289
 290         blocksize = crypto_blkcipher_blocksize(kctx->enc);
 291         data_start = ptr + GSS_KRB5_TOK_HDR_LEN + 8 + blocksize;
 292         orig_start = buf->head[0].iov_base + offset;
 293         data_len = (buf->head[0].iov_base + buf->head[0].iov_len) - data_start;
 294         memmove(orig_start, data_start, data_len);
 295         buf->head[0].iov_len -= (data_start - orig_start);
 296         buf->len -= (data_start - orig_start);
 297
 298         if (gss_krb5_remove_padding(buf, blocksize))
 299                 return GSS_S_DEFECTIVE_TOKEN;
 300
 301         return GSS_S_COMPLETE;
 302 }