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         size_t 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                 unsigned int last = (buf->page_base + len - 1)
  57                                         >>PAGE_CACHE_SHIFT;
  58                 unsigned int offset = (buf->page_base + len - 1)
  59                                         & (PAGE_CACHE_SIZE - 1);
  60                 ptr = kmap_atomic(buf->pages[last], KM_USER0);
  61                 pad = *(ptr + offset);
  62                 kunmap_atomic(ptr, KM_USER0);
  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         char                    cksumdata[16];
 124         struct xdr_netobj       md5cksum = {.len = 0, .data = cksumdata};
 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         u32                     seq_send;
 131
 132         dprintk("RPC:       gss_wrap_kerberos\n");
 133
 134         now = get_seconds();
 135
 136         blocksize = crypto_blkcipher_blocksize(kctx->enc);
 137         gss_krb5_add_padding(buf, offset, blocksize);
 138         BUG_ON((buf->len - offset) % blocksize);
 139         plainlen = blocksize + buf->len - offset;
 140
 141         headlen = g_token_size(&kctx->mech_used, 22 + plainlen) -
 142                                                 (buf->len - offset);
 143
 144         ptr = buf->head[0].iov_base + offset;
 145         /* shift data to make room for header. */
 146         /* XXX Would be cleverer to encrypt while copying. */
 147         /* XXX bounds checking, slack, etc. */
 148         memmove(ptr + headlen, ptr, buf->head[0].iov_len - offset);
 149         buf->head[0].iov_len += headlen;
 150         buf->len += headlen;
 151         BUG_ON((buf->len - offset - headlen) % blocksize);
 152
 153         g_make_token_header(&kctx->mech_used, 22 + plainlen, &ptr);
 154
 155
 156         *ptr++ = (unsigned char) ((KG_TOK_WRAP_MSG>>8)&0xff);
 157         *ptr++ = (unsigned char) (KG_TOK_WRAP_MSG&0xff);
 158
 159         /* ptr now at byte 2 of header described in rfc 1964, section 1.2.1: */
 160         krb5_hdr = ptr - 2;
 161         msg_start = krb5_hdr + 24;
 162
 163         *(__be16 *)(krb5_hdr + 2) = htons(SGN_ALG_DES_MAC_MD5);
 164         memset(krb5_hdr + 4, 0xff, 4);
 165         *(__be16 *)(krb5_hdr + 4) = htons(SEAL_ALG_DES);
 166
 167         make_confounder(msg_start, blocksize);
 168
 169         /* XXXJBF: UGH!: */
 170         tmp_pages = buf->pages;
 171         buf->pages = pages;
 172         if (make_checksum("md5", krb5_hdr, 8, buf,
 173                                 offset + headlen - blocksize, &md5cksum))
 174                 return GSS_S_FAILURE;
 175         buf->pages = tmp_pages;
 176
 177         if (krb5_encrypt(kctx->seq, NULL, md5cksum.data,
 178                           md5cksum.data, md5cksum.len))
 179                 return GSS_S_FAILURE;
 180         memcpy(krb5_hdr + 16,
 181                md5cksum.data + md5cksum.len - KRB5_CKSUM_LENGTH,
 182                KRB5_CKSUM_LENGTH);
 183
 184         spin_lock(&krb5_seq_lock);
 185         seq_send = kctx->seq_send++;
 186         spin_unlock(&krb5_seq_lock);
 187
 188         /* XXX would probably be more efficient to compute checksum
 189          * and encrypt at the same time: */
 190         if ((krb5_make_seq_num(kctx->seq, kctx->initiate ? 0 : 0xff,
 191                                seq_send, krb5_hdr + 16, krb5_hdr + 8)))
 192                 return GSS_S_FAILURE;
 193
 194         if (gss_encrypt_xdr_buf(kctx->enc, buf, offset + headlen - blocksize,
 195                                                                         pages))
 196                 return GSS_S_FAILURE;
 197
 198         return (kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE;
 199 }
 200
 201 u32
 202 gss_unwrap_kerberos(struct gss_ctx *ctx, int offset, struct xdr_buf *buf)
 203 {
 204         struct krb5_ctx         *kctx = ctx->internal_ctx_id;
 205         int                     signalg;
 206         int                     sealalg;
 207         char                    cksumdata[16];
 208         struct xdr_netobj       md5cksum = {.len = 0, .data = cksumdata};
 209         s32                     now;
 210         int                     direction;
 211         s32                     seqnum;
 212         unsigned char           *ptr;
 213         int                     bodysize;
 214         void                    *data_start, *orig_start;
 215         int                     data_len;
 216         int                     blocksize;
 217
 218         dprintk("RPC:       gss_unwrap_kerberos\n");
 219
 220         ptr = (u8 *)buf->head[0].iov_base + offset;
 221         if (g_verify_token_header(&kctx->mech_used, &bodysize, &ptr,
 222                                         buf->len - offset))
 223                 return GSS_S_DEFECTIVE_TOKEN;
 224
 225         if ((*ptr++ != ((KG_TOK_WRAP_MSG>>8)&0xff)) ||
 226             (*ptr++ !=  (KG_TOK_WRAP_MSG    &0xff))   )
 227                 return GSS_S_DEFECTIVE_TOKEN;
 228
 229         /* XXX sanity-check bodysize?? */
 230
 231         /* get the sign and seal algorithms */
 232
 233         signalg = ptr[0] + (ptr[1] << 8);
 234         if (signalg != SGN_ALG_DES_MAC_MD5)
 235                 return GSS_S_DEFECTIVE_TOKEN;
 236
 237         sealalg = ptr[2] + (ptr[3] << 8);
 238         if (sealalg != SEAL_ALG_DES)
 239                 return GSS_S_DEFECTIVE_TOKEN;
 240
 241         if ((ptr[4] != 0xff) || (ptr[5] != 0xff))
 242                 return GSS_S_DEFECTIVE_TOKEN;
 243
 244         if (gss_decrypt_xdr_buf(kctx->enc, buf,
 245                         ptr + 22 - (unsigned char *)buf->head[0].iov_base))
 246                 return GSS_S_DEFECTIVE_TOKEN;
 247
 248         if (make_checksum("md5", ptr - 2, 8, buf,
 249                  ptr + 22 - (unsigned char *)buf->head[0].iov_base, &md5cksum))
 250                 return GSS_S_FAILURE;
 251
 252         if (krb5_encrypt(kctx->seq, NULL, md5cksum.data,
 253                            md5cksum.data, md5cksum.len))
 254                 return GSS_S_FAILURE;
 255
 256         if (memcmp(md5cksum.data + 8, ptr + 14, 8))
 257                 return GSS_S_BAD_SIG;
 258
 259         /* it got through unscathed.  Make sure the context is unexpired */
 260
 261         now = get_seconds();
 262
 263         if (now > kctx->endtime)
 264                 return GSS_S_CONTEXT_EXPIRED;
 265
 266         /* do sequencing checks */
 267
 268         if (krb5_get_seq_num(kctx->seq, ptr + 14, ptr + 6, &direction,
 269                                     &seqnum))
 270                 return GSS_S_BAD_SIG;
 271
 272         if ((kctx->initiate && direction != 0xff) ||
 273             (!kctx->initiate && direction != 0))
 274                 return GSS_S_BAD_SIG;
 275
 276         /* Copy the data back to the right position.  XXX: Would probably be
 277          * better to copy and encrypt at the same time. */
 278
 279         blocksize = crypto_blkcipher_blocksize(kctx->enc);
 280         data_start = ptr + 22 + blocksize;
 281         orig_start = buf->head[0].iov_base + offset;
 282         data_len = (buf->head[0].iov_base + buf->head[0].iov_len) - data_start;
 283         memmove(orig_start, data_start, data_len);
 284         buf->head[0].iov_len -= (data_start - orig_start);
 285         buf->len -= (data_start - orig_start);
 286
 287         if (gss_krb5_remove_padding(buf, blocksize))
 288                 return GSS_S_DEFECTIVE_TOKEN;
 289
 290         return GSS_S_COMPLETE;
 291 }