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 inline void
  91 make_confounder(char *p, int blocksize)
  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         BUG_ON(blocksize != 8);
 106         *q = i++;
 107 }
 108
 109 /* Assumptions: the head and tail of inbuf are ours to play with.
 110  * The pages, however, may be real pages in the page cache and we replace
 111  * them with scratch pages from **pages before writing to them. */
 112 /* XXX: obviously the above should be documentation of wrap interface,
 113  * and shouldn't be in this kerberos-specific file. */
 114
 115 /* XXX factor out common code with seal/unseal. */
 116
 117 u32
 118 gss_wrap_kerberos(struct gss_ctx *ctx, int offset,
 119                 struct xdr_buf *buf, struct page **pages)
 120 {
 121         struct krb5_ctx         *kctx = ctx->internal_ctx_id;
 122         char                    cksumdata[16];
 123         struct xdr_netobj       md5cksum = {.len = 0, .data = cksumdata};
 124         int                     blocksize = 0, plainlen;
 125         unsigned char           *ptr, *krb5_hdr, *msg_start;
 126         s32                     now;
 127         int                     headlen;
 128         struct page             **tmp_pages;
 129         u32                     seq_send;
 130
 131         dprintk("RPC:       gss_wrap_kerberos\n");
 132
 133         now = get_seconds();
 134
 135         blocksize = crypto_blkcipher_blocksize(kctx->enc);
 136         gss_krb5_add_padding(buf, offset, blocksize);
 137         BUG_ON((buf->len - offset) % blocksize);
 138         plainlen = blocksize + buf->len - offset;
 139
 140         headlen = g_token_size(&kctx->mech_used, 24 + plainlen) -
 141                                                 (buf->len - offset);
 142
 143         ptr = buf->head[0].iov_base + offset;
 144         /* shift data to make room for header. */
 145         /* XXX Would be cleverer to encrypt while copying. */
 146         /* XXX bounds checking, slack, etc. */
 147         memmove(ptr + headlen, ptr, buf->head[0].iov_len - offset);
 148         buf->head[0].iov_len += headlen;
 149         buf->len += headlen;
 150         BUG_ON((buf->len - offset - headlen) % blocksize);
 151
 152         g_make_token_header(&kctx->mech_used, 24 + plainlen, &ptr);
 153
 154
 155         *ptr++ = (unsigned char) ((KG_TOK_WRAP_MSG>>8)&0xff);
 156         *ptr++ = (unsigned char) (KG_TOK_WRAP_MSG&0xff);
 157
 158         /* ptr now at byte 2 of header described in rfc 1964, section 1.2.1: */
 159         krb5_hdr = ptr - 2;
 160         msg_start = krb5_hdr + 24;
 161
 162         *(__be16 *)(krb5_hdr + 2) = htons(SGN_ALG_DES_MAC_MD5);
 163         memset(krb5_hdr + 4, 0xff, 4);
 164         *(__be16 *)(krb5_hdr + 4) = htons(SEAL_ALG_DES);
 165
 166         make_confounder(msg_start, blocksize);
 167
 168         /* XXXJBF: UGH!: */
 169         tmp_pages = buf->pages;
 170         buf->pages = pages;
 171         if (make_checksum("md5", krb5_hdr, 8, buf,
 172                                 offset + headlen - blocksize, &md5cksum))
 173                 return GSS_S_FAILURE;
 174         buf->pages = tmp_pages;
 175
 176         if (krb5_encrypt(kctx->seq, NULL, md5cksum.data,
 177                           md5cksum.data, md5cksum.len))
 178                 return GSS_S_FAILURE;
 179         memcpy(krb5_hdr + 16, md5cksum.data + md5cksum.len - 8, 8);
 180
 181         spin_lock(&krb5_seq_lock);
 182         seq_send = kctx->seq_send++;
 183         spin_unlock(&krb5_seq_lock);
 184
 185         /* XXX would probably be more efficient to compute checksum
 186          * and encrypt at the same time: */
 187         if ((krb5_make_seq_num(kctx->seq, kctx->initiate ? 0 : 0xff,
 188                                seq_send, krb5_hdr + 16, krb5_hdr + 8)))
 189                 return GSS_S_FAILURE;
 190
 191         if (gss_encrypt_xdr_buf(kctx->enc, buf, offset + headlen - blocksize,
 192                                                                         pages))
 193                 return GSS_S_FAILURE;
 194
 195         return (kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE;
 196 }
 197
 198 u32
 199 gss_unwrap_kerberos(struct gss_ctx *ctx, int offset, struct xdr_buf *buf)
 200 {
 201         struct krb5_ctx         *kctx = ctx->internal_ctx_id;
 202         int                     signalg;
 203         int                     sealalg;
 204         char                    cksumdata[16];
 205         struct xdr_netobj       md5cksum = {.len = 0, .data = cksumdata};
 206         s32                     now;
 207         int                     direction;
 208         s32                     seqnum;
 209         unsigned char           *ptr;
 210         int                     bodysize;
 211         void                    *data_start, *orig_start;
 212         int                     data_len;
 213         int                     blocksize;
 214
 215         dprintk("RPC:       gss_unwrap_kerberos\n");
 216
 217         ptr = (u8 *)buf->head[0].iov_base + offset;
 218         if (g_verify_token_header(&kctx->mech_used, &bodysize, &ptr,
 219                                         buf->len - offset))
 220                 return GSS_S_DEFECTIVE_TOKEN;
 221
 222         if ((*ptr++ != ((KG_TOK_WRAP_MSG>>8)&0xff)) ||
 223             (*ptr++ !=  (KG_TOK_WRAP_MSG    &0xff))   )
 224                 return GSS_S_DEFECTIVE_TOKEN;
 225
 226         /* XXX sanity-check bodysize?? */
 227
 228         /* get the sign and seal algorithms */
 229
 230         signalg = ptr[0] + (ptr[1] << 8);
 231         if (signalg != SGN_ALG_DES_MAC_MD5)
 232                 return GSS_S_DEFECTIVE_TOKEN;
 233
 234         sealalg = ptr[2] + (ptr[3] << 8);
 235         if (sealalg != SEAL_ALG_DES)
 236                 return GSS_S_DEFECTIVE_TOKEN;
 237
 238         if ((ptr[4] != 0xff) || (ptr[5] != 0xff))
 239                 return GSS_S_DEFECTIVE_TOKEN;
 240
 241         if (gss_decrypt_xdr_buf(kctx->enc, buf,
 242                         ptr + 22 - (unsigned char *)buf->head[0].iov_base))
 243                 return GSS_S_DEFECTIVE_TOKEN;
 244
 245         if (make_checksum("md5", ptr - 2, 8, buf,
 246                  ptr + 22 - (unsigned char *)buf->head[0].iov_base, &md5cksum))
 247                 return GSS_S_FAILURE;
 248
 249         if (krb5_encrypt(kctx->seq, NULL, md5cksum.data,
 250                            md5cksum.data, md5cksum.len))
 251                 return GSS_S_FAILURE;
 252
 253         if (memcmp(md5cksum.data + 8, ptr + 14, 8))
 254                 return GSS_S_BAD_SIG;
 255
 256         /* it got through unscathed.  Make sure the context is unexpired */
 257
 258         now = get_seconds();
 259
 260         if (now > kctx->endtime)
 261                 return GSS_S_CONTEXT_EXPIRED;
 262
 263         /* do sequencing checks */
 264
 265         if (krb5_get_seq_num(kctx->seq, ptr + 14, ptr + 6, &direction,
 266                                     &seqnum))
 267                 return GSS_S_BAD_SIG;
 268
 269         if ((kctx->initiate && direction != 0xff) ||
 270             (!kctx->initiate && direction != 0))
 271                 return GSS_S_BAD_SIG;
 272
 273         /* Copy the data back to the right position.  XXX: Would probably be
 274          * better to copy and encrypt at the same time. */
 275
 276         blocksize = crypto_blkcipher_blocksize(kctx->enc);
 277         data_start = ptr + 22 + blocksize;
 278         orig_start = buf->head[0].iov_base + offset;
 279         data_len = (buf->head[0].iov_base + buf->head[0].iov_len) - data_start;
 280         memmove(orig_start, data_start, data_len);
 281         buf->head[0].iov_len -= (data_start - orig_start);
 282         buf->len -= (data_start - orig_start);
 283
 284         if (gss_krb5_remove_padding(buf, blocksize))
 285                 return GSS_S_DEFECTIVE_TOKEN;
 286
 287         return GSS_S_COMPLETE;
 288 }