net/sunrpc/auth_gss/gss_krb5_wrap.c

   1 /*
   2  * COPYRIGHT (c) 2008
   3  * The Regents of the University of Michigan
   4  * ALL RIGHTS RESERVED
   5  *
   6  * Permission is granted to use, copy, create derivative works
   7  * and redistribute this software and such derivative works
   8  * for any purpose, so long as the name of The University of
   9  * Michigan is not used in any advertising or publicity
  10  * pertaining to the use of distribution of this software
  11  * without specific, written prior authorization.  If the
  12  * above copyright notice or any other identification of the
  13  * University of Michigan is included in any copy of any
  14  * portion of this software, then the disclaimer below must
  15  * also be included.
  16  *
  17  * THIS SOFTWARE IS PROVIDED AS IS, WITHOUT REPRESENTATION
  18  * FROM THE UNIVERSITY OF MICHIGAN AS TO ITS FITNESS FOR ANY
  19  * PURPOSE, AND WITHOUT WARRANTY BY THE UNIVERSITY OF
  20  * MICHIGAN OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING
  21  * WITHOUT LIMITATION THE IMPLIED WARRANTIES OF
  22  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
  23  * REGENTS OF THE UNIVERSITY OF MICHIGAN SHALL NOT BE LIABLE
  24  * FOR ANY DAMAGES, INCLUDING SPECIAL, INDIRECT, INCIDENTAL, OR
  25  * CONSEQUENTIAL DAMAGES, WITH RESPECT TO ANY CLAIM ARISING
  26  * OUT OF OR IN CONNECTION WITH THE USE OF THE SOFTWARE, EVEN
  27  * IF IT HAS BEEN OR IS HEREAFTER ADVISED OF THE POSSIBILITY OF
  28  * SUCH DAMAGES.
  29  */
  30
  31 #include <crypto/skcipher.h>
  32 #include <linux/types.h>
  33 #include <linux/jiffies.h>
  34 #include <linux/sunrpc/gss_krb5.h>
  35 #include <linux/pagemap.h>
  36
  37 #include "gss_krb5_internal.h"
  38
  39 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
  40 # define RPCDBG_FACILITY        RPCDBG_AUTH
  41 #endif
  42
  43 /*
  44  * We can shift data by up to LOCAL_BUF_LEN bytes in a pass.  If we need
  45  * to do more than that, we shift repeatedly.  Kevin Coffman reports
  46  * seeing 28 bytes as the value used by Microsoft clients and servers
  47  * with AES, so this constant is chosen to allow handling 28 in one pass
  48  * without using too much stack space.
  49  *
  50  * If that proves to a problem perhaps we could use a more clever
  51  * algorithm.
  52  */
  53 #define LOCAL_BUF_LEN 32u
  54
  55 static void rotate_buf_a_little(struct xdr_buf *buf, unsigned int shift)
  56 {
  57         char head[LOCAL_BUF_LEN];
  58         char tmp[LOCAL_BUF_LEN];
  59         unsigned int this_len, i;
  60
  61         BUG_ON(shift > LOCAL_BUF_LEN);
  62
  63         read_bytes_from_xdr_buf(buf, 0, head, shift);
  64         for (i = 0; i + shift < buf->len; i += LOCAL_BUF_LEN) {
  65                 this_len = min(LOCAL_BUF_LEN, buf->len - (i + shift));
  66                 read_bytes_from_xdr_buf(buf, i+shift, tmp, this_len);
  67                 write_bytes_to_xdr_buf(buf, i, tmp, this_len);
  68         }
  69         write_bytes_to_xdr_buf(buf, buf->len - shift, head, shift);
  70 }
  71
  72 static void _rotate_left(struct xdr_buf *buf, unsigned int shift)
  73 {
  74         int shifted = 0;
  75         int this_shift;
  76
  77         shift %= buf->len;
  78         while (shifted < shift) {
  79                 this_shift = min(shift - shifted, LOCAL_BUF_LEN);
  80                 rotate_buf_a_little(buf, this_shift);
  81                 shifted += this_shift;
  82         }
  83 }
  84
  85 static void rotate_left(u32 base, struct xdr_buf *buf, unsigned int shift)
  86 {
  87         struct xdr_buf subbuf;
  88
  89         xdr_buf_subsegment(buf, &subbuf, base, buf->len - base);
  90         _rotate_left(&subbuf, shift);
  91 }
  92
  93 u32
  94 gss_krb5_wrap_v2(struct krb5_ctx *kctx, int offset,
  95                  struct xdr_buf *buf, struct page **pages)
  96 {
  97         u8              *ptr;
  98         time64_t        now;
  99         u8              flags = 0x00;
 100         __be16          *be16ptr;
 101         __be64          *be64ptr;
 102         u32             err;
 103
 104         dprintk("RPC:       %s\n", __func__);
 105
 106         /* make room for gss token header */
 107         if (xdr_extend_head(buf, offset, GSS_KRB5_TOK_HDR_LEN))
 108                 return GSS_S_FAILURE;
 109
 110         /* construct gss token header */
 111         ptr = buf->head[0].iov_base + offset;
 112         *ptr++ = (unsigned char) ((KG2_TOK_WRAP>>8) & 0xff);
 113         *ptr++ = (unsigned char) (KG2_TOK_WRAP & 0xff);
 114
 115         if ((kctx->flags & KRB5_CTX_FLAG_INITIATOR) == 0)
 116                 flags |= KG2_TOKEN_FLAG_SENTBYACCEPTOR;
 117         if ((kctx->flags & KRB5_CTX_FLAG_ACCEPTOR_SUBKEY) != 0)
 118                 flags |= KG2_TOKEN_FLAG_ACCEPTORSUBKEY;
 119         /* We always do confidentiality in wrap tokens */
 120         flags |= KG2_TOKEN_FLAG_SEALED;
 121
 122         *ptr++ = flags;
 123         *ptr++ = 0xff;
 124         be16ptr = (__be16 *)ptr;
 125
 126         *be16ptr++ = 0;
 127         /* "inner" token header always uses 0 for RRC */
 128         *be16ptr++ = 0;
 129
 130         be64ptr = (__be64 *)be16ptr;
 131         *be64ptr = cpu_to_be64(atomic64_fetch_inc(&kctx->seq_send64));
 132
 133         err = (*kctx->gk5e->encrypt)(kctx, offset, buf, pages);
 134         if (err)
 135                 return err;
 136
 137         now = ktime_get_real_seconds();
 138         return (kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE;
 139 }
 140
 141 u32
 142 gss_krb5_unwrap_v2(struct krb5_ctx *kctx, int offset, int len,
 143                    struct xdr_buf *buf, unsigned int *slack,
 144                    unsigned int *align)
 145 {
 146         time64_t        now;
 147         u8              *ptr;
 148         u8              flags = 0x00;
 149         u16             ec, rrc;
 150         int             err;
 151         u32             headskip, tailskip;
 152         u8              decrypted_hdr[GSS_KRB5_TOK_HDR_LEN];
 153         unsigned int    movelen;
 154
 155
 156         dprintk("RPC:       %s\n", __func__);
 157
 158         ptr = buf->head[0].iov_base + offset;
 159
 160         if (be16_to_cpu(*((__be16 *)ptr)) != KG2_TOK_WRAP)
 161                 return GSS_S_DEFECTIVE_TOKEN;
 162
 163         flags = ptr[2];
 164         if ((!kctx->initiate && (flags & KG2_TOKEN_FLAG_SENTBYACCEPTOR)) ||
 165             (kctx->initiate && !(flags & KG2_TOKEN_FLAG_SENTBYACCEPTOR)))
 166                 return GSS_S_BAD_SIG;
 167
 168         if ((flags & KG2_TOKEN_FLAG_SEALED) == 0) {
 169                 dprintk("%s: token missing expected sealed flag\n", __func__);
 170                 return GSS_S_DEFECTIVE_TOKEN;
 171         }
 172
 173         if (ptr[3] != 0xff)
 174                 return GSS_S_DEFECTIVE_TOKEN;
 175
 176         ec = be16_to_cpup((__be16 *)(ptr + 4));
 177         rrc = be16_to_cpup((__be16 *)(ptr + 6));
 178
 179         /*
 180          * NOTE: the sequence number at ptr + 8 is skipped, rpcsec_gss
 181          * doesn't want it checked; see page 6 of rfc 2203.
 182          */
 183
 184         if (rrc != 0)
 185                 rotate_left(offset + 16, buf, rrc);
 186
 187         err = (*kctx->gk5e->decrypt)(kctx, offset, len, buf,
 188                                      &headskip, &tailskip);
 189         if (err)
 190                 return GSS_S_FAILURE;
 191
 192         /*
 193          * Retrieve the decrypted gss token header and verify
 194          * it against the original
 195          */
 196         err = read_bytes_from_xdr_buf(buf,
 197                                 len - GSS_KRB5_TOK_HDR_LEN - tailskip,
 198                                 decrypted_hdr, GSS_KRB5_TOK_HDR_LEN);
 199         if (err) {
 200                 dprintk("%s: error %u getting decrypted_hdr\n", __func__, err);
 201                 return GSS_S_FAILURE;
 202         }
 203         if (memcmp(ptr, decrypted_hdr, 6)
 204                                 || memcmp(ptr + 8, decrypted_hdr + 8, 8)) {
 205                 dprintk("%s: token hdr, plaintext hdr mismatch!\n", __func__);
 206                 return GSS_S_FAILURE;
 207         }
 208
 209         /* do sequencing checks */
 210
 211         /* it got through unscathed.  Make sure the context is unexpired */
 212         now = ktime_get_real_seconds();
 213         if (now > kctx->endtime)
 214                 return GSS_S_CONTEXT_EXPIRED;
 215
 216         /*
 217          * Move the head data back to the right position in xdr_buf.
 218          * We ignore any "ec" data since it might be in the head or
 219          * the tail, and we really don't need to deal with it.
 220          * Note that buf->head[0].iov_len may indicate the available
 221          * head buffer space rather than that actually occupied.
 222          */
 223         movelen = min_t(unsigned int, buf->head[0].iov_len, len);
 224         movelen -= offset + GSS_KRB5_TOK_HDR_LEN + headskip;
 225         BUG_ON(offset + GSS_KRB5_TOK_HDR_LEN + headskip + movelen >
 226                                                         buf->head[0].iov_len);
 227         memmove(ptr, ptr + GSS_KRB5_TOK_HDR_LEN + headskip, movelen);
 228         buf->head[0].iov_len -= GSS_KRB5_TOK_HDR_LEN + headskip;
 229         buf->len = len - (GSS_KRB5_TOK_HDR_LEN + headskip);
 230
 231         /* Trim off the trailing "extra count" and checksum blob */
 232         xdr_buf_trim(buf, ec + GSS_KRB5_TOK_HDR_LEN + tailskip);
 233
 234         *align = XDR_QUADLEN(GSS_KRB5_TOK_HDR_LEN + headskip);
 235         *slack = *align + XDR_QUADLEN(ec + GSS_KRB5_TOK_HDR_LEN + tailskip);
 236         return GSS_S_COMPLETE;
 237 }