package/network/services/hostapd/patches/135-mbedtls-fix-owe-association.patch

   1 The code for hostapd-mbedtls did not work when used for OWE association.
   2
   3 When handling association requests, the buffer offsets and length assumptions were incorrect, leading to never calculating the y point, thus denying association.
   4
   5 Also when crafting the association response, the buffer contained the trailing key-type.
   6
   7 Fix up both issues to adhere to the specification and make hostapd-mbedtls work with the OWE security type.
   8
   9 --- a/src/crypto/crypto_mbedtls.c
  10 +++ b/src/crypto/crypto_mbedtls.c
  11 @@ -2299,25 +2299,30 @@ struct crypto_ecdh * crypto_ecdh_init2(i
  12  struct wpabuf * crypto_ecdh_get_pubkey(struct crypto_ecdh *ecdh, int inc_y)
  13  {
  14         mbedtls_ecp_group *grp = &ecdh->grp;
  15 -       size_t len = CRYPTO_EC_plen(grp);
  16 +       size_t prime_len = CRYPTO_EC_plen(grp);
  17 +       size_t output_len = prime_len;
  18 +       u8 output_offset = 0;
  19 +       u8 buf[256];
  20 +
  21    #ifdef MBEDTLS_ECP_MONTGOMERY_ENABLED
  22         /* len */
  23    #endif
  24    #ifdef MBEDTLS_ECP_SHORT_WEIERSTRASS_ENABLED
  25 -       if (mbedtls_ecp_get_type(grp) == MBEDTLS_ECP_TYPE_SHORT_WEIERSTRASS)
  26 -               len = inc_y ? len*2+1 : len+1;
  27 +       if (mbedtls_ecp_get_type(grp) == MBEDTLS_ECP_TYPE_SHORT_WEIERSTRASS) {
  28 +               output_len = inc_y ? prime_len * 2 + 1 : prime_len + 1;
  29 +               output_offset = 1;
  30 +       }
  31    #endif
  32 -       struct wpabuf *buf = wpabuf_alloc(len);
  33 -       if (buf == NULL)
  34 +
  35 +       if (output_len > sizeof(buf))
  36                 return NULL;
  37 +
  38         inc_y = inc_y ? MBEDTLS_ECP_PF_UNCOMPRESSED : MBEDTLS_ECP_PF_COMPRESSED;
  39 -       if (mbedtls_ecp_point_write_binary(grp, &ecdh->Q, inc_y, &len,
  40 -                                          wpabuf_mhead_u8(buf), len) == 0) {
  41 -               wpabuf_put(buf, len);
  42 -               return buf;
  43 +       if (mbedtls_ecp_point_write_binary(grp, &ecdh->Q, inc_y, &output_len,
  44 +                                          buf, output_len) == 0) {
  45 +               return wpabuf_alloc_copy(buf + output_offset, output_len - output_offset);
  46         }
  47
  48 -       wpabuf_free(buf);
  49         return NULL;
  50  }
  51
  52 @@ -2379,10 +2384,7 @@ struct wpabuf * crypto_ecdh_set_peerkey(
  53                                 os_memcpy(buf+2, key, len);
  54                         }
  55                         len >>= 1; /*(repurpose len to prime_len)*/
  56 -               }
  57 -               else if (key[0] == 0x02 || key[0] == 0x03) { /* (inc_y == 0) */
  58 -                       --len; /*(repurpose len to prime_len)*/
  59 -
  60 +               } else { /* (inc_y == 0) */
  61                         /* mbedtls_ecp_point_read_binary() does not currently support
  62                          * MBEDTLS_ECP_PF_COMPRESSED format (buf[1] = 0x02 or 0x03)
  63                          * (returns MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE) */
  64 @@ -2390,22 +2392,21 @@ struct wpabuf * crypto_ecdh_set_peerkey(
  65                         /* derive y, amend buf[] with y for UNCOMPRESSED format */
  66                         if (sizeof(buf)-2 < len*2 || len == 0)
  67                                 return NULL;
  68 +
  69                         buf[0] = (u8)(1+len*2);
  70                         buf[1] = 0x04;
  71 +                       os_memcpy(buf+2, key, len);
  72 +
  73                         mbedtls_mpi bn;
  74                         mbedtls_mpi_init(&bn);
  75 -                       int ret = mbedtls_mpi_read_binary(&bn, key+1, len)
  76 -                              || crypto_mbedtls_short_weierstrass_derive_y(grp, &bn,
  77 -                                                                           key[0] & 1)
  78 +                       int ret = mbedtls_mpi_read_binary(&bn, key, len)
  79 +                              || crypto_mbedtls_short_weierstrass_derive_y(grp, &bn, 0)
  80                                || mbedtls_mpi_write_binary(&bn, buf+2+len, len);
  81                         mbedtls_mpi_free(&bn);
  82                         if (ret != 0)
  83                                 return NULL;
  84                 }
  85
  86 -               if (key[0] == 0) /*(repurpose len to prime_len)*/
  87 -                       len = CRYPTO_EC_plen(grp);
  88 -
  89                 if (mbedtls_ecdh_read_public(&ecdh->ctx, buf, buf[0]+1))
  90                         return NULL;
  91         }