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The code for hostapd-mbedtls did not work when used for OWE association.
When handling association requests, the buffer offsets and length assumptions were incorrect, leading to never calculating the y point, thus denying association.
Also when crafting the association response, the buffer contained the trailing key-type.
Fix up both issues to adhere to the specification and make hostapd-mbedtls work with the OWE security type.
--- a/src/crypto/crypto_mbedtls.c
+++ b/src/crypto/crypto_mbedtls.c
@@ -2299,25 +2299,30 @@ struct crypto_ecdh * crypto_ecdh_init2(i
struct wpabuf * crypto_ecdh_get_pubkey(struct crypto_ecdh *ecdh, int inc_y)
{
mbedtls_ecp_group *grp = &ecdh->grp;
- size_t len = CRYPTO_EC_plen(grp);
+ size_t prime_len = CRYPTO_EC_plen(grp);
+ size_t output_len = prime_len;
+ u8 output_offset = 0;
+ u8 buf[256];
+
#ifdef MBEDTLS_ECP_MONTGOMERY_ENABLED
/* len */
#endif
#ifdef MBEDTLS_ECP_SHORT_WEIERSTRASS_ENABLED
- if (mbedtls_ecp_get_type(grp) == MBEDTLS_ECP_TYPE_SHORT_WEIERSTRASS)
- len = inc_y ? len*2+1 : len+1;
+ if (mbedtls_ecp_get_type(grp) == MBEDTLS_ECP_TYPE_SHORT_WEIERSTRASS) {
+ output_len = inc_y ? prime_len * 2 + 1 : prime_len + 1;
+ output_offset = 1;
+ }
#endif
- struct wpabuf *buf = wpabuf_alloc(len);
- if (buf == NULL)
+
+ if (output_len > sizeof(buf))
return NULL;
+
inc_y = inc_y ? MBEDTLS_ECP_PF_UNCOMPRESSED : MBEDTLS_ECP_PF_COMPRESSED;
- if (mbedtls_ecp_point_write_binary(grp, &ecdh->Q, inc_y, &len,
- wpabuf_mhead_u8(buf), len) == 0) {
- wpabuf_put(buf, len);
- return buf;
+ if (mbedtls_ecp_point_write_binary(grp, &ecdh->Q, inc_y, &output_len,
+ buf, output_len) == 0) {
+ return wpabuf_alloc_copy(buf + output_offset, output_len - output_offset);
}
- wpabuf_free(buf);
return NULL;
}
@@ -2379,10 +2384,7 @@ struct wpabuf * crypto_ecdh_set_peerkey(
os_memcpy(buf+2, key, len);
}
len >>= 1; /*(repurpose len to prime_len)*/
- }
- else if (key[0] == 0x02 || key[0] == 0x03) { /* (inc_y == 0) */
- --len; /*(repurpose len to prime_len)*/
-
+ } else { /* (inc_y == 0) */
/* mbedtls_ecp_point_read_binary() does not currently support
* MBEDTLS_ECP_PF_COMPRESSED format (buf[1] = 0x02 or 0x03)
* (returns MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE) */
@@ -2390,22 +2392,21 @@ struct wpabuf * crypto_ecdh_set_peerkey(
/* derive y, amend buf[] with y for UNCOMPRESSED format */
if (sizeof(buf)-2 < len*2 || len == 0)
return NULL;
+
buf[0] = (u8)(1+len*2);
buf[1] = 0x04;
+ os_memcpy(buf+2, key, len);
+
mbedtls_mpi bn;
mbedtls_mpi_init(&bn);
- int ret = mbedtls_mpi_read_binary(&bn, key+1, len)
- || crypto_mbedtls_short_weierstrass_derive_y(grp, &bn,
- key[0] & 1)
+ int ret = mbedtls_mpi_read_binary(&bn, key, len)
+ || crypto_mbedtls_short_weierstrass_derive_y(grp, &bn, 0)
|| mbedtls_mpi_write_binary(&bn, buf+2+len, len);
mbedtls_mpi_free(&bn);
if (ret != 0)
return NULL;
}
- if (key[0] == 0) /*(repurpose len to prime_len)*/
- len = CRYPTO_EC_plen(grp);
-
if (mbedtls_ecdh_read_public(&ecdh->ctx, buf, buf[0]+1))
return NULL;
}
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