/*
- * Copyright 2011-2019 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright 2011-2021 The OpenSSL Project Authors. All Rights Reserved.
* Copyright (c) 2002, Oracle and/or its affiliates. All rights reserved
*
* Licensed under the OpenSSL license (the "License"). You may not use
ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_BUFFER_TOO_SMALL);
return 0;
}
- form = buf[0];
- y_bit = form & 1;
- form = form & ~1U;
+
+ /*
+ * The first octet is the point converison octet PC, see X9.62, page 4
+ * and section 4.4.2. It must be:
+ * 0x00 for the point at infinity
+ * 0x02 or 0x03 for compressed form
+ * 0x04 for uncompressed form
+ * 0x06 or 0x07 for hybrid form.
+ * For compressed or hybrid forms, we store the last bit of buf[0] as
+ * y_bit and clear it from buf[0] so as to obtain a POINT_CONVERSION_*.
+ * We error if buf[0] contains any but the above values.
+ */
+ y_bit = buf[0] & 1;
+ form = buf[0] & ~1U;
+
if ((form != 0) && (form != POINT_CONVERSION_COMPRESSED)
&& (form != POINT_CONVERSION_UNCOMPRESSED)
&& (form != POINT_CONVERSION_HYBRID)) {
return 0;
}
+ /* The point at infinity is represented by a single zero octet. */
if (form == 0) {
if (len != 1) {
ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
goto err;
}
if (form == POINT_CONVERSION_HYBRID) {
- if (!group->meth->field_div(group, yxi, y, x, ctx))
- goto err;
- if (y_bit != BN_is_odd(yxi)) {
- ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
- goto err;
+ /*
+ * Check that the form in the encoding was set correctly
+ * according to X9.62 4.4.2.a, 4(c), see also first paragraph
+ * of X9.62, 4.4.1.b.
+ */
+ if (BN_is_zero(x)) {
+ if (y_bit != 0) {
+ ECerr(ERR_LIB_EC, EC_R_INVALID_ENCODING);
+ goto err;
+ }
+ } else {
+ if (!group->meth->field_div(group, yxi, y, x, ctx))
+ goto err;
+ if (y_bit != BN_is_odd(yxi)) {
+ ECerr(ERR_LIB_EC, EC_R_INVALID_ENCODING);
+ goto err;
+ }
}
}