Files
openssl/crypto/param_build_set.c
Viktor Dukhovni 7e57092596 Handle NULL-buffer size probe in ossl_param_build_set_bn_pad()
ossl_param_build_set_bn_pad() is reached by two distinct caller
populations.  When an OSSL_PARAM_BLD template is supplied
(bld != NULL), the template allocates backing storage internally and
no caller-side sizing is required.  When an explicit OSSL_PARAM[]
array is supplied (bld == NULL), the caller follows the standard
OSSL_PARAM size-probe contract: invoke the primitive once with
p->data == NULL to learn the required size via p->return_size, then
allocate a buffer of that size and invoke again with the real
storage.

The bld == NULL branch did not honour the size-probe contract: with
p->data == NULL and a non-zero sz it fell through to
OSSL_PARAM_set_BN() and raised CRYPTO_R_TOO_SMALL_BUFFER, so callers
could never discover the required size.

The defect has been latent across several releases.  This primitive
is the *padded* BN setter: it emits a fixed-width encoding regardless
of the BN's actual magnitude, which is needed for the private key --
a minimal encoding would leak its bit-length through timing or
allocation side channels.  In practice the private key is the only
provider parameter that reaches this primitive.  Callers that want
private-key material have historically done so through
EVP_PKEY_todata() and its OSSL_PARAM_BLD template path, where the
bug is invisible.  EVP_PKEY_get_params() callers exist but have not
previously needed the private-key BN.  Any caller that does request
it on the explicit-params path -- whether by name or as part of
iterating a provider's full gettable list -- now sees the probe
behave as it does elsewhere.

Reviewed-by: Eugene Syromiatnikov <esyr@openssl.org>
Reviewed-by: Frederik Wedel-Heinen <fwh.openssl@gmail.com>
MergeDate: Sun Apr 26 13:35:32 2026
(Merged from https://github.com/openssl/openssl/pull/30942)
2026-04-26 15:35:31 +02:00

130 lines
3.6 KiB
C

/*
* Copyright 2020-2022 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the Apache License 2.0 (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
/*
* Key Management utility functions to share functionality between the export()
* and get_params() methods.
* export() uses OSSL_PARAM_BLD, and get_params() used the OSSL_PARAM[] to
* fill in parameter data for the same key and data fields.
*/
#include <openssl/core_names.h>
#include "internal/param_build_set.h"
DEFINE_SPECIAL_STACK_OF_CONST(BIGNUM_const, BIGNUM)
int ossl_param_build_set_int(OSSL_PARAM_BLD *bld, OSSL_PARAM *p,
const char *key, int num)
{
if (bld != NULL)
return OSSL_PARAM_BLD_push_int(bld, key, num);
p = OSSL_PARAM_locate(p, key);
if (p != NULL)
return OSSL_PARAM_set_int(p, num);
return 1;
}
int ossl_param_build_set_long(OSSL_PARAM_BLD *bld, OSSL_PARAM *p,
const char *key, long num)
{
if (bld != NULL)
return OSSL_PARAM_BLD_push_long(bld, key, num);
p = OSSL_PARAM_locate(p, key);
if (p != NULL)
return OSSL_PARAM_set_long(p, num);
return 1;
}
int ossl_param_build_set_utf8_string(OSSL_PARAM_BLD *bld, OSSL_PARAM *p,
const char *key, const char *buf)
{
if (bld != NULL)
return OSSL_PARAM_BLD_push_utf8_string(bld, key, buf, 0);
p = OSSL_PARAM_locate(p, key);
if (p != NULL)
return OSSL_PARAM_set_utf8_string(p, buf);
return 1;
}
int ossl_param_build_set_octet_string(OSSL_PARAM_BLD *bld, OSSL_PARAM *p,
const char *key,
const unsigned char *data,
size_t data_len)
{
if (bld != NULL)
return OSSL_PARAM_BLD_push_octet_string(bld, key, data, data_len);
p = OSSL_PARAM_locate(p, key);
if (p != NULL)
return OSSL_PARAM_set_octet_string(p, data, data_len);
return 1;
}
int ossl_param_build_set_bn_pad(OSSL_PARAM_BLD *bld, OSSL_PARAM *p,
const char *key, const BIGNUM *bn, size_t sz)
{
if (bld != NULL)
return OSSL_PARAM_BLD_push_BN_pad(bld, key, bn, sz);
p = OSSL_PARAM_locate(p, key);
if (p != NULL) {
/* Size probe: NULL data means "report the required size". */
if (p->data == NULL) {
p->return_size = sz;
return 1;
}
if (sz > p->data_size) {
ERR_raise(ERR_LIB_CRYPTO, CRYPTO_R_TOO_SMALL_BUFFER);
return 0;
}
p->data_size = sz;
return OSSL_PARAM_set_BN(p, bn);
}
return 1;
}
int ossl_param_build_set_bn(OSSL_PARAM_BLD *bld, OSSL_PARAM *p,
const char *key, const BIGNUM *bn)
{
if (bld != NULL)
return OSSL_PARAM_BLD_push_BN(bld, key, bn);
p = OSSL_PARAM_locate(p, key);
if (p != NULL)
return OSSL_PARAM_set_BN(p, bn) > 0;
return 1;
}
int ossl_param_build_set_multi_key_bn(OSSL_PARAM_BLD *bld, OSSL_PARAM *params,
const char *names[],
STACK_OF(BIGNUM_const) *stk)
{
int i, sz = sk_BIGNUM_const_num(stk);
OSSL_PARAM *p;
const BIGNUM *bn;
if (bld != NULL) {
for (i = 0; i < sz && names[i] != NULL; ++i) {
bn = sk_BIGNUM_const_value(stk, i);
if (bn != NULL && !OSSL_PARAM_BLD_push_BN(bld, names[i], bn))
return 0;
}
return 1;
}
for (i = 0; i < sz && names[i] != NULL; ++i) {
bn = sk_BIGNUM_const_value(stk, i);
p = OSSL_PARAM_locate(params, names[i]);
if (p != NULL && bn != NULL) {
if (!OSSL_PARAM_set_BN(p, bn))
return 0;
}
}
return 1;
}