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/* $OpenBSD: ssl_seclevel.c,v 1.8 2022/06/29 11:59:23 tb Exp $ */
/*
* Copyright (c) 2020 Theo Buehler <tb@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <stddef.h>
#include <openssl/dh.h>
#include <openssl/ossl_typ.h>
#include <openssl/ssl.h>
#include <openssl/tls1.h>
#include "ssl_locl.h"
static int
ssl_security_normalize_level(const SSL_CTX *ctx, const SSL *ssl, int *out_level)
{
int security_level;
if (ctx != NULL)
security_level = SSL_CTX_get_security_level(ctx);
else
security_level = SSL_get_security_level(ssl);
if (security_level < 0)
security_level = 0;
if (security_level > 5)
security_level = 5;
*out_level = security_level;
return 1;
}
static int
ssl_security_level_to_minimum_bits(int security_level, int *out_minimum_bits)
{
if (security_level < 0)
return 0;
if (security_level == 0)
*out_minimum_bits = 0;
else if (security_level == 1)
*out_minimum_bits = 80;
else if (security_level == 2)
*out_minimum_bits = 112;
else if (security_level == 3)
*out_minimum_bits = 128;
else if (security_level == 4)
*out_minimum_bits = 192;
else if (security_level >= 5)
*out_minimum_bits = 256;
return 1;
}
static int
ssl_security_level_and_minimum_bits(const SSL_CTX *ctx, const SSL *ssl,
int *out_level, int *out_minimum_bits)
{
int security_level = 0, minimum_bits = 0;
if (!ssl_security_normalize_level(ctx, ssl, &security_level))
return 0;
if (!ssl_security_level_to_minimum_bits(security_level, &minimum_bits))
return 0;
if (out_level != NULL)
*out_level = security_level;
if (out_minimum_bits != NULL)
*out_minimum_bits = minimum_bits;
return 1;
}
static int
ssl_security_secop_cipher(const SSL_CTX *ctx, const SSL *ssl, int bits,
void *arg)
{
const SSL_CIPHER *cipher = arg;
int security_level, minimum_bits;
if (!ssl_security_level_and_minimum_bits(ctx, ssl, &security_level,
&minimum_bits))
return 0;
if (security_level <= 0)
return 1;
if (bits < minimum_bits)
return 0;
/* No unauthenticated ciphersuites. */
if (cipher->algorithm_auth & SSL_aNULL)
return 0;
if (security_level <= 1)
return 1;
if (cipher->algorithm_enc == SSL_RC4)
return 0;
if (security_level <= 2)
return 1;
/* Security level >= 3 requires a cipher with forward secrecy. */
if ((cipher->algorithm_mkey & (SSL_kDHE | SSL_kECDHE)) == 0 &&
cipher->algorithm_ssl != SSL_TLSV1_3)
return 0;
return 1;
}
static int
ssl_security_secop_version(const SSL_CTX *ctx, const SSL *ssl, int version)
{
int min_version = TLS1_2_VERSION;
int security_level;
if (!ssl_security_level_and_minimum_bits(ctx, ssl, &security_level, NULL))
return 0;
if (security_level < 4)
min_version = TLS1_1_VERSION;
if (security_level < 3)
min_version = TLS1_VERSION;
return ssl_tls_version(version) >= min_version;
}
static int
ssl_security_secop_compression(const SSL_CTX *ctx, const SSL *ssl)
{
return 0;
}
static int
ssl_security_secop_tickets(const SSL_CTX *ctx, const SSL *ssl)
{
int security_level;
if (!ssl_security_level_and_minimum_bits(ctx, ssl, &security_level, NULL))
return 0;
return security_level < 3;
}
static int
ssl_security_secop_tmp_dh(const SSL_CTX *ctx, const SSL *ssl, int bits)
{
int security_level, minimum_bits;
if (!ssl_security_level_and_minimum_bits(ctx, ssl, &security_level,
&minimum_bits))
return 0;
/* Disallow DHE keys weaker than 1024 bits even at security level 0. */
if (security_level <= 0 && bits < 80)
return 0;
return bits >= minimum_bits;
}
static int
ssl_security_secop_default(const SSL_CTX *ctx, const SSL *ssl, int bits)
{
int minimum_bits;
if (!ssl_security_level_and_minimum_bits(ctx, ssl, NULL, &minimum_bits))
return 0;
return bits >= minimum_bits;
}
int
ssl_security_default_cb(const SSL *ssl, const SSL_CTX *ctx, int op, int bits,
int version, void *cipher, void *ex_data)
{
switch (op) {
case SSL_SECOP_CIPHER_SUPPORTED:
case SSL_SECOP_CIPHER_SHARED:
case SSL_SECOP_CIPHER_CHECK:
return ssl_security_secop_cipher(ctx, ssl, bits, cipher);
case SSL_SECOP_VERSION:
return ssl_security_secop_version(ctx, ssl, version);
case SSL_SECOP_COMPRESSION:
return ssl_security_secop_compression(ctx, ssl);
case SSL_SECOP_TICKET:
return ssl_security_secop_tickets(ctx, ssl);
case SSL_SECOP_TMP_DH:
return ssl_security_secop_tmp_dh(ctx, ssl, bits);
default:
return ssl_security_secop_default(ctx, ssl, bits);
}
}
int
ssl_security_dummy_cb(const SSL *ssl, const SSL_CTX *ctx, int op, int bits,
int version, void *cipher, void *ex_data)
{
return 1;
}
int
ssl_ctx_security(const SSL_CTX *ctx, int op, int bits, int nid, void *other)
{
return ctx->internal->cert->security_cb(NULL, ctx, op, bits, nid, other,
ctx->internal->cert->security_ex_data);
}
int
ssl_security(const SSL *ssl, int op, int bits, int nid, void *other)
{
return ssl->cert->security_cb(ssl, NULL, op, bits, nid, other,
ssl->cert->security_ex_data);
}
int
ssl_ctx_security_dh(const SSL_CTX *ctx, DH *dh)
{
#if defined(LIBRESSL_HAS_SECURITY_LEVEL)
return ssl_ctx_security(ctx, SSL_SECOP_TMP_DH, DH_security_bits(dh), 0,
dh);
#else
return 1;
#endif
}
int
ssl_security_dh(const SSL *ssl, DH *dh)
{
#if defined(LIBRESSL_HAS_SECURITY_LEVEL)
return ssl_security(ssl, SSL_SECOP_TMP_DH, DH_security_bits(dh), 0, dh);
#else
return 1;
#endif
}
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