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TLS v1.2 support for cryptoapicert -- RSA only

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- If an NCRYPT handle for the private key can be obtained, use
  NCryptSignHash from the Cryptography NG API to sign the hash.

  This should work for all keys in the Windows certifiate stores
  but may fail for keys in a legacy token, for example. In such
  cases, we disable TLS v1.2 and fall back to the current
  behaviour. A warning is logged unless TLS version is already
  restricted to <= 1.1

Signed-off-by: Selva Nair <selva.nair@gmail.com>
Acked-by: Steffan Karger <steffan.karger@fox-it.com>
Message-Id: <1516423974-22159-1-git-send-email-selva.nair@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg16288.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
This commit is contained in:
Selva Nair 2018-01-19 23:52:54 -05:00 committed by Gert Doering
parent e05aca4517
commit 51d57d7dad
3 changed files with 81 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
src/openvpn/Makefile.am
View File

@ -132,5 +132,5 @@ openvpn_LDADD = \
$(OPTIONAL_DL_LIBS)
if WIN32
openvpn_SOURCES += openvpn_win32_resources.rc block_dns.c block_dns.h
openvpn_LDADD += -lgdi32 -lws2_32 -lwininet -lcrypt32 -liphlpapi -lwinmm -lfwpuclnt -lrpcrt4
openvpn_LDADD += -lgdi32 -lws2_32 -lwininet -lcrypt32 -liphlpapi -lwinmm -lfwpuclnt -lrpcrt4 -lncrypt
endif

85
src/openvpn/cryptoapi.c
View File

@ -42,6 +42,7 @@
#include <openssl/err.h>
#include <windows.h>
#include <wincrypt.h>
#include <ncrypt.h>
#include <stdio.h>
#include <ctype.h>
#include <assert.h>
@ -83,6 +84,7 @@
#define CRYPTOAPI_F_CRYPT_SIGN_HASH 106
#define CRYPTOAPI_F_LOAD_LIBRARY 107
#define CRYPTOAPI_F_GET_PROC_ADDRESS 108
#define CRYPTOAPI_F_NCRYPT_SIGN_HASH 109
static ERR_STRING_DATA CRYPTOAPI_str_functs[] = {
{ ERR_PACK(ERR_LIB_CRYPTOAPI, 0, 0), "microsoft cryptoapi"},
@ -95,12 +97,13 @@ static ERR_STRING_DATA CRYPTOAPI_str_functs[] = {
{ ERR_PACK(0, CRYPTOAPI_F_CRYPT_SIGN_HASH, 0), "CryptSignHash" },
{ ERR_PACK(0, CRYPTOAPI_F_LOAD_LIBRARY, 0), "LoadLibrary" },
{ ERR_PACK(0, CRYPTOAPI_F_GET_PROC_ADDRESS, 0), "GetProcAddress" },
{ ERR_PACK(0, CRYPTOAPI_F_NCRYPT_SIGN_HASH, 0), "NCryptSignHash" },
{ 0, NULL }
};
typedef struct _CAPI_DATA {
const CERT_CONTEXT *cert_context;
HCRYPTPROV crypt_prov;
HCRYPTPROV_OR_NCRYPT_KEY_HANDLE crypt_prov;
DWORD key_spec;
BOOL free_crypt_prov;
} CAPI_DATA;
@ -210,6 +213,41 @@ rsa_pub_dec(int flen, const unsigned char *from, unsigned char *to, RSA *rsa, in
return 0;
}
/**
* Sign the hash in 'from' using NCryptSignHash(). This requires an NCRYPT
* key handle in cd->crypt_prov. On return the signature is in 'to'. Returns
* the length of the signature or 0 on error.
* For now we support only RSA and the padding is assumed to be PKCS1 v1.5
*/
static int
priv_enc_CNG(const CAPI_DATA *cd, const unsigned char *from, int flen,
unsigned char *to, int tlen, int padding)
{
NCRYPT_KEY_HANDLE hkey = cd->crypt_prov;
DWORD len;
ASSERT(cd->key_spec == CERT_NCRYPT_KEY_SPEC);
msg(D_LOW, "Signing hash using CNG: data size = %d", flen);
/* The hash OID is already in 'from'. So set the hash algorithm
* in the padding info struct to NULL.
*/
BCRYPT_PKCS1_PADDING_INFO padinfo = {NULL};
DWORD status;
status = NCryptSignHash(hkey, padding? &padinfo : NULL, (BYTE*) from, flen,
to, tlen, &len, padding? BCRYPT_PAD_PKCS1 : 0);
if (status != ERROR_SUCCESS)
{
SetLastError(status);
CRYPTOAPIerr(CRYPTOAPI_F_NCRYPT_SIGN_HASH);
len = 0;
}
/* Unlike CAPI, CNG signature is in big endian order. No reversing needed. */
return len;
}
/* sign arbitrary data */
static int
rsa_priv_enc(int flen, const unsigned char *from, unsigned char *to, RSA *rsa, int padding)
@ -230,6 +268,11 @@ rsa_priv_enc(int flen, const unsigned char *from, unsigned char *to, RSA *rsa, i
RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT, RSA_R_UNKNOWN_PADDING_TYPE);
return 0;
}
if (cd->key_spec == CERT_NCRYPT_KEY_SPEC)
{
return priv_enc_CNG(cd, from, flen, to, RSA_size(rsa), padding);
}
/* Unfortunately, there is no "CryptSign()" function in CryptoAPI, that would
* be way to straightforward for M$, I guess... So we have to do it this
* tricky way instead, by creating a "Hash", and load the already-made hash
@ -322,7 +365,14 @@ finish(RSA *rsa)
}
if (cd->crypt_prov && cd->free_crypt_prov)
{
CryptReleaseContext(cd->crypt_prov, 0);
if (cd->key_spec == CERT_NCRYPT_KEY_SPEC)
{
NCryptFreeObject(cd->crypt_prov);
}
else
{
CryptReleaseContext(cd->crypt_prov, 0);
}
}
if (cd->cert_context)
{
@ -458,8 +508,11 @@ SSL_CTX_use_CryptoAPI_certificate(SSL_CTX *ssl_ctx, const char *cert_prop)
}
/* set up stuff to use the private key */
if (!CryptAcquireCertificatePrivateKey(cd->cert_context, CRYPT_ACQUIRE_COMPARE_KEY_FLAG,
NULL, &cd->crypt_prov, &cd->key_spec, &cd->free_crypt_prov))
/* We prefer to get an NCRYPT key handle so that TLS1.2 can be supported */
DWORD flags = CRYPT_ACQUIRE_COMPARE_KEY_FLAG
| CRYPT_ACQUIRE_PREFER_NCRYPT_KEY_FLAG;
if (!CryptAcquireCertificatePrivateKey(cd->cert_context, flags, NULL,
&cd->crypt_prov, &cd->key_spec, &cd->free_crypt_prov))
{
/* if we don't have a smart card reader here, and we try to access a
* smart card certificate, we get:
@ -470,6 +523,21 @@ SSL_CTX_use_CryptoAPI_certificate(SSL_CTX *ssl_ctx, const char *cert_prop)
/* here we don't need to do CryptGetUserKey() or anything; all necessary key
* info is in cd->cert_context, and then, in cd->crypt_prov. */
/* if we do not have an NCRYPT key handle restrict TLS to v1.1 or lower */
int max_version = SSL_CTX_get_max_proto_version(ssl_ctx);
if ((!max_version || max_version > TLS1_1_VERSION)
&& cd->key_spec != CERT_NCRYPT_KEY_SPEC)
{
msg(M_WARN,"WARNING: cryptoapicert: private key is in a legacy store."
" Restricting TLS version to 1.1");
if (!SSL_CTX_set_max_proto_version(ssl_ctx, TLS1_1_VERSION))
{
msg(M_NONFATAL,"ERROR: cryptoapicert: unable to set max TLS version"
" to 1.1. Try config option --tls-version-min 1.1");
goto err;
}
}
my_rsa_method = RSA_meth_new("Microsoft Cryptography API RSA Method",
RSA_METHOD_FLAG_NO_CHECK);
check_malloc_return(my_rsa_method);
@ -550,7 +618,14 @@ err:
{
if (cd->free_crypt_prov && cd->crypt_prov)
{
CryptReleaseContext(cd->crypt_prov, 0);
if (cd->key_spec == CERT_NCRYPT_KEY_SPEC)
{
NCryptFreeObject(cd->crypt_prov);
}
else
{
CryptReleaseContext(cd->crypt_prov, 0);
}
}
if (cd->cert_context)
{

18
src/openvpn/options.c
View File

@ -3018,24 +3018,6 @@ options_postprocess_mutate(struct options *o)
}
#endif
#ifdef ENABLE_CRYPTOAPI
if (o->cryptoapi_cert)
{
const int tls_version_max =
(o->ssl_flags >> SSLF_TLS_VERSION_MAX_SHIFT)
&SSLF_TLS_VERSION_MAX_MASK;
if (tls_version_max == TLS_VER_UNSPEC || tls_version_max > TLS_VER_1_1)
{
msg(M_WARN, "Warning: cryptapicert used, setting maximum TLS "
"version to 1.1.");
o->ssl_flags &= ~(SSLF_TLS_VERSION_MAX_MASK
<<SSLF_TLS_VERSION_MAX_SHIFT);
o->ssl_flags |= (TLS_VER_1_1 << SSLF_TLS_VERSION_MAX_SHIFT);
}
}
#endif /* ENABLE_CRYPTOAPI */
#if P2MP
/*
* Save certain parms before modifying options via --pull