gnutls_tpm.c
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/*
* OpenConnect (SSL + DTLS) VPN client
*
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* Copyright © 2008-2015 Intel Corporation.
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*
* Author: David Woodhouse <dwmw2@infradead.org>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
* version 2.1, as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*/
/*
* TPM code based on client-tpm.c from
* Carolin Latze <latze@angry-red-pla.net> and Tobias Soder
*/
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#include <config.h>
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#include <errno.h>
#include <string.h>
#include <gnutls/gnutls.h>
#include "openconnect-internal.h"
#include "gnutls.h"
#ifdef HAVE_TROUSERS
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#include <trousers/tss.h>
#include <trousers/trousers.h>
struct oc_tpm1_ctx {
TSS_HCONTEXT tpm_context;
TSS_HKEY srk;
TSS_HPOLICY srk_policy;
TSS_HKEY tpm_key;
TSS_HPOLICY tpm_key_policy;
};
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/* Signing function for TPM privkeys, set with gnutls_privkey_import_ext() */
static int tpm_sign_fn(gnutls_privkey_t key, void *_vpninfo,
const gnutls_datum_t *data, gnutls_datum_t *sig)
{
struct openconnect_info *vpninfo = _vpninfo;
TSS_HHASH hash;
int err;
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vpn_progress(vpninfo, PRG_DEBUG,
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_("TPM sign function called for %d bytes.\n"),
data->size);
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err = Tspi_Context_CreateObject(vpninfo->tpm1->tpm_context, TSS_OBJECT_TYPE_HASH,
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TSS_HASH_OTHER, &hash);
if (err) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to create TPM hash object: %s\n"),
Trspi_Error_String(err));
return GNUTLS_E_PK_SIGN_FAILED;
}
err = Tspi_Hash_SetHashValue(hash, data->size, data->data);
if (err) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to set value in TPM hash object: %s\n"),
Trspi_Error_String(err));
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Tspi_Context_CloseObject(vpninfo->tpm1->tpm_context, hash);
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return GNUTLS_E_PK_SIGN_FAILED;
}
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err = Tspi_Hash_Sign(hash, vpninfo->tpm1->tpm_key, &sig->size, &sig->data);
Tspi_Context_CloseObject(vpninfo->tpm1->tpm_context, hash);
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if (err) {
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if (vpninfo->tpm1->tpm_key_policy || err != TPM_E_AUTHFAIL)
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vpn_progress(vpninfo, PRG_ERR,
_("TPM hash signature failed: %s\n"),
Trspi_Error_String(err));
if (err == TPM_E_AUTHFAIL)
return GNUTLS_E_INSUFFICIENT_CREDENTIALS;
else
return GNUTLS_E_PK_SIGN_FAILED;
}
return 0;
}
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int load_tpm1_key(struct openconnect_info *vpninfo, gnutls_datum_t *fdata,
gnutls_privkey_t *pkey, gnutls_datum_t *pkey_sig)
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{
static const TSS_UUID SRK_UUID = TSS_UUID_SRK;
gnutls_datum_t asn1;
unsigned int tss_len;
char *pass;
int ofs, err;
err = gnutls_pem_base64_decode_alloc("TSS KEY BLOB", fdata, &asn1);
if (err) {
vpn_progress(vpninfo, PRG_ERR,
_("Error decoding TSS key blob: %s\n"),
gnutls_strerror(err));
return -EINVAL;
}
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vpninfo->tpm1 = calloc(1, sizeof(*vpninfo->tpm1));
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/* Ick. We have to parse the ASN1 OCTET_STRING for ourselves. */
if (asn1.size < 2 || asn1.data[0] != 0x04 /* OCTET_STRING */) {
vpn_progress(vpninfo, PRG_ERR,
_("Error in TSS key blob\n"));
goto out_blob;
}
tss_len = asn1.data[1];
ofs = 2;
if (tss_len & 0x80) {
int lenlen = tss_len & 0x7f;
if (asn1.size < 2 + lenlen || lenlen > 3) {
vpn_progress(vpninfo, PRG_ERR,
_("Error in TSS key blob\n"));
goto out_blob;
}
tss_len = 0;
while (lenlen) {
tss_len <<= 8;
tss_len |= asn1.data[ofs++];
lenlen--;
}
}
if (tss_len + ofs != asn1.size) {
vpn_progress(vpninfo, PRG_ERR,
_("Error in TSS key blob\n"));
goto out_blob;
}
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err = Tspi_Context_Create(&vpninfo->tpm1->tpm_context);
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if (err) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to create TPM context: %s\n"),
Trspi_Error_String(err));
goto out_blob;
}
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err = Tspi_Context_Connect(vpninfo->tpm1->tpm_context, NULL);
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if (err) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to connect TPM context: %s\n"),
Trspi_Error_String(err));
goto out_context;
}
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err = Tspi_Context_LoadKeyByUUID(vpninfo->tpm1->tpm_context, TSS_PS_TYPE_SYSTEM,
SRK_UUID, &vpninfo->tpm1->srk);
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if (err) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to load TPM SRK key: %s\n"),
Trspi_Error_String(err));
goto out_context;
}
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err = Tspi_GetPolicyObject(vpninfo->tpm1->srk, TSS_POLICY_USAGE, &vpninfo->tpm1->srk_policy);
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if (err) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to load TPM SRK policy object: %s\n"),
Trspi_Error_String(err));
goto out_srk;
}
pass = vpninfo->cert_password;
vpninfo->cert_password = NULL;
while (1) {
static const char nullpass[20];
/* We don't seem to get the error here... */
if (pass)
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err = Tspi_Policy_SetSecret(vpninfo->tpm1->srk_policy,
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TSS_SECRET_MODE_PLAIN,
strlen(pass), (BYTE *)pass);
else /* Well-known NULL key */
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err = Tspi_Policy_SetSecret(vpninfo->tpm1->srk_policy,
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TSS_SECRET_MODE_SHA1,
sizeof(nullpass), (BYTE *)nullpass);
if (err) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to set TPM PIN: %s\n"),
Trspi_Error_String(err));
goto out_srkpol;
}
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free_pass(&pass);
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/* ... we get it here instead. */
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err = Tspi_Context_LoadKeyByBlob(vpninfo->tpm1->tpm_context, vpninfo->tpm1->srk,
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tss_len, asn1.data + ofs,
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&vpninfo->tpm1->tpm_key);
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if (!err)
break;
if (pass)
vpn_progress(vpninfo, PRG_ERR,
_("Failed to load TPM key blob: %s\n"),
Trspi_Error_String(err));
if (err != TPM_E_AUTHFAIL)
goto out_srkpol;
err = request_passphrase(vpninfo, "openconnect_tpm_srk",
&pass, _("Enter TPM SRK PIN:"));
if (err)
goto out_srkpol;
}
gnutls_privkey_init(pkey);
/* This would be nicer if there was a destructor callback. I could
allocate a data structure with the TPM handles and the vpninfo
pointer, and destroy that properly when the key is destroyed. */
gnutls_privkey_import_ext(*pkey, GNUTLS_PK_RSA, vpninfo, tpm_sign_fn, NULL, 0);
retry_sign:
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err = gnutls_privkey_sign_data(*pkey, GNUTLS_DIG_SHA1, 0, fdata, pkey_sig);
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if (err == GNUTLS_E_INSUFFICIENT_CREDENTIALS) {
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if (!vpninfo->tpm1->tpm_key_policy) {
err = Tspi_Context_CreateObject(vpninfo->tpm1->tpm_context,
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TSS_OBJECT_TYPE_POLICY,
TSS_POLICY_USAGE,
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&vpninfo->tpm1->tpm_key_policy);
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if (err) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to create key policy object: %s\n"),
Trspi_Error_String(err));
goto out_key;
}
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err = Tspi_Policy_AssignToObject(vpninfo->tpm1->tpm_key_policy,
vpninfo->tpm1->tpm_key);
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if (err) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to assign policy to key: %s\n"),
Trspi_Error_String(err));
goto out_key_policy;
}
}
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err = request_passphrase(vpninfo, "openconnect_tpm_key",
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&pass, _("Enter TPM key PIN:"));
if (err)
goto out_key_policy;
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err = Tspi_Policy_SetSecret(vpninfo->tpm1->tpm_key_policy,
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TSS_SECRET_MODE_PLAIN,
strlen(pass), (void *)pass);
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free_pass(&pass);
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if (err) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to set key PIN: %s\n"),
Trspi_Error_String(err));
goto out_key_policy;
}
goto retry_sign;
}
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free(asn1.data);
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return 0;
out_key_policy:
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Tspi_Context_CloseObject(vpninfo->tpm1->tpm_context, vpninfo->tpm1->tpm_key_policy);
vpninfo->tpm1->tpm_key_policy = 0;
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out_key:
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Tspi_Context_CloseObject(vpninfo->tpm1->tpm_context, vpninfo->tpm1->tpm_key);
vpninfo->tpm1->tpm_key = 0;
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out_srkpol:
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Tspi_Context_CloseObject(vpninfo->tpm1->tpm_context, vpninfo->tpm1->srk_policy);
vpninfo->tpm1->srk_policy = 0;
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out_srk:
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Tspi_Context_CloseObject(vpninfo->tpm1->tpm_context, vpninfo->tpm1->srk);
vpninfo->tpm1->srk = 0;
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out_context:
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Tspi_Context_Close(vpninfo->tpm1->tpm_context);
vpninfo->tpm1->tpm_context = 0;
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out_blob:
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free(asn1.data);
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free(vpninfo->tpm1);
vpninfo->tpm1 = NULL;
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return -EIO;
}
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void release_tpm1_ctx(struct openconnect_info *vpninfo)
{
if (!vpninfo->tpm1)
return;
if (vpninfo->tpm1->tpm_key_policy) {
Tspi_Context_CloseObject(vpninfo->tpm1->tpm_context, vpninfo->tpm1->tpm_key_policy);
vpninfo->tpm1->tpm_key = 0;
}
if (vpninfo->tpm1->tpm_key) {
Tspi_Context_CloseObject(vpninfo->tpm1->tpm_context, vpninfo->tpm1->tpm_key);
vpninfo->tpm1->tpm_key = 0;
}
if (vpninfo->tpm1->srk_policy) {
Tspi_Context_CloseObject(vpninfo->tpm1->tpm_context, vpninfo->tpm1->srk_policy);
vpninfo->tpm1->srk_policy = 0;
}
if (vpninfo->tpm1->srk) {
Tspi_Context_CloseObject(vpninfo->tpm1->tpm_context, vpninfo->tpm1->srk);
vpninfo->tpm1->srk = 0;
}
if (vpninfo->tpm1->tpm_context) {
Tspi_Context_Close(vpninfo->tpm1->tpm_context);
vpninfo->tpm1->tpm_context = 0;
}
free(vpninfo->tpm1);
vpninfo->tpm1 = NULL;
};
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#endif /* HAVE_TROUSERS */