pkinit.c

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/*
 * Copyright (c) 2003 - 2006 Kungliga Tekniska H鰃skolan
 * (Royal Institute of Technology, Stockholm, Sweden). 
 * All rights reserved. 
 *
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions 
 * are met: 
 *
 * 1. Redistributions of source code must retain the above copyright 
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. Redistributions in binary form must reproduce the above copyright 
 *    notice, this list of conditions and the following disclaimer in the 
 *    documentation and/or other materials provided with the distribution. 
 *
 * 3. Neither the name of the Institute nor the names of its contributors 
 *    may be used to endorse or promote products derived from this software 
 *    without specific prior written permission. 
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND 
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE 
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 
 * SUCH DAMAGE. 
 */

#include "kdc_locl.h"

RCSID("$Id: pkinit.c 22243 2007-12-08 23:39:30Z lha $");

#ifdef PKINIT

#include <heim_asn1.h>
#include <rfc2459_asn1.h>
#include <cms_asn1.h>
#include <pkinit_asn1.h>

#include <hx509.h>
#include "crypto-headers.h"

/* XXX copied from lib/krb5/pkinit.c */
struct krb5_pk_identity {
    hx509_context hx509ctx;
    hx509_verify_ctx verify_ctx;
    hx509_certs certs;
    hx509_certs anchors;
    hx509_certs certpool;
    hx509_revoke_ctx revoke;
};

enum pkinit_type {
    PKINIT_COMPAT_WIN2K = 1,
    PKINIT_COMPAT_27 = 3
};

struct pk_client_params {
    enum pkinit_type type;
    BIGNUM *dh_public_key;
    hx509_cert cert;
    unsigned nonce;
    DH *dh;
    EncryptionKey reply_key;
    char *dh_group_name;
    hx509_peer_info peer;
    hx509_certs client_anchors;
};

struct pk_principal_mapping {
    unsigned int len;
    struct pk_allowed_princ {
	krb5_principal principal;
	char *subject;
    } *val;
};

static struct krb5_pk_identity *kdc_identity;
static struct pk_principal_mapping principal_mappings;
static struct krb5_dh_moduli **moduli;

static struct {
    krb5_data data;
    time_t expire;
    time_t next_update;
} ocsp;

/*
 *
 */

static krb5_error_code
pk_check_pkauthenticator_win2k(krb5_context context,
			       PKAuthenticator_Win2k *a,
			       const KDC_REQ *req)
{
    krb5_timestamp now;

    krb5_timeofday (context, &now);

    /* XXX cusec */
    if (a->ctime == 0 || abs(a->ctime - now) > context->max_skew) {
	krb5_clear_error_string(context);
	return KRB5KRB_AP_ERR_SKEW;
    }
    return 0;
}

static krb5_error_code
pk_check_pkauthenticator(krb5_context context,
			 PKAuthenticator *a,
			 const KDC_REQ *req)
{
    u_char *buf = NULL;
    size_t buf_size;
    krb5_error_code ret;
    size_t len;
    krb5_timestamp now;
    Checksum checksum;

    krb5_timeofday (context, &now);

    /* XXX cusec */
    if (a->ctime == 0 || abs(a->ctime - now) > context->max_skew) {
	krb5_clear_error_string(context);
	return KRB5KRB_AP_ERR_SKEW;
    }

    ASN1_MALLOC_ENCODE(KDC_REQ_BODY, buf, buf_size, &req->req_body, &len, ret);
    if (ret) {
	krb5_clear_error_string(context);
	return ret;
    }
    if (buf_size != len)
	krb5_abortx(context, "Internal error in ASN.1 encoder");

    ret = krb5_create_checksum(context,
			       NULL,
			       0,
			       CKSUMTYPE_SHA1,
			       buf,
			       len,
			       &checksum);
    free(buf);
    if (ret) {
	krb5_clear_error_string(context);
	return ret;
    }
	
    if (a->paChecksum == NULL) {
	krb5_clear_error_string(context);
	ret = KRB5_KDC_ERR_PA_CHECKSUM_MUST_BE_INCLUDED;
	goto out;
    }

    if (der_heim_octet_string_cmp(a->paChecksum, &checksum.checksum) != 0) {
	krb5_clear_error_string(context);
	ret = KRB5KRB_ERR_GENERIC;
    }

out:
    free_Checksum(&checksum);

    return ret;
}

void
_kdc_pk_free_client_param(krb5_context context, 
			  pk_client_params *client_params)
{
    if (client_params->cert)
	hx509_cert_free(client_params->cert);
    if (client_params->dh)
	DH_free(client_params->dh);
    if (client_params->dh_public_key)
	BN_free(client_params->dh_public_key);
    krb5_free_keyblock_contents(context, &client_params->reply_key);
    if (client_params->dh_group_name)
	free(client_params->dh_group_name);
    if (client_params->peer)
	hx509_peer_info_free(client_params->peer);
    if (client_params->client_anchors)
	hx509_certs_free(&client_params->client_anchors);
    memset(client_params, 0, sizeof(*client_params));
    free(client_params);
}

static krb5_error_code
generate_dh_keyblock(krb5_context context, pk_client_params *client_params,
                     krb5_enctype enctype, krb5_keyblock *reply_key)
{
    unsigned char *dh_gen_key = NULL;
    krb5_keyblock key;
    krb5_error_code ret;
    size_t dh_gen_keylen, size;

    memset(&key, 0, sizeof(key));

    if (!DH_generate_key(client_params->dh)) {
	krb5_set_error_string(context, "Can't generate Diffie-Hellman keys");
	ret = KRB5KRB_ERR_GENERIC;
	goto out;
    }
    if (client_params->dh_public_key == NULL) {
	krb5_set_error_string(context, "dh_public_key");
	ret = KRB5KRB_ERR_GENERIC;
	goto out;
    }

    dh_gen_keylen = DH_size(client_params->dh);
    size = BN_num_bytes(client_params->dh->p);
    if (size < dh_gen_keylen)
	size = dh_gen_keylen;

    dh_gen_key = malloc(size);
    if (dh_gen_key == NULL) {
	krb5_set_error_string(context, "malloc: out of memory");
	ret = ENOMEM;
	goto out;
    }
    memset(dh_gen_key, 0, size - dh_gen_keylen);

    dh_gen_keylen = DH_compute_key(dh_gen_key + (size - dh_gen_keylen),
				   client_params->dh_public_key,
				   client_params->dh);
    if (dh_gen_keylen == -1) {
	krb5_set_error_string(context, "Can't compute Diffie-Hellman key");
	ret = KRB5KRB_ERR_GENERIC;
	goto out;
    }

    ret = _krb5_pk_octetstring2key(context,
				   enctype,
				   dh_gen_key, dh_gen_keylen,
				   NULL, NULL,
				   reply_key);

 out:
    if (dh_gen_key)
	free(dh_gen_key);
    if (key.keyvalue.data)
	krb5_free_keyblock_contents(context, &key);

    return ret;
}

static BIGNUM *
integer_to_BN(krb5_context context, const char *field, heim_integer *f)
{
    BIGNUM *bn;

    bn = BN_bin2bn((const unsigned char *)f->data, f->length, NULL);
    if (bn == NULL) {
	krb5_set_error_string(context, "PKINIT: parsing BN failed %s", field);
	return NULL;
    }
    BN_set_negative(bn, f->negative);
    return bn;
}

static krb5_error_code
get_dh_param(krb5_context context,
	     krb5_kdc_configuration *config,
	     SubjectPublicKeyInfo *dh_key_info,
	     pk_client_params *client_params)
{
    DomainParameters dhparam;
    DH *dh = NULL;
    krb5_error_code ret;

    memset(&dhparam, 0, sizeof(dhparam));

    if (der_heim_oid_cmp(&dh_key_info->algorithm.algorithm, oid_id_dhpublicnumber())) {
	krb5_set_error_string(context,
			      "PKINIT invalid oid in clientPublicValue");
	return KRB5_BADMSGTYPE;
    }

    if (dh_key_info->algorithm.parameters == NULL) {
	krb5_set_error_string(context, "PKINIT missing algorithm parameter "
			      "in clientPublicValue");
	return KRB5_BADMSGTYPE;
    }

    ret = decode_DomainParameters(dh_key_info->algorithm.parameters->data,
				  dh_key_info->algorithm.parameters->length,
				  &dhparam,
				  NULL);
    if (ret) {
	krb5_set_error_string(context, "Can't decode algorithm "
			      "parameters in clientPublicValue");
	goto out;
    }

    if ((dh_key_info->subjectPublicKey.length % 8) != 0) {
	ret = KRB5_BADMSGTYPE;
	krb5_set_error_string(context, "PKINIT: subjectPublicKey not aligned "
			      "to 8 bit boundary");
	goto out;
    }


    ret = _krb5_dh_group_ok(context, config->pkinit_dh_min_bits, 
			    &dhparam.p, &dhparam.g, &dhparam.q, moduli,
			    &client_params->dh_group_name);
    if (ret) {
	/* XXX send back proposal of better group */
	goto out;
    }

    dh = DH_new();
    if (dh == NULL) {
	krb5_set_error_string(context, "Cannot create DH structure");
	ret = ENOMEM;
	goto out;
    }
    ret = KRB5_BADMSGTYPE;
    dh->p = integer_to_BN(context, "DH prime", &dhparam.p);
    if (dh->p == NULL)
	goto out;
    dh->g = integer_to_BN(context, "DH base", &dhparam.g);
    if (dh->g == NULL)
	goto out;
    dh->q = integer_to_BN(context, "DH p-1 factor", &dhparam.q);
    if (dh->g == NULL)
	goto out;

    {
	heim_integer glue;
	size_t size;

	ret = decode_DHPublicKey(dh_key_info->subjectPublicKey.data,
				 dh_key_info->subjectPublicKey.length / 8,
				 &glue,
				 &size);
	if (ret) {
	    krb5_clear_error_string(context);
	    return ret;
	}

	client_params->dh_public_key = integer_to_BN(context,
						     "subjectPublicKey",
						     &glue);
	der_free_heim_integer(&glue);
	if (client_params->dh_public_key == NULL)
	    goto out;
    }

    client_params->dh = dh;
    dh = NULL;
    ret = 0;
    
 out:
    if (dh)
	DH_free(dh);
    free_DomainParameters(&dhparam);
    return ret;
}

krb5_error_code
_kdc_pk_rd_padata(krb5_context context,
		  krb5_kdc_configuration *config,
		  const KDC_REQ *req,
		  const PA_DATA *pa,
		  pk_client_params **ret_params)
{
    pk_client_params *client_params;
    krb5_error_code ret;
    heim_oid eContentType = { 0, NULL }, contentInfoOid = { 0, NULL };
    krb5_data eContent = { 0, NULL };
    krb5_data signed_content = { 0, NULL };
    const char *type = "unknown type";
    int have_data = 0;

    *ret_params = NULL;
    
    if (!config->enable_pkinit) {
	kdc_log(context, config, 0, "PK-INIT request but PK-INIT not enabled");
	krb5_clear_error_string(context);
	return 0;
    }

    hx509_verify_set_time(kdc_identity->verify_ctx, _kdc_now.tv_sec);

    client_params = calloc(1, sizeof(*client_params));
    if (client_params == NULL) {
	krb5_clear_error_string(context);
	ret = ENOMEM;
	goto out;
    }

    if (pa->padata_type == KRB5_PADATA_PK_AS_REQ_WIN) {
	PA_PK_AS_REQ_Win2k r;

	type = "PK-INIT-Win2k";

	ret = decode_PA_PK_AS_REQ_Win2k(pa->padata_value.data,
					pa->padata_value.length,
					&r,
					NULL);
	if (ret) {
	    krb5_set_error_string(context, "Can't decode "
				  "PK-AS-REQ-Win2k: %d", ret);
	    goto out;
	}
	
	ret = hx509_cms_unwrap_ContentInfo(&r.signed_auth_pack,
					   &contentInfoOid,
					   &signed_content,
					   &have_data);
	free_PA_PK_AS_REQ_Win2k(&r);
	if (ret) {
	    krb5_set_error_string(context, "Can't decode PK-AS-REQ: %d", ret);
	    goto out;
	}

    } else if (pa->padata_type == KRB5_PADATA_PK_AS_REQ) {
	PA_PK_AS_REQ r;

	type = "PK-INIT-IETF";

	ret = decode_PA_PK_AS_REQ(pa->padata_value.data,
				  pa->padata_value.length,
				  &r,
				  NULL);
	if (ret) {
	    krb5_set_error_string(context, "Can't decode PK-AS-REQ: %d", ret);
	    goto out;
	}
	
	/* XXX look at r.kdcPkId */
	if (r.trustedCertifiers) {
	    ExternalPrincipalIdentifiers *edi = r.trustedCertifiers;
	    unsigned int i;

	    ret = hx509_certs_init(kdc_identity->hx509ctx,
				   "MEMORY:client-anchors",
				   0, NULL,
				   &client_params->client_anchors);
	    if (ret) {
		krb5_set_error_string(context, "Can't allocate client anchors: %d", ret);
		goto out;

	    }
	    for (i = 0; i < edi->len; i++) {
		IssuerAndSerialNumber iasn;
		hx509_query *q;
		hx509_cert cert;
		size_t size;

		if (edi->val[i].issuerAndSerialNumber == NULL)
		    continue;

		ret = hx509_query_alloc(kdc_identity->hx509ctx, &q);
		if (ret) {
		    krb5_set_error_string(context, 
					  "Failed to allocate hx509_query");
		    goto out;
		}
		
		ret = decode_IssuerAndSerialNumber(edi->val[i].issuerAndSerialNumber->data,
						   edi->val[i].issuerAndSerialNumber->length,
						   &iasn,
						   &size);
		if (ret) {
		    hx509_query_free(kdc_identity->hx509ctx, q);
		    continue;
		}
		ret = hx509_query_match_issuer_serial(q, &iasn.issuer, &iasn.serialNumber);
		free_IssuerAndSerialNumber(&iasn);
		if (ret)
		    continue;

		ret = hx509_certs_find(kdc_identity->hx509ctx,
				       kdc_identity->certs,
				       q,
				       &cert);
		hx509_query_free(kdc_identity->hx509ctx, q);
		if (ret)
		    continue;
		hx509_certs_add(kdc_identity->hx509ctx, 
				client_params->client_anchors, cert);
		hx509_cert_free(cert);
	    }
	}

	ret = hx509_cms_unwrap_ContentInfo(&r.signedAuthPack,
					   &contentInfoOid,
					   &signed_content,
					   &have_data);
	free_PA_PK_AS_REQ(&r);
	if (ret) {
	    krb5_set_error_string(context, "Can't unwrap ContentInfo: %d", ret);
	    goto out;
	}

    } else { 
	krb5_clear_error_string(context);
	ret = KRB5KDC_ERR_PADATA_TYPE_NOSUPP;
	goto out;
    }

    ret = der_heim_oid_cmp(&contentInfoOid, oid_id_pkcs7_signedData());
    if (ret != 0) {
	krb5_set_error_string(context, "PK-AS-REQ-Win2k invalid content "
			      "type oid");
	ret = KRB5KRB_ERR_GENERIC;
	goto out;
    }
	
    if (!have_data) {
	krb5_set_error_string(context,
			      "PK-AS-REQ-Win2k no signed auth pack");
	ret = KRB5KRB_ERR_GENERIC;
	goto out;
    }

    {
	hx509_certs signer_certs;

	ret = hx509_cms_verify_signed(kdc_identity->hx509ctx,
				      kdc_identity->verify_ctx,
				      signed_content.data,
				      signed_content.length,
				      NULL,
				      kdc_identity->certpool,
				      &eContentType,
				      &eContent,
				      &signer_certs);
	if (ret) {
	    char *s = hx509_get_error_string(kdc_identity->hx509ctx, ret);
	    krb5_warnx(context, "PKINIT: failed to verify signature: %s: %d",
		       s, ret);
	    free(s);
	    goto out;
	}

	ret = hx509_get_one_cert(kdc_identity->hx509ctx, signer_certs,
				 &client_params->cert);
	hx509_certs_free(&signer_certs);
	if (ret)
	    goto out;
    }

    /* Signature is correct, now verify the signed message */
    if (der_heim_oid_cmp(&eContentType, oid_id_pkcs7_data()) != 0 &&
	der_heim_oid_cmp(&eContentType, oid_id_pkauthdata()) != 0)
    {
	krb5_set_error_string(context, "got wrong oid for pkauthdata");
	ret = KRB5_BADMSGTYPE;
	goto out;
    }