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openssl/crypto/ts/ts_rsp_verify.c

Index: openssl/crypto/ts/ts_rsp_verify.c
===================================================================
--- openssl/crypto/ts/ts_rsp_verify.c	(revision 0)
+++ openssl/crypto/ts/ts_rsp_verify.c	(revision 0)
@@ -0,0 +1,725 @@
+/* crypto/ts/ts_resp_verify.c */
+/* Written by Zoltan Glozik (zglozik@stones.com) for the OpenSSL
+ * project 2002.
+ */
+/* ====================================================================
+ * Copyright (c) 2006 The OpenSSL Project.  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. All advertising materials mentioning features or use of this
+ *    software must display the following acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
+ *
+ * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
+ *    endorse or promote products derived from this software without
+ *    prior written permission. For written permission, please contact
+ *    licensing@OpenSSL.org.
+ *
+ * 5. Products derived from this software may not be called "OpenSSL"
+ *    nor may "OpenSSL" appear in their names without prior written
+ *    permission of the OpenSSL Project.
+ *
+ * 6. Redistributions of any form whatsoever must retain the following
+ *    acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
+ * EXPRESSED 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 OpenSSL PROJECT OR
+ * ITS 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.
+ * ====================================================================
+ *
+ * This product includes cryptographic software written by Eric Young
+ * (eay@cryptsoft.com).  This product includes software written by Tim
+ * Hudson (tjh@cryptsoft.com).
+ *
+ */
+
+#include <stdio.h>
+#include "cryptlib.h"
+#include <openssl/objects.h>
+#include <openssl/ts.h>
+#include <openssl/pkcs7.h>
+
+/* Private function declarations. */
+
+static int TS_verify_cert(X509_STORE *store, STACK_OF(X509) *untrusted,
+			  X509 *signer, STACK_OF(X509) **chain);
+static int TS_check_signing_certs(PKCS7_SIGNER_INFO *si, STACK_OF(X509) *chain);
+static ESS_SIGNING_CERT *ESS_get_signing_cert(PKCS7_SIGNER_INFO *si);
+static int TS_find_cert(STACK_OF(ESS_CERT_ID) *cert_ids, X509 *cert);
+static int TS_issuer_serial_cmp(ESS_ISSUER_SERIAL *is, X509_CINF *cinfo);
+static int int_TS_RESP_verify_token(TS_VERIFY_CTX *ctx, 
+				 PKCS7 *token, TS_TST_INFO *tst_info);
+static int TS_check_status_info(TS_RESP *response);
+static char *TS_get_status_text(STACK_OF(ASN1_UTF8STRING) *text);
+static int TS_check_policy(ASN1_OBJECT *req_oid, TS_TST_INFO *tst_info);
+static int TS_compute_imprint(BIO *data, TS_TST_INFO *tst_info,
+			      X509_ALGOR **md_alg, 
+			      unsigned char **imprint, unsigned *imprint_len);
+static int TS_check_imprints(X509_ALGOR *algor_a, 
+			     unsigned char *imprint_a, unsigned len_a,
+			     TS_TST_INFO *tst_info);
+static int TS_check_nonces(const ASN1_INTEGER *a, TS_TST_INFO *tst_info);
+static int TS_check_signer_name(GENERAL_NAME *tsa_name, X509 *signer);
+static int TS_find_name(STACK_OF(GENERAL_NAME) *gen_names, GENERAL_NAME *name);
+
+/*
+ * Local mapping between response codes and descriptions.
+ * Don't forget to change TS_STATUS_BUF_SIZE when modifying 
+ * the elements of this array.
+ */
+static const char *TS_status_text[] =
+	{ "granted",
+	  "grantedWithMods",
+	  "rejection",
+	  "waiting",
+	  "revocationWarning",
+	  "revocationNotification" };
+
+#define TS_STATUS_TEXT_SIZE	(sizeof(TS_status_text)/sizeof(*TS_status_text))
+
+/*
+ * This must be greater or equal to the sum of the strings in TS_status_text
+ * plus the number of its elements.
+ */
+#define TS_STATUS_BUF_SIZE	256
+
+static struct
+	{
+	int code;
+	const char *text;
+	} TS_failure_info[] =
+		{ { TS_INFO_BAD_ALG, "badAlg" },
+		  { TS_INFO_BAD_REQUEST, "badRequest" },
+		  { TS_INFO_BAD_DATA_FORMAT, "badDataFormat" },
+		  { TS_INFO_TIME_NOT_AVAILABLE, "timeNotAvailable" },
+		  { TS_INFO_UNACCEPTED_POLICY, "unacceptedPolicy" },
+		  { TS_INFO_UNACCEPTED_EXTENSION, "unacceptedExtension" },
+		  { TS_INFO_ADD_INFO_NOT_AVAILABLE, "addInfoNotAvailable" },
+		  { TS_INFO_SYSTEM_FAILURE, "systemFailure" } };
+
+#define TS_FAILURE_INFO_SIZE	(sizeof(TS_failure_info) / \
+				sizeof(*TS_failure_info))
+
+/* Functions for verifying a signed TS_TST_INFO structure. */
+
+/*
+ * This function carries out the following tasks:
+ *	- Checks if there is one and only one signer.
+ *	- Search for the signing certificate in 'certs' and in the response.
+ *	- Check the extended key usage and key usage fields of the signer
+ *	certificate (done by the path validation).
+ *	- Build and validate the certificate path.
+ *	- Check if the certificate path meets the requirements of the
+ *	SigningCertificate ESS signed attribute.
+ *	- Verify the signature value.
+ *	- Returns the signer certificate in 'signer', if 'signer' is not NULL.
+ */
+int TS_RESP_verify_signature(PKCS7 *token, STACK_OF(X509) *certs,
+			     X509_STORE *store, X509 **signer_out)
+	{
+	STACK_OF(PKCS7_SIGNER_INFO) *sinfos = NULL;
+	PKCS7_SIGNER_INFO *si;
+	STACK_OF(X509) *signers = NULL;
+	X509	*signer;
+	STACK_OF(X509) *chain = NULL;
+	char	buf[4096];
+	int	i, j = 0, ret = 0;
+	BIO	*p7bio = NULL;
+
+	/* Some sanity checks first. */
+	if (!token)
+		{
+		TSerr(TS_F_TS_RESP_VERIFY_SIGNATURE, TS_R_INVALID_NULL_POINTER);
+		goto err;
+		}
+
+	/* Check for the correct content type */
+	if(!PKCS7_type_is_signed(token))
+		{
+		TSerr(TS_F_TS_RESP_VERIFY_SIGNATURE, TS_R_WRONG_CONTENT_TYPE);
+		goto err;
+		}
+
+	/* Check if there is one and only one signer. */
+	sinfos = PKCS7_get_signer_info(token);
+	if (!sinfos || sk_PKCS7_SIGNER_INFO_num(sinfos) != 1)
+		{
+		TSerr(TS_F_TS_RESP_VERIFY_SIGNATURE,
+		      TS_R_THERE_MUST_BE_ONE_SIGNER);
+		goto err;
+		}
+	si = sk_PKCS7_SIGNER_INFO_value(sinfos, 0);
+
+	/* Check for no content: no data to verify signature. */
+	if (PKCS7_get_detached(token))
+		{
+		TSerr(TS_F_TS_RESP_VERIFY_SIGNATURE, TS_R_NO_CONTENT);
+		goto err;
+		}
+	
+	/* Get hold of the signer certificate, search only internal
+	   certificates if it was requested. */
+	signers = PKCS7_get0_signers(token, certs, 0);
+	if (!signers || sk_X509_num(signers) != 1) goto err;
+	signer = sk_X509_value(signers, 0);
+
+	/* Now verify the certificate. */
+	if (!TS_verify_cert(store, certs, signer, &chain)) goto err;
+
+	/* Check if the signer certificate is consistent with the
+	   ESS extension. */
+	if (!TS_check_signing_certs(si, chain)) goto err;
+
+	/* Creating the message digest. */
+	p7bio = PKCS7_dataInit(token, NULL);
+
+	/* We now have to 'read' from p7bio to calculate digests etc. */
+	while ((i = BIO_read(p7bio,buf,sizeof(buf))) > 0);
+
+	/* Verifying the signature. */
+	j = PKCS7_signatureVerify(p7bio, token, si, signer);
+	if (j <= 0)
+		{
+		TSerr(TS_F_TS_RESP_VERIFY_SIGNATURE, TS_R_SIGNATURE_FAILURE);
+		goto err;
+		}
+
+	/* Return the signer certificate if needed. */
+	if (signer_out)
+		{
+		*signer_out = signer;
+		CRYPTO_add(&signer->references, 1, CRYPTO_LOCK_X509);
+		}
+
+	ret = 1;
+
+ err:
+	BIO_free_all(p7bio);
+	sk_X509_pop_free(chain, X509_free);
+	sk_X509_free(signers);
+
+	return ret;
+	}
+
+/*
+ * The certificate chain is returned in chain. Caller is responsible for
+ * freeing the vector.
+ */
+static int TS_verify_cert(X509_STORE *store, STACK_OF(X509) *untrusted,
+			  X509 *signer, STACK_OF(X509) **chain)
+	{
+	X509_STORE_CTX	cert_ctx;
+	int i;
+	int ret = 1;
+
+	/* chain is an out argument. */
+	*chain = NULL;
+	X509_STORE_CTX_init(&cert_ctx, store, signer, untrusted);
+	X509_STORE_CTX_set_purpose(&cert_ctx, X509_PURPOSE_TIMESTAMP_SIGN);
+	i = X509_verify_cert(&cert_ctx);
+	if (i <= 0)
+		{
+		int j = X509_STORE_CTX_get_error(&cert_ctx);
+		TSerr(TS_F_TS_VERIFY_CERT, TS_R_CERTIFICATE_VERIFY_ERROR);
+		ERR_add_error_data(2, "Verify error:",
+				   X509_verify_cert_error_string(j));
+		ret = 0;
+		}
+	else
+		{
+		/* Get a copy of the certificate chain. */
+		*chain = X509_STORE_CTX_get1_chain(&cert_ctx);
+		}
+
+	X509_STORE_CTX_cleanup(&cert_ctx);
+
+	return ret;
+	}
+
+static int TS_check_signing_certs(PKCS7_SIGNER_INFO *si, STACK_OF(X509) *chain)
+	{
+	ESS_SIGNING_CERT *ss = ESS_get_signing_cert(si);
+	STACK_OF(ESS_CERT_ID) *cert_ids = NULL;
+	X509 *cert;
+	int i = 0;
+	int ret = 0;
+
+	if (!ss) goto err;
+	cert_ids = ss->cert_ids;
+	/* The signer certificate must be the first in cert_ids. */
+	cert = sk_X509_value(chain, 0);
+	if (TS_find_cert(cert_ids, cert) != 0) goto err;
+	
+	/* Check the other certificates of the chain if there are more
+	   than one certificate ids in cert_ids. */
+	if (sk_ESS_CERT_ID_num(cert_ids) > 1)
+		{
+		/* All the certificates of the chain must be in cert_ids. */
+		for (i = 1; i < sk_X509_num(chain); ++i)
+			{
+			cert = sk_X509_value(chain, i);
+			if (TS_find_cert(cert_ids, cert) < 0) goto err;
+			}
+		}
+	ret = 1;
+ err:
+	if (!ret)
+		TSerr(TS_F_TS_CHECK_SIGNING_CERTS, 
+		      TS_R_ESS_SIGNING_CERTIFICATE_ERROR);
+	ESS_SIGNING_CERT_free(ss);
+	return ret;
+	}
+
+static ESS_SIGNING_CERT *ESS_get_signing_cert(PKCS7_SIGNER_INFO *si)
+	{
+	ASN1_TYPE *attr;
+	const unsigned char *p;
+	attr = PKCS7_get_signed_attribute(si, 
+					  NID_id_smime_aa_signingCertificate);
+	if (!attr) return NULL;
+	p = attr->value.sequence->data;
+	return d2i_ESS_SIGNING_CERT(NULL, &p, attr->value.sequence->length);
+	}
+
+/* Returns < 0 if certificate is not found, certificate index otherwise. */
+static int TS_find_cert(STACK_OF(ESS_CERT_ID) *cert_ids, X509 *cert)
+	{
+	int i;
+
+	if (!cert_ids || !cert) return -1;
+
+	/* Recompute SHA1 hash of certificate if necessary (side effect). */
+	X509_check_purpose(cert, -1, 0);
+
+	/* Look for cert in the cert_ids vector. */
+	for (i = 0; i < sk_ESS_CERT_ID_num(cert_ids); ++i)
+		{
+		ESS_CERT_ID *cid = sk_ESS_CERT_ID_value(cert_ids, i);
+
+		/* Check the SHA-1 hash first. */
+		if (cid->hash->length == sizeof(cert->sha1_hash)
+		    && !memcmp(cid->hash->data, cert->sha1_hash,
+			       sizeof(cert->sha1_hash)))
+			{
+			/* Check the issuer/serial as well if specified. */
+			ESS_ISSUER_SERIAL *is = cid->issuer_serial;
+			if (!is || !TS_issuer_serial_cmp(is, cert->cert_info))
+				return i;
+			}
+		}
+	
+	return -1;
+	}
+
+static int TS_issuer_serial_cmp(ESS_ISSUER_SERIAL *is, X509_CINF *cinfo)
+	{
+	GENERAL_NAME *issuer;
+
+	if (!is || !cinfo || sk_GENERAL_NAME_num(is->issuer) != 1) return -1;
+
+	/* Check the issuer first. It must be a directory name. */
+	issuer = sk_GENERAL_NAME_value(is->issuer, 0);
+	if (issuer->type != GEN_DIRNAME 
+	    || X509_NAME_cmp(issuer->d.dirn, cinfo->issuer))
+		return -1;
+
+	/* Check the serial number, too. */
+	if (ASN1_INTEGER_cmp(is->serial, cinfo->serialNumber))
+		return -1;
+
+	return 0;
+	}
+
+/*
+ * Verifies whether 'response' contains a valid response with regards 
+ * to the settings of the context:
+ *	- Gives an error message if the TS_TST_INFO is not present.
+ *	- Calls _TS_RESP_verify_token to verify the token content.
+ */
+int TS_RESP_verify_response(TS_VERIFY_CTX *ctx, TS_RESP *response)
+	{
+	PKCS7 *token = TS_RESP_get_token(response);
+	TS_TST_INFO *tst_info = TS_RESP_get_tst_info(response);
+	int ret = 0;
+
+	/* Check if we have a successful TS_TST_INFO object in place. */
+	if (!TS_check_status_info(response)) goto err;
+
+	/* Check the contents of the time stamp token. */
+	if (!int_TS_RESP_verify_token(ctx, token, tst_info))
+		goto err;
+
+	ret = 1;
+ err:
+	return ret;
+	}
+
+/*
+ * Tries to extract a TS_TST_INFO structure from the PKCS7 token and
+ * calls the internal int_TS_RESP_verify_token function for verifying it.
+ */
+int TS_RESP_verify_token(TS_VERIFY_CTX *ctx, PKCS7 *token)
+	{
+	TS_TST_INFO *tst_info = PKCS7_to_TS_TST_INFO(token);
+	int ret = 0;
+	if (tst_info)
+		{
+		ret = int_TS_RESP_verify_token(ctx, token, tst_info);
+		TS_TST_INFO_free(tst_info);
+		}
+	return ret;
+	}
+
+/*
+ * Verifies whether the 'token' contains a valid time stamp token 
+ * with regards to the settings of the context. Only those checks are
+ * carried out that are specified in the context:
+ *	- Verifies the signature of the TS_TST_INFO.
+ *	- Checks the version number of the response.
+ *	- Check if the requested and returned policies math.
+ *	- Check if the message imprints are the same.
+ *	- Check if the nonces are the same.
+ *	- Check if the TSA name matches the signer.
+ *	- Check if the TSA name is the expected TSA.
+ */
+static int int_TS_RESP_verify_token(TS_VERIFY_CTX *ctx, 
+				 PKCS7 *token, TS_TST_INFO *tst_info)
+	{
+	X509 *signer = NULL;
+	GENERAL_NAME *tsa_name = TS_TST_INFO_get_tsa(tst_info);
+	X509_ALGOR *md_alg = NULL;
+	unsigned char *imprint = NULL;
+	unsigned imprint_len = 0;
+	int ret = 0;
+
+	/* Verify the signature. */
+	if ((ctx->flags & TS_VFY_SIGNATURE)
+	    && !TS_RESP_verify_signature(token, ctx->certs, ctx->store,
+					 &signer))
+		goto err;
+	
+	/* Check version number of response. */
+	if ((ctx->flags & TS_VFY_VERSION)
+	    && TS_TST_INFO_get_version(tst_info) != 1)
+		{
+		TSerr(TS_F_INT_TS_RESP_VERIFY_TOKEN, TS_R_UNSUPPORTED_VERSION);
+		goto err;
+		}
+
+	/* Check policies. */
+	if ((ctx->flags & TS_VFY_POLICY)
+	    && !TS_check_policy(ctx->policy, tst_info))
+		goto err;
+	
+	/* Check message imprints. */
+	if ((ctx->flags & TS_VFY_IMPRINT)
+	    && !TS_check_imprints(ctx->md_alg, ctx->imprint, ctx->imprint_len,
+				  tst_info)) 
+		goto err;
+
+	/* Compute and check message imprints. */
+	if ((ctx->flags & TS_VFY_DATA)
+	    && (!TS_compute_imprint(ctx->data, tst_info,
+				    &md_alg, &imprint, &imprint_len)
+	    || !TS_check_imprints(md_alg, imprint, imprint_len, tst_info)))
+		goto err;
+
+	/* Check nonces. */
+	if ((ctx->flags & TS_VFY_NONCE)
+	    && !TS_check_nonces(ctx->nonce, tst_info))
+		goto err;
+
+	/* Check whether TSA name and signer certificate match. */
+	if ((ctx->flags & TS_VFY_SIGNER)
+	    && tsa_name && !TS_check_signer_name(tsa_name, signer))
+		{
+		TSerr(TS_F_INT_TS_RESP_VERIFY_TOKEN, TS_R_TSA_NAME_MISMATCH);
+		goto err;
+		}
+
+	/* Check whether the TSA is the expected one. */
+	if ((ctx->flags & TS_VFY_TSA_NAME)
+	    && !TS_check_signer_name(ctx->tsa_name, signer))
+		{
+		TSerr(TS_F_INT_TS_RESP_VERIFY_TOKEN, TS_R_TSA_UNTRUSTED);
+		goto err;
+		}
+
+	ret = 1;
+ err:
+	X509_free(signer);
+	X509_ALGOR_free(md_alg);
+	OPENSSL_free(imprint);
+	return ret;
+	}
+
+static int TS_check_status_info(TS_RESP *response)
+	{
+	TS_STATUS_INFO *info = TS_RESP_get_status_info(response);
+	long status = ASN1_INTEGER_get(info->status);
+	const char *status_text = NULL;
+	char *embedded_status_text = NULL;
+	char failure_text[TS_STATUS_BUF_SIZE] = "";
+
+	/* Check if everything went fine. */
+	if (status == 0 || status == 1) return 1;
+
+	/* There was an error, get the description in status_text. */
+	if (0 <= status && status < (long)TS_STATUS_TEXT_SIZE)
+		status_text = TS_status_text[status];
+	else
+		status_text = "unknown code";
+
+	/* Set the embedded_status_text to the returned description. */
+	if (sk_ASN1_UTF8STRING_num(info->text) > 0
+	    && !(embedded_status_text = TS_get_status_text(info->text)))
+		return 0;
+	
+	/* Filling in failure_text with the failure information. */
+	if (info->failure_info)
+		{
+		int i;
+		int first = 1;
+		for (i = 0; i < (int)TS_FAILURE_INFO_SIZE; ++i)
+			{
+			if (ASN1_BIT_STRING_get_bit(info->failure_info,
+						    TS_failure_info[i].code))
+				{
+				if (!first)
+					strcpy(failure_text, ",");
+				else
+					first = 0;
+				strcat(failure_text, TS_failure_info[i].text);
+				}
+			}
+		}
+	if (failure_text[0] == '\0')
+		strcpy(failure_text, "unspecified");
+
+	/* Making up the error string. */
+	TSerr(TS_F_TS_CHECK_STATUS_INFO, TS_R_NO_TIME_STAMP_TOKEN);
+	ERR_add_error_data(6,
+			   "status code: ", status_text,
+			   ", status text: ", embedded_status_text ? 
+			   embedded_status_text : "unspecified",
+			   ", failure codes: ", failure_text);
+	OPENSSL_free(embedded_status_text);
+
+	return 0;
+	}
+
+static char *TS_get_status_text(STACK_OF(ASN1_UTF8STRING) *text)
+	{
+	int i;
+	unsigned int length = 0;
+	char *result = NULL;
+	char *p;
+
+	/* Determine length first. */
+	for (i = 0; i < sk_ASN1_UTF8STRING_num(text); ++i)
+		{
+		ASN1_UTF8STRING *current = sk_ASN1_UTF8STRING_value(text, i);
+		length += ASN1_STRING_length(current);
+		length += 1;	/* separator character */
+		}
+	/* Allocate memory (closing '\0' included). */
+	if (!(result = OPENSSL_malloc(length)))
+		{
+		TSerr(TS_F_TS_GET_STATUS_TEXT, ERR_R_MALLOC_FAILURE);
+		return NULL;
+		}
+	/* Concatenate the descriptions. */
+	for (i = 0, p = result; i < sk_ASN1_UTF8STRING_num(text); ++i)
+		{
+		ASN1_UTF8STRING *current = sk_ASN1_UTF8STRING_value(text, i);
+		length = ASN1_STRING_length(current);
+		if (i > 0) *p++ = '/';
+		strncpy(p, (const char *)ASN1_STRING_data(current), length);
+		p += length;
+		}
+	/* We do have space for this, too. */
+	*p = '\0';
+	
+	return result;
+	}
+
+static int TS_check_policy(ASN1_OBJECT *req_oid, TS_TST_INFO *tst_info)
+	{
+	ASN1_OBJECT *resp_oid = TS_TST_INFO_get_policy_id(tst_info);
+
+	if (OBJ_cmp(req_oid, resp_oid) != 0)
+		{
+		TSerr(TS_F_TS_CHECK_POLICY, TS_R_POLICY_MISMATCH);
+		return 0;
+		}
+
+	return 1;
+	}
+
+static int TS_compute_imprint(BIO *data, TS_TST_INFO *tst_info,
+			      X509_ALGOR **md_alg, 
+			      unsigned char **imprint, unsigned *imprint_len)
+	{
+	TS_MSG_IMPRINT *msg_imprint = TS_TST_INFO_get_msg_imprint(tst_info);
+	X509_ALGOR *md_alg_resp = TS_MSG_IMPRINT_get_algo(msg_imprint);
+	const EVP_MD *md;
+	EVP_MD_CTX md_ctx;
+	unsigned char buffer[4096];
+	int length;
+
+	*md_alg = NULL;
+	*imprint = NULL;
+
+	/* Return the MD algorithm of the response. */
+	if (!(*md_alg = X509_ALGOR_dup(md_alg_resp))) goto err;
+
+	/* Getting the MD object. */
+	if (!(md = EVP_get_digestbyobj((*md_alg)->algorithm)))
+		{
+		TSerr(TS_F_TS_COMPUTE_IMPRINT, TS_R_UNSUPPORTED_MD_ALGORITHM);
+		goto err;
+		}
+
+	/* Compute message digest. */
+	length = EVP_MD_size(md);
+	if (length < 0)
+	    goto err;
+	*imprint_len = length;
+	if (!(*imprint = OPENSSL_malloc(*imprint_len))) 
+		{
+		TSerr(TS_F_TS_COMPUTE_IMPRINT, ERR_R_MALLOC_FAILURE);
+		goto err;
+		}
+
+	EVP_DigestInit(&md_ctx, md);
+	while ((length = BIO_read(data, buffer, sizeof(buffer))) > 0)
+		{
+		EVP_DigestUpdate(&md_ctx, buffer, length);
+		}
+	EVP_DigestFinal(&md_ctx, *imprint, NULL);
+
+	return 1;
+ err:
+	X509_ALGOR_free(*md_alg);
+	OPENSSL_free(*imprint);
+	*imprint_len = 0;
+	return 0;
+	}
+
+static int TS_check_imprints(X509_ALGOR *algor_a, 
+			     unsigned char *imprint_a, unsigned len_a,
+			     TS_TST_INFO *tst_info)
+	{
+	TS_MSG_IMPRINT *b = TS_TST_INFO_get_msg_imprint(tst_info);
+	X509_ALGOR *algor_b = TS_MSG_IMPRINT_get_algo(b);
+	int ret = 0;
+
+	/* algor_a is optional. */
+	if (algor_a)
+		{
+		/* Compare algorithm OIDs. */
+		if (OBJ_cmp(algor_a->algorithm, algor_b->algorithm)) goto err;
+
+		/* The parameter must be NULL in both. */
+		if ((algor_a->parameter 
+		     && ASN1_TYPE_get(algor_a->parameter) != V_ASN1_NULL)
+		    || (algor_b->parameter
+			&& ASN1_TYPE_get(algor_b->parameter) != V_ASN1_NULL))
+			goto err;
+		}
+
+	/* Compare octet strings. */
+	ret = len_a == (unsigned) ASN1_STRING_length(b->hashed_msg) &&
+		memcmp(imprint_a, ASN1_STRING_data(b->hashed_msg), len_a) == 0;
+ err:
+	if (!ret)
+		TSerr(TS_F_TS_CHECK_IMPRINTS, TS_R_MESSAGE_IMPRINT_MISMATCH);
+	return ret;
+	}
+
+static int TS_check_nonces(const ASN1_INTEGER *a, TS_TST_INFO *tst_info)
+	{
+	const ASN1_INTEGER *b = TS_TST_INFO_get_nonce(tst_info);
+
+	/* Error if nonce is missing. */
+	if (!b)
+		{
+		TSerr(TS_F_TS_CHECK_NONCES, TS_R_NONCE_NOT_RETURNED);
+		return 0;
+		}
+
+	/* No error if a nonce is returned without being requested. */
+	if (ASN1_INTEGER_cmp(a, b) != 0)
+		{
+		TSerr(TS_F_TS_CHECK_NONCES, TS_R_NONCE_MISMATCH);
+		return 0;
+		}
+
+	return 1;
+	}
+
+/* Check if the specified TSA name matches either the subject
+   or one of the subject alternative names of the TSA certificate. */
+static int TS_check_signer_name(GENERAL_NAME *tsa_name, X509 *signer)
+	{
+	STACK_OF(GENERAL_NAME) *gen_names = NULL;
+	int idx = -1;
+	int found = 0;
+
+	/* Check the subject name first. */
+	if (tsa_name->type == GEN_DIRNAME 
+	    && X509_name_cmp(tsa_name->d.dirn, signer->cert_info->subject) == 0)
+		return 1;
+
+	/* Check all the alternative names. */
+	gen_names = X509_get_ext_d2i(signer, NID_subject_alt_name,
+				     NULL, &idx);
+	while (gen_names != NULL
+	       && !(found = TS_find_name(gen_names, tsa_name) >= 0))
+		{
+		/* Get the next subject alternative name,
+		   although there should be no more than one. */
+		GENERAL_NAMES_free(gen_names);
+		gen_names = X509_get_ext_d2i(signer, NID_subject_alt_name,
+					     NULL, &idx);
+		}
+	if (gen_names) GENERAL_NAMES_free(gen_names);
+	
+	return found;
+	}
+
+/* Returns 1 if name is in gen_names, 0 otherwise. */
+static int TS_find_name(STACK_OF(GENERAL_NAME) *gen_names, GENERAL_NAME *name)
+	{
+	int i, found;
+	for (i = 0, found = 0; !found && i < sk_GENERAL_NAME_num(gen_names);
+	     ++i)
+		{
+		GENERAL_NAME *current = sk_GENERAL_NAME_value(gen_names, i);
+		found = GENERAL_NAME_cmp(current, name) == 0;
+		}
+	return found ? i - 1 : -1;
+	}