Upgrade chrome's OpenSSL to same version Android ships with.

openssl/crypto/ts/ts_rsp_verify.c

+/* 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;
+        }