]> WPIA git - cassiopeia.git/blobdiff - lib/openssl/crypto/ts/ts_rsp_verify.c
add: execute openssl fetcher to fetch openssl 1.0.1j
[cassiopeia.git] / lib / openssl / crypto / ts / ts_rsp_verify.c
diff --git a/lib/openssl/crypto/ts/ts_rsp_verify.c b/lib/openssl/crypto/ts/ts_rsp_verify.c
new file mode 100644 (file)
index 0000000..b7d170a
--- /dev/null
@@ -0,0 +1,729 @@
+/* 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;
+               }
+
+       if (!EVP_DigestInit(&md_ctx, md))
+               goto err;
+       while ((length = BIO_read(data, buffer, sizeof(buffer))) > 0)
+               {
+               if (!EVP_DigestUpdate(&md_ctx, buffer, length))
+                       goto err;
+               }
+       if (!EVP_DigestFinal(&md_ctx, *imprint, NULL))
+               goto err;
+
+       return 1;
+ err:
+       X509_ALGOR_free(*md_alg);
+       OPENSSL_free(*imprint);
+       *imprint_len = 0;
+       *imprint = NULL;
+       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;
+       }