schannel: add support for CURLOPT_CAINFO

- Move verify_certificate functionality in schannel.c into a new
  file called schannel_verify.c. Additionally, some structure defintions
  from schannel.c have been moved to schannel.h to allow them to be
  used in schannel_verify.c.

- Make verify_certificate functionality for Schannel available on
  all versions of Windows instead of just Windows CE. verify_certificate
  will be invoked on Windows CE or when the user specifies
  CURLOPT_CAINFO and CURLOPT_SSL_VERIFYPEER.

- In verify_certificate, create a custom certificate chain engine that
  exclusively trusts the certificate store backed by the CURLOPT_CAINFO
  file.

- doc updates of --cacert/CAINFO support for schannel

- Use CERT_NAME_SEARCH_ALL_NAMES_FLAG when invoking CertGetNameString
  when available. This implements a TODO in schannel.c to improve
  handling of multiple SANs in a certificate. In particular, all SANs
  will now be searched instead of just the first name.

- Update tool_operate.c to not search for the curl-ca-bundle.crt file
  when using Schannel to maintain backward compatibility. Previously,
  any curl-ca-bundle.crt file found in that search would have been
  ignored by Schannel. But, with CAINFO support, the file found by
  that search would have been used as the certificate store and
  could cause issues for any users that have curl-ca-bundle.crt in
  the search path.

- Update url.c to not set the build time CURL_CA_BUNDLE if the selected
  SSL backend is Schannel. We allow setting CA location for schannel
  only when explicitly specified by the user via CURLOPT_CAINFO /
  --cacert.

- Add new test cases 3000 and 3001. These test cases check that the first
  and last SAN, respectively, matches the connection hostname. New test
  certificates have been added for these cases. For 3000, the certificate
  prefix is Server-localhost-firstSAN and for 3001, the certificate
  prefix is Server-localhost-secondSAN.

- Remove TODO 15.2 (Add support for custom server certificate
  validation), this commit addresses it.

Closes https://github.com/curl/curl/pull/1325

1 files changed, 551 insertions, 0 deletions

diff --git a/lib/vtls/schannel_verify.c b/lib/vtls/schannel_verify.c
new file mode 100644
index 000000000..db187dd6b
--- /dev/null
+++ b/lib/vtls/schannel_verify.c
@@ -0,0 +1,551 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 2012 - 2016, Marc Hoersken, <info@marc-hoersken.de>
+ * Copyright (C) 2012, Mark Salisbury, <mark.salisbury@hp.com>
+ * Copyright (C) 2012 - 2018, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+
+/*
+ * Source file for SChannel-specific certificate verification. This code should
+ * only be invoked by code in schannel.c.
+ */
+
+#include "curl_setup.h"
+
+#ifdef USE_SCHANNEL
+
+#define EXPOSE_SCHANNEL_INTERNAL_STRUCTS
+
+#ifndef USE_WINDOWS_SSPI
+#  error "Can't compile SCHANNEL support without SSPI."
+#endif
+
+#include "schannel.h"
+#include "vtls.h"
+#include "sendf.h"
+#include "strerror.h"
+#include "curl_multibyte.h"
+#include "curl_printf.h"
+#include "hostcheck.h"
+#include "system_win32.h"
+
+/* The last #include file should be: */
+#include "curl_memory.h"
+#include "memdebug.h"
+
+#define BACKEND connssl->backend
+
+#define MAX_CAFILE_SIZE 1048576 /* 1 MiB */
+#define BEGIN_CERT "-----BEGIN CERTIFICATE-----\n"
+#define END_CERT "\n-----END CERTIFICATE-----"
+
+typedef struct {
+  DWORD cbSize;
+  HCERTSTORE hRestrictedRoot;
+  HCERTSTORE hRestrictedTrust;
+  HCERTSTORE hRestrictedOther;
+  DWORD cAdditionalStore;
+  HCERTSTORE *rghAdditionalStore;
+  DWORD dwFlags;
+  DWORD dwUrlRetrievalTimeout;
+  DWORD MaximumCachedCertificates;
+  DWORD CycleDetectionModulus;
+  HCERTSTORE hExclusiveRoot;
+  HCERTSTORE hExclusiveTrustedPeople;
+} CERT_CHAIN_ENGINE_CONFIG_WIN7, *PCERT_CHAIN_ENGINE_CONFIG_WIN7;
+
+
+static CURLcode add_certs_to_store(HCERTSTORE trust_store,
+                                   const char *ca_file,
+                                   struct connectdata *conn)
+{
+  CURLcode result;
+  struct Curl_easy *data = conn->data;
+  HANDLE ca_file_handle = INVALID_HANDLE_VALUE;
+  LARGE_INTEGER file_size;
+  char *ca_file_buffer = NULL;
+  char *current_ca_file_ptr = NULL;
+  const TCHAR *ca_file_tstr = NULL;
+  size_t ca_file_bufsize = 0;
+  DWORD total_bytes_read = 0;
+  bool more_certs = 0;
+  int num_certs = 0;
+  size_t END_CERT_LEN;
+
+  ca_file_tstr = Curl_convert_UTF8_to_tchar(ca_file);
+  if(!ca_file_tstr) {
+    failf(data,
+          "schannel: invalid path name for CA file '%s': %s",
+          ca_file, Curl_strerror(conn, GetLastError()));
+    result = CURLE_SSL_CACERT_BADFILE;
+    goto cleanup;
+  }
+
+  /*
+   * Read the CA file completely into memory before parsing it. This
+   * optimizes for the common case where the CA file will be relatively
+   * small ( < 1 MiB ).
+   */
+  ca_file_handle = CreateFile(ca_file_tstr,
+                              GENERIC_READ,
+                              0,
+                              NULL,
+                              OPEN_EXISTING,
+                              FILE_ATTRIBUTE_NORMAL,
+                              NULL);
+  if(ca_file_handle == INVALID_HANDLE_VALUE) {
+    failf(data,
+          "schannel: failed to open CA file '%s': %s",
+          ca_file, Curl_strerror(conn, GetLastError()));
+    result = CURLE_SSL_CACERT_BADFILE;
+    goto cleanup;
+  }
+
+  if(!GetFileSizeEx(ca_file_handle, &file_size)) {
+    failf(data,
+          "schannel: failed to determine size of CA file '%s': %s",
+          ca_file, Curl_strerror(conn, GetLastError()));
+    result = CURLE_SSL_CACERT_BADFILE;
+    goto cleanup;
+  }
+
+  if(file_size.QuadPart > MAX_CAFILE_SIZE) {
+    failf(data,
+          "schannel: CA file exceeds max size of %u bytes",
+          MAX_CAFILE_SIZE);
+    result = CURLE_OUT_OF_MEMORY;
+    goto cleanup;
+  }
+
+  ca_file_bufsize = (size_t)file_size.QuadPart;
+  ca_file_buffer = (char *)malloc(ca_file_bufsize + 1);
+  if(!ca_file_buffer) {
+    result = CURLE_OUT_OF_MEMORY;
+    goto cleanup;
+  }
+
+  result = CURLE_OK;
+  while(total_bytes_read < ca_file_bufsize) {
+    DWORD bytes_to_read = (DWORD)(ca_file_bufsize - total_bytes_read);
+    DWORD bytes_read = 0;
+
+    if(!ReadFile(ca_file_handle, ca_file_buffer + total_bytes_read,
+                 bytes_to_read, &bytes_read, NULL)) {
+
+      failf(data,
+            "schannel: failed to read from CA file '%s': %s",
+            ca_file, Curl_strerror(conn, GetLastError()));
+      result = CURLE_SSL_CACERT_BADFILE;
+      goto cleanup;
+    }
+    if(bytes_read == 0) {
+      /* Premature EOF -- adjust the bufsize to the new value */
+      ca_file_bufsize = total_bytes_read;
+    }
+    else {
+      total_bytes_read += bytes_read;
+    }
+  }
+
+  /* Null terminate the buffer */
+  ca_file_buffer[ca_file_bufsize] = '\0';
+
+  if(result != CURLE_OK) {
+    goto cleanup;
+  }
+
+  END_CERT_LEN = strlen(END_CERT);
+
+  more_certs = 1;
+  current_ca_file_ptr = ca_file_buffer;
+  while(more_certs && *current_ca_file_ptr != '\0') {
+    char *begin_cert_ptr = strstr(current_ca_file_ptr, BEGIN_CERT);
+    if(!begin_cert_ptr) {
+      more_certs = 0;
+    }
+    else {
+      char *end_cert_ptr = strstr(begin_cert_ptr, END_CERT);
+      if(!end_cert_ptr) {
+        failf(data,
+              "schannel: CA file '%s' is not correctly formatted",
+              ca_file);
+        result = CURLE_SSL_CACERT_BADFILE;
+        more_certs = 0;
+      }
+      else {
+        CERT_BLOB cert_blob;
+        CERT_CONTEXT *cert_context = NULL;
+        BOOL add_cert_result = FALSE;
+        DWORD actual_content_type = 0;
+        DWORD cert_size = (DWORD)
+          ((end_cert_ptr + END_CERT_LEN) - begin_cert_ptr);
+
+        cert_blob.pbData = (BYTE *)begin_cert_ptr;
+        cert_blob.cbData = cert_size;
+        if(!CryptQueryObject(CERT_QUERY_OBJECT_BLOB,
+                             &cert_blob,
+                             CERT_QUERY_CONTENT_FLAG_CERT,
+                             CERT_QUERY_FORMAT_FLAG_ALL,
+                             0,
+                             NULL,
+                             &actual_content_type,
+                             NULL,
+                             NULL,
+                             NULL,
+                             &cert_context)) {
+
+          failf(data,
+                "schannel: failed to extract certificate from CA file "
+                "'%s': %s",
+                ca_file, Curl_strerror(conn, GetLastError()));
+          result = CURLE_SSL_CACERT_BADFILE;
+          more_certs = 0;
+        }
+        else {
+          current_ca_file_ptr = begin_cert_ptr + cert_size;
+
+          /* Sanity check that the cert_context object is the right type */
+          if(CERT_QUERY_CONTENT_CERT != actual_content_type) {
+            failf(data,
+                  "schannel: unexpected content type '%d' when extracting "
+                  "certificate from CA file '%s'",
+                  actual_content_type, ca_file);
+            result = CURLE_SSL_CACERT_BADFILE;
+            more_certs = 0;
+          }
+          else {
+            add_cert_result =
+              CertAddCertificateContextToStore(trust_store,
+                                               cert_context,
+                                               CERT_STORE_ADD_ALWAYS,
+                                               NULL);
+            CertFreeCertificateContext(cert_context);
+            if(!add_cert_result) {
+              failf(data,
+                    "schannel: failed to add certificate from CA file '%s'"
+                    "to certificate store: %s",
+                    ca_file, Curl_strerror(conn, GetLastError()));
+              result = CURLE_SSL_CACERT_BADFILE;
+              more_certs = 0;
+            }
+            else {
+              num_certs++;
+            }
+          }
+        }
+      }
+    }
+  }
+
+  if(result == CURLE_OK) {
+    if(!num_certs) {
+      infof(data,
+            "schannel: did not add any certificates from CA file '%s'\n",
+            ca_file);
+    }
+    else {
+      infof(data,
+            "schannel: added %d certificate(s) from CA file '%s'\n",
+            num_certs, ca_file);
+    }
+  }
+
+cleanup:
+  if(ca_file_handle != INVALID_HANDLE_VALUE) {
+    CloseHandle(ca_file_handle);
+  }
+  Curl_safefree(ca_file_buffer);
+  Curl_unicodefree(ca_file_tstr);
+
+  return result;
+}
+
+static CURLcode verify_host(struct Curl_easy *data,
+                            CERT_CONTEXT *pCertContextServer,
+                            const char * const conn_hostname)
+{
+  CURLcode result = CURLE_PEER_FAILED_VERIFICATION;
+  TCHAR *cert_hostname_buff = NULL;
+  size_t cert_hostname_buff_index = 0;
+  DWORD len = 0;
+  DWORD actual_len = 0;
+
+  /* CertGetNameString will provide the 8-bit character string without
+   * any decoding */
+  DWORD name_flags = CERT_NAME_DISABLE_IE4_UTF8_FLAG;
+
+#ifdef CERT_NAME_SEARCH_ALL_NAMES_FLAG
+  name_flags |= CERT_NAME_SEARCH_ALL_NAMES_FLAG;
+#endif
+
+  /* Determine the size of the string needed for the cert hostname */
+  len = CertGetNameString(pCertContextServer,
+                          CERT_NAME_DNS_TYPE,
+                          name_flags,
+                          NULL,
+                          NULL,
+                          0);
+  if(len == 0) {
+    failf(data,
+          "schannel: CertGetNameString() returned no "
+          "certificate name information");
+    result = CURLE_PEER_FAILED_VERIFICATION;
+    goto cleanup;
+  }
+
+  /* CertGetNameString guarantees that the returned name will not contain
+   * embedded null bytes. This appears to be undocumented behavior.
+   */
+  cert_hostname_buff = (LPTSTR)malloc(len * sizeof(TCHAR));
+  actual_len = CertGetNameString(pCertContextServer,
+                                 CERT_NAME_DNS_TYPE,
+                                 name_flags,
+                                 NULL,
+                                 (LPTSTR) cert_hostname_buff,
+                                 len);
+
+  /* Sanity check */
+  if(actual_len != len) {
+    failf(data,
+          "schannel: CertGetNameString() returned certificate "
+          "name information of unexpected size");
+    result = CURLE_PEER_FAILED_VERIFICATION;
+    goto cleanup;
+  }
+
+  /* If HAVE_CERT_NAME_SEARCH_ALL_NAMES is available, the output
+   * will contain all DNS names, where each name is null-terminated
+   * and the last DNS name is double null-terminated. Due to this
+   * encoding, use the length of the buffer to iterate over all names.
+   */
+  result = CURLE_PEER_FAILED_VERIFICATION;
+  while(cert_hostname_buff_index < len &&
+        cert_hostname_buff[cert_hostname_buff_index] != TEXT('\0') &&
+        result == CURLE_PEER_FAILED_VERIFICATION) {
+
+    char *cert_hostname;
+
+    /* Comparing the cert name and the connection hostname encoded as UTF-8
+     * is acceptable since both values are assumed to use ASCII
+     * (or some equivalent) encoding
+     */
+    cert_hostname = Curl_convert_tchar_to_UTF8(
+        &cert_hostname_buff[cert_hostname_buff_index]);
+    if(!cert_hostname) {
+      result = CURLE_OUT_OF_MEMORY;
+    }
+    else {
+      int match_result;
+
+      match_result = Curl_cert_hostcheck(cert_hostname, conn_hostname);
+      if(match_result == CURL_HOST_MATCH) {
+        infof(data,
+              "schannel: connection hostname (%s) validated "
+              "against certificate name (%s)\n",
+              conn_hostname, cert_hostname);
+        result = CURLE_OK;
+      }
+      else {
+        size_t cert_hostname_len;
+
+        infof(data,
+              "schannel: connection hostname (%s) did not match "
+              "against certificate name (%s)\n",
+              conn_hostname, cert_hostname);
+
+        cert_hostname_len = _tcslen(
+            &cert_hostname_buff[cert_hostname_buff_index]);
+
+        /* Move on to next cert name */
+        cert_hostname_buff_index += cert_hostname_len + 1;
+
+        result = CURLE_PEER_FAILED_VERIFICATION;
+      }
+      Curl_unicodefree(cert_hostname);
+    }
+  }
+
+  if(result == CURLE_PEER_FAILED_VERIFICATION) {
+    failf(data,
+          "schannel: CertGetNameString() failed to match "
+          "connection hostname (%s) against server certificate names",
+          conn_hostname);
+  }
+  else if(result != CURLE_OK)
+    failf(data, "schannel: server certificate name verification failed");
+
+cleanup:
+  Curl_unicodefree(cert_hostname_buff);
+
+  return result;
+}
+
+CURLcode verify_certificate(struct connectdata *conn, int sockindex)
+{
+  SECURITY_STATUS status;
+  struct Curl_easy *data = conn->data;
+  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
+  CURLcode result = CURLE_OK;
+  CERT_CONTEXT *pCertContextServer = NULL;
+  const CERT_CHAIN_CONTEXT *pChainContext = NULL;
+  HCERTCHAINENGINE cert_chain_engine = NULL;
+  HCERTSTORE trust_store = NULL;
+  const char * const conn_hostname = SSL_IS_PROXY() ?
+    conn->http_proxy.host.name :
+    conn->host.name;
+
+  status = s_pSecFn->QueryContextAttributes(&BACKEND->ctxt->ctxt_handle,
+                                            SECPKG_ATTR_REMOTE_CERT_CONTEXT,
+                                            &pCertContextServer);
+
+  if((status != SEC_E_OK) || (pCertContextServer == NULL)) {
+    failf(data, "schannel: Failed to read remote certificate context: %s",
+          Curl_sspi_strerror(conn, status));
+    result = CURLE_PEER_FAILED_VERIFICATION;
+  }
+
+  if(result == CURLE_OK && SSL_CONN_CONFIG(CAfile) &&
+      BACKEND->use_manual_cred_validation) {
+    /*
+     * Create a chain engine that uses the certificates in the CA file as
+     * trusted certificates. This is only supported on Windows 7+.
+     */
+
+    if(Curl_verify_windows_version(6, 1, PLATFORM_WINNT, VERSION_LESS_THAN)) {
+      failf(data, "schannel: this version of Windows is too old to support "
+            "certificate verification via CA bundle file.");
+      result = CURLE_SSL_CACERT_BADFILE;
+    }
+    else {
+      /* Open the certificate store */
+      trust_store = CertOpenStore(CERT_STORE_PROV_MEMORY,
+                                  0,
+                                  (HCRYPTPROV)NULL,
+                                  CERT_STORE_CREATE_NEW_FLAG,
+                                  NULL);
+      if(!trust_store) {
+        failf(data, "schannel: failed to create certificate store: %s",
+              Curl_strerror(conn, GetLastError()));
+        result = CURLE_SSL_CACERT_BADFILE;
+      }
+      else {
+        result = add_certs_to_store(trust_store, SSL_CONN_CONFIG(CAfile),
+                                    conn);
+      }
+    }
+
+    if(result == CURLE_OK) {
+      CERT_CHAIN_ENGINE_CONFIG_WIN7 engine_config;
+      BOOL create_engine_result;
+
+      memset(&engine_config, 0, sizeof(engine_config));
+      engine_config.cbSize = sizeof(engine_config);
+      engine_config.hExclusiveRoot = trust_store;
+
+      /* CertCreateCertificateChainEngine will check the expected size of the
+       * CERT_CHAIN_ENGINE_CONFIG structure and fail if the specified size
+       * does not match the expected size. When this occurs, it indicates that
+       * CAINFO is not supported on the version of Windows in use.
+       */
+      create_engine_result =
+        CertCreateCertificateChainEngine(
+          (CERT_CHAIN_ENGINE_CONFIG *)&engine_config, &cert_chain_engine);
+      if(!create_engine_result) {
+        failf(data,
+              "schannel: failed to create certificate chain engine: %s",
+              Curl_strerror(conn, GetLastError()));
+        result = CURLE_SSL_CACERT_BADFILE;
+      }
+    }
+  }
+
+  if(result == CURLE_OK) {
+    CERT_CHAIN_PARA ChainPara;
+
+    memset(&ChainPara, 0, sizeof(ChainPara));
+    ChainPara.cbSize = sizeof(ChainPara);
+
+    if(!CertGetCertificateChain(cert_chain_engine,
+                                pCertContextServer,
+                                NULL,
+                                pCertContextServer->hCertStore,
+                                &ChainPara,
+                                (data->set.ssl.no_revoke ? 0 :
+                                 CERT_CHAIN_REVOCATION_CHECK_CHAIN),
+                                NULL,
+                                &pChainContext)) {
+      failf(data, "schannel: CertGetCertificateChain failed: %s",
+            Curl_sspi_strerror(conn, GetLastError()));
+      pChainContext = NULL;
+      result = CURLE_PEER_FAILED_VERIFICATION;
+    }
+
+    if(result == CURLE_OK) {
+      CERT_SIMPLE_CHAIN *pSimpleChain = pChainContext->rgpChain[0];
+      DWORD dwTrustErrorMask = ~(DWORD)(CERT_TRUST_IS_NOT_TIME_NESTED);
+      dwTrustErrorMask &= pSimpleChain->TrustStatus.dwErrorStatus;
+      if(dwTrustErrorMask) {
+        if(dwTrustErrorMask & CERT_TRUST_IS_REVOKED)
+          failf(data, "schannel: CertGetCertificateChain trust error"
+                " CERT_TRUST_IS_REVOKED");
+        else if(dwTrustErrorMask & CERT_TRUST_IS_PARTIAL_CHAIN)
+          failf(data, "schannel: CertGetCertificateChain trust error"
+                " CERT_TRUST_IS_PARTIAL_CHAIN");
+        else if(dwTrustErrorMask & CERT_TRUST_IS_UNTRUSTED_ROOT)
+          failf(data, "schannel: CertGetCertificateChain trust error"
+                " CERT_TRUST_IS_UNTRUSTED_ROOT");
+        else if(dwTrustErrorMask & CERT_TRUST_IS_NOT_TIME_VALID)
+          failf(data, "schannel: CertGetCertificateChain trust error"
+                " CERT_TRUST_IS_NOT_TIME_VALID");
+        else if(dwTrustErrorMask & CERT_TRUST_REVOCATION_STATUS_UNKNOWN)
+          failf(data, "schannel: CertGetCertificateChain trust error"
+                " CERT_TRUST_REVOCATION_STATUS_UNKNOWN");
+        else
+          failf(data, "schannel: CertGetCertificateChain error mask: 0x%08x",
+                dwTrustErrorMask);
+        result = CURLE_PEER_FAILED_VERIFICATION;
+      }
+    }
+  }
+
+  if(result == CURLE_OK) {
+    if(SSL_CONN_CONFIG(verifyhost)) {
+      result = verify_host(conn->data, pCertContextServer, conn_hostname);
+    }
+  }
+
+  if(cert_chain_engine) {
+    CertFreeCertificateChainEngine(cert_chain_engine);
+  }
+
+  if(trust_store) {
+    CertCloseStore(trust_store, 0);
+  }
+
+  if(pChainContext)
+    CertFreeCertificateChain(pChainContext);
+
+  if(pCertContextServer)
+    CertFreeCertificateContext(pCertContextServer);
+
+  return result;
+}
+
+#endif /* USE_SCHANNEL */