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curl/lib/vtls/schannel_verify.c
Jay Satiro 9c49824902 schannel_verify: Fix concurrent openings of CA file 
- Open the CA file using FILE_SHARE_READ mode so that others can read
  from it as well.

Prior to this change our schannel code opened the CA file without
sharing which meant concurrent openings (eg an attempt from another
thread or process) would fail during the time it was open without
sharing, which in curl's case would cause error:
"schannel: failed to open CA file".

Bug: https://curl.haxx.se/mail/lib-2019-10/0104.html
Reported-by: Richard Alcock
2019-11-01 18:02:59 -04:00

573 lines
19 KiB
C
Raw Blame History

/***************************************************************************
* _ _ ____ _
* Project ___| | | | _ \| |
* / __| | | | |_) | |
* | (__| |_| | _ <| |___
* \___|\___/|_| \_\_____|
*
* Copyright (C) 2012 - 2016, Marc Hoersken, <info@marc-hoersken.de>
* Copyright (C) 2012, Mark Salisbury, <mark.salisbury@hp.com>
* Copyright (C) 2012 - 2019, 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
#ifndef USE_WINDOWS_SSPI
# error "Can't compile SCHANNEL support without SSPI."
#endif
#define EXPOSE_SCHANNEL_INTERNAL_STRUCTS
#include "schannel.h"
#ifdef HAS_MANUAL_VERIFY_API
#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-----"
#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 int is_cr_or_lf(char c)
{
return c == '\r' || c == '\n';
}
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;
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((char *)ca_file);
if(!ca_file_tstr) {
char buffer[STRERROR_LEN];
failf(data,
"schannel: invalid path name for CA file '%s': %s",
ca_file, Curl_strerror(GetLastError(), buffer, sizeof(buffer)));
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,
FILE_SHARE_READ,
NULL,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL,
NULL);
if(ca_file_handle == INVALID_HANDLE_VALUE) {
char buffer[STRERROR_LEN];
failf(data,
"schannel: failed to open CA file '%s': %s",
ca_file, Curl_strerror(GetLastError(), buffer, sizeof(buffer)));
result = CURLE_SSL_CACERT_BADFILE;
goto cleanup;
}
if(!GetFileSizeEx(ca_file_handle, &file_size)) {
char buffer[STRERROR_LEN];
failf(data,
"schannel: failed to determine size of CA file '%s': %s",
ca_file, Curl_strerror(GetLastError(), buffer, sizeof(buffer)));
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_SSL_CACERT_BADFILE;
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)) {
char buffer[STRERROR_LEN];
failf(data,
"schannel: failed to read from CA file '%s': %s",
ca_file, Curl_strerror(GetLastError(), buffer, sizeof(buffer)));
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 || !is_cr_or_lf(begin_cert_ptr[strlen(BEGIN_CERT)])) {
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,
(const void **)&cert_context)) {
char buffer[STRERROR_LEN];
failf(data,
"schannel: failed to extract certificate from CA file "
"'%s': %s",
ca_file,
Curl_strerror(GetLastError(), buffer, sizeof(buffer)));
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) {
char buffer[STRERROR_LEN];
failf(data,
"schannel: failed to add certificate from CA file '%s' "
"to certificate store: %s",
ca_file,
Curl_strerror(GetLastError(), buffer, sizeof(buffer)));
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));
if(!cert_hostname_buff) {
result = CURLE_OUT_OF_MEMORY;
goto cleanup;
}
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 Curl_verify_certificate(struct connectdata *conn, int sockindex)
{
SECURITY_STATUS sspi_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;
sspi_status =
s_pSecFn->QueryContextAttributes(&BACKEND->ctxt->ctxt_handle,
SECPKG_ATTR_REMOTE_CERT_CONTEXT,
&pCertContextServer);
if((sspi_status != SEC_E_OK) || (pCertContextServer == NULL)) {
char buffer[STRERROR_LEN];
failf(data, "schannel: Failed to read remote certificate context: %s",
Curl_sspi_strerror(sspi_status, buffer, sizeof(buffer)));
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) {
char buffer[STRERROR_LEN];
failf(data, "schannel: failed to create certificate store: %s",
Curl_strerror(GetLastError(), buffer, sizeof(buffer)));
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) {
char buffer[STRERROR_LEN];
failf(data,
"schannel: failed to create certificate chain engine: %s",
Curl_strerror(GetLastError(), buffer, sizeof(buffer)));
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)) {
char buffer[STRERROR_LEN];
failf(data, "schannel: CertGetCertificateChain failed: %s",
Curl_strerror(GetLastError(), buffer, sizeof(buffer)));
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 /* HAS_MANUAL_VERIFY_API */
#endif /* USE_SCHANNEL */
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