nghttpx: Add --client-psk-secret option to enable PSK in backend

gennghttpxfun.py

@@ -154,6 +154,7 @@ OPTIONS = [
     "dns-max-try",
     "frontend-keep-alive-timeout",
     "psk-secrets",
+    "client-psk-secrets",
 ]
 
 LOGVARS = [

src/shrpx.cc

@@ -2112,6 +2112,13 @@ SSL/TLS:
               are skipped.  The default  enabled cipher list might not
               contain any PSK cipher suite.  In that case, desired PSK
               cipher suites must be enabled using --ciphers option.
+  --client-psk-secrets=<PATH>
+              Read PSK identity and secrets from <PATH>.  This is used
+              for backend connection.  The each  line of input file is
+              formatted  as <identity>:<hex-secret>,  where <identity>
+              is PSK identity, and <hex-secret>  is secret in hex.  An
+              empty line, and line which  starts with '#' are skipped.
+              The first identity and secret pair encountered is used.
 
 HTTP/2 and SPDY:
   -c, --frontend-http2-max-concurrent-streams=<N>
@@ -3088,6 +3095,7 @@ int main(int argc, char **argv) {
         {SHRPX_OPT_FRONTEND_KEEP_ALIVE_TIMEOUT.c_str(), required_argument,
          &flag, 146},
         {SHRPX_OPT_PSK_SECRETS.c_str(), required_argument, &flag, 147},
+        {SHRPX_OPT_CLIENT_PSK_SECRETS.c_str(), required_argument, &flag, 148},
         {nullptr, 0, nullptr, 0}};
 
     int option_index = 0;
@@ -3782,6 +3790,10 @@ int main(int argc, char **argv) {
         // --psk-secrets
         cmdcfgs.emplace_back(SHRPX_OPT_PSK_SECRETS, StringRef{optarg});
         break;
+      case 148:
+        // --client-psk-secrets
+        cmdcfgs.emplace_back(SHRPX_OPT_CLIENT_PSK_SECRETS, StringRef{optarg});
+        break;
       default:
         break;
       }

src/shrpx_config.cc

@@ -1263,6 +1263,66 @@ int parse_psk_secrets(Config *config, const StringRef &path) {
 }
 } // namespace
 
+namespace {
+// Reads PSK secrets from path, and parses each line.  The result is
+// directly stored into config->tls.client_psk.  This function returns
+// 0 if it succeeds, or -1.
+int parse_client_psk_secrets(Config *config, const StringRef &path) {
+  auto &tlsconf = config->tls;
+
+  std::ifstream f(path.c_str(), std::ios::binary);
+  if (!f) {
+    LOG(ERROR) << SHRPX_OPT_CLIENT_PSK_SECRETS << ": could not open file "
+               << path;
+    return -1;
+  }
+
+  size_t lineno = 0;
+  std::string line;
+  while (std::getline(f, line)) {
+    ++lineno;
+    if (line.empty() || line[0] == '#') {
+      continue;
+    }
+
+    auto sep_it = std::find(std::begin(line), std::end(line), ':');
+    if (sep_it == std::end(line)) {
+      LOG(ERROR) << SHRPX_OPT_CLIENT_PSK_SECRETS
+                 << ": could not fine separator at line " << lineno;
+      return -1;
+    }
+
+    if (sep_it == std::begin(line)) {
+      LOG(ERROR) << SHRPX_OPT_CLIENT_PSK_SECRETS << ": empty identity at line "
+                 << lineno;
+      return -1;
+    }
+
+    if (sep_it + 1 == std::end(line)) {
+      LOG(ERROR) << SHRPX_OPT_CLIENT_PSK_SECRETS << ": empty secret at line "
+                 << lineno;
+      return -1;
+    }
+
+    if (!util::is_hex_string(StringRef{sep_it + 1, std::end(line)})) {
+      LOG(ERROR) << SHRPX_OPT_CLIENT_PSK_SECRETS
+                 << ": secret must be hex string at line " << lineno;
+      return -1;
+    }
+
+    tlsconf.client_psk.identity =
+        make_string_ref(config->balloc, StringRef{std::begin(line), sep_it});
+
+    tlsconf.client_psk.secret =
+        util::decode_hex(config->balloc, StringRef{sep_it + 1, std::end(line)});
+
+    return 0;
+  }
+
+  return 0;
+}
+} // namespace
+
 // generated by gennghttpxfun.py
 int option_lookup_token(const char *name, size_t namelen) {
   switch (namelen) {
@@ -1620,6 +1680,11 @@ int option_lookup_token(const char *name, size_t namelen) {
         return SHRPX_OPTID_ADD_REQUEST_HEADER;
       }
       break;
+    case 's':
+      if (util::strieq_l("client-psk-secret", name, 17)) {
+        return SHRPX_OPTID_CLIENT_PSK_SECRETS;
+      }
+      break;
     case 't':
       if (util::strieq_l("dns-lookup-timeou", name, 17)) {
         return SHRPX_OPTID_DNS_LOOKUP_TIMEOUT;
@@ -3207,6 +3272,8 @@ int parse_config(Config *config, int optid, const StringRef &opt,
                           optarg);
   case SHRPX_OPTID_PSK_SECRETS:
     return parse_psk_secrets(config, optarg);
+  case SHRPX_OPTID_CLIENT_PSK_SECRETS:
+    return parse_client_psk_secrets(config, optarg);
   case SHRPX_OPTID_CONF:
     LOG(WARN) << "conf: ignored";
 

src/shrpx_config.h

@@ -320,6 +320,8 @@ constexpr auto SHRPX_OPT_DNS_MAX_TRY = StringRef::from_lit("dns-max-try");
 constexpr auto SHRPX_OPT_FRONTEND_KEEP_ALIVE_TIMEOUT =
     StringRef::from_lit("frontend-keep-alive-timeout");
 constexpr auto SHRPX_OPT_PSK_SECRETS = StringRef::from_lit("psk-secrets");
+constexpr auto SHRPX_OPT_CLIENT_PSK_SECRETS =
+    StringRef::from_lit("client-psk-secrets");
 
 constexpr size_t SHRPX_OBFUSCATED_NODE_LENGTH = 8;
 
@@ -550,6 +552,13 @@ struct TLSConfig {
     StringRef cert_file;
   } client;
 
+  // Client PSK configuration
+  struct {
+    // identity must be NULL terminated string.
+    StringRef identity;
+    StringRef secret;
+  } client_psk;
+
   // PSK secrets.  The key is identity, and the associated value is
   // its secret.
   std::map<StringRef, StringRef> psk_secrets;
@@ -918,6 +927,7 @@ enum {
   SHRPX_OPTID_CLIENT_CERT_FILE,
   SHRPX_OPTID_CLIENT_PRIVATE_KEY_FILE,
   SHRPX_OPTID_CLIENT_PROXY,
+  SHRPX_OPTID_CLIENT_PSK_SECRETS,
   SHRPX_OPTID_CONF,
   SHRPX_OPTID_DAEMON,
   SHRPX_OPTID_DH_PARAM_FILE,

src/shrpx_ssl.cc

@@ -549,6 +549,39 @@ unsigned int psk_server_cb(SSL *ssl, const char *identity, unsigned char *psk,
 }
 } // namespace
 
+namespace {
+unsigned int psk_client_cb(SSL *ssl, const char *hint, char *identity_out,
+                           unsigned int max_identity_len, unsigned char *psk,
+                           unsigned int max_psk_len) {
+  auto config = get_config();
+  auto &tlsconf = config->tls;
+
+  auto &identity = tlsconf.client_psk.identity;
+  auto &secret = tlsconf.client_psk.secret;
+
+  if (identity.empty()) {
+    return 0;
+  }
+
+  if (identity.size() + 1 > max_identity_len) {
+    LOG(ERROR) << "The size of PSK identity is " << identity.size()
+               << ", but the acceptable maximum size is " << max_identity_len;
+    return 0;
+  }
+
+  if (secret.size() > max_psk_len) {
+    LOG(ERROR) << "The size of PSK secret is " << secret.size()
+               << ", but the acceptable maximum size is " << max_psk_len;
+    return 0;
+  }
+
+  *std::copy(std::begin(identity), std::end(identity), identity_out) = '\0';
+  std::copy(std::begin(secret), std::end(secret), psk);
+
+  return (unsigned int)secret.size();
+}
+} // namespace
+
 struct TLSProtocol {
   StringRef name;
   long int mask;
@@ -899,6 +932,8 @@ SSL_CTX *create_ssl_client_context(
 #endif // HAVE_NEVERBLEED
   }
 
+  SSL_CTX_set_psk_client_callback(ssl_ctx, psk_client_cb);
+
   // NPN selection callback.  This is required to set SSL_CTX because
   // OpenSSL does not offer SSL_set_next_proto_select_cb.
   SSL_CTX_set_next_proto_select_cb(ssl_ctx, next_proto_select_cb, nullptr);
@@ -1181,8 +1216,10 @@ int verify_hostname(X509 *cert, const StringRef &hostname,
 int check_cert(SSL *ssl, const Address *addr, const StringRef &host) {
   auto cert = SSL_get_peer_certificate(ssl);
   if (!cert) {
-    LOG(ERROR) << "No certificate found";
+    // By the protocol definition, TLS server always sends certificate
-    return -1;
+    // if it has.  If certificate cannot be retrieved, authentication
+    // without certificate is used, such as PSK.
+    return 0;
   }
   auto cert_deleter = defer(X509_free, cert);
   auto verify_res = SSL_get_verify_result(ssl);