Release v0.60.1

verify_cert_with_windows_schannel() rejected a chain whenever
TrustStatus.dwErrorStatus was non-zero, before
CertVerifyCertificateChainPolicy() ran. The
CERT_CHAIN_POLICY_IGNORE_ALL_REV_UNKNOWN_FLAGS flag passed to that
policy check was therefore dead code: a certificate without revocation
information, or one whose CRL could not be fetched, failed with
CERT_TRUST_REVOCATION_STATUS_UNKNOWN.

Drop the pre-check so the SSL chain policy is the only judge.
Revocation checking becomes best-effort: a revoked certificate and
every other chain error are still rejected, while an undetermined
revocation status is accepted.

On a rejected chain, ssl_backend_error() now holds the policy status,
such as CERT_E_UNTRUSTEDROOT, instead of the trust status bit mask.

README-websocket.md

@@ -119,7 +119,7 @@ using SubProtocolSelector =
     std::function<std::string(const std::vector<std::string> &protocols)>;
 ```
 
-The `SubProtocolSelector` receives the list of subprotocols proposed by the client (from the `Sec-WebSocket-Protocol` header) and returns the selected one. Return an empty string to decline all proposed subprotocols.
+The `SubProtocolSelector` receives the list of subprotocols proposed by the client (from the `Sec-WebSocket-Protocol` header) and returns the selected one. Return an empty string to decline all proposed subprotocols. A returned value that the client did not propose is ignored.
 
 ### WebSocket (Server-side)
 

README.md

@@ -230,7 +230,7 @@ cpp-httplib automatically integrates with the OS certificate store on macOS and
 | Platform | Behavior | Disable (compile time) |
 | :------- | :------- | :--------------------- |
 | macOS | Loads system certs from Keychain (link `CoreFoundation` and `Security` with `-framework`). Requires Apple Clang; GCC is not supported for this feature. | `CPPHTTPLIB_DISABLE_MACOSX_AUTOMATIC_ROOT_CERTIFICATES` |
-| Windows | Verifies certs via CryptoAPI (`CertGetCertificateChain` / `CertVerifyCertificateChainPolicy`) with revocation checking | `CPPHTTPLIB_DISABLE_WINDOWS_AUTOMATIC_ROOT_CERTIFICATES_UPDATE` |
+| Windows | Verifies the certificate chain with CryptoAPI (`CertGetCertificateChain` / `CertVerifyCertificateChainPolicy`) instead of the TLS backend. Revocation checking is best-effort: a revoked server certificate is rejected, while one whose revocation status cannot be determined is accepted. Windows fetches missing roots and intermediates on demand. With a custom CA, the TLS backend verifies the chain instead; with `set_server_certificate_verifier()`, both do. | `CPPHTTPLIB_DISABLE_WINDOWS_AUTOMATIC_ROOT_CERTIFICATES_UPDATE` |
 
 On Windows, verification can also be disabled at runtime:
 

docs-src/config.toml

@@ -4,7 +4,7 @@ langs = ["en", "ja"]
 
 [site]
 title = "cpp-httplib"
-version = "0.58.0"
+version = "0.60.1"
 hostname = "https://yhirose.github.io"
 base_path = "/cpp-httplib"
 footer_message = "© 2026 Yuji Hirose. All rights reserved."

httplib.h

@@ -8,8 +8,8 @@
 #ifndef CPPHTTPLIB_HTTPLIB_H
 #define CPPHTTPLIB_HTTPLIB_H
 
-#define CPPHTTPLIB_VERSION "0.58.0"
-#define CPPHTTPLIB_VERSION_NUM "0x003a00"
+#define CPPHTTPLIB_VERSION "0.60.1"
+#define CPPHTTPLIB_VERSION_NUM "0x003c01"
 
 #ifdef _WIN32
 #if defined(_WIN32_WINNT) && _WIN32_WINNT < 0x0A00
@@ -831,14 +831,21 @@ inline from_chars_result<double> from_chars(const char *first, const char *last,
   return {p, std::errc{}};
 }
 
-inline bool parse_port(const char *s, size_t len, int &port) {
+inline bool parse_int_in_range(const char *s, size_t len, int lo, int hi,
+                               int &out) {
   int val = 0;
   auto r = from_chars(s, s + len, val);
-  if (r.ec != std::errc{} || val < 1 || val > 65535) { return false; }
-  port = val;
+  if (r.ec != std::errc{} || r.ptr != s + len || val < lo || val > hi) {
+    return false;
+  }
+  out = val;
   return true;
 }
 
+inline bool parse_port(const char *s, size_t len, int &port) {
+  return parse_int_in_range(s, len, 1, 65535, port);
+}
+
 inline bool parse_port(const std::string &s, int &port) {
   return parse_port(s.data(), s.size(), port);
 }
@@ -3442,6 +3449,9 @@ private:
 
 #ifdef CPPHTTPLIB_WINDOWS_AUTOMATIC_ROOT_CERTIFICATES_UPDATE
   bool enable_windows_cert_verification_ = true;
+  // Like ca_cert_store_set_, tracks what ctx_ cannot report back: whether
+  // set_server_certificate_verifier() installed a verifier.
+  bool server_certificate_verifier_set_ = false;
 #endif
 
   friend class ClientImpl;
@@ -4366,7 +4376,8 @@ public:
   void stop();
 
 private:
-  bool parse_sse_line(const std::string &line, SSEMessage &msg, int &retry_ms);
+  bool parse_sse_line(const std::string &line, SSEMessage &msg, int &retry_ms,
+                      bool &has_data, bool &has_id);
   void run_event_loop();
   void dispatch_event(const SSEMessage &msg);
   bool should_reconnect(int count) const;
@@ -4401,6 +4412,8 @@ private:
 
 namespace ws {
 
+class WebSocketClient;
+
 enum class Opcode : uint8_t {
   Continuation = 0x0,
   Text = 0x1,
@@ -4502,7 +4515,7 @@ public:
 
 private:
   friend class httplib::Server;
-  friend class WebSocketClient;
+  friend class httplib::ws::WebSocketClient;
 
   WebSocket(
       Stream &strm, const Request &req, bool is_server,
@@ -4876,30 +4889,24 @@ inline void SSEClient::stop() {
 }
 
 inline bool SSEClient::parse_sse_line(const std::string &line, SSEMessage &msg,
-                                      int &retry_ms) {
+                                      int &retry_ms, bool &has_data,
+                                      bool &has_id) {
   // Blank line signals end of event
-  if (line.empty() || line == "\r") { return true; }
+  if (line.empty()) { return true; }
 
   // Lines starting with ':' are comments (ignored)
-  if (!line.empty() && line[0] == ':') { return false; }
+  if (line[0] == ':') { return false; }
 
   // Find the colon separator
   auto colon_pos = line.find(':');
-  if (colon_pos == std::string::npos) {
-    // Line with no colon is treated as field name with empty value
-    return false;
-  }
-
   auto field = line.substr(0, colon_pos);
   std::string value;
 
   // Value starts after colon, skip optional single space
-  if (colon_pos + 1 < line.size()) {
+  if (colon_pos != std::string::npos && colon_pos + 1 < line.size()) {
     auto value_start = colon_pos + 1;
     if (line[value_start] == ' ') { value_start++; }
     value = line.substr(value_start);
-    // Remove trailing \r if present
-    if (!value.empty() && value.back() == '\r') { value.pop_back(); }
   }
 
   // Handle known fields
@@ -4907,11 +4914,13 @@ inline bool SSEClient::parse_sse_line(const std::string &line, SSEMessage &msg,
     msg.event = value;
   } else if (field == "data") {
     // Multiple data lines are concatenated with newlines
-    if (!msg.data.empty()) { msg.data += "\n"; }
+    if (has_data) { msg.data += "\n"; }
     msg.data += value;
+    has_data = true;
   } else if (field == "id") {
     // Empty id is valid (clears the last event ID)
     msg.id = value;
+    has_id = true;
   } else if (field == "retry") {
     // Parse retry interval in milliseconds
     // Per the SSE spec, a value that is not all ASCII digits is ignored.
@@ -4982,6 +4991,8 @@ inline void SSEClient::run_event_loop() {
     // Event receiving loop
     std::string buffer;
     SSEMessage current_msg;
+    auto has_data = false;
+    auto has_id = false;
 
     while (running_.load() && result.next()) {
       buffer.append(result.data(), result.size());
@@ -4995,18 +5006,26 @@ inline void SSEClient::run_event_loop() {
         auto line = buffer.substr(line_start, newline_pos - line_start);
         line_start = newline_pos + 1;
 
+        // Strip the \r of a CRLF line ending so that every field, including
+        // one without a colon, sees the same line
+        if (!line.empty() && line.back() == '\r') { line.pop_back(); }
+
         // Parse the line and check if event is complete
-        auto event_complete =
-            parse_sse_line(line, current_msg, reconnect_interval_ms_);
+        auto event_complete = parse_sse_line(
+            line, current_msg, reconnect_interval_ms_, has_data, has_id);
 
-        if (event_complete && !current_msg.data.empty()) {
-          // Update last_event_id for reconnection
-          if (!current_msg.id.empty()) { last_event_id_ = current_msg.id; }
+        if (event_complete) {
+          // Update last_event_id for reconnection, even for an event that
+          // has no data. An empty id clears it.
+          if (has_id) { last_event_id_ = current_msg.id; }
 
-          // Dispatch event to appropriate handler
-          dispatch_event(current_msg);
+          // An event without a data field is not dispatched
+          if (has_data) { dispatch_event(current_msg); }
 
+          // Reset the message for the next event either way
           current_msg.clear();
+          has_data = false;
+          has_id = false;
         }
       }
 
@@ -5120,6 +5139,9 @@ bool is_peer_closed(session_t session, socket_t sock);
 
 // Certificate verification
 cert_t get_peer_cert(const_session_t session);
+// The certificates the peer sent, leaf first. Free each with free_cert(), and
+// do not use them after free_session(), as with get_peer_cert().
+size_t get_peer_certs(const_session_t session, std::vector<cert_t> &certs);
 void free_cert(cert_t cert);
 bool verify_hostname(cert_t cert, const char *hostname);
 uint64_t hostname_mismatch_code();
@@ -6608,18 +6630,30 @@ inline bool keep_alive(const std::atomic<socket_t> &svr_sock, socket_t sock,
   return false;
 }
 
-template <typename T>
-inline bool
-process_server_socket_core(const std::atomic<socket_t> &svr_sock, socket_t sock,
-                           size_t keep_alive_max_count,
-                           time_t keep_alive_timeout_sec, T callback) {
+// `has_buffered_request` reports whether the connection's stream already holds
+// bytes of the next request. A client may pipeline its requests (RFC 9112
+// 9.3.2), so reading one request can pull the start of the next one into the
+// stream's buffer; that request must be served without waiting for the socket
+// to become readable again, since its bytes are no longer on the socket.
+// `callback` is told whether keep_alive() has just seen the socket go readable.
+template <typename P, typename T>
+inline bool process_server_socket_core(const std::atomic<socket_t> &svr_sock,
+                                       socket_t sock,
+                                       size_t keep_alive_max_count,
+                                       time_t keep_alive_timeout_sec,
+                                       P has_buffered_request, T callback) {
   assert(keep_alive_max_count > 0);
   auto ret = false;
   auto count = keep_alive_max_count;
-  while (count > 0 && keep_alive(svr_sock, sock, keep_alive_timeout_sec)) {
+  while (count > 0) {
+    auto socket_readable = false;
+    if (!has_buffered_request()) {
+      if (!keep_alive(svr_sock, sock, keep_alive_timeout_sec)) { break; }
+      socket_readable = true;
+    }
     auto close_connection = count == 1;
     auto connection_closed = false;
-    ret = callback(close_connection, connection_closed);
+    ret = callback(socket_readable, close_connection, connection_closed);
     if (!ret || connection_closed) { break; }
     count--;
   }
@@ -6633,14 +6667,16 @@ process_server_socket(const std::atomic<socket_t> &svr_sock, socket_t sock,
                       time_t keep_alive_timeout_sec, time_t read_timeout_sec,
                       time_t read_timeout_usec, time_t write_timeout_sec,
                       time_t write_timeout_usec, T callback) {
+  // One stream per connection: its read buffer can already hold the start of
+  // the next, pipelined request.
+  SocketStream strm(sock, read_timeout_sec, read_timeout_usec,
+                    write_timeout_sec, write_timeout_usec);
   return process_server_socket_core(
       svr_sock, sock, keep_alive_max_count, keep_alive_timeout_sec,
-      [&](bool close_connection, bool &connection_closed) {
-        SocketStream strm(sock, read_timeout_sec, read_timeout_usec,
-                          write_timeout_sec, write_timeout_usec);
-        // process_server_socket_core() only gets here once keep_alive() has
-        // seen the socket go readable.
-        strm.set_readable_hint();
+      [&]() { return strm.is_readable(); },
+      [&](bool socket_readable, bool close_connection,
+          bool &connection_closed) {
+        if (socket_readable) { strm.set_readable_hint(); }
         return callback(strm, close_connection, connection_closed);
       });
 }
@@ -8238,9 +8274,11 @@ struct WebSocketUpgradeResponse {
   std::string selected_subprotocol;
 };
 
-inline bool read_websocket_upgrade_response(Stream &strm,
-                                            const std::string &expected_accept,
-                                            WebSocketUpgradeResponse &upgrade) {
+inline bool
+read_websocket_upgrade_response(Stream &strm,
+                                const std::string &expected_accept,
+                                const std::string &offered_subprotocols,
+                                WebSocketUpgradeResponse &upgrade) {
   // Read status line
   const auto bufsiz = 2048;
   char buf[bufsiz];
@@ -8297,6 +8335,22 @@ inline bool read_websocket_upgrade_response(Stream &strm,
     upgrade.selected_subprotocol = proto_it->second;
   }
 
+  // Verify the subprotocol is one the client offered (RFC 6455 4.1)
+  if (!upgrade.selected_subprotocol.empty()) {
+    auto was_offered = false;
+    split(offered_subprotocols.data(),
+          offered_subprotocols.data() + offered_subprotocols.size(), ',',
+          [&](const char *b, const char *e) {
+            if (std::string(b, e) == upgrade.selected_subprotocol) {
+              was_offered = true;
+            }
+          });
+    if (!was_offered) {
+      upgrade.error = Error::WebSocketHandshake;
+      return false;
+    }
+  }
+
   return true;
 }
 
@@ -8942,6 +8996,9 @@ inline bool redirect(T &cli, Request &req, Response &res,
     new_req.method = "GET";
     new_req.body.clear();
     new_req.headers.clear();
+    new_req.content_length_ = 0;
+    new_req.content_provider_ = nullptr;
+    new_req.is_chunked_content_provider_ = false;
   }
 
   Response new_res;
@@ -9855,8 +9912,10 @@ inline bool range_error(Request &req, Response &res) {
         last_pos = content_len;
       }
 
+      // RFC 9110 14.1.2: a suffix-length longer than the representation
+      // selects the entire representation.
       if (first_pos == -1) {
-        first_pos = content_len - last_pos;
+        first_pos = (std::max)(static_cast<ssize_t>(0), content_len - last_pos);
         last_pos = content_len - 1;
       }
 
@@ -10099,6 +10158,19 @@ inline std::string unescape_quoted_pairs(const std::string &s) {
   return out;
 }
 
+// Inverse of unescape_quoted_pairs: prepares a value to sit inside a
+// quoted-string. RFC 9110 §5.6.4 requires a literal '\' or '"' to be sent as a
+// quoted-pair, so the recipient recovers the original value.
+inline std::string escape_quoted_pairs(const std::string &s) {
+  std::string out;
+  out.reserve(s.size());
+  for (auto c : s) {
+    if (c == '\\' || c == '"') { out += '\\'; }
+    out += c;
+  }
+  return out;
+}
+
 inline bool parse_www_authenticate(const Response &res,
                                    std::map<std::string, std::string> &auth,
                                    bool is_proxy) {
@@ -10278,7 +10350,10 @@ inline bool perform_websocket_handshake(Stream &strm, Request &req,
 
   // Verify 101 response and Sec-WebSocket-Accept header
   auto expected_accept = websocket_accept_key(client_key);
-  return read_websocket_upgrade_response(strm, expected_accept, upgrade);
+  auto offered_subprotocols =
+      get_combined_header_value(req.headers, "Sec-WebSocket-Protocol");
+  return read_websocket_upgrade_response(strm, expected_accept,
+                                         offered_subprotocols, upgrade);
 }
 
 inline bool is_ip_address(const std::string &host) {
@@ -10555,13 +10630,16 @@ inline bool process_server_socket_ssl(
     socket_t sock, size_t keep_alive_max_count, time_t keep_alive_timeout_sec,
     time_t read_timeout_sec, time_t read_timeout_usec, time_t write_timeout_sec,
     time_t write_timeout_usec, T callback) {
+  // See process_server_socket(). The TLS library keeps already decrypted bytes
+  // of a pipelined request, which keep_alive() cannot see on the socket.
+  SSLSocketStream strm(sock, session, read_timeout_sec, read_timeout_usec,
+                       write_timeout_sec, write_timeout_usec);
   return process_server_socket_core(
       svr_sock, sock, keep_alive_max_count, keep_alive_timeout_sec,
-      [&](bool close_connection, bool &connection_closed) {
-        SSLSocketStream strm(sock, session, read_timeout_sec, read_timeout_usec,
-                             write_timeout_sec, write_timeout_usec);
-        // See the non-TLS path in process_server_socket().
-        strm.set_readable_hint();
+      [&]() { return strm.is_readable(); },
+      [&](bool socket_readable, bool close_connection,
+          bool &connection_closed) {
+        if (socket_readable) { strm.set_readable_hint(); }
         return callback(strm, close_connection, connection_closed);
       });
 }
@@ -10602,7 +10680,13 @@ inline std::pair<std::string, std::string> make_digest_authentication_header(
   }
 
   std::string algo = "MD5";
-  if (auth.find("algorithm") != auth.end()) { algo = auth.at("algorithm"); }
+  if (auth.find("algorithm") != auth.end()) {
+    // algorithm is an unquoted token (RFC 7616 §3.4). A server value that is
+    // not a token would otherwise be emitted verbatim and could carry commas
+    // or quotes that inject further auth-params into the header below.
+    const auto &a = auth.at("algorithm");
+    if (fields::is_token(a)) { algo = a; }
+  }
 
   std::string response;
   {
@@ -10625,14 +10709,23 @@ inline std::pair<std::string, std::string> make_digest_authentication_header(
 
   auto opaque = (auth.find("opaque") != auth.end()) ? auth.at("opaque") : "";
 
-  auto field = "Digest username=\"" + username + "\", realm=\"" +
-               auth.at("realm") + "\", nonce=\"" + auth.at("nonce") +
-               "\", uri=\"" + req.path + "\", algorithm=" + algo +
-               (qop.empty() ? ", response=\""
-                            : ", qop=" + qop + ", nc=" + nc + ", cnonce=\"" +
-                                  cnonce + "\", response=\"") +
-               response + "\"" +
-               (opaque.empty() ? "" : ", opaque=\"" + opaque + "\"");
+  // Every value placed inside a quoted-string is escaped so a '"' in it cannot
+  // close the string early. realm, nonce and opaque come straight from the
+  // server's challenge (parse_www_authenticate() already de-escaped them), so
+  // without this a crafted challenge injects extra auth-params into the header.
+  auto field =
+      "Digest username=\"" + detail::escape_quoted_pairs(username) +
+      "\", realm=\"" + detail::escape_quoted_pairs(auth.at("realm")) +
+      "\", nonce=\"" + detail::escape_quoted_pairs(auth.at("nonce")) +
+      "\", uri=\"" + detail::escape_quoted_pairs(req.path) +
+      "\", algorithm=" + algo +
+      (qop.empty() ? ", response=\""
+                   : ", qop=" + qop + ", nc=" + nc + ", cnonce=\"" + cnonce +
+                         "\", response=\"") +
+      response + "\"" +
+      (opaque.empty()
+           ? ""
+           : ", opaque=\"" + detail::escape_quoted_pairs(opaque) + "\"");
 
   auto key = is_proxy ? "Proxy-Authorization" : "Authorization";
   return std::make_pair(key, field);
@@ -10697,7 +10790,7 @@ inline bool match_hostname(const std::string &pattern,
 #ifdef _WIN32
 // Verify certificate using Windows CertGetCertificateChain API.
 // This provides real-time certificate validation with Windows Update
-// integration, independent of the TLS backend (OpenSSL or MbedTLS).
+// integration, independent of the TLS backend.
 inline bool verify_cert_with_windows_schannel(
     const std::vector<unsigned char> &der_cert, const std::string &hostname,
     bool verify_hostname, uint64_t &out_error, tls::const_session_t session) {
@@ -10718,28 +10811,37 @@ inline bool verify_cert_with_windows_schannel(
   auto cert_guard =
       scope_exit([&] { CertFreeCertificateContext(cert_context); });
 
-#ifdef CPPHTTPLIB_OPENSSL_SUPPORT
-  // Add the intermediates the server sent. Without them CryptoAPI follows the
-  // leaf's AIA URL, which may lead to an issuer under an untrusted root.
+  // Give CryptoAPI the certificates the server sent. Without them it follows
+  // the leaf's AIA URL, which may lead to an issuer under an untrusted root.
+  std::vector<tls::cert_t> peer_certs;
+  tls::get_peer_certs(session, peer_certs);
   auto store = CertOpenStore(CERT_STORE_PROV_MEMORY, 0, 0, 0, nullptr);
-  auto store_guard = scope_exit([&] { CertCloseStore(store, 0); });
-  auto sk = SSL_get_peer_cert_chain(static_cast<const SSL *>(session));
-  for (int i = 1; sk && i < sk_X509_num(sk); i++) {
+  auto store_guard = scope_exit([&] {
+    for (auto cert : peer_certs) {
+      tls::free_cert(cert);
+    }
+    if (store) { CertCloseStore(store, 0); }
+  });
+  for (auto cert : peer_certs) {
     std::vector<unsigned char> der;
-    tls::get_cert_der(sk_X509_value(sk, i), der);
-    CertAddEncodedCertificateToStore(store, X509_ASN_ENCODING, der.data(),
-                                     static_cast<DWORD>(der.size()),
-                                     CERT_STORE_ADD_USE_EXISTING, nullptr);
+    if (store && tls::get_cert_der(cert, der)) {
+      CertAddEncodedCertificateToStore(store, X509_ASN_ENCODING, der.data(),
+                                       static_cast<DWORD>(der.size()),
+                                       CERT_STORE_ADD_USE_EXISTING, nullptr);
+    }
   }
-#else
-  (void)session;
-  auto store = cert_context->hCertStore;
-#endif
 
   // Setup chain parameters
   CERT_CHAIN_PARA chain_para = {};
   chain_para.cbSize = sizeof(chain_para);
 
+  // Require the server authentication usage along the chain, which also
+  // rejects roots that Windows trusts only for other purposes.
+  LPSTR server_auth = const_cast<LPSTR>(szOID_PKIX_KP_SERVER_AUTH);
+  chain_para.RequestedUsage.dwType = USAGE_MATCH_TYPE_AND;
+  chain_para.RequestedUsage.Usage.cUsageIdentifier = 1;
+  chain_para.RequestedUsage.Usage.rgpszUsageIdentifier = &server_auth;
+
   // Build certificate chain with revocation checking
   PCCERT_CHAIN_CONTEXT chain_context = nullptr;
   auto chain_result = CertGetCertificateChain(
@@ -10756,12 +10858,6 @@ inline bool verify_cert_with_windows_schannel(
   auto chain_guard =
       scope_exit([&] { CertFreeCertificateChain(chain_context); });
 
-  // Check if chain has errors
-  if (chain_context->TrustStatus.dwErrorStatus != CERT_TRUST_NO_ERROR) {
-    out_error = chain_context->TrustStatus.dwErrorStatus;
-    return false;
-  }
-
   // Verify SSL policy
   SSL_EXTRA_CERT_CHAIN_POLICY_PARA extra_policy_para = {};
   extra_policy_para.cbSize = sizeof(extra_policy_para);
@@ -10851,6 +10947,9 @@ struct ClientTlsSessionOptions {
   // The caller decides whether Schannel has anything to say about this
   // connection; see SSLClient::initialize_ssl().
   bool windows_cert_verification = false;
+  // A server certificate verifier works on the backend's chain verification,
+  // so the backend keeps deciding and Schannel only adds its own check.
+  bool server_certificate_verifier_set = false;
 #endif
 };
 
@@ -10885,12 +10984,24 @@ inline bool setup_client_tls_session(
     return fail(Error::SSLConnection, 0, 0);
   }
 
+  // With Windows verification on and no server certificate verifier set,
+  // Schannel is the only chain verifier. The backend's trust store is a
+  // snapshot of the Windows stores that lacks the roots Windows fetches on
+  // demand, so the backend's verdict is not used.
+  auto windows_verifies_chain = false;
+#ifdef CPPHTTPLIB_WINDOWS_AUTOMATIC_ROOT_CERTIFICATES_UPDATE
+  windows_verifies_chain = options.windows_cert_verification &&
+                           !options.server_certificate_verifier_set;
+#endif
+
 #if defined(CPPHTTPLIB_MBEDTLS_SUPPORT) || defined(CPPHTTPLIB_WOLFSSL_SUPPORT)
   // Mbed TLS and wolfSSL need the verification mode set explicitly; OpenSSL
-  // uses SSL_VERIFY_NONE and does all verification post-handshake. Chain
-  // verification happens during the handshake even for IP hosts; the
-  // certificate identity is verified post-handshake via verify_hostname().
-  set_verify_client(ctx, server_certificate_verification);
+  // uses SSL_VERIFY_NONE and does all verification post-handshake. Unless
+  // Schannel verifies the chain instead, chain verification happens during
+  // the handshake even for IP hosts; the certificate identity is verified
+  // post-handshake via verify_hostname().
+  set_verify_client(ctx,
+                    server_certificate_verification && !windows_verifies_chain);
 #endif
 
   {
@@ -10935,10 +11046,12 @@ inline bool setup_client_tls_session(
 
   if (verification_status == SSLVerifierResponse::NoDecisionMade &&
       server_certificate_verification) {
-    auto verify_result = get_verify_result(session);
-    if (verify_result != 0) {
-      return fail(Error::SSLServerVerification, 0,
-                  static_cast<uint64_t>(verify_result));
+    if (!windows_verifies_chain) {
+      auto verify_result = get_verify_result(session);
+      if (verify_result != 0) {
+        return fail(Error::SSLServerVerification, 0,
+                    static_cast<uint64_t>(verify_result));
+      }
     }
 
     auto server_cert = get_peer_cert(session);
@@ -10958,18 +11071,17 @@ inline bool setup_client_tls_session(
     }
 
 #ifdef CPPHTTPLIB_WINDOWS_AUTOMATIC_ROOT_CERTIFICATES_UPDATE
-    // Additional Windows Schannel verification.
-    // This provides real-time certificate validation with Windows Update
-    // integration, working with both OpenSSL and MbedTLS backends.
+    // Windows Schannel verification, which lets Windows fetch missing roots
+    // and intermediates on demand. It must not be skipped: unless a server
+    // certificate verifier is set, it is the only chain check.
     if (options.windows_cert_verification) {
       std::vector<unsigned char> der;
-      if (get_cert_der(server_cert, der)) {
-        uint64_t wincrypt_error = 0;
-        if (!verify_cert_with_windows_schannel(
-                der, host, options.server_hostname_verification, wincrypt_error,
-                session)) {
-          return fail(Error::SSLServerVerification, 0, wincrypt_error);
-        }
+      uint64_t wincrypt_error = 0;
+      if (!get_cert_der(server_cert, der) ||
+          !verify_cert_with_windows_schannel(
+              der, host, options.server_hostname_verification, wincrypt_error,
+              session)) {
+        return fail(Error::SSLServerVerification, 0, wincrypt_error);
       }
     }
 #endif
@@ -12437,14 +12549,10 @@ inline bool parse_no_proxy_entry(const std::string &token, NoProxyEntry &out) {
     struct in_addr v4;
     if (inet_pton(AF_INET, addr_part.c_str(), &v4) == 1) {
       int prefix = 32;
-      if (!prefix_part.empty()) {
-        auto r = from_chars(prefix_part.data(),
-                            prefix_part.data() + prefix_part.size(), prefix);
-        if (r.ec != std::errc{} ||
-            r.ptr != prefix_part.data() + prefix_part.size()) {
-          return false;
-        }
-        if (prefix < 0 || prefix > 32) { return false; }
+      if (!prefix_part.empty() &&
+          !parse_int_in_range(prefix_part.data(), prefix_part.size(), 0, 32,
+                              prefix)) {
+        return false;
       }
       out.kind = NoProxyKind::IPv4Cidr;
       std::memcpy(out.net.data(), &v4, sizeof(v4));
@@ -12456,14 +12564,10 @@ inline bool parse_no_proxy_entry(const std::string &token, NoProxyEntry &out) {
   struct in6_addr v6;
   if (inet_pton(AF_INET6, addr_part.c_str(), &v6) == 1) {
     int prefix = 128;
-    if (!prefix_part.empty()) {
-      auto r = from_chars(prefix_part.data(),
-                          prefix_part.data() + prefix_part.size(), prefix);
-      if (r.ec != std::errc{} ||
-          r.ptr != prefix_part.data() + prefix_part.size()) {
-        return false;
-      }
-      if (prefix < 0 || prefix > 128) { return false; }
+    if (!prefix_part.empty() &&
+        !parse_int_in_range(prefix_part.data(), prefix_part.size(), 0, 128,
+                            prefix)) {
+      return false;
     }
     out.kind = NoProxyKind::IPv6Cidr;
     std::memcpy(out.net.data(), &v6, sizeof(v6));
@@ -14386,6 +14490,13 @@ Server::process_request(Stream &strm, const std::string &remote_addr,
   // Connection has been closed on client
   if (!line_reader.getline()) { return false; }
 
+  // RFC 9112 2.2: ignore an empty line received before the request-line. Some
+  // clients send an extra CRLF after a request body, which would otherwise be
+  // parsed as the next request on a persistent connection.
+  if (strcmp(line_reader.ptr(), "\r\n") == 0 && !line_reader.getline()) {
+    return false;
+  }
+
   Request req;
   req.start_time_ = std::chrono::steady_clock::now();
   req.remote_addr = remote_addr;
@@ -14579,6 +14690,12 @@ Server::process_request(Stream &strm, const std::string &remote_addr,
                             protocols.emplace_back(b, e);
                           });
             selected_subprotocol = entry.sub_protocol_selector(protocols);
+
+            // Ignore a selection the client did not offer (RFC 6455 4.2.2)
+            if (std::find(protocols.begin(), protocols.end(),
+                          selected_subprotocol) == protocols.end()) {
+              selected_subprotocol.clear();
+            }
           }
         }
 
@@ -15649,7 +15766,7 @@ inline bool ClientImpl::redirect(Request &req, Response &res, Error &error) {
   if (next_host.empty()) { next_host = host_; }
   if (next_path.empty()) { next_path = "/"; }
 
-  auto path = decode_path_component(next_path) + next_query;
+  auto path = std::move(next_path) + next_query;
 
   // Same host redirect - use current client
   if (next_scheme == scheme && next_host == host_ && next_port == port_) {
@@ -15904,9 +16021,9 @@ inline bool ClientImpl::write_request(Stream &strm, Request &req,
     // Write request line and headers
     if (detail::write_request_line(bstrm, req.method, path_with_query) < 0) {
       // A rejected method (not a token, e.g. carrying CR/LF) or target (e.g.
-      // CR/LF smuggled in via a decoded redirect Location under
-      // set_path_encode(false)) must fail the request cleanly instead of
-      // emitting a request-line-less, header-injecting request.
+      // CR/LF in a caller-supplied path under set_path_encode(false)) must
+      // fail the request cleanly instead of emitting a request-line-less,
+      // header-injecting request.
       error = Error::Write;
       rejected_locally = true;
       output_error_log(error, &req);
@@ -18510,6 +18627,9 @@ inline void SSLClient::set_ca_cert_store(tls::ca_store_t ca_cert_store) {
 inline void
 SSLClient::set_server_certificate_verifier(tls::VerifyCallback verifier) {
   if (!ctx_) { return; }
+#ifdef CPPHTTPLIB_WINDOWS_AUTOMATIC_ROOT_CERTIFICATES_UPDATE
+  server_certificate_verifier_set_ = static_cast<bool>(verifier);
+#endif
   tls::set_verify_callback(ctx_, verifier);
 }
 
@@ -18571,6 +18691,9 @@ inline bool SSLClient::initialize_ssl(Socket &socket, Error &error) {
       enable_windows_cert_verification_ &&
       system_ca_mode_ != SystemCAMode::Disabled && ca_cert_file_path_.empty() &&
       ca_cert_dir_path_.empty() && ca_cert_pem_.empty() && !ca_cert_store_set_;
+  // Only a verifier set through set_server_certificate_verifier() is seen
+  // here, not one installed with tls::set_verify_callback() directly.
+  options.server_certificate_verifier_set = server_certificate_verifier_set_;
 #endif
 
   tls::session_t session = nullptr;
@@ -19540,6 +19663,24 @@ inline cert_t get_peer_cert(const_session_t session) {
       static_cast<SSL *>(const_cast<void *>(session))));
 }
 
+inline size_t get_peer_certs(const_session_t session,
+                             std::vector<cert_t> &certs) {
+  certs.clear();
+  if (!session) { return 0; }
+  auto ssl = static_cast<const SSL *>(session);
+  // On the server side, the chain leaves out the peer's own certificate
+  if (SSL_is_server(ssl)) {
+    if (auto leaf = get_peer_cert(session)) { certs.push_back(leaf); }
+  }
+  auto sk = SSL_get_peer_cert_chain(ssl);
+  for (int i = 0; sk && i < sk_X509_num(sk); i++) {
+    auto x509 = sk_X509_value(sk, i);
+    X509_up_ref(x509);
+    certs.push_back(static_cast<cert_t>(x509));
+  }
+  return certs.size();
+}
+
 inline void free_cert(cert_t cert) {
   if (cert) { X509_free(static_cast<X509 *>(cert)); }
 }
@@ -20884,6 +21025,18 @@ inline cert_t get_peer_cert(const_session_t session) {
   return const_cast<mbedtls_x509_crt *>(cert);
 }
 
+inline size_t get_peer_certs(const_session_t session,
+                             std::vector<cert_t> &certs) {
+  certs.clear();
+  // Mbed TLS parses the whole received chain into a list headed by the peer
+  // certificate, owned by the session like get_peer_cert()'s result
+  for (auto crt = static_cast<mbedtls_x509_crt *>(get_peer_cert(session));
+       crt && crt->raw.len > 0; crt = crt->next) {
+    certs.push_back(static_cast<cert_t>(crt));
+  }
+  return certs.size();
+}
+
 inline void free_cert(cert_t cert) {
   // Mbed TLS: peer certificate is owned by the SSL context.
   // No-op here, but callers should still call this for cross-backend
@@ -20901,29 +21054,24 @@ inline bool verify_hostname(cert_t cert, const char *hostname) {
   auto ip_len = impl::parse_ip_address(host_str, ip_bytes);
   auto is_ip = ip_len > 0;
 
-  // Check Subject Alternative Names (SAN)
-  // In Mbed TLS 3.x, subject_alt_names contains raw values without ASN.1 tags
-  // - DNS names: raw string bytes
-  // - IP addresses: raw IP bytes (4 for IPv4, 16 for IPv6)
+  // Check Subject Alternative Names (SAN). Mbed TLS keeps the GeneralName type
+  // in buf.tag and the raw value in buf.p / buf.len.
   const mbedtls_x509_sequence *san = &mcert->subject_alt_names;
   while (san != nullptr && san->buf.p != nullptr && san->buf.len > 0) {
     const unsigned char *p = san->buf.p;
     size_t len = san->buf.len;
+    auto san_type = san->buf.tag & MBEDTLS_ASN1_TAG_VALUE_MASK;
 
     if (is_ip) {
       // For an IP host, only a matching iPAddress SAN of the same family
       // (4 bytes for IPv4, 16 bytes for IPv6) may authenticate it.
-      if (len == ip_len && memcmp(p, ip_bytes, ip_len) == 0) { return true; }
-    } else {
-      // Check if this SAN is a DNS name (printable ASCII string)
-      bool is_dns = len > 0;
-      for (size_t i = 0; i < len && is_dns; i++) {
-        if (p[i] < 32 || p[i] > 126) { is_dns = false; }
-      }
-      if (is_dns) {
-        std::string san_name(reinterpret_cast<const char *>(p), len);
-        if (detail::match_hostname(san_name, host_str)) { return true; }
+      if (san_type == MBEDTLS_X509_SAN_IP_ADDRESS && len == ip_len &&
+          memcmp(p, ip_bytes, ip_len) == 0) {
+        return true;
       }
+    } else if (san_type == MBEDTLS_X509_SAN_DNS_NAME) {
+      std::string san_name(reinterpret_cast<const char *>(p), len);
+      if (detail::match_hostname(san_name, host_str)) { return true; }
     }
     san = san->next;
   }
@@ -21002,65 +21150,45 @@ inline bool get_cert_sans(cert_t cert, std::vector<SanEntry> &sans) {
   const mbedtls_x509_sequence *cur = &x509->subject_alt_names;
   while (cur != nullptr) {
     if (cur->buf.len > 0) {
-      // Mbed TLS stores SAN as ASN.1 sequences
-      // The tag byte indicates the type
       const unsigned char *p = cur->buf.p;
-      size_t len = cur->buf.len;
+      size_t value_len = cur->buf.len;
 
-      // First byte is the tag
-      unsigned char tag = *p;
-      p++;
-      len--;
-
-      // Parse length (simple single-byte length assumed)
-      if (len > 0 && *p < 0x80) {
-        size_t value_len = *p;
-        p++;
-        len--;
-
-        if (value_len <= len) {
-          SanEntry entry;
-          // ASN.1 context tags for GeneralName
-          switch (tag & 0x1F) {
-          case 2: // dNSName
-            entry.type = SanType::DNS;
-            entry.value =
-                std::string(reinterpret_cast<const char *>(p), value_len);
-            break;
-          case 7: // iPAddress
-            entry.type = SanType::IP;
-            if (value_len == 4) {
-              // IPv4
-              char buf[16];
-              snprintf(buf, sizeof(buf), "%d.%d.%d.%d", p[0], p[1], p[2], p[3]);
-              entry.value = buf;
-            } else if (value_len == 16) {
-              // IPv6
-              char buf[64];
-              snprintf(buf, sizeof(buf),
-                       "%02x%02x:%02x%02x:%02x%02x:%02x%02x:"
-                       "%02x%02x:%02x%02x:%02x%02x:%02x%02x",
-                       p[0], p[1], p[2], p[3], p[4], p[5], p[6], p[7], p[8],
-                       p[9], p[10], p[11], p[12], p[13], p[14], p[15]);
-              entry.value = buf;
-            }
-            break;
-          case 1: // rfc822Name (email)
-            entry.type = SanType::EMAIL;
-            entry.value =
-                std::string(reinterpret_cast<const char *>(p), value_len);
-            break;
-          case 6: // uniformResourceIdentifier
-            entry.type = SanType::URI;
-            entry.value =
-                std::string(reinterpret_cast<const char *>(p), value_len);
-            break;
-          default: entry.type = SanType::OTHER; break;
-          }
-
-          if (!entry.value.empty()) { sans.push_back(std::move(entry)); }
+      SanEntry entry;
+      switch (cur->buf.tag & MBEDTLS_ASN1_TAG_VALUE_MASK) {
+      case MBEDTLS_X509_SAN_DNS_NAME:
+        entry.type = SanType::DNS;
+        entry.value = std::string(reinterpret_cast<const char *>(p), value_len);
+        break;
+      case MBEDTLS_X509_SAN_IP_ADDRESS:
+        entry.type = SanType::IP;
+        if (value_len == 4) {
+          // IPv4
+          char buf[16];
+          snprintf(buf, sizeof(buf), "%d.%d.%d.%d", p[0], p[1], p[2], p[3]);
+          entry.value = buf;
+        } else if (value_len == 16) {
+          // IPv6
+          char buf[64];
+          snprintf(buf, sizeof(buf),
+                   "%02x%02x:%02x%02x:%02x%02x:%02x%02x:"
+                   "%02x%02x:%02x%02x:%02x%02x:%02x%02x",
+                   p[0], p[1], p[2], p[3], p[4], p[5], p[6], p[7], p[8], p[9],
+                   p[10], p[11], p[12], p[13], p[14], p[15]);
+          entry.value = buf;
         }
+        break;
+      case MBEDTLS_X509_SAN_RFC822_NAME:
+        entry.type = SanType::EMAIL;
+        entry.value = std::string(reinterpret_cast<const char *>(p), value_len);
+        break;
+      case MBEDTLS_X509_SAN_UNIFORM_RESOURCE_IDENTIFIER:
+        entry.type = SanType::URI;
+        entry.value = std::string(reinterpret_cast<const char *>(p), value_len);
+        break;
+      default: entry.type = SanType::OTHER; break;
       }
+
+      if (!entry.value.empty()) { sans.push_back(std::move(entry)); }
     }
     cur = cur->next;
   }
@@ -22041,6 +22169,24 @@ inline cert_t get_peer_cert(const_session_t session) {
   return static_cast<cert_t>(cert);
 }
 
+inline size_t get_peer_certs(const_session_t session,
+                             std::vector<cert_t> &certs) {
+  certs.clear();
+  if (!session) { return 0; }
+  // wolfSSL keeps the received chain only when built with SESSION_CERTS
+#ifdef SESSION_CERTS
+  auto wsession =
+      static_cast<impl::WolfSSLSession *>(const_cast<void *>(session));
+  auto chain = wolfSSL_get_peer_chain(wsession->ssl);
+  auto count = chain ? wolfSSL_get_chain_count(chain) : 0;
+  for (int i = 0; i < count; i++) {
+    auto x509 = wolfSSL_get_chain_X509(chain, i);
+    if (x509) { certs.push_back(static_cast<cert_t>(x509)); }
+  }
+#endif
+  return certs.size();
+}
+
 inline void free_cert(cert_t cert) {
   if (cert) { wolfSSL_X509_free(static_cast<WOLFSSL_X509 *>(cert)); }
 }
@@ -22684,9 +22830,9 @@ inline void WebSocket::start_heartbeat() {
   if (ping_interval_sec_ == 0) { return; }
   ping_thread_ = std::thread([this]() {
     std::unique_lock<std::mutex> lock(ping_mutex_);
-    while (!closed_) {
-      ping_cv_.wait_for(lock, std::chrono::seconds(ping_interval_sec_));
-      if (closed_) { break; }
+    // The predicate keeps a spurious wakeup from sending a ping early
+    while (!ping_cv_.wait_for(lock, std::chrono::seconds(ping_interval_sec_),
+                              [this]() { return closed_.load(); })) {
       // If the peer has failed to respond to the previous pings, give up.
       // RFC 6455 does not define a pong-timeout mechanism; this is an
       // opt-in liveness check controlled by max_missed_pongs_.

test/CMakeLists.txt

@@ -146,6 +146,13 @@ if(HTTPLIB_IS_USING_OPENSSL)
         WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
         COMMAND_ERROR_IS_FATAL ANY
     )
+    # cert_san_types.pem: the bytes of each SAN read as the other type:
+    #                 DNS:a.zz is 97.46.122.122, IP:42.46.122.122 is "*.zz".
+    execute_process(
+        COMMAND ${OPENSSL_COMMAND} req -x509 -key key.pem -sha256 -days 3650 -nodes -subj /CN=san-types -addext subjectAltName=DNS:a.zz,IP:42.46.122.122 -out cert_san_types.pem
+        WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
+        COMMAND_ERROR_IS_FATAL ANY
+    )
 endif()
 
 add_subdirectory(fuzzing)

test/gen-certs.sh

@@ -33,3 +33,7 @@ openssl req -x509 -key key.pem -sha256 -days 3650 -nodes -subj "/CN=127.0.0.1" -
 #                 different address. The SAN address must match; the CN address
 #                 must be ignored.
 openssl req -x509 -key key.pem -sha256 -days 3650 -nodes -subj "/CN=::1" -addext "subjectAltName=IP:2001:db8::1" -out cert_ipv6.pem
+
+# cert_san_types.pem: the bytes of each SAN read as the other type:
+#                 DNS:a.zz is 97.46.122.122, IP:42.46.122.122 is "*.zz".
+openssl req -x509 -key key.pem -sha256 -days 3650 -nodes -subj "/CN=san-types" -addext "subjectAltName=DNS:a.zz,IP:42.46.122.122" -out cert_san_types.pem

test/meson.build

@@ -137,6 +137,15 @@ cert_ipv6_pem = custom_target(
   command: [openssl, 'req', '-x509', '-key', '@INPUT@', '-sha256', '-days', '3650', '-nodes', '-subj', '/CN=::1', '-addext', 'subjectAltName=IP:2001:db8::1', '-out', '@OUTPUT@']
 )
 
+# cert_san_types.pem: the bytes of each SAN read as the other type: DNS:a.zz is
+# 97.46.122.122, IP:42.46.122.122 is "*.zz".
+cert_san_types_pem = custom_target(
+  'cert_san_types_pem',
+  input: key_pem,
+  output: 'cert_san_types.pem',
+  command: [openssl, 'req', '-x509', '-key', '@INPUT@', '-sha256', '-days', '3650', '-nodes', '-subj', '/CN=san-types', '-addext', 'subjectAltName=DNS:a.zz,IP:42.46.122.122', '-out', '@OUTPUT@']
+)
+
 # Copy test files to the build directory
 configure_file(input: 'ca-bundle.crt', output: 'ca-bundle.crt', copy: true)
 configure_file(input: 'image.jpg',     output: 'image.jpg',     copy: true)
@@ -178,7 +187,8 @@ test(
     client_encrypted_pbes1_key_pem,
     client_encrypted_cert_pem,
     cert_ip_cn_pem,
-    cert_ipv6_pem
+    cert_ipv6_pem,
+    cert_san_types_pem
   ],
   workdir: meson.current_build_dir(),
   timeout: 300