Enhancement/options cutom handling

lib/inc/drogon/HttpRequest.h

@@ -501,6 +501,37 @@ class DROGON_EXPORT HttpRequest
         return toRequest(std::forward<T>(obj));
     }
 
+    /*! \brief Check if the request is a CORS request.
+     *  \details It should contain:
+     *              - Origin: origination page
+     *  \returns true if the Origin header is present
+     */
+    inline bool isCorsRequest() const
+    {
+        // Check presence of required headers
+        return headers().find("origin") != headers().end();
+    }
+
+    /*! \brief Check if the request is a CORS pre-flight request.
+     *  \details Check if the method of the request is OPTIONS and if it is
+     *           a CORS pre-flight request.\n
+     *           It should contain:
+     *              - Origin: origination page
+     *              - Access-Control-Request-Method: method to be used in the
+     *                actual request
+     *  \returns true if the method is OPTIONS and the required CORS pre-flight
+     *                headers are present
+     */
+    inline bool isCorsPreflightRequest() const
+    {
+        if (method() != HttpMethod::Options)
+            return false;
+        // Check presence of required headers
+        return isCorsRequest() &&
+               headers().find("access-control-request-method") !=
+                   headers().end();
+    }
+
     virtual bool isOnSecureConnection() const noexcept = 0;
     virtual void setContentTypeString(const char *typeString,
                                       size_t typeStringLength) = 0;

lib/inc/drogon/HttpResponse.h

@@ -558,6 +558,141 @@ class DROGON_EXPORT HttpResponse
         return toResponse(std::forward<T>(obj));
     }
 
+    /*! \brief Create an OPTIONS or CORS pre-flight response
+     *  \details If the request is not an OPTIONS request, returns a NULL
+     *           response\n
+     *           If it is a generic OPTIONS request, returns a 204 No Content
+     *           response with the Allow header\n
+     *           If it is a CORS pre-flight request, returns a 204 No Content
+     *           response with the CORS headers set
+     *
+     *           Other status codes for CORS pre-flight answers:
+     * 			 - 400 Bad Request: if the request is malformed (missing
+     *             required headers)
+     * 			 - 403 Forbidden: if the Origin is not allowed + reason
+     *             in a X-Cors-Error header
+     * 			 - 403 Forbidden: if one of the headers in
+     *             Access-Control-Request-Headers is not allowed + reason in
+     *             a X-Cors-Error header
+     * 			 - 405 Method Not Allowed: if the requested method is
+     *             not allowed
+     *  \note CORS is a browser-side security mechanism.\n
+     *        Do not rely on Origin for authentication/authorization:
+     *        non-browser clients can spoof or omit it.\n
+     *        Enforce access control independently.
+     *  \param[in] request          Drogon (OPTIONS) request
+     *  \param[in] allowedHeaders   Set of allowed headers (for
+     *                              Access-Control-Allow-Headers header)\n
+     *                              (headers allowed by the controller path
+     *                              handler)
+     *  \param[in] originValidator  Function to validate the Origin header value
+     *                              (allow the origin or not)\n
+     *                              If allowCredentials is true, originValidator
+     *                              _SHOULD_ enforce a strict allowlist
+     *  \param[in] allowNullOrigin  Should be true to accept the "Origin: null"
+     *                              header\n
+     *                              (set for local file:// pages, sandboxed
+     *                              iframes, opaque origins, data: URIs)
+     *  \param[in] allowCredentials Should be true to add the header
+     *                              "Access-Control-Allow-Credentials: true"
+     *                              (controls whether the browser may include
+     *                              credentials such as cookies, HTTP auth, or
+     *                              client certificates)\n
+     *                              Note: Authorization (bearer) is not a
+     *                              credential header; allow it via
+     *                              allowedHeaders when needed
+     *  \param[in] allowPNA         Should be true to accept the header
+     *                              "Access-Control-Request-Private-Network"
+     *                              (when a page from a less private address
+     *                              space is trying to reach a more private
+     *                              one, like internet -> intranet)\n
+     *                              Note: specific to Chromium & derivatives
+     *                              (Edge, Opera, Brave, ...), not in Firefox
+     *                              or Safari
+     *  \param[in] maxAgeSeconds    If set, adds the "Access-Control-Max-Age"
+     *                              header with the given value (in seconds,
+     *                              how long the results of a preflight
+     *                              request can be cached by the navigator)
+     *  \returns the OPTIONS or CORS pre-flight response, or a null pointer if
+     *           the request is not an OPTIONS request
+     */
+    static HttpResponsePtr newOptionsResponse(
+        const HttpRequestPtr &request,
+        const std::function<bool(std::string_view)> &originValidator = nullptr,
+        bool allowNullOrigin = false,
+        bool allowCredentials = false,
+        bool allowPNA = true,
+        std::optional<unsigned int> maxAgeSeconds = {},
+        const std::optional<std::set<std::string_view>> &allowedHeaders =
+            std::nullopt);
+
+    /*! \copydoc newOptionsResponse(const HttpRequestPtr&,
+     *                         const std::function<bool(std::string_view)>&,
+     *                         bool, bool, bool,
+     *                         std::optional<unsigned int>,
+     *                         const std::optional<std::set<std::string_view>>&)
+     *  \remarks Helper when specifying the allowed headers, when other
+     *           parameters may be default, to avoid having to specify them all
+     */
+    inline static HttpResponsePtr newOptionsResponse(
+        const HttpRequestPtr &request,
+        const std::set<std::string_view> &allowedHeaders,
+        const std::function<bool(std::string_view)> &originValidator = nullptr,
+        bool allowNullOrigin = false,
+        bool allowCredentials = false,
+        bool allowPNA = true,
+        std::optional<unsigned int> maxAgeSeconds = {})
+    {
+        return newOptionsResponse(request,
+                                  originValidator,
+                                  allowNullOrigin,
+                                  allowCredentials,
+                                  allowPNA,
+                                  maxAgeSeconds,
+                                  allowedHeaders);
+    }
+
+    /*! \brief Add CORS headers to a response
+     *  \details Adds the CORS headers to a response for a normal request (a
+     *           CORS request but not a CORS preflight request):
+     *              - does nothing if it's an OPTIONS request, or
+     *              - if it's not a CORS request, or
+     *              - if it's a CORS preflight request
+     *           Else:
+     *              - adds Access-Control-Allow-Origin (if not yet present)
+     *              - adds Origin to the Vary header,
+     *              - sets or clears Access-Control-Allow-Credentials (if
+     *                allowCredentials is set)
+     *              - completes Access-Control-Expose-Headers
+     *  \param[in] request          Drogon request (to get Origin)
+     *  \param[in] allowCredentials If set and true, adds the
+     *                              "Access-Control-Allow-Credentials: true
+     *                              header"\n
+     *                              If set and false, removes the
+     *                              "Access-Control-Allow-Credentials" header\n
+     *                              If not set, leaves the
+     *                              "Access-Control-Allow-Credentials" header
+     *                              untouched\n
+     *                              *MUST MATCH THE newOptionsResponse()
+     *                              PRE-FLIGHT RESPONSE VALUE*
+     *  \param[in] exposedHeaders   Set of exposed headers (for
+     *                              Access-Control-Expose-Headers header)\n
+     *                              These are the headers allowed to be exposed
+     *                              to javascript by the remote browser\n
+     *                              Note: they are *APPENDED* to any already
+     *                              present in the response, they are not
+     *                              REPLACED.\n
+     *                              This allows to complete them in the
+     *                              controller path handler.\n
+     *                              If you want to REPLACE them, remove the
+     *                              header before calling this function.
+     * \note may be use both in the controller path handler and in a
+     *       pre-sending advice
+     */
+    void addCorsHeaders(const HttpRequestPtr &request,
+                        const std::set<std::string_view> &exposedHeaders = {},
+                        const std::optional<bool> &allowCredentials = {});
+
     /**
      * @brief If the response is a file response (i.e. created by
      * newFileResponse) returns the path on the filesystem. Otherwise a

lib/inc/drogon/utils/Utilities.h

@@ -124,6 +124,165 @@ DROGON_EXPORT std::set<std::string> splitStringToSet(
     const std::string &str,
     const std::string &separator);
 
+/*! \brief Compare two string_views for equality, ignoring case.
+ *  \warning This is locale dependent
+ *  \param[in] str1 The first string_view.
+ *  \param[in] str2 The second string_view.
+ *  \return true if the string_views are equal, ignoring case; false otherwise.
+ */
+inline bool ci_equals(std::string_view str1, std::string_view str2)
+{
+    if (str1.size() != str2.size())
+        return false;
+    return std::equal(str1.begin(),
+                      str1.end(),
+                      str2.begin(),
+                      [](unsigned char a, unsigned char b) {
+                          return std::tolower(a) == std::tolower(b);
+                      });
+}
+
+/*! \details Trim leading and trailing spaces and tabs from a string_view,
+ *           modifying it.
+ *  \param[in,out] str The string_view to trim.
+ *  \return The trimmed string_view.
+ */
+inline std::string_view &trim_inplace(std::string_view &str)
+{
+    auto pos = str.find_first_not_of(" \t");
+    // defeat Windows macro "min"
+    str.remove_prefix((std::min)(pos, str.size()));
+    if (str.empty())
+        return str;
+    pos = str.find_last_not_of(" \t");
+    str.remove_suffix(str.size() - pos - 1);
+    return str;
+}
+
+/*! \brief Trim leading and trailing spaces and tabs from a string_view.
+ *  \param[in] str The string_view to trim.
+ *  \return A string_view with leading and trailing spaces and tabs removed.
+ */
+inline std::string_view trim(std::string_view str)
+{
+    return trim_inplace(str);
+}
+
+/*! \brief Trim leading and trailing spaces and tabs from a rvalue string.
+ *  \param[in] str The string to trim.
+ *  \return The string with leading and trailing spaces and tabs removed.
+ */
+inline std::string trim(std::string &&str)
+{
+    auto pos = str.find_last_not_of(" \t");
+    if (pos == std::string::npos)
+        return {};
+    str.resize(pos + 1);
+    pos = str.find_first_not_of(" \t");
+    if (pos > 0)
+        str.erase(0, pos);
+    return str;
+}
+
+/*! \brief Split a string_view into a vector of string_views.
+ *  \param[in] str The string_view to split.
+ *  \param[in] separator The separator to use for splitting.
+ *  \param[in] trimValues Whether to trim whitespace from the resulting
+ *                        string_views.
+ *  \param[in] acceptEmptyString Whether to include empty strings in the result.
+ *  \return A vector of string_views obtained by splitting the input
+ *          string_view.
+ */
+inline std::vector<std::string_view> splitStringView(
+    std::string_view str,
+    std::string_view separator,
+    bool trimValues = true,
+    bool acceptEmptyString = false)
+{
+    std::vector<std::string_view> result;
+    if (separator.empty())
+    {
+        if (trimValues)
+            trim_inplace(str);
+        if (acceptEmptyString || !str.empty())
+            result.push_back(str);
+        return result;
+    }
+    size_t start = 0;
+    size_t end = 0;
+    while ((end = str.find(separator, start)) != std::string_view::npos)
+    {
+        auto token = str.substr(start, end - start);
+        if (trimValues)
+            trim_inplace(token);
+        if (acceptEmptyString || !token.empty())
+            result.push_back(token);
+        start = end + separator.size();
+    }
+    auto token = str.substr(start);
+    if (trimValues)
+        trim_inplace(token);
+    if (acceptEmptyString || !token.empty())
+    {
+        result.push_back(token);
+    }
+    return result;
+}
+
+/*! \brief Split a string_view into a set of string_views.
+ *  \copyparams splitStringView
+ *  \return A set of (unique) string_views obtained by splitting the input
+ *          string_view.
+ *  \note Uniqueness is case-sensitive: "A" and "a" are considered different
+ *        values.
+ */
+inline std::set<std::string_view> splitStringViewToSet(
+    std::string_view str,
+    std::string_view separator,
+    bool trimValues = true,
+    bool acceptEmptyString = false)
+{
+    auto v = splitStringView(str, separator, trimValues, acceptEmptyString);
+    return std::set<std::string_view>(v.begin(), v.end());
+}
+
+/*! \brief Join a vector of string_view into a string.
+ *  \param[in] strs The vector of string_views to join.
+ *  \param[in] separator The separator to use between string_views.
+ *  \return A single string obtained by joining the input string_views with the
+ *          specified separator.
+ *  \note Empty values are skipped.
+ */
+inline std::string joinStringViews(const std::vector<std::string_view> &strs,
+                                   std::string_view separator)
+{
+    std::string result;
+    for (std::string_view str : strs)
+    {
+        if (trim_inplace(str).empty())
+            continue;
+        if (!result.empty())
+            result.append(separator);
+        result.append(str);
+    }
+    return result;
+}
+
+/*! \brief Join a set of string_view into a string.
+ *  \param[in] strs The set of string_views to join.
+ *  \param[in] separator The separator to use between string_views.
+ *  \return A single string obtained by joining the input string_views with the
+ *          specified separator.
+ *  \note Empty values are skipped.
+ */
+inline std::string joinStringViews(const std::set<std::string_view> &strs,
+                                   std::string_view separator)
+{
+    return joinStringViews(std::vector<std::string_view>{strs.begin(),
+                                                         strs.end()},
+                           separator);
+}
+
 /// Get UUID string.
 DROGON_EXPORT std::string getUuid(bool lowercase = true);