Ensure URLSession and curl agree on the host

CoreFoundation/URL.subproj/CFURLSessionInterface.c

@@ -657,3 +657,22 @@ CFURLSessionSList *_Nullable CFURLSessionSListAppend(CFURLSessionSList *_Nullabl
 void CFURLSessionSListFreeAll(CFURLSessionSList *_Nullable list) {
     curl_slist_free_all((struct curl_slist *) list);
 }
+
+bool CFURLSessionCurlHostIsEqual(const char *_Nonnull url, const char *_Nonnull expectedHost) {
+#if LIBCURL_VERSION_MAJOR > 7 || (LIBCURL_VERSION_MAJOR == 7 && LIBCURL_VERSION_MINOR >= 62)
+    bool isEqual = false;
+    CURLU *h = curl_url();
+    if (0 == curl_url_set(h, CURLUPART_URL, url, 0)) {
+        char *curlHost = NULL;
+        if (0 == curl_url_get(h, CURLUPART_HOST, &curlHost, 0)) {
+            isEqual = (strlen(curlHost) == strlen(expectedHost) &&
+                       strncmp(curlHost, expectedHost, strlen(curlHost)) == 0);
+            curl_free(curlHost);
+        }
+        curl_free(h);
+    }
+    return isEqual;
+#else
+    return true;
+#endif
+}

CoreFoundation/URL.subproj/CFURLSessionInterface.h

@@ -642,6 +642,7 @@ typedef struct CFURLSessionSList CFURLSessionSList;
 CF_EXPORT CFURLSessionSList *_Nullable CFURLSessionSListAppend(CFURLSessionSList *_Nullable list, const char * _Nullable string);
 CF_EXPORT void CFURLSessionSListFreeAll(CFURLSessionSList *_Nullable list);
 
+CF_EXPORT bool CFURLSessionCurlHostIsEqual(const char *_Nonnull url, const char *_Nonnull expectedHost);
 
 
 CF_EXTERN_C_END

Sources/FoundationNetworking/URLSession/FTP/FTPURLProtocol.swift

@@ -56,7 +56,21 @@ internal class _FTPURLProtocol: _NativeProtocol {
         easyHandle.set(debugOutputOn: enableLibcurlDebugOutput, task: task!)
         easyHandle.set(skipAllSignalHandling: true)
         guard let url = request.url else { fatalError("No URL in request.") }
-        easyHandle.set(url: url)
+        guard url.host != nil else {
+            self.internalState = .transferFailed
+            let error = NSError(domain: NSURLErrorDomain, code: NSURLErrorBadURL,
+                                userInfo: [NSLocalizedDescriptionKey: "FTP URL must have a host"])
+            failWith(error: error, request: request)
+            return
+        }
+        do {
+            try easyHandle.set(url: url)
+        } catch {
+            self.internalState = .transferFailed
+            let nsError = error as? NSError ?? NSError(domain: NSURLErrorDomain, code: NSURLErrorBadURL)
+            failWith(error: nsError, request: request)
+            return
+        }
         easyHandle.set(preferredReceiveBufferSize: Int.max)
         do {
             switch (body, try body.getBodyLength()) {

Sources/FoundationNetworking/URLSession/HTTP/HTTPURLProtocol.swift

@@ -311,7 +311,21 @@ internal class _HTTPURLProtocol: _NativeProtocol {
         guard let url = request.url else {
             fatalError("No URL in request.")
         }
-        easyHandle.set(url: url)
+        guard url.host != nil else {
+            self.internalState = .transferFailed
+            let error = NSError(domain: NSURLErrorDomain, code: NSURLErrorBadURL,
+                                userInfo: [NSLocalizedDescriptionKey: "HTTP URL must have a host"])
+            failWith(error: error, request: request)
+            return
+        }
+        do {
+            try easyHandle.set(url: url)
+        } catch {
+            self.internalState = .transferFailed
+            let nsError = error as? NSError ?? NSError(domain: NSURLErrorDomain, code: NSURLErrorBadURL)
+            failWith(error: nsError, request: request)
+            return
+        }
         let session = task?.session as! URLSession
         let _config = session._configuration
         easyHandle.set(sessionConfig: _config)

Sources/FoundationNetworking/URLSession/libcurl/EasyHandle.swift

@@ -165,10 +165,16 @@ extension _EasyHandle {
     }
     /// URL to use in the request
     /// - SeeAlso: https://curl.haxx.se/libcurl/c/CURLOPT_URL.html
-    func set(url: URL) {
+    func set(url: URL) throws {
         _url = url
-        url.absoluteString.withCString {
-            try! CFURLSession_easy_setopt_ptr(rawHandle, CFURLSessionOptionURL, UnsafeMutablePointer(mutating: $0)).asError()
+        try url.absoluteString.withCString { urlPtr in
+            try url.host?.withCString { hostPtr in
+                guard CFURLSessionCurlHostIsEqual(urlPtr, hostPtr) else {
+                    throw NSError(domain: NSURLErrorDomain, code: NSURLErrorBadURL,
+                                  userInfo: [NSLocalizedDescriptionKey: "URLSession and curl did not agree on URL host"])
+                }
+            }
+            try! CFURLSession_easy_setopt_ptr(rawHandle, CFURLSessionOptionURL, UnsafeMutablePointer(mutating: urlPtr)).asError()
         }
     }