Fix WebServerSecure streamFile() (esp8266#4545)

* Fix WebServerSecure streamFile()

ESP8266WebServerSecure's streamFile was using the base class' method
which did not use SSL encrypt before transmitting, leading to failure.

Add a new template method and required support for
WiFiClientSecure::write(Stream&) (using a local temp buffer since the
SSL libs do not grok Arduino Streams at all).

Fixes esp8266#4544

* Match ClientContext buffer and yield() behavior

ClientContext sends out 256 bytes at a time and gives a yield after
each chunk to ensure the WDT doesn't fire.  Mimic that behavior in
WiFiClientSecure::write(Stream&).

(cherry picked from commit 42f824b)

libraries/ESP8266WebServer/src/ESP8266WebServerSecure.h

@@ -42,6 +42,12 @@ class ESP8266WebServerSecure : public ESP8266WebServer
   void handleClient() override;
   void close() override;
 
+  template<typename T>
+  size_t streamFile(T &file, const String& contentType) {
+    _streamFileCore(file.size(), file.name(), contentType);
+    return _currentClientSecure.write(file);
+  }
+
 private:
   size_t _currentClientWrite (const char *bytes, size_t len) override { return _currentClientSecure.write((const uint8_t *)bytes, len); }
   size_t _currentClientWrite_P (PGM_P bytes, size_t len) override { return _currentClientSecure.write_P(bytes, len); }

libraries/ESP8266WiFi/src/WiFiClientSecure.cpp

@@ -564,6 +564,30 @@ size_t WiFiClientSecure::write_P(PGM_P buf, size_t size)
     return write(copy, size);
 }
 
+// The axTLS bare libs don't understand anything about Arduino Streams,
+// so we have to manually read and send individual chunks.
+size_t WiFiClientSecure::write(Stream& stream)
+{
+    size_t totalSent = 0;
+    size_t countRead;
+    size_t countSent;
+    if (!_ssl)
+    {
+        return 0;
+    }
+    do {
+        uint8_t temp[256]; // Temporary chunk size same as ClientContext
+        countSent = 0;
+        countRead = stream.readBytes(temp, sizeof(temp));
+        if (countRead) {
+            countSent = write(temp, countRead);
+            totalSent += countSent;
+        }
+        yield(); // Feed the WDT
+    } while ( (countSent == countRead) && (countSent > 0) );
+    return totalSent;
+}
+
 int WiFiClientSecure::read(uint8_t *buf, size_t size)
 {
     if (!_ssl) {

libraries/ESP8266WiFi/src/WiFiClientSecure.h

@@ -43,6 +43,7 @@ class WiFiClientSecure : public WiFiClient {
   uint8_t connected() override;
   size_t write(const uint8_t *buf, size_t size) override;
   size_t write_P(PGM_P buf, size_t size) override;
+  size_t write(Stream& stream); // Note this is not virtual
   int read(uint8_t *buf, size_t size) override;
   int available() override;
   int read() override;