OTA firmware MD5 check + password support for esp-idf (#2507)

Co-authored-by: Maurice Makaay <account-github@makaay.nl>

esphome/components/md5/md5.h

@@ -0,0 +1,58 @@
+#pragma once
+
+#include "esphome/core/defines.h"
+
+#ifdef USE_ESP_IDF
+#include "esp32/rom/md5_hash.h"
+#define MD5_CTX_TYPE MD5Context
+#endif
+
+#if defined(USE_ARDUINO) && defined(USE_ESP32)
+#include "rom/md5_hash.h"
+#define MD5_CTX_TYPE MD5Context
+#endif
+
+#if defined(USE_ARDUINO) && defined(USE_ESP8266)
+#include <md5.h>
+#define MD5_CTX_TYPE md5_context_t
+#endif
+
+namespace esphome {
+namespace md5 {
+
+class MD5Digest {
+ public:
+  MD5Digest() = default;
+  ~MD5Digest() = default;
+
+  /// Initialize a new MD5 digest computation.
+  void init();
+
+  /// Add bytes of data for the digest.
+  void add(const uint8_t *data, size_t len);
+  void add(const char *data, size_t len) { this->add((const uint8_t *) data, len); }
+
+  /// Compute the digest, based on the provided data.
+  void calculate();
+
+  /// Retrieve the MD5 digest as bytes.
+  /// The output must be able to hold 16 bytes or more.
+  void get_bytes(uint8_t *output);
+
+  /// Retrieve the MD5 digest as hex characters.
+  /// The output must be able to hold 32 bytes or more.
+  void get_hex(char *output);
+
+  /// Compare the digest against a provided byte-encoded digest (16 bytes).
+  bool equals_bytes(const char *expected);
+
+  /// Compare the digest against a provided hex-encoded digest (32 bytes).
+  bool equals_hex(const char *expected);
+
+ protected:
+  MD5_CTX_TYPE ctx_{};
+  uint8_t digest_[16];
+};
+
+}  // namespace md5
+}  // namespace esphome