Fix handling of timestamps in Teleinfo component. (#2392)

* teleinfo: avoid a buffer overflow.

When reading tag or values, data is written to the buffer even if the
size if bigger than the buffer. Add a new 'max_len' argument to
get_field() to avoid this error.

Signed-off-by: 0hax <0hax@protonmail.com>

* teleinfo: read extra timestamp field for some tags.

Some tags has an extra timestamp field that need to be read before the
actual data.
The code is inspired by Jpsy work:

29339c14f9

Signed-off-by: 0hax <0hax@protonmail.com>

* teleinfo: increase MAX_BUF_SIZE to suffice for 3-phase Linky in Standard mode.

* teleinfo: handle DATE tag correctly.

The DATE tag is special due its format and need to be handled
separately.
Fix from DrCoolzic.

Signed-off-by: 0hax <0hax@protonmail.com>

Co-authored-by: Jörg Wagner <jwagner@digilog.de>

esphome/components/teleinfo/teleinfo.cpp

@@ -7,7 +7,7 @@ namespace teleinfo {
 static const char *const TAG = "teleinfo";
 
 /* Helpers */
-static int get_field(char *dest, char *buf_start, char *buf_end, int sep) {
+static int get_field(char *dest, char *buf_start, char *buf_end, int sep, int max_len) {
   char *field_end;
   int len;
 
@@ -15,6 +15,8 @@ static int get_field(char *dest, char *buf_start, char *buf_end, int sep) {
   if (!field_end)
     return 0;
   len = field_end - buf_start;
+  if (len >= max_len)
+    return len;
   strncpy(dest, buf_start, len);
   dest[len] = '\0';
 
@@ -106,9 +108,22 @@ void TeleInfo::loop() {
        * 0xa | Tag | 0x9 | Data | 0x9 | CRC | 0xd
        *     ^^^^^^^^^^^^^^^^^^^^^^^^^
        * Checksum is computed on the above in standard mode.
+       *
+       * Note that some Tags may have a timestamp in Standard mode. In this case
+       * the group would looks like this:
+       * 0xa | Tag | 0x9 | Timestamp | 0x9 | Data | 0x9 | CRC | 0xd
+       *
+       * The DATE tag is a special case. The group looks like this
+       * 0xa | Tag | 0x9 | Timestamp | 0x9 | 0x9 | CRC | 0xd
+       *
        */
       while ((buf_finger = static_cast<char *>(memchr(buf_finger, (int) 0xa, buf_index_ - 1))) &&
              ((buf_finger - buf_) < buf_index_)) {
+        /*
+         * Make sure timesamp is nullified between each tag as some tags don't
+         * have a timestamp
+         */
+        timestamp_[0] = '\0';
         /* Point to the first char of the group after 0xa */
         buf_finger += 1;
 
@@ -123,7 +138,7 @@ void TeleInfo::loop() {
           continue;
 
         /* Get tag */
-        field_len = get_field(tag_, buf_finger, grp_end, separator_);
+        field_len = get_field(tag_, buf_finger, grp_end, separator_, MAX_TAG_SIZE);
         if (!field_len || field_len >= MAX_TAG_SIZE) {
           ESP_LOGE(TAG, "Invalid tag.");
           break;
@@ -132,8 +147,22 @@ void TeleInfo::loop() {
         /* Advance buf_finger to after the tag and the separator. */
         buf_finger += field_len + 1;
 
-        /* Get value (after next separator) */
+        /*
-        field_len = get_field(val_, buf_finger, grp_end, separator_);
+         * If there is two separators and the tag is not equal to "DATE",
+         * it means there is a timestamp to read first.
+         */
+        if (std::count(buf_finger, grp_end, separator_) == 2 && strcmp(tag_, "DATE") != 0) {
+          field_len = get_field(timestamp_, buf_finger, grp_end, separator_, MAX_TIMESTAMP_SIZE);
+          if (!field_len || field_len >= MAX_TIMESTAMP_SIZE) {
+            ESP_LOGE(TAG, "Invalid Timestamp");
+            break;
+          }
+
+          /* Advance buf_finger to after the first data and the separator. */
+          buf_finger += field_len + 1;
+        }
+
+        field_len = get_field(val_, buf_finger, grp_end, separator_, MAX_VAL_SIZE);
         if (!field_len || field_len >= MAX_VAL_SIZE) {
           ESP_LOGE(TAG, "Invalid Value");
           break;

esphome/components/teleinfo/teleinfo.h

@@ -11,7 +11,8 @@ namespace teleinfo {
  */
 static const uint8_t MAX_TAG_SIZE = 64;
 static const uint16_t MAX_VAL_SIZE = 256;
-static const uint16_t MAX_BUF_SIZE = 1024;
+static const uint16_t MAX_BUF_SIZE = 2048;
+static const uint16_t MAX_TIMESTAMP_SIZE = 14;
 
 class TeleInfoListener {
  public:
@@ -36,6 +37,7 @@ class TeleInfo : public PollingComponent, public uart::UARTDevice {
   uint32_t buf_index_{0};
   char tag_[MAX_TAG_SIZE];
   char val_[MAX_VAL_SIZE];
+  char timestamp_[MAX_TIMESTAMP_SIZE];
   enum State {
     OFF,
     ON,