visomat-data-downloader: more precise data validation in decode_eeprom()

diff --git a/src/visomat-data-downloader.c b/src/visomat-data-downloader.c
index 1b4cde9..a53f72c 100644 (file)
--- a/src/visomat-data-downloader.c
+++ b/src/visomat-data-downloader.c
@@ -133,8 +133,15 @@ static int decode_eeprom(uint8_t *buffer,
        struct datetime d;
        struct pressure p;
 
-       if (buffer[0] != STX || buffer[1] != 'M' || buffer[len - 1] != ETX)
+       if (buffer[0] != STX || buffer[1] != 'M') {
+               fprintf(stderr, "Usupported data.\n");
                return -EINVAL;
+       }
+
+       if (buffer[len - 1] != ETX) {
+               fprintf(stderr, "Bad terminator in data. Buffer too small?\n");
+               return -EINVAL;
+       }
 
        /* skip the initial STX */
        i = 1;