Detect invalid sizes when encoding bytes fields.

pb_encode.c

@@ -521,7 +521,10 @@ bool checkreturn pb_enc_fixed32(pb_ostream_t *stream, const pb_field_t *field, c
 bool checkreturn pb_enc_bytes(pb_ostream_t *stream, const pb_field_t *field, const void *src)
 {
     const pb_bytes_array_t *bytes = (const pb_bytes_array_t*)src;
-    UNUSED(field);
+
+    if (bytes->size + offsetof(pb_bytes_array_t, bytes) > field->data_size)
+        PB_RETURN_ERROR(stream, "bytes size exceeded");
+    
     return pb_encode_string(stream, bytes->bytes, bytes->size);
 }
 

tests/common/unittestproto.proto

@@ -12,6 +12,10 @@ message StringMessage {
     required string data = 1 [(nanopb).max_size = 10];
 }
 
+message BytesMessage {
+    required bytes data = 1 [(nanopb).max_size = 16];
+}
+
 message CallbackArray {
     // We cheat a bit and use this message for testing other types, too.
     // Nanopb does not care about the actual defined data type for callback

tests/encode_unittests/encode_unittests.c

@@ -172,9 +172,9 @@ int main()
         struct { size_t size; uint8_t bytes[5]; } value = {5, {'x', 'y', 'z', 'z', 'y'}};
     
         COMMENT("Test pb_enc_bytes")
-        TEST(WRITES(pb_enc_bytes(&s, NULL, &value), "\x05xyzzy"))
+        TEST(WRITES(pb_enc_bytes(&s, &BytesMessage_fields[0], &value), "\x05xyzzy"))
         value.size = 0;
-        TEST(WRITES(pb_enc_bytes(&s, NULL, &value), "\x00"))
+        TEST(WRITES(pb_enc_bytes(&s, &BytesMessage_fields[0], &value), "\x00"))
     }
     
     {
@@ -258,6 +258,20 @@ int main()
                     "\x0A\x07\x0A\x05\x01\x02\x03\x04\x05"))
     }
     
+    {
+        uint8_t buffer[32];
+        pb_ostream_t s;
+        BytesMessage msg = {{3, "xyz"}};
+        
+        COMMENT("Test pb_encode with bytes message.")
+        TEST(WRITES(pb_encode(&s, BytesMessage_fields, &msg),
+                    "\x0A\x03xyz"))
+        
+        msg.data.size = 17; /* More than maximum */
+        TEST(!pb_encode(&s, BytesMessage_fields, &msg))
+    }
+        
+    
     {
         uint8_t buffer[20];
         pb_ostream_t s;