Fixed NULL += 0 undefined behaviour

diff --git a/src/monocypher.c b/src/monocypher.c
index 0257fb5e7c7dc018f3c24869868a920bb76f4961..7fdebb0a94e9fc31a4f4807acf0730a485ca72e4 100644 (file)
--- a/src/monocypher.c
+++ b/src/monocypher.c
@@ -377,6 +377,11 @@ void crypto_poly1305_init(crypto_poly1305_ctx *ctx, const u8 key[32])
 void crypto_poly1305_update(crypto_poly1305_ctx *ctx,
                             const u8 *message, size_t message_size)
 {
+       // Avoid undefined NULL pointer increments with empty messages
+       if (message_size == 0) {
+               return;
+       }
+
        // Align ourselves with block boundaries
        size_t aligned = MIN(gap(ctx->c_idx, 16), message_size);
        FOR (i, 0, aligned) {