Buffer overflow

A buffer overflow issue was discovered in the Yubico-Piv 1.5.0 smartcard driver. The file lib/ykpiv.c contains the following code in the function ykpiv_transfer_data(): {% highlight c %} if(*out_len + recv_len - 2 > max_out) { fprintf(stderr, “Output buffer to small, wanted to write %lu, max was %lu.”, *out_len + recv_len - 2, max_out); } if(out_data) { memcpy(out_data, data, recv_len - 2); out_data += recv_len - 2; *out_len += recv_len - 2; } {% endhighlight %} – it is clearly checked whether the buffer is big enough to hold the data copied using memcpy(), but no error handling happens to avoid the memcpy() in such cases. This code path can be triggered with malicious data coming from a smartcard.