CURL-CVE-2017-1000100

TFTP sends more than buffer size

When doing a TFTP transfer and curl/libcurl is given a URL that contains a long filename (longer than about 515 bytes), the filename is truncated to fit within the buffer boundaries, but the buffer size is still wrongly updated to use the original length. This too large value is then used in the `sendto()` call, making curl attempt to send more data than what is actually put into the buffer. The `sendto()` function then reads beyond the end of the heap based buffer. A malicious HTTP(S) server could redirect a vulnerable libcurl-using client to a crafted TFTP URL (if the client has not restricted which protocols it allows redirects to) and trick it to send private memory contents to a remote server over UDP. Limit curl's redirect protocols with `--proto-redir` and libcurl's with `CURLOPT_REDIR_PROTOCOLS`.