This PR fixes a few bugs in `sslv2_sockets()`. The main issue is that a server may not send the entire ServerHello in a single packet. If it doesn't and the full response is being parsed (i.e., certificate and list of ciphers), then `parse_sslv2_serverhello()` will encounter errors, since it assumes that it has the entire ServerHello. This PR compares the length of the response to the length of the ServerHello as specified in the first two bytes of the response and requests more data from the server if the response appears incomplete.
This PR also modifies `parse_sslv2_serverhello()` to check for more errors. It compares the length of the response it has been provided to the specified length (`$v2_hello_length`) and returns an error if the response is shorter than `$v2_hello_length` and the full response is supposed to be parsed. It will also check whether there was an error in converting the certificate from DER to PEM format and will return an error if there was (and it will suppress the error message).
Some servers respond to an SSLv2 ClientHello with a list of all SSLv2 ciphers that the server supports rather than just a list of ciphers that it supports in common with the client (i.e., that appear in the ClientHello). This PR changes the sockets version of `std_cipherlists()` so that, if `sslv2_sockets()` is successful, it checks whether there are any ciphers in common between the ClientHello and the ServerHello before declaring that the server supports the specified cipher list.
Some servers respond to an SSLv2 ClientHello with a list of all SSLv2 ciphers that the server supports rather than just a list of ciphers that it supports in common with the client (i.e., that appear in the ClientHello). This PR changes the sockets version of `run_freak()` so that, if `sslv2_sockets()` is successful, it checks whether there are any ciphers in common between the ClientHello and the ServerHello before declaring that the server supports an export RSA cipher.
If `determine_tls_extensions()` does not create a temporary file (`$TEMPDIR/$NODEIP.determine_tls_extensions.txt`) then `run_server_defaults()` will display error messages when an attempt is made to copy this file or to search (grep) it. This may happen if `$OPTIMAL_PROTO` is `-ssl2` or if `determine_tls_extensions()` uses sockets and `parse_tls_serverhello()` encountered an error and did not create a temporary file (`$TEMPDIR/$NODEIP.parse_tls_serverhello.txt`). This PR fixes this by only trying to copy and search `$TEMPDIR/$NODEIP.determine_tls_extensions.txt` is `$OPTIMAL_PROTO` is not `-ssl2` and `determine_tls_extensions()` was successful (return value 0).
In response to your request in #572, this PR provides a starting point for addressing #120. It adds code to `run_logjam()` to try connecting to the server using any cipher that uses an ephemeral DH key. If successful, it gets the server's ephemeral key (in OpenSSL's PEM format) and then extracts the prime from the key and places it in `$dh_p`. So, all that needs to be done at this point is to compare `$dh_p` against a set of "bad" primes. I'm not sure if I'll be able to work on that part soon, so if someone else has the time, that would be great.
I actually found the `-msg` option easy to use. I moved the code in `parse_tls_serverhello()` that extracts the DH ephemeral public key from the ServerKeyExchange message into a separate function. Then, if using OpenSSL with the `-msg` option, I extract the ServerKeyExchange message from `$TMPFILE` and call this new function to extract the key and convert it to PEM format. That way the new code in `run_logjam()` can use either `$OPENSSL` or `tls_sockets()`.
David Cooper
Dirk Wetter