Make banner read options configurable via CLI

[svbatalov]

Currently the banner module waits 10ms before closing connection. In my use case an XMPP server sends an initial response immediately and some additional data after a delay of about 300ms. With netcat we get the full response (note the <stream:features> at the end)

$ cat /tmp/xmpp_probe.txt | nc -w 1 -v 186.28.231.211 5222
Connection to 186.28.231.211 5222 port [tcp/xmpp-client] succeeded!
<?xml version='1.0' encoding='UTF-8'?><stream:stream xmlns:stream="http://etherx.jabber.org/streams" xmlns="jabber:client" from="taxserver" id="8sah4gmt6i" xml:lang="en" version="1.0"><stream:features><starttls xmlns="urn:ietf:params:xml:ns:xmpp-tls"></starttls><mechanisms xmlns="urn:ietf:params:xml:ns:xmpp-sasl"><mechanism>PLAIN</mechanism><mechanism>SCRAM-SHA-1</mechanism><mechanism>CRAM-MD5</mechanism><mechanism>DIGEST-MD5</mechanism></mechanisms><compression xmlns="http://jabber.org/features/compress"><method>zlib</method></compression><ver xmlns="urn:xmpp:features:rosterver"/><register xmlns="http://jabber.org/features/iq-register"/><c xmlns="http://jabber.org/protocol/caps" hash="sha-1" node="https://www.igniterealtime.org/projects/openfire/" ver="HGEf1bz7upaMudXxphDOpv49az0="/></stream:features>

while with zgrab2 we get only the initial response:

$ echo 186.28.231.211 | ./zgrab2 banner -p 5222 --probe-file /tmp/xmpp_probe.txt 2>/dev/null | jq -r .data.banner.result.banner
<?xml version='1.0' encoding='UTF-8'?><stream:stream xmlns:stream="http://etherx.jabber.org/streams" xmlns="jabber:client" from="taxserver" id="1w7w1fs3id" xml:lang="en" version="1.0">

In both cases the following request was sent:

$ cat /tmp/xmpp_probe.txt
<?xml version='1.0'?>
        <stream:stream
        from='juliet@im.example.com'
        to='im.example.com'
        version='1.0'
        xml:lang='en'
        xmlns='jabber:client'
        xmlns:stream='http://etherx.jabber.org/streams'>

The proposed change introduces a new command line flag --read-timeout, which allows to change the default read timeout:

$ echo 186.28.231.211 | ./zgrab2 banner -p 5222 --probe-file /tmp/xmpp_probe.txt --read-timeout=400 2>/dev/null | jq -r .data.banner.result.banner
<?xml version='1.0' encoding='UTF-8'?><stream:stream xmlns:stream="http://etherx.jabber.org/streams" xmlns="jabber:client" from="taxserver" id="ansjqzpech" xml:lang="en" version="1.0"><stream:features><starttls xmlns="urn:ietf:params:xml:ns:xmpp-tls"></starttls><mechanisms xmlns="urn:ietf:params:xml:ns:xmpp-sasl"><mechanism>PLAIN</mechanism><mechanism>SCRAM-SHA-1</mechanism><mechanism>CRAM-MD5</mechanism><mechanism>DIGEST-MD5</mechanism></mechanisms><compression xmlns="http://jabber.org/features/compress"><method>zlib</method></compression><ver xmlns="urn:xmpp:features:rosterver"/><register xmlns="http://jabber.org/features/iq-register"/><c xmlns="http://jabber.org/protocol/caps" hash="sha-1" node="https://www.igniterealtime.org/projects/openfire/" ver="HGEf1bz7upaMudXxphDOpv49az0="/></stream:features>

Since banner module is a generic way to handle protocols not already built into zgrab2, I though that it makes sense to make other read options configurable as well. Namely, in addition to --read-timeout, this PR introduces options --buffer-size and --max-read-size. Relevant part of zgrab2 banner --help:

     --read-timeout=              Read timeout in milliseconds (default: 10)
     --buffer-size=               Read buffer size in bytes (default: 8209)
     --max-read-size=             Maximum amount of data to read in KiB (1024 bytes) (default: 512)

Default values are kept the same, so this should not have unintended side effects.