Handle error conditions better

[kost]

Display stack trace, but do not fail and exit (losing shells can be nightmare)

For example, dnscat2 server fails with following error messages on long running servers:

Caught an error: DNS packet was truncated (or we messed up parsing it)! /pentest/dnscat2/server/libs/dnser.rb:179:in unpack' /pentest/dnscat2/server/libs/dnser.rb:634:in parse' /pentest/dnscat2/server/libs/dnser.rb:849:in block (2 levels) in on_request' /pentest/dnscat2/server/libs/dnser.rb:843:in loop' /pentest/dnscat2/server/libs/dnser.rb:843:in `block in on_request'

Protocol exception caught in dnscat DNS module (for more information, check window 'dns1'): #<DnscatException: Received a packet with no questions> Caught an error: undefined method serialize' for nil:NilClass /pentest/dnscat2/server/libs/dnser.rb:678:in block in serialize' /pentest/dnscat2/server/libs/dnser.rb:677:in each' /pentest/dnscat2/server/libs/dnser.rb:677:in serialize' /pentest/dnscat2/server/libs/dnser.rb:819:in reply!' /pentest/dnscat2/server/libs/dnser.rb:775:in error!' /pentest/dnscat2/server/tunnel_drivers/driver_dns.rb:357:in rescue in block in initialize' /pentest/dnscat2/server/tunnel_drivers/driver_dns.rb:293:in block in initialize' /pentest/dnscat2/server/libs/dnser.rb:879:in block (2 levels) in on_request' /pentest/dnscat2/server/libs/dnser.rb:843:in loop' /pentest/dnscat2/server/libs/dnser.rb:843:in block in on_request' /pentest/dnscat2/server/libs/dnser.rb:883:in rescue in block (2 levels) in on_request': undefined method response_template' for #<DNSer::Transaction:0x0000000000dd6a58> (NoMethodError) Did you mean? respond_to? from /pentest/dnscat2/server/libs/dnser.rb:878:in block (2 levels) in on_request' from /pentest/dnscat2/server/libs/dnser.rb:843:in loop' from /pentest/dnscat2/server/libs/dnser.rb:843:in block in on_request'

[iagox86]

I totally agree. I've started re-writing the client in rust, with solid error handling (and testing) built in. Unfortunately, it's a bit of a long project.

On Wed, Dec 5, 2018 at 6:35 AM kost [email protected] wrote:

Display stack trace, but do not fail and exit (losing shells can be nightmare)

For example, dnscat2 server fails with following error messages on long running servers:

Caught an error: DNS packet was truncated (or we messed up parsing it)! /pentest/dnscat2/server/libs/dnser.rb:179:in unpack' /pentest/dnscat2/server/libs/dnser.rb:634:in parse' /pentest/dnscat2/server/libs/dnser.rb:849:in block (2 levels) in on_request' /pentest/dnscat2/server/libs/dnser.rb:843:in loop' /pentest/dnscat2/server/libs/dnser.rb:843:in `block in on_request'

Protocol exception caught in dnscat DNS module (for more information, check window 'dns1'): #<DnscatException: Received a packet with no questions> Caught an error: undefined method serialize' for nil:NilClass /pentest/dnscat2/server/libs/dnser.rb:678:in block in serialize' /pentest/dnscat2/server/libs/dnser.rb:677:in each' /pentest/dnscat2/server/libs/dnser.rb:677:in serialize' /pentest/dnscat2/server/libs/dnser.rb:819:in reply!' /pentest/dnscat2/server/libs/dnser.rb:775:in error!' /pentest/dnscat2/server/tunnel_drivers/driver_dns.rb:357:in rescue in block in initialize' /pentest/dnscat2/server/tunnel_drivers/driver_dns.rb:293:in block in initialize' /pentest/dnscat2/server/libs/dnser.rb:879:in block (2 levels) in on_request' /pentest/dnscat2/server/libs/dnser.rb:843:in loop' /pentest/dnscat2/server/libs/dnser.rb:843:in block in on_request' /pentest/dnscat2/server/libs/dnser.rb:883:in rescue in block (2 levels) in on_request': undefined method response_template' for #DNSer::Transaction:0x0000000000dd6a58 (NoMethodError) Did you mean? respond_to? from /pentest/dnscat2/server/libs/dnser.rb:878:in block (2 levels) in on_request' from /pentest/dnscat2/server/libs/dnser.rb:843:in loop' from /pentest/dnscat2/server/libs/dnser.rb:843:in block in on_request'

You can view, comment on, or merge this pull request online at:

https://github.com/iagox86/dnscat2/pull/135 Commit Summary

• Handle error conditions better

File Changes

• M server/libs/dnser.rb https://github.com/iagox86/dnscat2/pull/135/files#diff-0 (13)

Patch Links:

• https://github.com/iagox86/dnscat2/pull/135.patch
• https://github.com/iagox86/dnscat2/pull/135.diff

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[kost]

Regarding client in C, i have few patches to retry connection. They are bit hacky, but I will make pull request anyway, so feel free to decide what you want with it.

[iagox86]

Cool! I was thinking of forking them into new processes, so if the client exits the main app would stick around. But that would require shared state, which is kind of non-trivial, so I haven't done it.

On Thu, Dec 6, 2018 at 7:27 AM kost [email protected] wrote:

Regarding client in C, i have few patches to retry connection. They are bit hacky, but I will make pull request anyway, so feel free to decide what you want with it.

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