Use .blank? instead of .empty? when handling SSH Key details to prevent crashes

[MegaManSec]

blank? should be used instead of empty?. When running this script on a host which has a blank SSH key, an error is encountered:

[-] Post failed: NoMethodError undefined method `empty?' for nil:NilClass
[-] Call stack:
[-]   /opt/metasploit-framework/embedded/framework/modules/post/multi/gather/jenkins_gather.rb:235:in `block in pretty_print_gathered'
[-]   /opt/metasploit-framework/embedded/framework/modules/post/multi/gather/jenkins_gather.rb:231:in `each'
[-]   /opt/metasploit-framework/embedded/framework/modules/post/multi/gather/jenkins_gather.rb:231:in `pretty_print_gathered'
[-]   /opt/metasploit-framework/embedded/framework/modules/post/multi/gather/jenkins_gather.rb:348:in `gathernix'
[-]   /opt/metasploit-framework/embedded/framework/modules/post/multi/gather/jenkins_gather.rb:363:in `run'

[gwillcox-r7]

.blank? would also check if the object is nil as well and so the first part of this code would not be needed. Might I suggest this instead to simplify the code?

Suggested change

	print_status(" Description: #{e[1]}") if !e[1].nil? || !e[1].blank?
	print_status(" Passphrase: #{e[2]}") if !e[2].nil? || !e[2].blank?
	print_status(" Username: #{e[3]}") if !e[3].nil? || !e[3].blank?
	print_status(" Description: #{e[1]}") if !e[1].blank?
	print_status(" Passphrase: #{e[2]}") if !e[2].blank?
	print_status(" Username: #{e[3]}") if !e[3].blank?

For reference this is what happens with a .blank? call on nil object:

>> nil.blank?
=> true
>> !nil.blank?
=> false
>> 

https://blog.appsignal.com/2018/09/11/differences-between-nil-empty-blank-and-present.html has more details on this if you wish to read up more about this 👍

[gwillcox-r7]

Fixed with latest updates.

[gwillcox-r7]

Will go ahead and rebase this against the latest code changes on master so that this passes tests. Then will make the changes so this can be landed.

[gwillcox-r7]

With latest updates this should be good to go, will just wait for tests to pass before landing this.

[gwillcox-r7]

Release Notes

The jenkins_gather.rb module has been updated to use .blank? instead of .empty? when handling SSH Key details to prevent crashes should the various elements of the SSH Key be empty or nil.