VIRTS-1807 Adding exfil file download capability to the UI

[mrengstrom]

Description

adding the capability to download the exfilled files from agents via the UI

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

How Has This Been Tested?

I created multiple directories and operations and tested to make sure exfilled files were properly shown in the UI and that when downloaded files were un-encrypted and able to be extracted/read without having to pass through any additional scripts.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works

[codecov]

Codecov Report

Merging #2060 (1168eb0) into master (a689901) will decrease coverage by 0.47%.
The diff coverage is 21.15%.

@@            Coverage Diff             @@
##           master    #2060      +/-   ##
==========================================
- Coverage   64.55%   64.07%   -0.48%     
==========================================
  Files          61       61              
  Lines        4672     4724      +52     
==========================================
+ Hits         3016     3027      +11     
- Misses       1656     1697      +41     

Impacted Files	Coverage Δ
app/service/file_svc.py	53.98% <7.69%> (-4.02%)	⬇️
app/api/rest_api.py	58.62% <18.18%> (-9.47%)	⬇️
app/service/rest_svc.py	42.25% <18.18%> (-0.61%)	⬇️
app/api/packs/advanced.py	75.00% <66.66%> (-1.09%)	⬇️

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[clenk]

Looks good aside from one bug.

And a couple things I don't think should hold this PR up:

• In the future we may want to add a "check all" button. The ability I used when testing only exfilled a single file, but if it's very many this would be easier than having to check each checkbox.
• I noticed we aren't consistent as far as capitalization with our http error messages, such as in download_exfil_file(). This isn't limited to this PR though; see also

  caldera/app/service/rest_svc.py

  Lines 281 to 283 in 0dcafce

  	raise web.HTTPBadRequest(body='This operation has already finished.')
  	elif state not in op[0].states.values():
  	raise web.HTTPBadRequest(body='state must be one of {}'.format(op[0].states.values()))

[clenk]

I went to the Exfills UI before running any operations, selected "all" and got an Internal Server Error on this line:
FileNotFoundError: [Errno 2] No such file or directory: '/tmp/caldera'

[mrengstrom]

yup, looks like I forgot to check that, a simple validation should help prevent that. I'll push up a change.

[mrengstrom]

Also @clenk I can address you other two issues when I push up my fix, both should be fairly simple to address, and I agree that we should have a consistency in our messages returned to the user.