Add DICOM (Digital Imaging and Communications in Medicine) protocol support

[tmart234]

Summary

DICOM communications is used in medical imaging systems. This PR adds Scapy layers for the DICOM Upper Layer Protocol (DICOM PS3.8).

Features

• Full PDU support: A-ASSOCIATE-RQ/AC/RJ, P-DATA-TF, A-RELEASE-RQ/RP, A-ABORT
• Variable item negotiation: Application Context, Presentation Context, User Information, User Identity, Async Operations, Role Selection
• DIMSE command packets: C-ECHO, C-STORE, C-FIND, C-MOVE, C-GET

Usage

from scapy.contrib.dicom import *

# Build an A-ASSOCIATE-RQ
pkt = DICOM() / A_ASSOCIATE_RQ(
    called_ae_title=_pad_ae_title("SERVER"),
    calling_ae_title=_pad_ae_title("CLIENT"),
    variable_items=[
        DICOMVariableItem() / DICOMApplicationContext(),
        build_presentation_context_rq(1, VERIFICATION_SOP_CLASS_UID, [DEFAULT_TRANSFER_SYNTAX_UID]),
        build_user_information(max_pdu_length=16384),
    ]
)

# Build a C-MOVE-RQ
move_rq = C_MOVE_RQ(message_id=1, move_destination=b"DEST_AE")

Testing

• 59 unit tests in test/contrib/dicom.uts
• All tests pass on Python 3.9+

References

• DICOM PS3.8: https://dicom.nema.org/medical/dicom/current/output/html/part08.html

[codecov]

Codecov Report

❌ Patch coverage is 47.57282% with 378 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.35%. Comparing base (40fc5ec) to head (ea5cced).

Files with missing lines	Patch %	Lines
scapy/contrib/dicom.py	47.57%	378 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4891      +/-   ##
==========================================
- Coverage   80.85%   80.35%   -0.50%     
==========================================
  Files         369      370       +1     
  Lines       90961    91682     +721     
==========================================
+ Hits        73542    73671     +129     
- Misses      17419    18011     +592     

Files with missing lines	Coverage Δ
scapy/contrib/dicom.py	47.57% <47.57%> (ø)

... and 20 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[polydroi]

Thanks for the PR. I’ve stared the unit tests. Looks good, however, could you please add type hints to your layer?

[polydroi]

I would recommend to introduced a StrFixedLenFieldWithPadding instead of the explicit call to the padding function for certain fields

[gpotter2]

We have a PadField for that ! You can use pas with=" "

[polybassa]

I recommend to create a dedicated UID field (e.g. DICOMUIDField) which applies "_uid_to_bytes" internally.

[polybassa]

I would recommend to use a different "name", since Scapy uses the term "Session" for a different term. From you implementation, I would treat this class as a "DICOMSocket". This would indicate the application layer functionality.