The document discusses provenance-based security audits applied to COVID-19 contact tracing apps, particularly the German 'Corona Warn App'. It details the methodology for extracting and analyzing provenance information from Git-based projects using various tools, and highlights the importance of external contributions in improving app security. The authors advocate for the application of their audit methodologies to similar public apps for enhanced security and insights.

1. Provenance-based Security Audits and its Application
to COVID-19 Contact Tracing Apps
Andreas Schreiber1, Tim Sonnekalb1, Thomas S. Heinze1,
Lynn von Kurnatowski1, Jesus M. Gonzalez-Barahona2, Heather Packer3
1 German Aerospace Center (DLR), Germany
2 Universidad Rey Juan Carlos, Spain
3 University of Southampton, United Kingdom
> IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
DLR.de • Chart 1

2. Coronavirus “Contact Tracing Apps”
German “Corona Warn App” (CWA)
• App for Exposure Notification
• Based on APIs by Apple and Google
• Developed as Open-Source Software
by SAP and Telekom
• External contributors (via pull requests)
• https://github.com/corona-warn-app
• 12 repositories (update: 23)
Our Mission
• To analyze the quality of CWA and its Open-
Source development process
• Generate advice for other government apps
> IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
DLR.de • Chart 2
Image: © 2020 Marlene Brüggemann

3. Development of the “Corona Warn App”
> IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
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https://cauldron.io/project/3860

4. Getting Knowledge from git-based Projects
1. Repository Mining
• Extraction of Provenance information from git projects
(files, issues, pull requests, etc.) in PROV format
 Directed Acyclic Graphs (DAGs)
• Tools: Git2prov, GitHub2Prov, GitLab2Prov
2. Graph Storage
• Storing Provenance in graph databases
 Property Graphs
• Tools: Neo4j, prov-db-connector, prov2neo
3. Generate Insights
• Graph analytics and graph visualization
• Tools: Cypher, Neo4j Bloom, Gephi, Mathematica
> IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
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5. Repository Mining: Extraction of Provenance Information from git Projects
> IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
DLR.de • Chart 5
Extract provenance
GitHub
Organization corona-warn-app
git
Repository
cwa-
server
git
Repository
cwa-app-
ios
git
Repository
cwa-app-
android
git
Repository
cwa-
website
git
Repository
cwa-
documenta
tion
…
Graph
Database
Neo4j
PROV
JSON / RDF
Git*2PROV
prov2neo
Contributors/
Team Query
CYPHER
request
(PyGithub)
Extract additional data
MERGE

6. GitHub2PROV
GitHub2PROV
• See paper at 11th International Workshop on
Theory and Practice of Provenance (TaPP 2019),
Philadelphia, June 2019
• https://www.usenix.org/conferenc
e/tapp2019/presentation/packer
Based on Git2PROV (by de Nies et al.)
• Extends the PROV model of Git2PROV
> IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
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7. > IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
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Provenance Graph – Example
Visualization with Graphviz/dot

8. > IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
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Which files have commits by
team members as well as
external contributors?

9. Query Data for Visualization from Neo4j with Cypher Queries
> IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
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10. > IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
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11. > IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
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12. > IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
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13. > IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
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File (Entity)
Developer (Agent)
External contribution
Team member
contribution
Project: cwa-documentation
Visualization: Contributions of Team Members and External Contributors
(Tool: Gephi)

14. Project: cwa-server
Tool: Gephi
> IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
DLR.de • Chart 14
File (Entity)
Developer (Agent)
External contribution
Team member
contribution

15. Static Application Security Testing (SAST) Pipeline
> IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
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Graph
Database
Neo4j
GitHub
Organization
corona-warn-app
git
Repository
cwa-
server
…
commit
hashes
JSON
QUERY
Snapshot
git merge
<commit hash>
Code Filter
Static Code Analysis
- PMD
- Xanitizer
- Infer
- Spotbugs
- Detect
- Flowdroid
Security
Findings
JSON
SAST
Database
File Paths
Parse
results
Store results
with commit hashes

16. SAST Database Schema
> IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
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tool
id INTEGER
name TEXT
config TEXT
version TEXT
repo
id INTEGER
name TEXT
url TEXT
snapshot
id TEXT
committer_date TEXT
author_date TEXT
commit_message TEXT
repo INTEGER
branches
id INTEGER
branch TEXT
snapshot TEXT
run
id INTEGER
snapshot TEXT
tool INTEGER
success INTEGER
warning
id INTEGER
message TEXT
location TEXT
severity TEXT
run INTEGER

17. Number of Code Analysis Warnings for cwa-server Repository
> IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
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Jul 2020 Sep 2020 Nov 2020 Jan 2021 Mar 2021
0
2
4
6
8
10
Date
Number
of
warnings
Jul 2020 Sep 2020 Nov 2020 Jan 2021 Mar 2021
0
5
10
15
20
25
30
35
40
45
Date
Number
of
warnings
PMD Xanitizer

18. Four Steps of the Provenance-driven Code Analysis
> IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
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Step 2
Step 4
Step 3
Step 1
Graph
Database
Neo4j
commit hashes
DataFrame
QUERY
CYPHER
Filter and
clean results
SAST
Database
SQLite
store
commit hashes
Analyze and
plot
QUERY
SQL Results
Diagrams,
Reports,
…
generate

19. Cypher Query for Getting Commits by External Contributors
> IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
DLR.de • Chart 19

20. > IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
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21. 0 10 20 30 40 50
0
10
20
30
40
50
60
70
External Contributors Team Members
Warnings per commit
Sum
of
commits
with
#
warnings
Distribution of Number of all SAST Warnings for Commits
> IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
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22. −1
5 −1
0 −5 0 5 1
0 1
5
1
2
5
1
0
2
5
1
0
0
2
Changes in number of warnings induced by commit
Sum
of
commits
with
#
diffs
(log
scale)
Distribution of Change in Number of SAST Warnings Caused by Commits
> IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
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23. Current & Future Work
Applying the methodology to other projects
• DLR Inner Source: aerospace software
• Apps with high public relevance:
Luca App, CovPass App, …
Automation and visual analytics
• Easy setup for new projects
(GitHub/GitLab)
• (Public) interactive dashboard
Adding additional data sources
• App execution traces
• Social media mentions
> IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
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24. Thank You!
Questions?
Andreas Schreiber
Andreas.Schreiber@dlr.de
DLR Institute for Software Technology,
Intelligent and Distributed Systems
http://www.DLR.de/sc/ivs
@onyame | @DLR_software
> IPAW 2021 > A. Schreiber et al. • Provenance-based Security Audits and its Application to COVID-19 Contact Tracing Apps > 19.07.2021
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