Secrets analyzer buffer overflow on large files

Summary

When running our new secrets SAST analyzer against the GitLab-EE repository, sast job will fail due to a buffer overflow. This should be investigated.

Steps to reproduce

1. Execute sast job against https://gitlab.com/gitlab-org/gitlab-ee

Example Project

https://gitlab.com/gitlab-org/gitlab-ee/-/jobs/173735273

What is the current bug behavior?

secrets analyzer fails on gitlab-ee project

What is the expected correct behavior?

secrets analyzer should execute correctly on gitlab-ee project

Relevant logs and/or screenshots

Found project in /tmp/app
2019/03/07 19:47:11 [tslint] Detect project using plugin
2019/03/07 19:47:11 [tslint] Project not compatible
2019/03/07 19:47:11 [secrets] Detect project using plugin
2019/03/07 19:47:11 [secrets] Project is compatible
2019/03/07 19:47:11 [secrets] Starting analyzer...
2: Pulling from gitlab-org/security-products/analyzers/secrets
6c40cc604d8e: Pulling fs layer
1a6c538d4ed9: Pulling fs layer
1b11cbdb9364: Pulling fs layer
6c40cc604d8e: Verifying Checksum
6c40cc604d8e: Download complete
1b11cbdb9364: Verifying Checksum
1b11cbdb9364: Download complete
1a6c538d4ed9: Verifying Checksum
1a6c538d4ed9: Download complete
6c40cc604d8e: Pull complete
1a6c538d4ed9: Pull complete
1b11cbdb9364: Pull complete
Digest: sha256:ddfa70b7fba6b6aaedbd73a34f92d01d72f5204dfedf4b330818a47c989c5f92
Status: Downloaded newer image for registry.gitlab.com/gitlab-org/security-products/analyzers/secrets:2
Problem while reading source file app/assets/images/file_icons.svg: bufio.Scanner: token too long
Gitleaks analysis failed: bufio.Scanner: token too long
2019/03/07 19:49:13 bufio.Scanner: token too long
2019/03/07 19:49:13 Container exited with non zero status code
Running after script...
$ date
Thu Mar  7 19:49:15 UTC 2019
Uploading artifacts...
WARNING: gl-sast-report.json: no matching files    
ERROR: No files to upload                          
ERROR: Job failed: exit code 1

Output of checks

This bug happens on GitLab.com

Results of GitLab environment info

Expand for output related to GitLab environment info

(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:env:info)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production)

Results of GitLab application Check

Expand for output related to the GitLab application check

(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:check SANITIZE=true)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)
(we will only investigate if the tests are passing)

Possible fixes