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[BUG] AWS CreateAccessKey: unquoted field names make the cross-user filter a no-op (fires on self-key creation)

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
72/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
aws, yaml
Domain
cloud, security

Research direction

Start with detections/cloud/aws_createaccesskey.yml and inspect the cross-user filter plus aws_createaccesskey_filter. Run the self-contained SPL reproduction to confirm the current results, then verify the rule excludes self-key creation while retaining cross-user creation, including requests without requestParameters.userName. Review the console-exclusion behavior described in the issue and ensure the final scope is reflected in the rule.

Written by the indexing model from the issue text.

Description

bug
Describe the bug

AWS CreateAccessKey (detections/cloud/aws_createaccesskey.yml, id 2a9b80d3-6340-4345-11ad-212bf3d0d111) is meant to surface a user creating an access key for a different user:

| eval match=if(match(userIdentity.userName,requestParameters.userName),1,0)
| search match=0

Inside eval, the dotted field names are not single-quoted, so SPL parses userIdentity.userName as the . concatenation of the (non-existent) fields userIdentity and userName. Both arguments to match() evaluate to null, match is always 0, and search match=0 keeps every event. As shipped, the filter does nothing: the rule fires on every successful non-console CreateAccessKey, including the routine case of a user rotating their own key.

Repro

Self-contained, with no data needed:

| makeresults count=2
| streamstats count as n
| eval _raw=if(n==1, "{\"userIdentity\":{\"userName\":\"alice\"},\"requestParameters\":{\"userName\":\"alice\"}}", "{\"userIdentity\":{\"userName\":\"alice\"},\"requestParameters\":{\"userName\":\"bob\"}}")
| spath
| eval case=if(n==1,"self: alice creates a key for alice","cross-user: alice creates a key for bob")
| eval match=if(match(userIdentity.userName,requestParameters.userName),1,0)
| eval match_quoted=if('userIdentity.userName'=='requestParameters.userName',1,0)
| table case userIdentity.userName requestParameters.userName match match_quoted

Output:

case userIdentity.userName requestParameters.userName match (shipped) match_quoted
self: alice creates a key for alice alice alice 0 1
cross-user: alice creates a key for bob alice bob 0 0

The self-key row should be excluded (match=1), but the shipped expression returns 0.

Expected behavior

Only cross-user key creation should produce a result. A minimal fix quotes the fields and compares them directly. match() also treats its second argument as a regex, so a username like svc. would match svcX:

| eval match=if('userIdentity.userName'=='requestParameters.userName',1,0)
| search match=0

One related case to consider: when requestParameters.userName is absent (the key is for the caller), the request is a self-key and should also be excluded, e.g. if(isnull('requestParameters.userName') OR 'userIdentity.userName'=='requestParameters.userName',1,0).

Additional context: the console exclusion no longer matches console calls

The base search excludes console activity with userAgent!=console.amazonaws.com. A real console-issued CreateAccessKey captured from an AWS account in 2026 records a browser user agent (Mozilla/5.0 ... Chrome/...) together with "sessionCredentialFromConsole": "true", not console.amazonaws.com. Keys created in the console today therefore aren't excluded. A scripted caller can also evade the rule by sending the literal console.amazonaws.com user agent.

sessionCredentialFromConsole is not a clean replacement key. It marks console-session credentials, not the client, and AWS's own log examples show CloudShell CLI calls (exec-env/CloudShell) carrying it, including IAM calls. Excluding on it would hide cross-user key creation scripted from CloudShell. Once the cross-user filter works, dropping the console exclusion altogether and suppressing known provisioning principals in aws_createaccesskey_filter may be the better trade-off.

App Version:
  • ESCU: reproduced on 5.26.0; SPL unchanged on develop (64acde7bf6, rule version 11)
  • Splunk Enterprise 9.3.10, Splunk_TA_aws 7.11.0
Dominant language
Python
Stars
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Forks
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Avg merge
2d 10h
Merged PRs (30d)
31

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