jq: error (at <stdin>:173): Cannot iterate over null (null)

[domvo]

When running the checker, I get the following jq error:

-------------------------------------------------------------
Prerequisites for check-ecs-exec.sh v0.7
-------------------------------------------------------------
  jq      | OK (/opt/homebrew/bin/jq)
  AWS CLI | OK (/opt/homebrew/bin/aws)

-------------------------------------------------------------
Prerequisites for the AWS CLI to use ECS Exec
-------------------------------------------------------------
  AWS CLI Version        | OK (aws-cli/2.15.17 Python/3.11.7 Darwin/23.0.0 source/arm64 prompt/off)
  Session Manager Plugin | OK (1.2.553.0)

-------------------------------------------------------------
Checks on ECS task and other resources
-------------------------------------------------------------
Region : eu-central-1
Cluster: REDACTED
Task   : REDACTED
-------------------------------------------------------------
  Cluster Configuration  | Audit Logging Not Configured
  Can I ExecuteCommand?  | arn:aws:iam::xxxxxxxxxxxxx:user/[email protected]
     ecs:ExecuteCommand: allowed
     ssm:StartSession denied?: allowed
  Task Status            | RUNNING
  Launch Type            | Fargate
  Platform Version       | 1.4.0
  Exec Enabled for Task  | OK
  Container-Level Checks |
    ----------
      Managed Agent Status
    ----------
jq: error (at <stdin>:173): Cannot iterate over null (null)

I found out that not all containers have a managedAgent property. I was able to fix it by changing line 422 to

agentsStatus=$(echo "${describedTaskJson}" | jq -r ".tasks[0].containers[] | (.managedAgents // [])[].lastStatus // \"FallbackValue\"")

This is of course only a quick fix. The underlying issue is that we have AWS GuardDuty enabled. GuardDuty injects a container into each task but those GuardDuty containers do not have a managedAgent.

This is how the container comes back after describing it:

{
  "containerArn": "arn:aws:ecs:eu-central-1:xxxxxxxxx:container/xxx-cluster-xxx/xxxxx/9efcbebb-1204-4212-84fa-1471bcadbf8c",
  "taskArn": "arn:aws:ecs:eu-central-1:xxxxxxxxx:task/xxxx-cluster-xxx/xxx",
  "name": "aws-guardduty-agent-GAhgQ",
  "imageDigest": "sha256:9f8cd438fb66f62d09bfc641286439f7ed5177988a314a6021ef4ff880642e68",
  "runtimeId": "c9103216b805432497d68c0190237d44-4043820195",
  "lastStatus": "RUNNING",
  "networkBindings": [
    
  ],
  "networkInterfaces": [
    {
      "attachmentId": "c88ab07b-c263-419c-ba64-adea5c51eb07",
      "privateIpv4Address": "10.10.4.210"
    }
  ],
  "healthStatus": "UNKNOWN"
},

[domvo]

I found that not all containers have a managedAgent property. I was able to fix it by changing line 422 to

  agentsStatus=$(echo "${describedTaskJson}" | jq -r ".tasks[0].containers[] | select(.managedAgents != null) | .managedAgents[].lastStatus")