Allow "." and long usernames in the DCV authenticator

[hanwen-cluster]

Description of changes

The DCV external rejected valid usernames in two ways:

1. USER_REGEX did not permit ".", so usernames such as "first.last" failed validation with "The authUser parameter is not valid".

2. Session ownership was verified by parsing ps aux, whose USER column is truncated to 8 characters. For usernames longer than 8 characters the truncated name never matched, so valid sessions were reported as non-existent.

Changes:

• Add "." to the allowed characters in USER_REGEX.
• Resolve the username to its numeric UID (pwd.getpwnam) and match it against the UID column from ps -eo uid,args instead of comparing the (truncatable) username from ps aux. This is robust for names of any length and avoids the fragile fixed-column parsing.
• Raise error when the user does not exist on the system.

Note: usernames containing uppercase characters are still rejected by USER_REGEX; that is a separate, pre-existing limitation and is out of scope here.

This commit addresses aws/aws-parallelcluster#7352, #2472, aws/aws-parallelcluster#7345

Tests

The following tests have been passed

{%- import 'common.jinja2' as common with context -%}
{{- common.OSS_COMMERCIAL_X86.append("rocky8") or "" -}}
{{- common.OSS_COMMERCIAL_X86.append("rocky9") or "" -}}
---
test-suites:
  ad_integration:
    test_ad_integration.py::test_ad_integration:
      dimensions:
        - regions: [ "ap-southeast-1" ]
          instances: {{ common.INSTANCES_DEFAULT_X86 }}
          oss: [ {{ LUSTRE_OS_X86_0 }}, {{ LUSTRE_OS_X86_2 }}, {{ LUSTRE_OS_X86_4 }}]
          schedulers: ["slurm"]
  dcv:
    test_dcv.py::test_dcv_configuration:
      dimensions:
        # DCV on GPU enabled instance
        - regions: [{{ g4dn_2xlarge_CAPACITY_RESERVATION_2_INSTANCES_1_HOURS_NOPG_DCV_OS_X86_1 }}]
          instances: ["g4dn.2xlarge"]
          oss: [{{ DCV_OS_X86_1 }}]
          schedulers: ["slurm"]
        # DCV on ARM + GPU
        - regions: [{{ g5g_2xlarge_CAPACITY_RESERVATION_2_INSTANCES_1_HOURS_NOPG_DCV_OS_X86_3 }}]
          instances: ["g5g.2xlarge"]
          oss: [{{ DCV_OS_X86_3 }}]
          schedulers: ["slurm"]
    test_dcv.py::test_dcv_with_remote_access:
      dimensions:
        - regions: ["ap-southeast-2"]
          instances: {{ common.INSTANCES_DEFAULT_X86 }}
          oss: [{{ DCV_OS_X86_1 }}]
          schedulers: ["slurm"]

References

• [integ-tests] Add DCV authentication coverage for dotted and long AD usernames aws-parallelcluster#7453 contains integration test coverage

Checklist

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