dlio_s3torch_checkpoint fails with TLS (SSL) negotiation failed errors

I have set the certificates properly and verified that the S3 bucket is accessible. However, the tests/object-store/dlio_s3torch_checkpoint.sh fails during [Writer] ERROR: Failed to create storage writer: Client error: Unknown CRT error: CRT error 1029: aws-c-io: AWS_IO_TLS_ERROR_NEGOTIATION_FAILURE, TLS (SSL) negotiation failed.

FWIW, Using s3dlio library, CHECKPOINTS=1 NP=2 bash tests/object-store/dlio_s3dlio_checkpoint.sh works successfully on the same setup.

cc: @russfellows

- Details:

$ echo $AWS_CA_BUNDLE
/home/nodeadmin/ca.pem

$ python3 -c "import s3dlio; print(s3dlio.list('s3://s3torch-chckpt-test1/', recursive=False))"
[]

$ CHECKPOINTS=1 NP=2 bash tests/object-store/dlio_s3torch_checkpoint.sh 
[env] Loading credentials from .env

════════════════════════════════════════════════════════
  DLIO Checkpoint — s3torchconnector + MinIO  (llama3-8b)
════════════════════════════════════════════════════════
  Bucket      : s3torch-chckpt-test1
  Objects at  : s3://s3torch-chckpt-test1/s3torch/llama3-8b/
  Endpoint    : https://192.168.7.124:8111
  MPI ranks   : 2   (default=1; full run: NP=8 bash tests/object-store/dlio_s3torch_checkpoint.sh)
  Checkpoints : 1 write + 1 read
  Per-rank    : ~13.1 GB per checkpoint  (ZeRO-3, 8 ranks)
  Run dir     : /tmp/dlio-s3torch-checkpoint-20260409_153733
════════════════════════════════════════════════════════

Checking bucket reachability: s3://s3torch-chckpt-test1/ ...
  Bucket accessible — 0 top-level entries

--------------------------------------------------------------------------
..
..
--------------------------------------------------------------------------
[DEBUG DLIOBenchmark.__init__] After LoadConfig:
  storage_type   = <StorageType.S3: 's3'>
  storage_root   = 's3torch-chckpt-test1'
  storage_options= {'endpoint_url': 'https://192.168.7.124:8111', 'region': 'us-east-1', 'storage_library': 's3torchconnector'}
  data_folder    = './data/'
  framework      = <FrameworkType.PYTORCH: 'pytorch'>
  num_files_train= 8
  record_length  = 65536
  generate_data  = False
  do_train       = False
  do_checkpoint  = True
  epochs         = 1
  batch_size     = 1
[DEBUG DLIOBenchmark.__init__] After LoadConfig:
  storage_type   = <StorageType.S3: 's3'>
  storage_root   = 's3torch-chckpt-test1'
  storage_options= {'endpoint_url': 'https://192.168.7.124:8111', 'region': 'us-east-1', 'storage_library': 's3torchconnector'}
  data_folder    = './data/'
  framework      = <FrameworkType.PYTORCH: 'pytorch'>
  num_files_train= 8
  record_length  = 65536
  generate_data  = False
  do_train       = False
  do_checkpoint  = True
  epochs         = 1
  batch_size     = 1
[OUTPUT] 2026-04-09T15:37:37.559203 Running DLIO [Checkpointing] with 2 process(es)
[OUTPUT] ================================================================================
[OUTPUT] Data Generation Method: DGEN (default)
[OUTPUT]   dgen-py zero-copy BytesView — 155x faster than NumPy, 0 MB overhead
[OUTPUT] ================================================================================
[OUTPUT] ================================================================================
[OUTPUT] Data Generation Method: DGEN (default)
[OUTPUT]   dgen-py zero-copy BytesView — 155x faster than NumPy, 0 MB overhead
[OUTPUT] ================================================================================
..
..
[Main] Creating 4 buffers...
================================================================================
STREAMING CHECKPOINT - Producer-Consumer Pattern
================================================================================
Output:      s3://s3torch-chckpt-test1/s3torch/llama3-8b/global_epoch1_step1/zero_pp_rank_0_mp_rank_0_model_states.pt
Backend:     s3torchconnector
Total size:  7.48 GB
Buffer size: 32 MB
Buffer pool: 4 × 32 MB = 0.12 GB
Direct I/O:  False
Use dgen-py: True
================================================================================

[Main] Creating 4 buffers...
[Main] Buffer pool ready: 0.12 GB
[Main] Initializing dgen-py (MPI world_size=2, threads=24/48 CPUs)...
[Main] Buffer pool ready: 0.12 GB
[Main] Initializing dgen-py (MPI world_size=2, threads=24/48 CPUs)...
[Main] Generator ready
[Main] Generator ready

[Main] Writer process started (PID=2952630)
[Main] Starting producer at 15368685.043s
[Main] Starting producer (buffer pool reuse pattern)...
[Writer] Starting (PID=2952630)
[Writer] DEBUG: AWS_ACCESS_KEY_ID = PSEZ***
[Writer] DEBUG: AWS_ENDPOINT_URL = https://192.168.7.124:8111
[Writer] Attached to 4 buffers (32 MB each)

[Main] Writer process started (PID=2952631)
[Main] Starting producer at 15368685.047s
[Main] Starting producer (buffer pool reuse pattern)...
[Writer] Starting (PID=2952631)
[Writer] DEBUG: AWS_ACCESS_KEY_ID = PSEZ***
[Writer] DEBUG: AWS_ENDPOINT_URL = https://192.168.7.124:8111
[Writer] Attached to 4 buffers (32 MB each)
[Writer] ERROR: Failed to create storage writer: Client error: Unknown CRT error: CRT error 1029: aws-c-io: AWS_IO_TLS_ERROR_NEGOTIATION_FAILURE, TLS (SSL) negotiation failed
[Writer] ERROR: Failed to create storage writer: Client error: Unknown CRT error: CRT error 1029: aws-c-io: AWS_IO_TLS_ERROR_NEGOTIATION_FAILURE, TLS (SSL) negotiation failed

Start with tests/object-store/dlio_s3torch_checkpoint.sh and compare its configuration and execution with the working tests/object-store/dlio_s3dlio_checkpoint.sh on the same S3 endpoint. Reproduce the TLS negotiation failure, then identify the differing checkpoint path or settings and verify that the s3torch checkpoint write and read complete successfully.