bascule-oss/docs/observability.md
Tyler King 043b9b9bdc feat: bascule-shell — identity-aware shell with TPM attestation
New crate: bascule-shell (471 lines, 1.8MB binary)
  Login shell that detects identity + platform attestation at startup.
  Wraps bash/zsh/fish — operator works normally, identity travels with them.

Identity detection (priority order):
  1. Entra via WSL2 interop
  2. Azure CLI
  3. Kerberos TGT
  4. Cached OIDC token
  5. System user (fallback)

Platform attestation:
  TPM 2.0 PCR values via tpm2_pcrread (PCRs 0,1,2,7,10,14)
  IMA measurement log hash + count
  Keylime agent state
  Entra device compliance (WSL2 only)
  Composite SHA-256 hash over all evidence

Shell features:
  Banner with identity + attestation summary
  BASCULE_* env vars injected into inner shell
  --info mode for dry-run display
  --json mode for machine-readable output
  --exec mode for single-command execution
  Configurable via ~/.config/bascule/shell.toml

Tested on Fedora with real TPM 2.0:
  6 PCRs successfully read from hardware
  All env vars propagated to inner shell
  1.8MB binary, 0 substrate deps

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-04-05 09:47:46 -04:00

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Markdown

# Observability
## Structured Logging
Bascule logs structured events via the `tracing` crate. Every log includes session context (session ID, principal, backend, source IP).
### JSON format
```bash
BASCULE_LOG_FORMAT=json ./bascule --config config.toml
```
Output:
```json
{"timestamp":"2026-04-04T20:30:00Z","level":"INFO","message":"Auth accepted","method":"ssh-key","principal":"tking","peer":"192.168.1.10:54321"}
{"timestamp":"2026-04-04T20:30:00Z","level":"INFO","message":"Shell session starting","session.id":"abc-123","session.principal":"tking","session.backend":"container","session.source_ip":"192.168.1.10"}
```
### Log levels
```bash
RUST_LOG=debug ./bascule --config config.toml # verbose
RUST_LOG=info ./bascule --config config.toml # standard
RUST_LOG=warn ./bascule --config config.toml # quiet
RUST_LOG=bascule=debug ./bascule --config config.toml # debug bascule only
```
## Key Events
| Event | Level | When |
|-------|-------|------|
| Auth accepted | INFO | SSH authentication succeeds |
| Auth rejected | WARN | SSH authentication fails |
| Shell session starting | INFO | New session with backend type |
| Exec request | INFO | Non-interactive command execution |
| Container spawning | INFO | Container session starting |
| Upstream connected | INFO | Proxy session connected to target |
| Session ended | INFO | Disconnect or exit |
## OTel Tracing (Planned)
OpenTelemetry OTLP export is planned as an optional feature flag (`--features telemetry`). Not yet implemented. Session lifecycle will map to OTel spans:
```
session (root)
├── auth (ssh-key / agent-id)
├── backend_setup (pty / proxy / container)
└── session_active (commands, I/O)
```
## Prometheus Metrics (Planned)
Prometheus-compatible metrics endpoint is planned as `--features metrics`. Not yet implemented. Planned metrics:
```
bascule_sessions_total{backend,auth_method,outcome}
bascule_sessions_active
bascule_session_duration_seconds{backend}
bascule_auth_attempts_total{method,outcome}
```