|
| 1 | +""" |
| 2 | +Silent Standby state machine for coercion-safe UI transitions. |
| 3 | +
|
| 4 | +Provides a configurable hotkey-triggered transition from sensitive UI state |
| 5 | +to a non-sensitive standby state. Recovery requires re-authentication. |
| 6 | +
|
| 7 | +State diagram: |
| 8 | + active → standby → sealed |
| 9 | + sealed → active (re-authentication required) |
| 10 | + sealed → dummy_disclosure (coercion-safe path) |
| 11 | +
|
| 12 | +What standby does: |
| 13 | + - Removes sensitive UI state from the visible surface. |
| 14 | + - Detaches true-profile UI references. |
| 15 | + - Transitions to a non-sensitive screen. |
| 16 | +
|
| 17 | +What standby does NOT do: |
| 18 | + - Erase key material from process memory. |
| 19 | + - Forge logs, fake system events, or perform anti-forensic tampering. |
| 20 | + - Hide the Phasmid process from the system process list. |
| 21 | + - Prevent live memory capture from recovering in-use key material. |
| 22 | +""" |
| 23 | + |
| 24 | +from __future__ import annotations |
| 25 | + |
| 26 | +import threading |
| 27 | +from enum import Enum |
| 28 | + |
| 29 | + |
| 30 | +class StandbyState(str, Enum): |
| 31 | + ACTIVE = "active" |
| 32 | + STANDBY = "standby" |
| 33 | + SEALED = "sealed" |
| 34 | + DUMMY_DISCLOSURE = "dummy_disclosure" |
| 35 | + |
| 36 | + |
| 37 | +class InvalidTransitionError(Exception): |
| 38 | + """Raised when a state transition is not allowed.""" |
| 39 | + |
| 40 | + |
| 41 | +class StandbyStateMachine: |
| 42 | + """ |
| 43 | + Thread-safe standby state machine. |
| 44 | +
|
| 45 | + Transitions: |
| 46 | + active → standby (trigger_standby) |
| 47 | + standby → sealed (seal — automatic on standby activation) |
| 48 | + sealed → active (recover — requires re-authentication) |
| 49 | + sealed → dummy_disclosure (enter_dummy_disclosure) |
| 50 | + dummy_disclosure → sealed (seal_dummy) |
| 51 | +
|
| 52 | + Re-entry to active from standby is disallowed without re-authentication. |
| 53 | + """ |
| 54 | + |
| 55 | + _VALID_TRANSITIONS: dict[StandbyState, set[StandbyState]] = { |
| 56 | + StandbyState.ACTIVE: {StandbyState.STANDBY}, |
| 57 | + StandbyState.STANDBY: {StandbyState.SEALED}, |
| 58 | + StandbyState.SEALED: {StandbyState.ACTIVE, StandbyState.DUMMY_DISCLOSURE}, |
| 59 | + StandbyState.DUMMY_DISCLOSURE: {StandbyState.SEALED}, |
| 60 | + } |
| 61 | + |
| 62 | + def __init__(self) -> None: |
| 63 | + self._state = StandbyState.ACTIVE |
| 64 | + self._lock = threading.Lock() |
| 65 | + |
| 66 | + @property |
| 67 | + def state(self) -> StandbyState: |
| 68 | + with self._lock: |
| 69 | + return self._state |
| 70 | + |
| 71 | + def trigger_standby(self) -> None: |
| 72 | + """ |
| 73 | + Transition from active to standby, then immediately to sealed. |
| 74 | +
|
| 75 | + This is the hotkey-triggered path. After this call, the state is SEALED. |
| 76 | + """ |
| 77 | + with self._lock: |
| 78 | + if self._state != StandbyState.ACTIVE: |
| 79 | + raise InvalidTransitionError( |
| 80 | + f"Cannot trigger standby from state '{self._state}'; " |
| 81 | + "must be in ACTIVE state." |
| 82 | + ) |
| 83 | + self._state = StandbyState.STANDBY |
| 84 | + self._state = StandbyState.SEALED |
| 85 | + |
| 86 | + def recover(self) -> None: |
| 87 | + """ |
| 88 | + Transition from sealed back to active. |
| 89 | +
|
| 90 | + Caller is responsible for verifying re-authentication before calling this. |
| 91 | + Direct restoration of previous sensitive UI state is disallowed by design. |
| 92 | + """ |
| 93 | + with self._lock: |
| 94 | + if self._state != StandbyState.SEALED: |
| 95 | + raise InvalidTransitionError( |
| 96 | + f"Cannot recover from state '{self._state}'; " |
| 97 | + "must be in SEALED state." |
| 98 | + ) |
| 99 | + self._state = StandbyState.ACTIVE |
| 100 | + |
| 101 | + def enter_dummy_disclosure(self) -> None: |
| 102 | + """ |
| 103 | + Transition from sealed to dummy_disclosure. |
| 104 | +
|
| 105 | + Used in coercion-safe recognition fallback and manual operator choice. |
| 106 | + """ |
| 107 | + with self._lock: |
| 108 | + if self._state != StandbyState.SEALED: |
| 109 | + raise InvalidTransitionError( |
| 110 | + f"Cannot enter dummy disclosure from state '{self._state}'; " |
| 111 | + "must be in SEALED state." |
| 112 | + ) |
| 113 | + self._state = StandbyState.DUMMY_DISCLOSURE |
| 114 | + |
| 115 | + def seal_dummy(self) -> None: |
| 116 | + """Return from dummy_disclosure back to sealed.""" |
| 117 | + with self._lock: |
| 118 | + if self._state != StandbyState.DUMMY_DISCLOSURE: |
| 119 | + raise InvalidTransitionError( |
| 120 | + f"Cannot seal dummy from state '{self._state}'; " |
| 121 | + "must be in DUMMY_DISCLOSURE state." |
| 122 | + ) |
| 123 | + self._state = StandbyState.SEALED |
| 124 | + |
| 125 | + def is_active(self) -> bool: |
| 126 | + return self.state == StandbyState.ACTIVE |
| 127 | + |
| 128 | + def is_sealed(self) -> bool: |
| 129 | + return self.state == StandbyState.SEALED |
| 130 | + |
| 131 | + def is_in_standby_or_sealed(self) -> bool: |
| 132 | + return self.state in (StandbyState.STANDBY, StandbyState.SEALED) |
| 133 | + |
| 134 | + def is_dummy_disclosure(self) -> bool: |
| 135 | + return self.state == StandbyState.DUMMY_DISCLOSURE |
| 136 | + |
| 137 | + def status_dict(self) -> dict[str, object]: |
| 138 | + """Return a status dict safe for diagnostics. Contains no key material.""" |
| 139 | + return {"state": self.state.value} |
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