Object Ownership

OBJECT_OWNERSHIP Skill

Trigger Pattern: Always required for Sui Move audits -- object lifecycle and ownership model Inject Into: Breadth agents, depth-state-trace, depth-token-flow Finding prefix: [OO-N] Rules referenced: R4, R5, R9, R10, R13

Sui's object-centric model is fundamentally different from account-based chains. Every struct with the key ability is an on-chain object with a globally unique ID, and its ownership model (owned/shared/frozen/wrapped) determines who can access and mutate it. Incorrect ownership choices, missing transfer restrictions, orphaned UIDs, and uncontrolled dynamic fields are the primary Sui-specific vulnerability classes.

1. Object Inventory

For EVERY struct with key ability in the codebase, build this table:

Ability rules:

• key alone: Object can exist on-chain but CANNOT be transferred by generic transfer::public_transfer (requires module-defined transfer logic).
• key + store: Object CAN be transferred by anyone via transfer::public_transfer. This is a permissive choice -- verify it is intentional.
• key + store + copy: Object can be duplicated -- extremely rare for value-bearing objects. FLAG if found on any object holding balances.
• key + store + drop: Object can be silently discarded without calling a destructor. FLAG if the object holds Balance<T> or other value -- tokens can be lost.

Ownership model classification:

• OWNED: Created and transferred to a specific address via transfer::transfer or transfer::public_transfer. Only the owner can pass it as a transaction argument.
• SHARED: Made accessible to all via transfer::public_share_object. Any transaction can read/write it. CRITICAL access control implications.
• FROZEN: Made immutable via transfer::public_freeze_object. Anyone can read, no one can mutate.
• WRAPPED: Stored as a field inside another object (not directly addressable on-chain). Accessible only through the parent.
• MIXED: Object starts as one type and transitions to another (e.g., created as owned, then shared). Document the transition path.

2. Ownership Model Analysis

2a. Owned Object Audit

For each OWNED object:

Check patterns:

• Should this be shared? If multiple unrelated parties need to mutate the object in the same epoch, owned model creates bottlenecks or requires trust delegation. Common mistake: config objects that should be shared are kept owned, forcing single-admin bottleneck.
• Ownership change undermines assumptions? If code assumes "only admin holds AdminCap", but AdminCap has store ability, it can be transferred to anyone. Verify that transfer does not break invariants downstream.
• Phantom ownership: Object is "owned" but the owner address is a PDA-like derived address that nobody controls (e.g., @0x0). The object is effectively inaccessible -- equivalent to locked funds if it holds value.

2b. Shared Object Audit

For each SHARED object:

CRITICAL checks:

• Access control on mutation: Shared objects can be passed as arguments by ANY transaction. If a function takes &mut SharedObj without verifying the caller has authority (e.g., checking a capability object), anyone can mutate it. This is the #1 Sui vulnerability pattern.
• Public mutable reference getters: A public function that returns &mut internal state, calls borrow_mut, or exposes dynamic-field mutable access is externally callable by attacker packages. It must be public(package) or require a capability unless external mutation is explicitly safe.
• Helper visibility: Internal helpers that mutate state or expose sensitive references should not be public only because another module in the same package needs them. Use public(package) for same-package helpers.
• Consensus ordering: Transactions touching the same shared object are ordered by Sui's consensus. If the protocol relies on specific transaction ordering (e.g., "admin sets fee before user trades"), front-running is possible because consensus ordering is non-deterministic from the user's perspective.
• Race conditions: Two transactions that both mutate the same shared object field can produce different final states depending on execution order. If the protocol assumes sequential access, this is a bug.
• Gas-based DoS: An attacker can submit many transactions touching a shared object to increase contention and gas costs for legitimate users.

2c. Frozen Object Audit

For each FROZEN object:

Check: If frozen object holds configuration that may need updating (fee rates, oracle addresses, admin keys), freezing is likely wrong -- should be shared with access control instead.

2d. Wrapped Object Audit

For each WRAPPED object:

Check patterns:

• No unwrap path: If a wrapped object holds value (Balance, Coin) but there is no function to extract it, funds are permanently locked inside the parent. Apply Rule 9: stranded asset = minimum MEDIUM.
• Parent destruction without unwrap: If the parent object can be destroyed (has drop ability or explicit destructor) without first unwrapping/extracting the inner object, the inner object's value is lost.
• Dynamic fields on wrapped objects: Dynamic fields added to a wrapped object's UID are NOT accessible when the object is wrapped. They become orphaned until unwrap. If the protocol adds dynamic fields and then wraps, those fields are inaccessible.

3. Object Transfer Analysis

For each transfer::transfer, transfer::public_transfer, transfer::share_object, transfer::public_share_object, transfer::freeze_object, transfer::public_freeze_object call:

Check patterns:

• store ability gate: transfer::public_transfer requires store. transfer::transfer does not -- it is module-restricted. If an object should NOT be freely transferable by holders, it should NOT have store.
• Recipient validation: If an object is transferred to an arbitrary address and that address does not have the matching module to use it, the object is stranded. This is especially dangerous for capability objects (AdminCap sent to a contract that cannot invoke admin functions).
• Transfer to self: Transferring an object to the transaction sender is sometimes used as a "commit" pattern. Verify this does not bypass any state transitions.
• Conditional transfer: If transfer happens inside a conditional branch, check the else branch -- does the object leak (neither transferred, shared, frozen, wrapped, nor destroyed)?

4. Shared Object Mutation Safety

For each shared object, build the mutation map:

Sui-specific re-entrancy note: Move's borrow checker prevents re-entrancy within a single module (you cannot pass &mut Obj to a function that also borrows &mut Obj). However, cross-module re-entrancy is possible if Object A's mutation calls a function in Module B that calls back to Module A with a different entry point that accesses a DIFFERENT shared object whose state is coupled with Object A.

Concurrent mutation checklist:

• Can two independent transactions mutate the same field to conflicting values?
• Does the protocol rely on reading a value from the shared object and then writing back a derived value? (TOCTOU with consensus ordering)
• Can an attacker observe a pending transaction on a shared object and submit a competing transaction that front-runs it?
• Are balance operations on shared objects atomic? (Balance::split + Balance::join should not be interruptible across objects)

5. Object Wrapping/Unwrapping

For each wrapping relationship (object stored as field in another object):

Check patterns:

• Dynamic field orphaning: If dynamic_field::add(child_uid, ...) is called before child is wrapped into parent, those dynamic fields become inaccessible. They still exist on-chain (consuming storage) but cannot be read or removed until the child is unwrapped.
• UID preservation: When an object is unwrapped and re-created, does it get the same UID or a new one? If new UID, all dynamic fields on the old UID are orphaned permanently.
• Nested wrapping depth: Objects wrapped inside objects wrapped inside objects create deep access chains. Each level adds complexity and potential for state inconsistency.
• Balance preservation invariant: If the wrapped object holds Balance<T>, verify that total balance is preserved across wrap/unwrap cycles. No balance should be created or destroyed during wrapping.

6. UID Lifecycle Audit

Every call to object::new(ctx) creates a UID. Every UID must be either:

1. Stored in an object with key ability (the object's id field), OR
2. Explicitly destroyed via object::delete(id)

For each object::new(ctx) call:

Check patterns:

• Orphaned UID: If object::new(ctx) is called but the resulting UID is not stored in an object that gets transferred/shared/frozen, and not deleted, it is a resource leak. The UID exists on-chain consuming storage but is unreachable.
• UID in error paths: If a function creates a UID, then hits an abort/assert before storing it -- the transaction reverts, so no leak. BUT if the function returns early (non-abort) with the UID in a local variable -- this is a compiler error in Move (linear type), so it should not be possible. Verify the compiler catches this.
• UID reuse: A UID should never be reused after object::delete. Move's type system should prevent this, but verify in any unsafe or native code paths.
• Dynamic field cleanup before delete: Before calling object::delete(id), ALL dynamic fields on that UID should be removed. Otherwise, the dynamic fields become permanently orphaned (the UID no longer exists to access them through). Apply Rule 9: orphaned dynamic fields holding value = stranded assets = minimum MEDIUM.

7. Dynamic Field Audit

For each dynamic_field::add, dynamic_field::remove, dynamic_object_field::add, dynamic_object_field::remove:

Check patterns:

• Unbounded growth: If dynamic_field::add is called in a loop or user-facing function without a cap, the parent object's dynamic field set grows without limit. This increases gas costs for operations that iterate related state and can be used as a DoS vector.
• Unauthorized field addition: If ANY caller can add dynamic fields to a shared object's UID, an attacker can pollute the object's field namespace. This may cause dynamic_field::borrow to return unexpected data if field names collide.
• Name collision: Dynamic fields are keyed by (TypeTag, name_value). If two different code paths add fields with the same key type and value, they overwrite each other. Verify field name uniqueness across all add operations on the same UID.
• Type safety: dynamic_field::borrow<Name, Value> will abort if the stored value type does not match Value. Verify all borrow calls use consistent type parameters with the corresponding add calls.
• Object fields vs value fields: dynamic_object_field::add stores objects (with key ability) that retain their own UID and are independently addressable. dynamic_field::add wraps values. Using the wrong variant can make objects inaccessible or create unexpected behavior.
• Removal completeness: Before an object is destroyed (object::delete), ALL dynamic fields must be removed. Build a removal completeness table:

Finding Template

## Finding [OO-N]: Title

**Verdict**: CONFIRMED / PARTIAL / REFUTED / CONTESTED
**Step Execution**: checkmark1,2,3,4,5,6,7 | x(reasons) | ?(uncertain)
**Rules Applied**: [R4:Y/N, R5:Y/N, R9:Y/N, R10:Y/N, R13:Y/N]
**Severity**: Critical/High/Medium/Low/Info
**Location**: sources/{module}.move:LineN
**Description**: [Specific ownership/lifecycle issue with code reference]
**Impact**: [What can happen -- fund loss, state corruption, DoS, stranded assets]

### Precondition Analysis (if PARTIAL or REFUTED)
**Missing Precondition**: [What blocks this attack]
**Precondition Type**: STATE / ACCESS / TIMING / EXTERNAL / BALANCE
**Why This Blocks**: [Specific reason]

### Postcondition Analysis (if CONFIRMED or PARTIAL)
**Postconditions Created**: [What conditions this creates]
**Postcondition Types**: [STATE, ACCESS, TIMING, EXTERNAL, BALANCE]
**Who Benefits**: [Who can use these]

Step Execution Checklist (MANDATORY)

Cross-Reference Markers

After Section 2b (Shared Object Audit): Feed unguarded mutation functions to SEMI_TRUSTED_ROLES skill if roles are involved in access control.

After Section 3 (Transfer Analysis): Feed objects with store ability to TOKEN_FLOW_TRACING skill for balance flow analysis.

After Section 6 (UID Lifecycle): Feed orphaned UIDs and incomplete dynamic field cleanup to depth-edge-case for stranded asset analysis (Rule 9).

After Section 7 (Dynamic Field Audit): Feed unbounded growth patterns to ECONOMIC_DESIGN_AUDIT for DoS cost analysis.