Security Considerations

Security analysis and best practices for ERC-7866.

Core Security Properties

Soul Bound (Non-Transferable)

Profiles cannot be transferred between addresses:

Property: Profile ownership is immutable

// Profile is permanently tied to msg.sender
profiles[msg.sender] = Profile(...);

// No transfer function exists
// No approve/transferFrom mechanism

Security Benefit: Prevents profile theft or hijacking

Immutable Usernames

Usernames cannot be changed after creation:

Property: Username → Address mapping is permanent

usernameToAddress[username] = msg.sender;  // Never updated

Security Benefit:

• Prevents username squatting and takeover
• Enables reliable reverse lookups
• Prevents social engineering via username changes

Ownership Verification

Only profile owners can modify their profiles:

Property: Access control at function level

modifier onlyProfileOwner(address account) {
    require(msg.sender == account, "Only profile owner can perform this action");
    _;
}

Security Benefit: Unauthorized modifications prevented

Privacy Enforcement

Private avatar URIs are hidden from non-owners:

Property: Privacy check at read time

if (!avatar.isPublic && msg.sender != owner) {
    return DappAvatar({dappName: dappName, avatarURI: "", isPublic: false});
}

Security Benefit: User data confidentiality enforced

Attack Vectors & Mitigations

1. Username Squatting

Attack: Attacker claims popular usernames, sells them

Mitigation:

• First-come, first-served prevents changing ownership
• No transfer/sale mechanism exists
• Usernames are tied to addresses

Recommendation: Reserve popular names through governance (future enhancement)

2. Flash Loan Attacks

Attack: Use flash loan funds to create profile, then repay

Status: Not applicable

• Profile creation doesn't transfer tokens
• SoulProfile has no external token dependencies
• Flash loans don't help attack this contract

3. Reentrancy

Attack: Attacker calls back into contract during function execution

Mitigation:

• No external calls in state-changing functions
• State updates happen before any external interactions
• Checks-Effects-Interactions pattern followed

Code Example:

function setDefaultAvatar(string memory avatarURI)
    external
    onlyProfileOwner(msg.sender)
{
    // Effect: State change happens first
    profiles[msg.sender].defaultAvatarURI = avatarURI;

    // Interaction: Event emitted after state change
    emit DefaultAvatarUpdated(msg.sender, avatarURI);
}

4. Private Avatar Exposure

Attack: Non-owner reads private avatar URI

Mitigation:

• Privacy check enforces at smart contract level
• Returns empty URI to non-owners
• No way to bypass privacy at Solidity level

Limitation: Events are always public

event DappAvatarSet(
    address indexed owner,
    string dappName,
    string avatarURI,      // URI exposed in event
    bool isPublic
);

Recommendation:

• Users should be aware events are public
• Don't put sensitive data in avatar URIs
• Use encryption for highly sensitive data

5. URI Injection Attacks

Attack: Inject malicious content in avatar URIs (javascript:, data:, etc.)

Mitigation:

• Contract accepts any URI (by design)
• Validation happens in frontend/consumer
• No on-chain URI execution

Recommendation: Frontend should validate URIs

const SAFE_PROTOCOLS = ['ipfs://', 'ar://', 'https://', 'http://'];

function isValidURI(uri: string): boolean {
    return SAFE_PROTOCOLS.some(proto => uri.startsWith(proto));
}

6. Storage Collision

Attack: Exploit storage layout to modify other data

Status: Not vulnerable

• Storage is properly separated by address
• Mappings prevent cross-user access
• Solidity compiler handles layout

mapping(address => Profile) private profiles;
mapping(address => mapping(string => DappAvatar)) private dappAvatars;

7. Username Registration Race

Attack: Two users try to register same username simultaneously

Mitigation:

• Blockchain enforces transaction ordering
• First transaction to be mined gets the username
• Subsequent attempts fail atomically

Code:

require(usernameToAddress[username] == address(0), "Username already taken");
usernameToAddress[username] = msg.sender;

8. Sybil Attacks

Attack: Create many profiles on one address

Status: Not prevented

• One profile per address limit exists
• But addresses are free to create
• Attacker can create many addresses

Recommendation:

• Use reputation systems on top
• Require KYC for sensitive features
• Consider proof-of-personhood mechanisms

Access Control

Public vs. Internal

Public Functions (anyone can call):

• createProfile() — Create own profile
• setDefaultAvatar() — Update own avatar
• setDappAvatar() — Set own dApp avatar
• removeDappAvatar() — Remove own avatar
• getProfile() — Read any profile
• getDefaultAvatar() — Read any avatar
• getDappAvatar() — Read avatar (with privacy check)
• getProfileByUsername() — Lookup by username
• hasProfile() — Check profile existence

Private Storage:

• profiles — Only readable via getProfile()
• dappAvatars — Only readable via getDappAvatar()
• usernameToAddress — Only readable via getProfileByUsername()
• _hasProfile — Only readable via hasProfile()

Ownership Checks

Owner verified through:

require(msg.sender == owner, "Only profile owner can perform this action");

Not through:

• Token balances
• Signature verification
• Delegation
• Proxy patterns

Input Validation

Username Validation

modifier validUsername(string memory username) {
    bytes memory usernameBytes = bytes(username);
    require(usernameBytes.length > 0 && usernameBytes.length <= 32,
        "Invalid username length");
    _;
}

Validated:

• Length: 1-32 characters
• Uniqueness: Must not exist
• Format: Any UTF-8 valid

Not Validated:

• Offensive content
• Homograph attacks (visually similar characters)
• Normalization (NFD vs NFC)

Recommendation: Implement content moderation off-chain

URI Validation

No on-chain validation. Contract accepts any string.

Why:

• Protocols evolve (IPFS, Arweave, new standards)
• Storage schemes vary
• Centralized whitelist would limit extensibility

Frontend Should Validate:

const isValidURI = (uri: string) => {
    try {
        new URL(uri); // Basic URL check
        return true;
    } catch {
        return false;
    }
};

Gas Limit Attacks

Unbounded Loops

Status: Not vulnerable

• No loops in contract
• No iteration over mappings
• All operations are constant time O(1)

Storage Explosion

Status: Considered but acceptable

• Each user can create one profile
• Multiple dApp avatars per user (unbounded)
• But limited by gas per transaction

Practical Limit: ~100 dApp avatars per user per transaction

External Dependencies

None

SoulProfile has zero external dependencies:

• No other contracts imported
• No libraries used (except Solidity standard)
• No oracles or external calls
• Pure EVM smart contract

Security Benefit: Minimal attack surface

Admin Functions

None

SoulProfile has no admin functions:

• No owner/admin account
• No pausing mechanism
• No upgrade path
• Fully decentralized

Consequence: Contract is immutable. Choose carefully before deployment.

Testing Recommendations

Unit Tests

function testUsername uniqueness() { ... }
function testOwnershipEnforcement() { ... }
function testPrivacyEnforcement() { ... }
function testProfileCreation() { ... }
function testAvatarUpdates() { ... }
function testEventEmission() { ... }

Fuzz Testing

function testFuzzUsernames(string memory username) public {
    vm.prank(alice);
    try soulProfile.createProfile(username, "ipfs://") {
        // Success
    } catch {
        // Failure is fine for invalid inputs
    }
}

Invariant Testing

Invariants that should always hold:

1. One profile per address
2. One username per address (immutable)
3. Only owner can modify profile
4. Private avatars hidden from non-owners
5. All operations are O(1)

Audit Recommendations

If auditing this contract:

1. Ownership Verification

   • Verify access controls work correctly
   • Test unauthorized access denied

2. Privacy Enforcement

   • Confirm private avatars hidden
   • Test edge cases (zero address, empty dApp name)

3. Storage Safety

   • Verify no storage collisions
   • Check mapping access patterns

4. Input Validation

   • Test boundary conditions
   • Test UTF-8 handling in usernames

5. Gas Efficiency

   • Check O(1) complexity
   • Verify no unexpected loops

Deployment Checklist

• [ ] Code reviewed by team
• [ ] Unit tests passing
• [ ] Fuzz tests passing
• [ ] Testnet deployment successful
• [ ] External audit performed (optional but recommended)
• [ ] Events tested and emitting correctly
• [ ] Gas costs benchmarked
• [ ] Frontend validation in place
• [ ] Documentation reviewed
• [ ] Emergency procedures documented

Incident Response

If vulnerability is discovered:

1. Don't disclose publicly until fix is deployed
2. Notify users to stop using contract
3. Deploy fix on new address
4. Migrate users (via off-chain indexing)
5. Publish postmortem with details

Security Assumptions

This contract assumes:

1. Ethereum network security — 51% attack resistance
2. No critical Solidity bugs — Compiler is secure
3. Private keys are secure — Users manage keys safely
4. Users validate URIs — Frontends check avatar URIs
5. Usernames are public — Can't hide registration

Future Hardening

Potential v2 improvements:

• Username allowlists/governance
• Reputation system integration
• Rate limiting on updates
• Batch operations support
• Account recovery mechanisms
• Cross-chain synchronization