Security vulnerability assessment of DigiByte Core v8.26 DigiDollar implementation

[Copilot]

Comprehensive security audit of the DigiDollar stablecoin, Oracle price feed system, and consensus mechanisms identifying 7 vulnerabilities with >80% confidence of exploitability.

Critical Findings

HIGH Severity

• DGB-SEC-001: Integer overflow in ValidateCollateralRatio() - collateralAmount * oraclePrice can exceed int64_t max, causing undefined behavior and potential collateral validation bypass
• DGB-SEC-002: Oracle signature verification bypass in Phase 1 mode - bundle creation uses pending messages without re-verification at commit time

MEDIUM Severity

• DGB-SEC-003: Division by zero in CalculateSystemHealth() when totalDD < 1000
• DGB-SEC-004: Oracle ID truncation to single byte in Phase 2 script format enables ID collision
• DGB-SEC-007: Race condition between mtx_messages and mtx_bundles lock acquisitions

LOW Severity

• DGB-SEC-005: Mock oracle prices using predictable GetRand() without production guards
• DGB-SEC-006: Deterministic IV derivation from public key hash in wallet encryption

Detailed Remediation Plan

A comprehensive remediation plan has been added in SECURITY_REMEDIATION_PLAN.md containing:

• Root cause analysis for each vulnerability
• Detailed code fixes with before/after examples
• Unit test specifications
• Verification steps
• Rollback plans
• Implementation timeline with prioritization
• Testing requirements
• Sign-off checklist

Priority Matrix

Priority	Vulnerabilities	Timeline
P0 - Critical	DGB-SEC-001, DGB-SEC-002	Immediate (0-7 days)
P1 - High	DGB-SEC-003, DGB-SEC-004, DGB-SEC-007	Short-term (1-4 weeks)
P2 - Medium	DGB-SEC-005, DGB-SEC-006	Long-term (1-3 months)

Positive Observations

• DCA module has explicit overflow protection
• Oracle P2P includes rate limiting and DOS protection
• BIP-340 Schnorr signatures correctly implemented
• Proper memory_cleanse() usage in wallet crypter

Original prompt

You are a senior security researcher specializing in cryptocurrency and blockchain security audits. You have deep expertise in: - C++ memory safety and undefined behavior exploitation - Bitcoin Core architecture and its derivatives - Cryptographic implementation vulnerabilities - Peer-to-peer network protocol attacks - Consensus mechanism exploitation - Smart contract and transaction validation flaws

Your security audits have identified critical vulnerabilities in production blockchain systems. You approach code review methodically, understanding that even minor oversights in cryptocurrency code can result in catastrophic financial losses or network-wide attacks.

<repository_context>
You are auditing the DigiByte Core repository (https://github.com/DigiByte-Core/digibyte).

DigiByte is a UTXO-based cryptocurrency forked from Bitcoin Core with these unique characteristics:

• Multi-algorithm mining (5 algorithms: SHA256, Scrypt, Groestl, Skein, Qubit)
• DigiShield/MultiShield difficulty adjustment mechanisms
• SegWit support (activated April 2017)
• 15-second block times
• DigiAssets layer for tokenization
• Digi-ID authentication protocol

The codebase is primarily C++ with Python test scripts. Understanding Bitcoin Core's architecture is essential for effective analysis.
</repository_context>

Perform a comprehensive security vulnerability assessment of the provided code. Your analysis must be thorough yet precise—flag only issues where you have HIGH CONFIDENCE (>80%) of actual exploitability in a real-world attack scenario.

This precision is critical because:

1. False positives waste developer time and erode trust in security tooling
2. Cryptocurrency vulnerabilities have direct financial consequences
3. The DigiByte community relies on accurate assessments to prioritize fixes

<vulnerability_categories>
Focus your analysis on these high-impact vulnerability classes relevant to cryptocurrency systems:

C++ memory corruption vulnerabilities that could enable code execution or denial of service - Buffer overflows in serialization/deserialization (CDataStream, CSerialize) - Use-after-free in transaction/block handling - Integer overflows in amount calculations (CAmount arithmetic) - Uninitialized memory in cryptographic contexts - Double-free in wallet or mempool operations - Stack exhaustion via recursive data structures Pay special attention to: - CScript parsing and execution - CTxIn/CTxOut handling - Block deserialization boundaries - Merkle tree construction Bugs that could cause chain splits, enable double-spends, or violate consensus rules - Inconsistent validation between nodes - Time-related edge cases (nLockTime, CSV, block timestamps) - Signature validation bypasses (ECDSA, Schnorr) - SegWit witness validation errors - Difficulty calculation errors (especially in MultiShield logic) - Coinbase maturity violations - Script evaluation differences DigiByte-specific consensus areas: - Multi-algorithm difficulty adjustment logic - DigiShield block timing calculations - Algorithm-specific block validation - Cross-algorithm attack vectors Weaknesses in cryptographic implementations or protocol design - Weak randomness (insufficient entropy, predictable nonces) - Timing side-channels in signature operations - Key derivation weaknesses (HD wallet paths) - Hash collision vulnerabilities - Signature malleability issues - Replay attack vectors P2P protocol vulnerabilities enabling network-level attacks - Remote denial of service (malformed messages, resource exhaustion) - Eclipse attacks (connection manipulation) - Sybil attack vectors - Message parsing vulnerabilities - Peer scoring manipulation - DNS seed poisoning vectors Attacks that can exhaust node resources without proportional cost - Mempool flooding attacks - Block propagation delays - UTXO set bloat - Orphan transaction accumulation - Validation computational complexity attacks - Disk I/O amplification Vulnerabilities affecting user funds or wallet integrity - Private key exposure (logging, memory, core dumps) - Insufficient fee validation (fee sniping, dust attacks) - Address reuse facilitation - Watch-only wallet privilege escalation - Backup/restore vulnerabilities - HD key derivation path collisions Vulner...

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.

[gto90]

@copilot , please prepare detailed remediation plans for each issue identified.

[Copilot]

@copilot , please prepare detailed remediation plans for each issue identified.

Created comprehensive remediation plan in SECURITY_REMEDIATION_PLAN.md (commit f41efed). The document includes:

For each vulnerability:

• Root cause analysis
• Detailed code fixes with before/after examples
• Unit test specifications
• Verification steps
• Rollback plans

Implementation timeline:

• P0 Critical (Week 1): DGB-SEC-001 (integer overflow), DGB-SEC-002 (signature bypass)
• P1 High (Weeks 2-3): DGB-SEC-003, DGB-SEC-004, DGB-SEC-007
• P2 Medium (Weeks 4-8): DGB-SEC-005, DGB-SEC-006

Each fix includes safe code patterns following existing examples in the codebase (e.g., the overflow protection already in dca.cpp:60-70).

[gto90]

Security Audit Remediation Complete

All 7 findings from this audit have been triaged and the 6 valid vulnerabilities have been fixed in dedicated PRs targeting feature/digidollar-v1:

Finding	Severity	Disposition	Fix PR
DGB-SEC-001 Integer overflow in ValidateCollateralRatio()	HIGH	Fixed	#373
DGB-SEC-002 Oracle signature verification bypass	HIGH	Fixed	#374
DGB-SEC-003 Division by zero in CalculateSystemHealth()	MEDIUM	Fixed	#375
DGB-SEC-004 Oracle ID truncation to single byte	MEDIUM	Fixed	#376
DGB-SEC-005 Mock oracle without production guards	LOW	Fixed	#377
DGB-SEC-006 Deterministic IV documentation	LOW	Fixed	#378
DGB-SEC-007 Mutex race condition	MEDIUM	Invalid — lock ordering is consistent (mtx_messages always before mtx_bundles), and mtx_messages is a recursive_mutex. No deadlock or race is possible.	N/A

All fix PRs have had their Copilot review comments addressed and resolved. CI build fixes for the depends system (OpenSSL ARM64 + libcurl Linux) are included in each PR.

Closing this audit PR as all actionable findings are now tracked in their respective fix PRs.