Implements comprehensive validation layer on top of protobuf schema to
prevent malformed data, DoS attacks, and business logic violations.
Changes:
- Created Towerops.Agent.Validator module with strict validation for all
agent message types (AgentHeartbeat, MetricBatch, SnmpResult, AgentError,
CredentialTestResult, MikrotikResult)
- Added validation limits to prevent memory exhaustion and DoS attacks
(max string lengths, collection sizes, numeric ranges)
- Added format validation for UUIDs, IP addresses, versions, hostnames
- Added enum validation for status and protocol fields
- Modified AgentChannel handlers to validate all incoming messages before
processing
- Added comprehensive typespecs to AgentChannel for better static analysis
- Created safe_base64_decode/1 helper with error handling
- Added 32 comprehensive tests covering valid cases, invalid inputs, and
edge cases
Security improvements:
- Prevents memory exhaustion via oversized strings and collections
- Validates all numeric fields are within expected ranges
- Checks UUID format for all ID fields
- Validates IP addresses and hostnames against RFC standards
- Rejects future timestamps and excessive values
Backward compatibility:
- Empty version and hostname strings allowed for older agents