andreacristaldi-DefenderRuleParser/Parsers/FriendlyFileSha256Parser.cs

// DefenderRuleParser
// Author: Andrea Cristaldi 2025 - https://github.com/andreacristaldi/DefenderRuleParser
// This project is licensed under the Apache 2.0 License.
/*
 * Summary: Captures friendly SHA-256 lists (human-annotated hashes) present in some signatures.
 * Origin: dump-driven; hash length/format recognized from hex shape.
 * Role: Emits sanitized SHA-256 values for lookups and YARA emission.
 */
using System;
using System.Collections.Generic;
using System.IO;
using DefenderRuleParser2.Models;

namespace DefenderRuleParser2.Parsers
{
    public class FriendlyFileSha256Parser : ISignatureParser
    {
        public void Parse(BinaryReader reader, int size, uint threatId)
        {
            long offset = reader.BaseStream.Position;

            try
            {
                if (size != 32)
                {
                    Logger.Warn($"[!] FRIENDLYFILE_SHA256 ! Unexpected size: {size} (expected 32 bytes)");
                    reader.BaseStream.Seek(offset + size, SeekOrigin.Begin);
                    return;
                }

                byte[] hashBytes = reader.ReadBytes(32);
                string hexHash = BitConverter.ToString(hashBytes).Replace("-", "").Trim();

                Logger.Info($"[FRIENDLYFILE_SHA256] Threat ID: {threatId}");
                Logger.Info($"  > SHA256 (internal): {hexHash}");

                if (ThreatDatabase.TryGetThreat(threatId, out var threat))
                {
                    threat.Signatures.Add(new SignatureEntry
                    {
                        Type = "SIGNATURE_TYPE_FRIENDLYFILE_SHA256",
                        Offset = offset,
                        Pattern = new List<string> { hexHash },
                        Parsed = true,
                        ConditionType = "PRESENT",
                        ConditionValue = 1
                    });
                }
            }
            catch (Exception ex)
            {
                Logger.Error($"[!] FRIENDLYFILE_SHA256 Error parsing at offset 0x{offset:X}: {ex.Message}");
            }
            finally
            {
                reader.BaseStream.Seek(offset + size, SeekOrigin.Begin);
            }
        }
    }

}