Merge pull request #8 from 505e06b2/master

Implement ELF header parsing

UnionPatcher.Gui/MainForm.cs

@@ -1,4 +1,5 @@
 using System;
+using System.IO;
 using System.Diagnostics;
 using Eto;
 using Eto.Drawing;
@@ -53,21 +54,38 @@ namespace LBPUnion.UnionPatcher.Gui {
             };
 
             control.Click += delegate {
-                if(string.IsNullOrEmpty(this.filePicker.FilePath)) {
+                if(string.IsNullOrWhiteSpace(this.filePicker.FilePath)) {
                     this.CreateOkDialog("Form Error", "No file specified!").ShowModal();
                     return;
                 }
 
-                if(string.IsNullOrEmpty(this.serverUrl.Text)) {
+                if(string.IsNullOrWhiteSpace(this.serverUrl.Text)) {
                     this.CreateOkDialog("Form Error", "No server URL specified!").ShowModal();
                     return;
                 }
 
-                if(string.IsNullOrEmpty(this.outputFileName.FilePath)) {
+                if(string.IsNullOrWhiteSpace(this.outputFileName.FilePath)) {
                     this.CreateOkDialog("Form Error", "No output file specified!").ShowModal();
                     return;
                 }
 
+                ElfFile eboot = new(this.filePicker.FilePath);
+
+                if(eboot.IsValid == false) {
+                    this.CreateOkDialog("EBOOT Error", $"{eboot.Name} is not a valid ELF file (magic number mismatch)\nThe EBOOT must be decrypted before using this tool").ShowModal();
+                    return;
+                }
+
+                if(eboot.Is64Bit == null) {
+                    this.CreateOkDialog("EBOOT Error", $"{eboot.Name} does not target a valid system").ShowModal();
+                    return;
+                }
+
+                if(string.IsNullOrWhiteSpace(eboot.Architecture)) {
+                    this.CreateOkDialog("EBOOT Error", $"{eboot.Name} does not target a valid architecture (PowerPC or ARM)").ShowModal();
+                    return;
+                }
+
                 try {
                     Patcher.PatchFile(this.filePicker.FilePath, this.serverUrl.Text, this.outputFileName.FilePath);
                 }

UnionPatcher/ElfFile.cs

@@ -0,0 +1,77 @@
+using System;
+using System.IO;
+using System.Linq;
+using System.Buffers.Binary;
+
+/*
+Linux ELF header refspec: https://refspecs.linuxfoundation.org/elf/gabi4+/ch4.eheader.html
+Wikipedia entry on ELF: https://en.wikipedia.org/wiki/Executable_and_Linkable_Format
+*/
+
+namespace LBPUnion.UnionPatcher {
+    public class ElfFile {
+        private enum WordSize : byte {
+            ThirtyTwoBits = 0x01,
+            SixtyFourBits = 0x02
+        }
+
+        private enum Endianness : byte {
+            Little = 0x01,
+            Big = 0x02
+        }
+
+        private enum InstructionSetArchitecture : UInt16 {
+            PowerPC = 0x15, //64-bit PowerPC (PS3)
+            ARM = 0x28 //32-bit ARM (Vita)
+        }
+
+        public string Name { get; } = "Binary Blob";
+
+        public bool IsValid { get; } = false;
+        public bool? Is64Bit { get; } = null;
+        public bool? IsBigEndian { get; } = null;
+        public string Architecture { get; } = null;
+
+        public byte[] Contents { get; } = null;
+
+        public ElfFile(byte[] fileContents) {
+            if(fileContents.Length < 52)
+                return;
+
+            IsValid = fileContents[0x00..0x04].SequenceEqual(new byte[] {0x7F, (byte)'E', (byte)'L', (byte)'F'});
+            if(!IsValid) return;
+
+            byte identClassValue = fileContents[0x04];
+            byte identDataValue = fileContents[0x05];
+
+            if(identClassValue == (byte)WordSize.ThirtyTwoBits || identClassValue == (byte)WordSize.SixtyFourBits)
+                Is64Bit = identClassValue == (byte)WordSize.SixtyFourBits;
+
+            if(identDataValue == (byte)Endianness.Little || identDataValue == (byte)Endianness.Big)
+                IsBigEndian = identDataValue == (byte)Endianness.Big;
+
+            Architecture = GetFileArchitecture(fileContents, IsBigEndian == true);
+
+            Contents = fileContents;
+        }
+
+        public ElfFile(FileInfo file) : this(File.ReadAllBytes(file.FullName)) {
+            Name = file.Name;
+        }
+
+        public ElfFile(string fileName) : this(new FileInfo(fileName)) {}
+
+        private string GetFileArchitecture(byte[] elfHeader, bool isBigEndian) {
+            byte[] architectureBytes = elfHeader[0x12..0x14];
+            UInt16 fileArch = (isBigEndian) ?
+                BinaryPrimitives.ReadUInt16BigEndian(architectureBytes) :
+                BinaryPrimitives.ReadUInt16LittleEndian(architectureBytes);
+
+            foreach(InstructionSetArchitecture arch in Enum.GetValues(typeof(InstructionSetArchitecture))) {
+                if(fileArch == (UInt16)arch)
+                    return arch.ToString();
+            }
+            return null;
+        }
+    }
+}

UnionPatcher/Program.cs

@@ -22,6 +22,26 @@ namespace LBPUnion.UnionPatcher {
                 return;
             }
 
+            ElfFile eboot = new(new FileInfo(args[0]));
+
+            if(!eboot.IsValid) {
+                Console.WriteLine($"{eboot.Name} is not a valid ELF file (magic number mismatch)");
+                Console.WriteLine("The EBOOT must be decrypted before using this tool");
+                return;
+            }
+
+            if(eboot.Is64Bit == null) {
+                Console.WriteLine($"{eboot.Name} does not target a valid system");
+                return;
+            }
+
+            if(string.IsNullOrWhiteSpace(eboot.Architecture)) {
+                Console.WriteLine($"{eboot.Name} does not target a valid architecture (PowerPC or ARM)");
+                return;
+            }
+
+            Console.WriteLine($"{eboot.Name} targets {eboot.Architecture}");
+
             Patcher.PatchFile(args[0], args[1], args[2]);
             Console.WriteLine($"Successfully patched Server URL to {args[1]}.");
         }