Preliminary ELF file checks

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)").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 +1,74 @@
+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; }
+		public bool? Is64Bit { get; } = null;
+		public bool? IsBigEndian { get; } = null;
+		public string Architecture { get; } = null;
+
+		public byte[] Contents { get; } = null;
+
+		public ElfFile(byte[] fileContents) {
+			IsValid = fileContents[0x00..0x04].SequenceEqual(new byte[] {0x7F, (byte)'E', (byte)'L', (byte)'F'});
+			if(IsValid == false) 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 +22,25 @@ namespace LBPUnion.UnionPatcher {
                 return;
             }
 
+            ElfFile eboot = new(new FileInfo(args[0]));
+
+            if(eboot.IsValid == false) {
+				Console.WriteLine($"{eboot.Name} is not a valid ELF file (magic number mismatch)");
+				return;
+			}
+
+			if(eboot.Is64Bit == null) {
+				Console.WriteLine($"{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]}.");
         }