Add EC title check patch

docs/README.md

@@ -6,4 +6,5 @@ Contents:
 It does not attempt to handle things such as client certificates or user passwords.
  - [`patch_overwrite_ios.md`](patch_overwrite_ios.md): An explanation over why and how IOS is patched for operation of the Wii Shop Channel.
  - [`patch_custom_ca_ios.md`](patch_custom_ca_ios.md): The logistics of inserting our custom CA into IOS as well for EC usage.
- - [`patch_base_domain.md`](patch_base_domain.md): Information about what URLs are present within the main DOL and information about patching them.
+ - [`patch_base_domain.md`](patch_base_domain.md): Information about what URLs are present within the main DOL and information about patching them.
+ - [`patch_ec_title_check.md`](patch_ec_title_check.md): Information about title checks run by EC, and why they were negated.

docs/patch_ec_title_check.md

@@ -0,0 +1,25 @@
+# Patch: Negate EC Title Check
+
+## Motivation
+A check on the title type is present, preventing installation of `00010008` (hidden) titles. We would like to do so.
+
+## Explanation
+Via symbols within the main ARC, we are able to see function names.
+
+Prior to downloading a title in three scenarios - normal downloading, gifting, or purchasing - EC runs a function called `ec::allowDownloadByApp`.
+
+Within this, four conditions are checked:
+  - Is the channel a downloadable title/NAND title? (`00010001`)
+  - Is the channel a game channel? This checks two types: 
+    - `00010000`, typically used for discs
+    - `00010004`.
+  - Is the channel a "service title"?  (`00010100`)
+    - Name taken from `ec::isServiceTitle`.
+
+If any of these are true, installation of the title is permitted.
+Otherwise, installation is forbidden.
+
+## Execution
+This behavior is not ideal. `ec::allowDownloadByApp` is patched to immediately return `1`, or true.
+
+In the future, `ec::isManagedTitle` and `ec::isManagedTicket` may wish to be patched as well due to similar reasons.

modify_dol.go

@@ -93,4 +93,5 @@ func applyDefaultPatches() {
 	applyPatchSet("Overwrite IOS Syscall for ES", OverwriteIOSPatch)
 	applyPatchSet("Load Custom CA within IOS", LoadCustomCA())
 	applyPatchSet("Change Base Domain", PatchBaseDomain())
+	applyPatchSet("Negate EC Title Check", NegateECTitle)
 }

patch_ec_title_check.go

@@ -0,0 +1,20 @@
+package main
+
+var NegateECTitle = PatchSet{
+	Patch{
+		Name:     "Allow all titles",
+		AtOffset: 619648,
+
+		// Generic function prolog
+		Before: Instructions{
+			STWU(R1, R1, 0xffe0),
+			MFSPR(),
+		}.toBytes(),
+
+		// Immediately return true
+		After: Instructions{
+			LI(R3, 1),
+			BLR(),
+		}.toBytes(),
+	},
+}

patch_overwrite.go

@@ -110,8 +110,7 @@ var OverwriteIOSPatch = PatchSet{
 		// We inject in the epilog of the function.
 		Before: Instructions{
 			LWZ(R0, 0x14, R1),
-			// mtspr LR, r0
-			Instruction{0x7C, 0x08, 0x03, 0xA6},
+			MTSPR(),
 			ADDI(R1, R1, 0x10),
 			BLR(),
 			padding,
@@ -120,8 +119,7 @@ var OverwriteIOSPatch = PatchSet{
 			LWZ(R0, 0x14, R1),
 			// bl overwriteIOSMemory @ 0x80014428
 			Instruction{0x4B, 0xDB, 0xB1, 0x01},
-			// mtspr LR, r0
-			Instruction{0x7C, 0x08, 0x03, 0xA6},
+			MTSPR(),
 			ADDI(R1, R1, 0x10),
 			BLR(),
 		}.toBytes(),

powerpc.go

@@ -85,3 +85,20 @@ func NOP() Instruction {
 func CMPWI(rA Register, value uint16) Instruction {
 	return EncodeInstrDForm(11, 0, rA, value)
 }
+
+// MTSPR is a hack, hardcoding LR, r0.
+// TODO(spotlightishere): actually encode this
+func MTSPR() Instruction {
+	return [4]byte{0x7c, 0x08, 0x03, 0xa6}
+}
+
+// MFSPR is a hack, hardcoding r0, LR.
+// TODO(spotlightishere): actually encode this
+func MFSPR() Instruction {
+	return [4]byte{0x7c, 0x08, 0x02, 0xa6}
+}
+
+// STWU represents the stwu PowerPC instruction.
+func STWU(rS Register, rA Register, offset uint16) Instruction {
+	return EncodeInstrDForm(37, rS, rA, offset)
+}