discord-krisp: Fix patch for newer discord versions

pkgs/discord-krisp/default.nix

@@ -1,19 +1,22 @@
 { prev, ... }:
 let
-  patch-krisp = prev.writeScript "patch-krisp" ''
-    discord_version="${prev.discord.version}"
-    file="$HOME/.config/discord/$discord_version/modules/discord_krisp/discord_krisp.node"
-    if [ -f "$file" ]; then
-    addr=$("${prev.rizin}/bin/rz-find" -x '4881ec00010000' "$file" | head -n1)
-    "${prev.rizin}/bin/rizin" -q -w -c "s $addr + 0x30 ; wao nop" "$file"
-    fi
-  '';
+  # krisp-patcher.py courtesy of https://github.com/sersorrel/sys
+  patch-krisp = prev.writers.writePython3 "krisp-patcher" {
+    libraries = with prev.python3Packages; [ capstone pyelftools ];
+    # Ignore syntax checker error codes that affect krisp-patcher.py
+    flakeIgnore = [
+      "E501"
+      "F403"
+      "F405"
+    ];
+  } (builtins.readFile ./krisp-patcher.py);
   binaryName = "Discord";
+  node_module="\\$HOME/.config/discord/${prev.discord.version}/modules/discord_krisp/discord_krisp.node";
 in
 prev.discord.overrideAttrs (previousAttrs: {
   postInstall = previousAttrs.postInstall + ''
     wrapProgramShell $out/opt/${binaryName}/${binaryName} \
-    --run "${patch-krisp}"
+    --run "${patch-krisp} ${node_module}"
   '';
   passthru = removeAttrs previousAttrs.passthru [ "updateScript" ];
   meta = {

pkgs/discord-krisp/krisp-patcher.py

@@ -0,0 +1,93 @@
+# krisp-patcher.py courtesy of https://github.com/sersorrel/sys
+import sys
+import shutil
+
+from elftools.elf.elffile import ELFFile
+from capstone import *
+from capstone.x86 import *
+
+if len(sys.argv) < 2:
+    print(f"Usage: {sys.argv[0]} [path to discord_krisp.node]")
+    # "Unix programs generally use 2 for command line syntax errors and 1 for all other kind of errors."
+    exit()
+
+executable = sys.argv[1]
+
+elf: ELFFile
+
+try:
+    elf = ELFFile(open(executable, "rb"))
+except FileNotFoundError:
+    print("Krisp executable could not be located. Skipping.")
+    exit()
+
+symtab = elf.get_section_by_name('.symtab')
+
+krisp_initialize_address = symtab.get_symbol_by_name("_ZN7discord15KrispInitializeEv")[0].entry.st_value
+isSignedByDiscord_address = symtab.get_symbol_by_name("_ZN7discord4util17IsSignedByDiscordERKNSt4__Cr12basic_stringIcNS1_11char_traitsIcEENS1_9allocatorIcEEEE")[0].entry.st_value
+
+text = elf.get_section_by_name('.text')
+text_start = text['sh_addr']
+text_start_file = text['sh_offset']
+# This seems to always be zero (.text starts at the right offset in the file). Do it just in case?
+address_to_file = text_start_file - text_start
+
+# Done with the ELF now.
+# elf.close()
+
+krisp_initialize_offset = krisp_initialize_address - address_to_file
+isSignedByDiscord_offset = krisp_initialize_address - address_to_file
+
+f = open(executable, "rb")
+f.seek(krisp_initialize_offset)
+krisp_initialize = f.read(64)
+f.close()
+
+# States
+found_issigned_by_discord_call = False
+found_issigned_by_discord_test = False
+found_issigned_by_discord_je = False
+found_already_patched = False
+je_location = None
+je_size = 0
+
+# We are looking for a call to IsSignedByDiscord, followed by a test, followed by a je.
+# Then we replace the je with nops.
+
+md = Cs(CS_ARCH_X86, CS_MODE_64)
+md.detail = True
+for i in md.disasm(krisp_initialize, krisp_initialize_address):
+    if i.id == X86_INS_CALL:
+        if i.operands[0].type == X86_OP_IMM:
+            if i.operands[0].imm == isSignedByDiscord_address:
+                found_issigned_by_discord_call = True
+
+    if i.id == X86_INS_TEST:
+        if found_issigned_by_discord_call:
+            found_issigned_by_discord_test = True
+
+    if i.id == X86_INS_JE:
+        if found_issigned_by_discord_test:
+            found_issigned_by_discord_je = True
+            je_location = i.address
+            je_size = len(i.bytes)
+            break
+
+    if i.id == X86_INS_NOP:
+        if found_issigned_by_discord_test:
+            found_already_patched = True
+            break
+
+if je_location:
+    print(f"Found patch location: 0x{je_location:x}")
+
+    shutil.copyfile(executable, executable + ".orig")
+    f = open(executable, 'rb+')
+    f.seek(je_location - address_to_file)
+    f.write(b'\x90' * je_size)   # je can be larger than 2 bytes given a large enough displacement :(
+    f.close()
+else:
+    if found_already_patched:
+        print("Couldn't find patch location - already patched.")
+    else:
+        print("Couldn't find patch location - review manually. Sorry.")