From 0737e1f9208f26d073d49118b3aec8ebad420cd4 Mon Sep 17 00:00:00 2001
From: tv <tv@krebsco.de>
Date: Mon, 4 Jan 2021 15:01:52 +0100
Subject: crxid: get ID from CRX3 file

---
 crxid | 46 +++++++++++++++++++++++++++++++++++-----------
 1 file changed, 35 insertions(+), 11 deletions(-)

diff --git a/crxid b/crxid
index 7c0236c..e3f7c1b 100755
--- a/crxid
+++ b/crxid
@@ -1,23 +1,47 @@
 #! /bin/sh
-# Get CRX id from RSA key
-# usage: crxid PEM_FILE
+# Get CRX id from RSA key or CRX3 file
+# usage: crxid FILE
 
 set -efu
 
-pem_path=$1
+path=$1
+type=$(file -b "$path")
 
-digest=$(
-  openssl rsa  -in "$pem_path" -pubout -outform der 2>/dev/null |
-  openssl dgst -sha256 -hex |
-  sed 's/^(stdin)= //;s/.*/\U&/'
-)
+case $type in
+  'Google Chrome extension, version 3')
+    # For details about CRX3 format see
+    # https://chromium.googlesource.com/chromium/src/+/HEAD/components/crx_file/crx3.proto
+    header_length=$(od -An -j8 -N4 -tu4 "$path")
+    binary_crx_id_length=16
+    binary_crx_id_offset=$(expr 12 + $header_length - $binary_crx_id_length)
+    crx_id_hexstring=$(
+      od -An -j"$binary_crx_id_offset" -N"$binary_crx_id_length" -tx1 "$path" |
+      tr a-f A-F |
+      tr -d ' '
+    )
+  ;;
+  'PEM RSA private key')
+    digest=$(
+      openssl rsa  -in "$path" -pubout -outform der 2>/dev/null |
+      openssl dgst -sha256 -hex |
+      sed 's/^(stdin)= //;s/.*/\U&/'
+    )
+    crx_id_hexstring=$(
+      echo "$digest" | cut -b-32
+    )
+  ;;
+  *)
+    echo "crxid: error: $path has unsupported type: $type" >&2
+    exit 1
+esac
 
 script="
   obase=16;
   ibase=16;
   ascii_a=61;
-  $(echo $digest | cut -b-32 | sed 's/./ascii_a + &;/g')
+  $(echo $crx_id_hexstring | sed 's/./ascii_a + &;/g')
 "
 
-echo "$script" | bc | xxd -r -p
-echo
+crx_id=$(echo "$script" | bc | xxd -r -p)
+
+echo "$crx_id"
-- 
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