$ cd ~
$ cp dumpdecrypted.dylib /var/mobile/Containers/Data/Application/54EF9A70-8E3A-4B6D-B7F4-554AB256C48B/Documents/
$ cd /var/mobile/Containers/Data/Application/54EF9A70-8E3A-4B6D-B7F4-554AB256C48B/Documents/
$ DYLD_INSERT_LIBRARIES=dumpdecrypted.dylib /var/mobile/Containers/Bundle/Application/3AE519BF-2FD2-43FC-A14B-2893190B8E1E/WeChat.app/WeChat
mach-o decryption dumper
DISCLAIMER: This tool is only meant for security research purposes, not for application crackers.
[+] detected 64bit ARM binary in memory.
[+] offset to cryptid found: @0x1000c0ca8(from 0x1000c0000) = ca8
[+] Found encrypted data at address 00004000 of length 51200000 bytes - type 1.
[+] Opening /private/var/mobile/Containers/Bundle/Application/3AE519BF-2FD2-43FC-A14B-2893190B8E1E/WeChat.app/WeChat for reading.
[+] Reading header
[+] Detecting header type
[+] Executable is a plain MACH-O image
[+] Opening WeChat.decrypted for writing.
[+] Copying the not encrypted start of the file
[+] Dumping the decrypted data into the file
[+] Copying the not encrypted remainder of the file
[+] Setting the LC_ENCRYPTION_INFO->cryptid to 0 at offset ca8
[+] Closing original file
[+] Closing dump file
$ ls WeChat.decrypted
WeChat.decrypted
$ pwd
/var/mobile/Containers/Data/Application/54EF9A70-8E3A-4B6D-B7F4-554AB256C48B/Documents