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@dnaroma dnaroma/
Last active Apr 5, 2019

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Gen Proto BanG Dream

This is the code rewritten in Python 3 from the original code of esterTion's PHP version

from struct import unpack
import re
import sys
dumpcs = open('dump.cs').read()
prog = open('', 'rb')
definedClass = []
targetClass = sys.argv[1] #'SuiteMasterGetResponse' # change to get different classes
outputPath = './{}.proto'.format(targetClass)
outputFile = open(outputPath, 'w')
# write first line
outputFile.write('syntax = "proto2";\n')
typeMap = {
'uint': 'uint32',
'string': 'string',
'ulong': 'uint64',
'float': 'float',
'int': 'int32',
'double': 'double',
'bool': 'bool',
'long': 'int64'
def getTag(address):
offset = address & 0xFFFFFFFF
inst =
inst = int.from_bytes(inst, byteorder='little', signed=False)
if inst == 0xe5900004: #0x080440f9: + 4)
retnum = int.from_bytes(, 'little', signed=False)
rotate_flag = int.from_bytes(, 'little', signed=False)
if rotate_flag == 0xA0:
# rotate tag number
rotate_num = (retnum >> 8) & 0xF
tag = retnum & 0xFF
for i in range(rotate_num * 2):
tag = rotr(tag, 32)
return tag
return retnum & 0xfff
elif inst == 0xe92d4c10: + 12)
return int.from_bytes(, 'little', signed=False) & 0xfff
print(hex(inst), hex(address))
def rotr(num, bits):
num &= (2**bits-1)
bit = num & 1
num >>= 1
num |= (1 << (bits-1))
return num
def writeMessage(target, message):
outputFile.write('message {} {{\n'.format(target))
for item, info in message.items():
typ = info[0]
if type(info[1]).__name__ == 'str':
tag = getTag(int(info[1], 16))
tag = info[1]
hint = info[2]
comment = info[3]
if hint == 'map':
outputFile.write(' {}{} {} = {};\n'.format(hint, typ, item, tag))
outputFile.write(' {} {} {} = {};\n'.format(hint, typ, item, tag))
def readClass(level, target):
shownClass = True
except ValueError:
shownClass = False
message = {}
classDef ='\[ProtoContractAttribute\].*?\n.*?class ' + target + ' [^\{\}]*?\{((.*\n)*?)?\s+(//\s+Properties(.*\n)*?)?\s+(//\s+Methods(.*\n)*?)?\}\s*?', dumpcs)
if not classDef:
print('{} not found'.format(target))
propList = re.findall('(\[ProtoMemberAttribute\] //.*Offset: 0x([0-9A-F]+)\n \w+ ([^\ \<]+(\<(.*?)\>)?) ([^\ ;]+))', classDef[0])
for prop in propList:
typ = jumpTyp(level, prop[2], prop[5])
message[typ[0]] = [typ[1], prop[1], typ[2], typ[3]]
if not shownClass:
# print('{} \n'.format(target))
writeMessage(target, message)
def jumpTyp(level, typ, name):
if typ[-2:] == '[]':
sub = jumpTyp(level + 2, typ[0:-2], 'entry')
return [name, sub[1], 'repeated', 'array']
elif typ[0:11] == 'Dictionary`':
subType ='<(\w+), (\w+)>', typ)
readClass(level + 1, subType[2])
# prefix = '{}_{}'.format(subType[1], subType[2])
# try:
# definedClass.index(prefix)
# shownClass = True
# except ValueError:
# definedClass.append(prefix)
# shownClass = False
# message = {}
# sub = jumpTyp(level + 1, subType[1], '{}_key'.format(prefix))
# message[sub[0]] = [sub[1], 1, sub[2], sub[3]]
# sub = jumpTyp(level + 1, subType[2], '{}_value'.format(prefix))
# message[sub[0]] = [sub[1], 2, sub[2], sub[3]]
# if not shownClass:
# writeMessage(prefix, message)
return [name, '<{}, {}>'.format(typeMap.get(subType[1], subType[1]), typeMap.get(subType[2], subType[2])), 'map', 'dictionary']
elif typ[0:5] == 'List`':
subType ='<(\w+)>', typ)
sub = jumpTyp(level + 1, subType[1], 'entry')
return [name, sub[1], 'repeated', 'list']
elif typ[0:9] == 'Nullable`':
subType ='<(\w+)>', typ)
sub = jumpTyp(level, subType[1], name)
sub[3] = 'nullable'
return sub
expectTyp = ['uint','string','ulong','float','int','double', 'bool','long']
isType = True
except ValueError:
isType = False
if isType:
return [name, typeMap[typ], 'optional', 'normal type']
readClass(level + 1, typ)
return [name, typ, 'optional', 'sub class']
readClass(0, targetClass)

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esterTion commented Sep 18, 2018

Great analyze & rewrite! Just found the article from googling.
And yes my code is dealing with ARM64 MachO binary, for android arm elf binary, I just dropped an so into ida.
04 00 90 E5 function looks as

.text:01BD5348 sub_1BD5348
.text:01BD5348                 LDR             R0, [R0,#4]
.text:01BD534C                 MOV             R1, #1                        ; tag id
.text:01BD5350                 MOV             R2, #0
.text:01BD5354                 LDR             R0, [R0]
.text:01BD5358                 B               ProtoMemberAttribute$$.ctor
.text:01BD5358 ; End of function sub_1BD5348

compared to ios arm64

__text:0000000101320B5C sub_101320B5C                           ; DATA XREF: __const:000000010256B948↓o
__text:0000000101320B5C LDR             X8, [X0,#8]
__text:0000000101320B60 LDR             X0, [X8]
__text:0000000101320B64 MOV             W1, #1                    ; tag id
__text:0000000101320B68 MOV             X2, #0
__text:0000000101320B6C B               ProtoMemberAttribute$$.ctor
__text:0000000101320B6C ; End of function sub_101320B5C

And 10 4C 2D E9 function looks as

.text:01BAD68C sub_1BAD68C
.text:01BAD68C                 STMFD           SP!, {R4,R10,R11,LR}
.text:01BAD690                 ADD             R11, SP, #8
.text:01BAD694                 LDR             R0, [R0,#4]
.text:01BAD698                 MOV             R1, #4              ; tag id
.text:01BAD69C                 MOV             R2, #0
.text:01BAD6A0                 LDR             R4, [R0]
.text:01BAD6A4                 MOV             R0, R4
.text:01BAD6A8                 BL              ProtoMemberAttribute$$.ctor
.text:01BAD6AC                 MOV             R0, R4
.text:01BAD6B0                 MOV             R1, #1
.text:01BAD6B4                 MOV             R2, #0
.text:01BAD6B8                 LDMFD           SP!, {R4,R10,R11,LR}
.text:01BAD6BC                 B               ProtoMemberAttribute$$set_IsRequired
.text:01BAD6BC ; End of function sub_1BAD68C

compared to ios arm64

__text:00000001012DC8B8 sub_1012DC8B8                           ; DATA XREF: __const:0000000102557B50↓o
__text:00000001012DC8B8                 STP             X20, X19, [SP,#-0x10+var_10]!
__text:00000001012DC8BC                 STP             X29, X30, [SP,#0x10+var_s0]
__text:00000001012DC8C0                 ADD             X29, SP, #0x10
__text:00000001012DC8C4                 LDR             X8, [X0,#8]
__text:00000001012DC8C8                 LDR             X19, [X8]
__text:00000001012DC8CC                 MOV             W1, #3               ; tag id
__text:00000001012DC8D0                 MOV             X0, X19
__text:00000001012DC8D4                 MOV             X2, #0
__text:00000001012DC8D8                 BL              ProtoMemberAttribute$$.ctor
__text:00000001012DC8DC                 MOV             W1, #1
__text:00000001012DC8E0                 MOV             X0, X19
__text:00000001012DC8E4                 MOV             X2, #0
__text:00000001012DC8E8                 LDP             X29, X30, [SP,#0x10+var_s0]
__text:00000001012DC8EC                 LDP             X20, X19, [SP+0x10+var_10],#0x20
__text:00000001012DC8F0                 B               ProtoMemberAttribute$$set_IsRequired
__text:00000001012DC8F0 ; End of function sub_1012DC8B8

Also, about that 300(0x12c) encoding problem, it's because how arm encode immediate values.
Found in this article, those 12 bits are not just straight up immediate values, but encoded with 4 bit rotation and 8 bit value.

For this 300 encoding case, which last 12 bits are 1111 0100 1011, which means 00000000 00000000 00000000 01001011 rotate to the right 0xf * 2 times, or to the left 2 times, and becomes 00000000 00000000 00000001 00101100, and that is exactly 0x12c(300).

(I actually found this article when I was searching for arm64 immediate value, but this doesn't help me as it's complete different encoding system from armv7, so I managed to found this)

And another thing, I didn't know about the map syntax in proto, that's pretty new to me, otherwise I wouldn't split dict like that. But changing it seems like would make my current code a lot messier (which is already a mess), so I decided not to bother with it :P.


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dnaroma commented Oct 11, 2018

@esterTion I'm glad to hear from you!

I didn't do much analyse of the arm code, just wondering how can I made a quick adaption. Thanks for your reply, now I know why the tag id is there and how to get them from the rotated value.

For the map syntax, it is a new syntax for proto2. It can make the decoded file somehow cleaner. Your code is amazing, don't bother to change it :-P

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