hilda 1.2.2

LLDB wrapped and empowered by iPython's features

• Description
• Installation
• How to use

  • Starting a Hilda shell

    • Bare mode
    • Remote mode

  • Usage

  • Symbol objects

  • Globalized symbols

    • Searching for the right symbol
    • Objective-C Classes

  • Objective-C Objects

  • Using snippets

  • Contributing

Description

Hilda is a debugger which combines both the power of LLDB and iPython for easier debugging.

The name originates from the TV show "Hilda", which is the best friend of Frida. Both Frida and Hilda are meant for pretty much the same purpose, except Hilda takes the more " debugger-y" approach (based on LLDB).

Currently, the project is intended for iOS/OSX debugging, but in the future we will possibly add support for the following platforms as well:

• Linux
• Android

Since LLDB allows abstraction for both platform and architecture, it should be possible to make the necessary changes without too many modifications.

Pull requests are more than welcome 😊.

If you need help or have an amazing idea you would like to suggest, feel free to start a discussion 💬.

Installation

Requirements for remote iOS device (not required for debugging a local OSX process):

• Jailbroken iOS device
• debugserver in device's PATH
  • You can use this tool in order to obtain the binary
  • After re-signing with new entitlements, you can put the binary in the following path: /usr/bin/debugserver

In order to install please run:

xcrun python3 -m pip install --user -U hilda

⚠️ Please note that Hilda is installed on top of XCode's python so LLDB will be able to use its features.

How to use

Starting a Hilda shell

Attach mode

Use the attach sub-command in order to start an LLDB shell attached to given process.

hilda attach [-p pid] [-n process-name]

After attaching, simply execute hilda command to enter the hilda shell.

Bare mode

Use "Bare mode" to get a "bare-bones" lldb shell, whereas hilda plugin is already loaded and ready to start. This mode is useful when you need to have custom commands for attaching to the target process (for example when debugging OSX processes).

To start this mode simply use:

hilda bare

Please refer to the following help page if you require help on the command available to you within the lldb shell:

lldb command map.

As a cheatsheet, connecting to a remote platform like so:

platform connect connect://ip:port

... and attaching to a local process:

process attach -n proccess_name
process attach -p proccess_pid

When you are ready, just execute hilda to move to Hilda's iPython shell.

Remote mode

This mode will auto-connect to the remote device and attach to your target process assuming you are trying to debug a remote jailbroken iOS device.

Please note the following:

• script assumes the connected device already has a running ssh server, which doesn't require a password (you can use ssh-copy-id to achieve this).

From this point the flow diverges into 2 flows:

The connected device is connected via network

Run the following command:

hilda remote HOSTNAME PORT

Usage

Upon starting Hilda shell, you are greeted with:

Hilda has been successfully loaded! 😎
Use the p global to access all features.
Have a nice flight ✈️! Starting an IPython shell...

Here is a gist of methods you can access from p:

• hd
  • Print an hexdump of given buffer
• lsof
  • Get dictionary of all open FDs
• bt
  • Print an improved backtrace.
• disable_jetsam_memory_checks
  • Disable jetsam memory checks, prevent raising: error: Execution was interrupted, reason: EXC_RESOURCE RESOURCE_TYPE_MEMORY (limit=15 MB, unused=0x0). when evaluating expression.
• symbol
  • Get symbol object for a given address
• objc_symbol
  • Get objc symbol wrapper for given address
• inject
  • Inject a single library into currently running process
• rebind_symbols
  • Reparse all loaded images symbols
• poke
  • Write data at given address
• peek
  • Read data at given address
• peek_str
  • Peek a buffer till null termination
• stop
  • Stop process.
• cont
  • Continue process.
• detach
  • Detach from process. Useful in order to exit gracefully so process doesn't get killed while you exit
• disass
  • Print disassembly from a given address
• file_symbol
  • Calculate symbol address without ASLR
• get_register
  • Get value for register by its name
• set_register
  • Set value for register by its name
• objc_call
  • Simulate a call to an objc selector
• call
  • Call function at given address with given parameters
• monitor
  • Monitor every time a given address is called The following options are available:

    regs={reg1: format}
    will print register values
    
             Available formats:
                 x: hex
                 s: string
                 cf: use CFCopyDescription() to get more informative description of the object
                 po: use LLDB po command
                 User defined function, will be called like `format_function(hilda_client, value)`.
    
             For example:
                 regs={'x0': 'x'} -> x0 will be printed in HEX format
         expr={lldb_expression: format}
             lldb_expression can be for example '$x0' or '$arg1'
             format behaves just like 'regs' option
         retval=format
             Print function's return value. The format is the same as regs format.
         stop=True
             force a stop at every hit
         bt=True
             print backtrace
         cmd=[cmd1, cmd2]
             run several LLDB commands, one by another
         force_return=value
             force a return from function with the specified value
         name=some_value
             use `some_name` instead of the symbol name automatically extracted from the calling frame
         override=True
             override previous break point at same location
    

• show_current_source
  • print current source code if possible
• finish
  • Run current frame till its end.
• step_into
  • Step into current instruction.
• step_over
  • Step over current instruction.
• remove_all_hilda_breakpoints
  • Remove all breakpoints created by Hilda
• remove_hilda_breakpoint
  • Remove a single breakpoint placed by Hilda
• force_return
  • Prematurely return from a stack frame, short-circuiting exection of newer frames and optionally yielding a specified value.
• proc_info
  • Print information about currently running mapped process.
• print_proc_entitlements
  • Get the plist embedded inside the process' __LINKEDIT section.
• bp
  • Add a breakpoint
• show_hilda_breakpoints
  • Show existing breakpoints created by Hilda.
• show_commands
  • Show available commands.
• save
  • Save loaded symbols map (for loading later using the load() command)
• load
  • Load an existing symbols map (previously saved by the save() command)
• po

  • Print given object using LLDB's po command Can also run big chunks of native code:

    po('NSMutableString *s = [NSMutableString string]; [s appendString:@"abc"]; [s description]')

• globalize_symbols
  • Make all symbols in python's global scope
• jump
  • jump to given symbol
• lldb_handle_command
  • Execute an LLDB command For example: lldb_handle_command('register read')
• objc_get_class
  • Get ObjC class object
• CFSTR
  • Create CFStringRef object from given string
• ns
  • Create NSObject from given data
• from_ns
  • Create python object from NS object.
• evaluate_expression

  • Wrapper for LLDB's EvaluateExpression. Used for quick code snippets.

    Feel free to use local variables inside the expression using format string. For example: currentDevice = objc_get_class('UIDevice').currentDevice evaluate_expression(f'[[{currentDevice} systemName] hasPrefix:@"2"]')

• import_module
  • Import & reload given python module (intended mainly for external snippets)
• set_evaluation_unwind
  • Set whether LLDB will attempt to unwind the stack whenever an expression evaluation error occurs. Use unwind() to restore when an error is raised in this case.
• get_evaluation_unwind
  • Get evaluation unwind state. When this value is True, LLDB will attempt unwinding the stack on evaluation errors. Otherwise, the stack frame will remain the same on errors to help you investigate the error.
• set_evaluation_ignore_breakpoints
  • Set whether to ignore breakpoints while evaluating expressions
• get_evaluation_ignore_breakpoints
  • Get evaluation "ignore-breakpoints" state.
• unwind
  • Unwind the stack (useful when get_evaluation_unwind() == False)

UI Configuration

Hilda contains minimal UI for examining the target state. The UI is divided into views:

• Registers
• Disassembly
• Stack
• Backtrace

This UI can be displayed at any time be executing:

ui.show()

By default step_into and step_over will show this UI automatically. You may disable this behaviour by executing:

ui.active = False

Attentively, if you want to display UI after hitting a breakpoint, you can register ui.show as callback:

p.symbol(0x7ff7b97c21b0).bp(ui.show)

Try playing with the UI settings by yourself:

# Disable stack view
ui.views.stack.active = False

# View words from the stack
ui.views.stack.depth = 10

# View last 10 frames
ui.views.backtrace.depth = 10

# Disassemble 5 instructions
ui.views.disassembly.instruction_count = 5

# Change disassembly syntax to AT&T
ui.views.disassembly.flavor = 'att'

# View floating point registers
ui.views.registers.rtype = 'float'

# Change addresses print color
ui.colors.address = 'red'

# Change titles color
ui.color.title = 'green'

Symbol objects

In Hilda, almost everything is wrapped using the Symbol Object. Symbol is just a nicer way for referring to addresses encapsulated with an object allowing to deref the memory inside, or use these addresses as functions.

In order to create a symbol from a given address, please use:

s = p.symbol(0x12345678)

# the Symbol object extends `int`
True == isinstance(s, int)

# print the un-shifted file address 
# (calculating the ASLR shift for you, so you can just view it in IDA)
print(s.file_address)

# or.. if you know the file address, but don't wanna mess
# with ASLR calculations
s = p.file_symbol(0x12345678)

# peek(/read) 20 bytes of memory
print(s.peek(20))

# write into this memory
s.poke('abc')

# let LLDB print-object (it should guess the type automatically
# based on its memory layout)
print(s.po())

# or you can help LLDB with telling it its type manually
print(s.po('char *'))

# jump to `s` as a function, passing (1, "string") as its args 
s(1, "string")

# change the size of each item_size inside `s` for derefs
s.item_size = 1

# *(char *)s = 1
s[0] = 1

# *(((char *)s)+1) = 1
s[1] = 1

# symbol inherits from int, so all int operations apply
s += 4

# change s item size back to 8 to store pointers
s.item_size = 8

# *(intptr_t *)s = 1
s[0] = 1

# storing the return value of the function executed at `0x11223344`
# into `*s`
s[0] = p.symbol(0x11223344)()  # calling symbols also returns symbols 

# attempt to resolve symbol's name
print(p.symbol(0x11223344).lldb_symbol)

# monitor each time a symbol is called into console and print its backtrace (`bt` option)
# this will create a scripted breakpoint which prints your desired data and continue
s.monitor(bt=True)

# you can also:
#   bt -> view the backtrace
#   regs -> view registers upon each call in your desired format
#   retval -> view the return value upon each call in your desired format
#   cmd -> execute a list of LLDB commands on each hit
s.monitor(regs={'x0': 'x'},  # print `x0` in HEX form
          retval='po',  # use LLDB's `po` for printing the returned value
          bt=True,  # view backtrace (will also resolve ASLR addresses for you)
          cmd=['thread list'],  # show thread list 
          )

# we can also just `force_return` with a hard-coded value to practically disable 
# a specific functionality
s.monitor(force_return=0)  # cause the function to always return `0`

# as for everything, if you need help understanding each such feature, 
# simply execute the following to view its help (many such features even contain examples) 
s.monitor?

# create a scripted_breakpoint manually
def scripted_breakpoint(hilda, *args):
    # like everything in hilda, registers are also
    # just simple `Symbol` objects, so feel free to 
    # use them to your heart's content :)
    if hilda.registers.x0.peek(4) == b'\x11\x22\x33\x44':
        hilda.registers.x0 = hilda.symbols.malloc(200)
        hilda.registers.x0.poke(b'\x22' * 200)

    # just continue the process
    hilda.cont()


s.bp(scripted_breakpoint)

# Place a breakpoint at a symbol not yet loaded by it's name
p.bp('symbol_name')

# In case you need to specify a specific library it's loaded from
p.bp('symbol_name', module_name='ModuleName')

Globalized symbols

Usually you would want/need to use the symbols already mapped into the currently running process. To do so, you can access them using symbols.<symbol-name>. The symbols global object is of type SymbolsJar, which is a wrapper to dict for accessing all exported symbols. For example, the following will generate a call to the exported malloc function with 20 as its only argument:

x = p.symbols.malloc(20)

You can also just write their name as if they already were in the global scope. Hilda will check if no name collision exists, and if so, will perform the following lazily for you:

x = malloc(20)

# is equivalent to:
malloc = p.symbols.malloc
x = malloc(20)

Searching for the right symbol

Sometimes you don't really know where to start your research. All you have is just theories of how your desired exported symbol should be called (if any).

For that reason alone, we have the rebind_symbols() command - to help you find the symbol you are looking for.

p.rebind_symbols()  # this might take some time

# find all symbols prefixed as `mem*` AND don't have `cpy`
# in their name
jar = p.symbols.startswith('mem') - p.symbols.find('cpy')

# filter only symbols of type "code" (removing data global for example)
jar = jar.code()

# monitor every time each one is called, print its `x0` in HEX
# form and show the backtrace
jar.monitor(regs={'x0': 'x'}, bt=True)

Objective-C Classes

The same as symbols applies to Objective-C classes name resolution. You can either:

d = NSDictionary.new()  # call its `new` selector

# which is equivalent to:
NSDictionary = p.objc_get_class('NSDictionary')
d = NSDictionary.new()

This is possible only since NSDictionary is exported. In case it is not, you must call objc_get_class() explicitly.

As you can see, you can directly access all the class' methods.

Please look what more stuff you can do as shown below:

# show the class' ivars
print(NSDictionary.ivars)

# show the class' methods
print(NSDictionary.methods)

# show the class' proprties
print(NSDictionary.properties)

# view class' selectors which are prefixed with 'init'
print(NSDictionary.symbols_jar.startswith('-[NSDictionary init'))

# you can of course use any of `SymbolsJar` over them, for example:
# this will `po` (print object) all those selectors returned value
NSDictionary.symbols_jar.startswith('-[NSDictionary init').monitior(retval='po')

# monitor each time any selector in NSDictionary is called
NSDictionary.monitor()

# `force_return` for some specific selector with a hard-coded value (4)
NSDictionary.get_method('valueForKey:').address.monitor(force_return=4)

# capture the `self` object at the first hit of any selector
# `True` for busy-wait for object to be captured
dictionary = NSDictionary.capture_self(True)

# print a colored and formatted version for class layout
dictionary.show()

Objective-C Objects

In order to work with ObjC objects, each symbol contains a property called objc_symbol. After calling, you can work better with each object:

dict = NSDictionary.new().objc_symbol
dict.show()  # print object layout

# just like class, you can access its ivars, method, etc...
print(dict.ivars)

# except now they have values you can view
print(dict._ivarName)

# or edit
dict._ivarName = value

# and of course you can call the object's methods
# hilda will checks if the method returned an ObjC object:
#   - if so, call `objc_symbol` upon it for you
#   - otherwise, leave it as a simple `Symbol` object
arr = dict.objectForKey_('keyContainingNSArray')

# you can also call class-methods
# hilda will call it using either the instance object,
# or the class object respectively of the use
newDict = dict.dictionary()

# print the retrieved object
print(arr.po())

Also, working with Objective-C objects like this can be somewhat exhausting, so we created the ns and from_ns commands so you are able to use complicated types when parsing values and passing as arguments:

import datetime

# using the `ns` command we can just pass a python-native dictionary
function_requiring_a_specfic_dictionary(ns({
    'key1': 'string',  # will convert to NSString
    'key2': True,  # will convert to NSNumber
    'key3': b'1234',  # will convert to NSData
    'key4': datetime.datetime(2021, 1, 1)  # will convert to NSDate
}))

# and also parse one
normal_python_dict = p.cf({
    'key1': 'string',  # will convert to NSString
    'key2': True,  # will convert to NSNumber
    'key3': b'1234',  # will convert to NSData
    'key4': datetime.datetime(2021, 1, 1)  # will convert to NSDate
}).py()

On last resort, if the object is not serializable for this to work, you can just run pure Objective-C code:

# let LLDB compile and execute the expression
abc_string = p.evaluate_expression('[NSString stringWithFormat:@"abc"]')

# will print "abc"
print(abc_string.po())

Using snippets

Snippets are extensions for normal functionality used as quick cookbooks for day-to-day tasks of a debugger.

They all use the following concept to use:

from hilda.snippets import snippet_name

snippet_name.do_domething()  

For example, XPC sniffing can be done using:

from hilda.snippets import xpc

xpc.sniff_all()

This will monitor all XPC related traffic in the given process.

Contributing

Please run the tests as follows before submitting a PR:

xcrun python3 -m tests aggregated

# wait for lldb shell prompt

run_tests