Types
Radare2 supports the C-syntax data types description.
Those types are parsed by a C11-compatible parser and stored in
the internal SDB, thus are introspectable with k command.
Most of the related commands are located in t namespace:
[0x00000000]> t?
| Usage: t # cparse types commands
| t List all loaded types
| tj List all loaded types as json
| t <type> Show type in 'pf' syntax
| t* List types info in r2 commands
| t- <name> Delete types by its name
| t-* Remove all types
| tail [filename] Output the last part of files
| tc [type.name] List all/given types in C output format
| te[?] List all loaded enums
| td[?] <string> Load types from string
| tf List all loaded functions signatures
| tk <sdb-query> Perform sdb query
| tl[?] Show/Link type to an address
| tn[?] [-][addr] manage noreturn function attributes and marks
| to - Open cfg.editor to load types
| to <path> Load types from C header file
| toe [type.name] Open cfg.editor to edit types
| tos <path> Load types from parsed Sdb database
| tp <type> [addr|varname] cast data at <address> to <type> and print it (XXX: type can contain spaces)
| tpv <type> @ [value] Show offset formatted for given type
| tpx <type> <hexpairs> Show value for type with specified byte sequence (XXX: type can contain spaces)
| ts[?] Print loaded struct types
| tu[?] Print loaded union types
| tx[f?] Type xrefs
| tt[?] List all loaded typedefs
Note that the basic (atomic) types are not those from C standard -
not char, _Bool, or short. Because those types can be different
from one platform to another, radare2 uses definite types like as
int8_t or uint64_t and will convert int to int32_t or int64_t
depending on the binary or debuggee platform/compiler.
Basic types can be listed using t command. For the structured types
you need to use ts, for unions use tu and for enums — te.
[0x00000000]> t
char
char *
double
float
gid_t
int
int16_t
int32_t
int64_t
int8_t
long
long long
pid_t
short
size_t
uid_t
uint16_t
uint32_t
uint64_t
uint8_t
unsigned char
unsigned int
unsigned short
void *
Loading types
There are three easy ways to define a new type:
- Directly from the string using
tdcommand - From the file using
to <filename>command - Open an
$EDITORto type the definitions in place usingto -
[0x00000000]> "td struct foo {char* a; int b;}"
[0x00000000]> cat ~/radare2-regressions/bins/headers/s3.h
struct S1 {
int x[3];
int y[4];
int z;
};
[0x00000000]> to ~/radare2-regressions/bins/headers/s3.h
[0x00000000]> ts
foo
S1
Also note there is a config option to specify include directories for types parsing
[0x00000000]> e? dir.types
dir.types: Default path to look for cparse type files
[0x00000000]> e dir.types
/usr/include
Printing types
Notice below we have used ts command, which basically converts
the C type description (or to be precise it's SDB representation)
into the sequence of pf commands. See more about print format.
The tp command uses the pf string to print all the members of type at the current offset/given address:
[0x00000000]> "td struct foo {char* a; int b;}"
[0x00000000]> wx 68656c6c6f000c000000
[0x00000000]> wz world @ 0x00000010 ; wx 17 @ 0x00000016
[0x00000000]> px
[0x00000000]> ts foo
pf zd a b
[0x00000000]> tp foo
a : 0x00000000 = "hello"
b : 0x00000006 = 12
[0x00000000]> tp foo @ 0x00000010
a : 0x00000010 = "world"
b : 0x00000016 = 23
Also, you could fill your own data into the struct and print it using tpx command
[0x00000000]> tpx foo 414243440010000000
a : 0x00000000 = "ABCD"
b : 0x00000005 = 16
Linking Types
The tp command just performs a temporary cast. But if we want to link some address or variable
with the chosen type, we can use tl command to store the relationship in SDB.
[0x000051c0]> tl S1 = 0x51cf
[0x000051c0]> tll
(S1)
x : 0x000051cf = [ 2315619660, 1207959810, 34803085 ]
y : 0x000051db = [ 2370306049, 4293315645, 3860201471, 4093649307 ]
z : 0x000051eb = 4464399
Moreover, the link will be shown in the disassembly output or visual mode:
[0x000051c0 15% 300 /bin/ls]> pd $r @ entry0
;-- entry0:
0x000051c0 xor ebp, ebp
0x000051c2 mov r9, rdx
0x000051c5 pop rsi
0x000051c6 mov rdx, rsp
0x000051c9 and rsp, 0xfffffffffffffff0
0x000051cd push rax
0x000051ce push rsp
(S1)
x : 0x000051cf = [ 2315619660, 1207959810, 34803085 ]
y : 0x000051db = [ 2370306049, 4293315645, 3860201471, 4093649307 ]
z : 0x000051eb = 4464399
0x000051f0 lea rdi, loc._edata ; 0x21f248
0x000051f7 push rbp
0x000051f8 lea rax, loc._edata ; 0x21f248
0x000051ff cmp rax, rdi
0x00005202 mov rbp, rsp
Once the struct is linked, radare2 tries to propagate structure offset in the function at current offset, to run this analysis on whole program or at any targeted functions after all structs are linked you have aat command:
[0x00000000]> aa?
| aat [fcn] Analyze all/given function to convert immediate to linked structure offsets (see tl?)
Note sometimes the emulation may not be accurate, for example as below :
|0x000006da push rbp
|0x000006db mov rbp, rsp
|0x000006de sub rsp, 0x10
|0x000006e2 mov edi, 0x20 ; "@"
|0x000006e7 call sym.imp.malloc ; void *malloc(size_t size)
|0x000006ec mov qword [local_8h], rax
|0x000006f0 mov rax, qword [local_8h]
The return value of malloc may differ between two emulations, so you have to set the hint for return value manually using ahr command, so run tl or aat command after setting up the return value hint.
[0x000006da]> ah?
| ahr val set hint for return value of a function
Structure Immediates
There is one more important aspect of using types in radare2 - using aht you
can change the immediate in the opcode to the structure offset.
Lets see a simple example of [R]SI-relative addressing
[0x000052f0]> pd 1
0x000052f0 mov rax, qword [rsi + 8] ; [0x8:8]=0
Here 8 - is some offset in the memory, where rsi probably holds
some structure pointer. Imagine that we have the following structures
[0x000052f0]> "td struct ms { char b[8]; int member1; int member2; };"
[0x000052f0]> "td struct ms1 { uint64_t a; int member1; };"
[0x000052f0]> "td struct ms2 { uint16_t a; int64_t b; int member1; };"
Now we need to set the proper structure member offset instead of 8 in this instruction.
At first, we need to list available types matching this offset:
[0x000052f0]> ahts 8
ms.member1
ms1.member1
Note, that ms2 is not listed, because it has no members with offset 8.
After listing available options we can link it to the chosen offset at
the current address:
[0x000052f0]> aht ms1.member1
[0x000052f0]> pd 1
0x000052f0 488b4608 mov rax, qword [rsi + ms1.member1] ; [0x8:8]=0
Managing enums
- Printing all fields in enum using
tecommand
[0x00000000]> "td enum Foo {COW=1,BAR=2};"
[0x00000000]> te Foo
COW = 0x1
BAR = 0x2
- Finding matching enum member for given bitfield and vice-versa
[0x00000000]> te Foo 0x1
COW
[0x00000000]> teb Foo COW
0x1
Internal representation
To see the internal representation of the types you can use tk command:
[0x000051c0]> tk~S1
S1=struct
struct.S1=x,y,z
struct.S1.x=int32_t,0,3
struct.S1.x.meta=4
struct.S1.y=int32_t,12,4
struct.S1.y.meta=4
struct.S1.z=int32_t,28,0
struct.S1.z.meta=0
[0x000051c0]>
Defining primitive types requires an understanding of basic pf formats,
you can find the whole list of format specifier in pf??:
-----------------------------------------------------
| format | explanation |
|---------------------------------------------------|
| b | byte (unsigned) |
| c | char (signed byte) |
| d | 0x%%08x hexadecimal value (4 bytes) |
| f | float value (4 bytes) |
| i | %%i integer value (4 bytes) |
| o | 0x%%08o octal value (4 byte) |
| p | pointer reference (2, 4 or 8 bytes) |
| q | quadword (8 bytes) |
| s | 32bit pointer to string (4 bytes) |
| S | 64bit pointer to string (8 bytes) |
| t | UNIX timestamp (4 bytes) |
| T | show Ten first bytes of buffer |
| u | uleb128 (variable length) |
| w | word (2 bytes unsigned short in hex) |
| x | 0x%%08x hex value and flag (fd @ addr) |
| X | show formatted hexpairs |
| z | \0 terminated string |
| Z | \0 terminated wide string |
-----------------------------------------------------
there are basically 3 mandatory keys for defining basic data types:
X=type
type.X=format_specifier
type.X.size=size_in_bits
For example, let's define UNIT, according to Microsoft documentation
UINT is just equivalent of standard C unsigned int (or uint32_t in terms of TCC engine).
It will be defined as:
UINT=type
type.UINT=d
type.UINT.size=32
Now there is an optional entry:
X.type.pointto=Y
This one may only be used in case of pointer type.X=p, one good example is LPFILETIME definition,
it is a pointer to _FILETIME which happens to be a structure.
Assuming that we are targeting only 32-bit windows machine, it will be defined as the following:
LPFILETIME=type
type.LPFILETIME=p
type.LPFILETIME.size=32
type.LPFILETIME.pointto=_FILETIME
This last field is not mandatory because sometimes the data structure internals will be proprietary, and we will not have a clean representation for it.
There is also one more optional entry:
type.UINT.meta=4
This entry is for integration with C parser and carries the type class information: integer size, signed/unsigned, etc.
Structures
Those are the basic keys for structs (with just two elements):
X=struct
struct.X=a,b
struct.X.a=a_type,a_offset,a_number_of_elements
struct.X.b=b_type,b_offset,b_number_of_elements
The first line is used to define a structure called X, the second line
defines the elements of X as comma separated values. After that, we just define each element info.
For example. we can have a struct like this one:
struct _FILETIME {
DWORD dwLowDateTime;
DWORD dwHighDateTime;
}
assuming we have DWORD defined, the struct will look like this
_FILETIME=struct
struct._FILETIME=dwLowDateTime,dwHighDateTime
struct._FILETIME.dwLowDateTime=DWORD,0,0
struct._FILETIME.dwHighDateTime=DWORD,4,0
Note that the number of elements field is used in case of arrays only to identify how many elements are in arrays, other than that it is zero by default.
Unions
Unions are defined exactly like structs the only difference is that you will replace the word struct with the word union.
Function prototypes
Function prototypes representation is the most detail oriented and the most important one of them all. Actually, this is the one used directly for type matching
X=func
func.X.args=NumberOfArgs
func.x.arg0=Arg_type,arg_name
.
.
.
func.X.ret=Return_type
func.X.cc=calling_convention
It should be self-explanatory. Let's do strncasecmp as an example for x86 arch for Linux machines. According to man pages, strncasecmp is defined as the following:
int strcasecmp(const char *s1, const char *s2, size_t n);
When converting it into its sdb representation it will look like the following:
strcasecmp=func
func.strcasecmp.args=3
func.strcasecmp.arg0=char *,s1
func.strcasecmp.arg1=char *,s2
func.strcasecmp.arg2=size_t,n
func.strcasecmp.ret=int
func.strcasecmp.cc=cdecl
Note that the .cc part is optional and if it didn't exist the default calling-convention for your target architecture will be used instead.
There is one extra optional key
func.x.noreturn=true/false
This key is used to mark functions that will not return once called, such as exit and _exit.