NID

Abbreviation of Numeric Identifier.

Usage

Dynamic linking of modules (by SceKernelModulemgr) is performed based on NIDs of functions/variables instead of names.

For example, a module that wants to import sceDisplayGetFrameBuf will indicate that it needs SceDisplayForDriver:0xEEDA2E54 in its libstub structures.

This solution provides multiple benefits:

• Names of functions and variables are not included in modules - this reveals much less information to attackers
• Lookup inside a NID table is faster
  • Equality testing is a simple 32-bit comparison instead of a costy strncmp().
  • A dichotomic search can be performed in O(log2(n)) if NID tables are sorted.
    • While NID tables appear to be sorted, this optimization is seemingly not used by SCE.

Calculation

By default, NIDs are derived from a symbol's name using the following algorithm:

1. Calculate the SHA-1 hash of the (optionally salted) name: hash = sha1(name + suffix) = ZZ YY XX WW VV UU TT SS RR QQ PP OO NN MM LL KK JJ II HH GG
   • suffix acts as salt and may be a string or raw binary data
   • name + suffix corresponds to concatenation in this context
     • For example, name="sceFunc" and suffix="MySuffix" results in hash = sha1("sceFuncMySuffix")
2. Truncate the result to 32 bits: tr = truncate32(hash) = 0xZZYYXXWW
3. Reverse endianness of the truncated result: NID = swap32(tr) = 0xWWXXYYZZ

Notes:

• For C++, derivation is performed using the symbol's mangled name.
• libname_nid is derived using the same suffix as the rest of the library.
  • Since library names are always known, this makes it (in theory) possible to bruteforce the suffix used for NID derivation of any library.
• The NID of functions and variables can be set to arbitrary values.
  • It is possible to encounter NIDs that do not match the "expected" NID found by deriving using this algorithm.
• The following online tool can be used for NID calculations.

Example 1: suffixless

sceDisplayGetFrameBuf

sha1("sceDisplayGetFrameBuf") = 54 2E DA EE DA 61 8E 3F 07 9A C7 46 92 24 6D F1 2A A8 F7 C7

Truncate to 32 bits: 0x542EDAEE
Reverse endianness: 0xEEDA2E54

The NID of sceDisplayGetFrameBuf is 0xEEDA2E54.

Known suffixless libraries

Verifying is a library doesn't use a suffix for NID derivation is trivial: derive a NID based on the library name and check if it matches the libname_nid field of the libent structure of that library.

List of known suffixless libraries
SceDisplayForDriver
SceFt2
SceKernelForMono
SceKernelForVM
SceRtabi

Example 2: plaintext suffix

The SceIpmi library uses libipmi as suffix.

//N.B. "SceIpmilibipmi" is "SceIpmi" + "libipmi
sha1("SceIpmilibipmi") = DB 4E E3 F4 E9 A8 6C 3F 79 4B 5A 28 CF 26 07 36 14 42 70 B0

Truncate to 32 bits: 0xDB4EE3F4
Reverse endianness: 0xF4E34EDB

NID of the SceIpmi library is 0xF4E34EDB.

For C++ exports, the NID is derived from the mangled name.

//IPMI::Client::Config::estimateClientMemorySize() =mangling=> _ZN4IPMI6Client6Config24estimateClientMemorySizeEv
sha1("_ZN4IPMI6Client6Config24estimateClientMemorySizeEvlibipmi") = 31 5C 25 4E FE AE B4 34 CA B5 9F 43 03 3D 62 BC 11 6F FC AB

Truncate to 32 bits: 0x315C254E
Reverse endianness: 0x4E255C31

The NID of IPMI::Client::Config::estimateClientMemorySize() is 0x4E255C31.

Known plaintext suffixes

Plaintext suffixes follow patterns across some modules.

List of libraries with a known plaintext suffix
Library name	Suffix
Library name
SceAvcdecForPlayer	SceAvcdecForPlayer
SceAudiodecUser	SceAudiodecUser
SceAudioencUser	SceAudioencUser
SceCodecEngineUser	SceCodecEngineUser
SceJpegUser	SceJpegUser
SceJpegEncUser	SceJpegEncUser
SceLibMonoBridge	SceLibMonoBridge
SceVideodecUser	SceVideodecUser
SceVideodecAsyncUser	SceVideodecAsyncUser
SceVideodecLowDelayUser	SceVideodecLowDelayUser
SceVideodecRecoveryPointUser	SceVideodecRecoveryPointUser
SceVideoencUser	SceVideoencUser
Library name + User
SceAtrac	SceAtracUser
SceG729	SceG729User
Library name without Sce
SceWebUIPlugin	WebUIPlugin
SceAppSettings	AppSettings
SceBackupRestore	BackupRestore
SceDbRecovery	DbRecovery
SceLibLocationPermission	LibLocationPermission
libXXX
SceLibMtp	libmtp
SceIpmi	libipmi
lib + Library name
ScePsp2Compat	libScePsp2Compat
SceWebKit	libSceWebKit
Others
All libraries in libpaf.suprx	PAF

Example 3: binary suffix

Used for NONAME exports.

sha1("module_start" + vita_NONAME_lib_nid_suffix) = 96 D1 5C 93 65 10 32 1C 7D 60 7B 4D FC 06 BC 73 06 3E 25 61

Truncate to 32 bits: 0x96D15C93
Reverse endianness: 0x935CD196

The NID of module_start is 0x935CD196.

Known binary suffixes

The following suffixes are used by SCE for NID derivation:

//Default suffix for all PS3 NIDs derivations, except NONAME library.
const char PS3_default_nid_suffix[] = {
    0x67, 0x59, 0x65, 0x99, 0x04, 0x25, 0x04, 0x90, 0x56, 0x64, 0x27, 0x49, 0x94, 0x89, 0x74, 0x1a
};

//Suffix for PS3 NONAME library NIDs derivation.
const char PS3_NONAME_lib_nid_suffix[] = {
    0xbc, 0x5e, 0xba, 0x9e, 0x04, 0x25, 0x04, 0x90, 0x5b, 0x64, 0x27, 0x49, 0x94, 0xd9, 0xc4, 0x1f
};

//Suffix for Vita NONAME library NIDs derivation.
const char vita_NONAME_lib_nid_suffix[] = {
    0xc1, 0xb8, 0x86, 0xaf, 0x5c, 0x31, 0x84, 0x64, 0x67, 0xe7, 0xba, 0x5e, 0x2c, 0xff, 0xd6, 0x4a
};