NID

Abbreviation of Numeric Identifier.

The function NID is a value that is statically assigned by a toolchain in relation to a function exported in a library so that it is unique within that library. The function name can be determined by searching for the symbol name with the same value as the function NID from the program file before the symbol information has been stripped.

In PS Vita, each library has its own NID. In PSP, libraries did not have NIDs so they were parsed by name.

Usage

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

For example, a module that needs 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 costly strncmp() of length strlen(name).
  • 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. Compute 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:

• On the HENkaku wiki, most kernel functions/variables names have an added "For..." suffix that has to be removed for NID computation.
• In the vitasdk headers, most kernel functions/variables names have an added "k" prefix that has to be removed for NID computation.
• For C++ symbols, 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.

Suffixless NIDs

Example

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 that a library does not 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
Most PSP libraries before some System Software version around 3.50
SceKblForKernel
ScePowerForDriver
SceDisplayForDriver
SceHpremoteForDriver
SceFt2
SceKernelForMono
SceKernelForVM
SceRtabi

The following PS Vita libraries are reusing some NIDs from PSP (to investigate):

SceFace
SceFios2KernelForDriver
SceIdStorageForDriver
SceLedForDriver
ScePower
SceSmart
SceVoice
SceVoiceQoS

Plaintext Suffix NIDs

Example

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
libname
?SceAvcodecUser?	?SceAvcodecUser?
SceAvcdecForPlayer	SceAvcdecForPlayer
SceAudiodecUser	SceAudiodecUser
SceAudioencUser	SceAudioencUser
SceCodecEngineUser	SceCodecEngineUser
SceJpegUser	SceJpegUser
SceJpegEncUser	SceJpegEncUser
SceLibMonoBridge	SceLibMonoBridge
SceVideodecUser	SceVideodecUser
SceVideodecAsyncUser	SceVideodecAsyncUser
SceVideodecLowDelayUser	SceVideodecLowDelayUser
SceVideodecRecoveryPointUser	SceVideodecRecoveryPointUser
SceVideoencUser	SceVideoencUser
libname + "User"
SceAtrac	SceAtracUser
SceG729	SceG729User
SceSas (in SceSasUser module)	SceSasUser
"Sce"^-1 + libname
SceWebUIPlugin	WebUIPlugin
SceAppSettings	AppSettings
SceBackupRestore	BackupRestore
SceDbRecovery	DbRecovery
SceLibLocationPermission	LibLocationPermission
"lib" + downcase(shortened(libname))
SceLibMtp	libmtp
SceIpmi	libipmi
"lib" + libname
ScePsp2Compat	libScePsp2Compat
SceWebKit	libSceWebKit
uppercase(camel_case("Sce"^-1 + libname))
All libraries in libpaf.suprx (ScePaf module)	PAF
All libraries in libpaf_web_map_view.suprx (ScePafWebMapView module)	PAF_WEB_MAP_VIEW
?modulename?
All libraries in paflib.suprx (some SCE downloadable apps like LiveTweet, Flickr)	ScePafLib
No pattern
All PS3 libraries except NONAME ones	0xbc5eba9e042504905b64274994d9c41f

Binary Suffix NIDs

Used for PS Vita NONAME exports and PS3 named exports.

Example

sha1("module_start" + psvita_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

// 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 PSP2 NONAME library NIDs derivation.
const char PSP2_NONAME_lib_nid_suffix[] = {
    0xc1, 0xb8, 0x86, 0xaf, 0x5c, 0x31, 0x84, 0x64, 0x67, 0xe7, 0xba, 0x5e, 0x2c, 0xff, 0xd6, 0x4a
};

NID Theory

Basics

Lemma: Library and function/variable NIDs depend on name.

Proof: All known algorithms use the function/variable/library name as a parameter.

Lemma: Library and function/variable NIDs can depend on other things than name.

Proof: Some known algorithms append a salt suffix to the name.

Per-library NID suffix

Theorem: Every PS Vita function/variable NID suffix is common to the whole library.

Proof: see avcodec_us.elf.

Remark: NID suffix is not per module even though module name could be the same as the suffix. For example the "User" appendix in suffix and/or in module name and/or in library name can be confusing.

Theorem: NID suffix is the same for libraries and functions/variables.

Proof:

1. For old PS Vita libraries there was no NID suffix, nor for the functions. Ex: ScePower#ScePowerForDriver.

2. All known functions/variables NID suffixes also apply to their respective library.

Theorem: At least before SDK 3.630.011, PS Vita function/variable NID is not generated from something library-related other than library name.

Proof: Some ForDriver and ForKernel libraries have different library NIDs but same function NID and same function name prefix (without ForDriver, ForKernel, etc... suffix).

Example 1: SceKernelThreadMgr#sceKernelGetMutexInfo_089

Example 2: Some functions have been moved from one library to another but the function names have not changed.

Per-library function naming convention

Theorem: When a PS Vita library name is "SceXForY" then the functions names are usually "sceXForYCommand".

Proof: see SceAvcdecForPlayer#sceAvcdecForPlayerDecodeStop function inside SceAvcdecForPlayer#SceAvcdecForPlayer library.

Algorithm for unknown official names

Conjecture: It is possible that for some libraries, SCE switched from sha1 to sha256 algorithm at some point on PS Vita because everywhere PS3 used sha1, PS Vita and PS4 used instead sha256. It would mean that when bruteforcing the suffix of a library, we are not even sure if the algorithm is still sha1(name+suffix).

Proof: We have no evidence that sha256 is used for any PS Vita NID.

Function or variable NID change

Lemma: When a PS Vita function/variable NID changes, its name has been changed or its library NID has been changed or both.

Theorem: If a PS Vita function NID changes but its library NID does not change, then the function has been renamed.

Proof: When a typo in function/variable name is fixed, the function/variable NID changes as in:

• SceLowio#sceDsiQeuryResolutionSizeForDriver that became SceLowio#sceDsiQueryResolutionSizeForDriver

SDK 3.63 library NIDs change

Lemma: SCE changed many PS Vita library NIDs since SDK 3.630.011, after SDK 3.610.011.

Proof: SceKernelModulemgr#SceModulemgrForKernel library NID changed since FW 3.63, but libname, libver and all its library information have not changed.

A non-exhaustive list of affected libraries is:

SceExcpmgrForKernel
SceSysmemForKernel
SceCpuForKernel
SceDebugForKernel
SceUartForKernel
SceThreadmgrForKernel
SceProcessmgrForKernel
SceModulemgrForKernel

Theorem: If a library NID changes without changing name, then all its functions/variables NIDs change. Moreover, it is likely that the algorithm is hash(name+lib_suffix) and that the only modification was the library suffix.

Proof: every function/variable NIDs whose library NID changed since SDK 3.630.000 while keeping library name, was also changed.

Remarks

• See article by dots-tb
• In PS Vita System Software version 0.990, SceSqliteVsh and SceSqlite modules shared the same suffix despite having nothing in common.
• In PS Vita System Software version 0.990, SceLibMtp ?module? was named libmtp. Later the library name was changed to SceLibMtp, but NID suffix remained the same.
• JSStringCreateWithUTF8CString -> SHA1 match with javascriptcore_5487D441
• javascriptcore is also known as libSceJsc.