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Implement llvm.x86.aesni.* intrinsics
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@eduardosm
eduardosm committed Oct 2, 2023
1 parent 7555cbb commit 18baa9a
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384 changes: 384 additions & 0 deletions src/shims/x86/aesni.rs
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use rustc_middle::ty::layout::LayoutOf as _;
use rustc_middle::ty::Ty;
use rustc_span::Symbol;
use rustc_target::spec::abi::Abi;

use crate::*;
use shims::foreign_items::EmulateByNameResult;

impl<'mir, 'tcx: 'mir> EvalContextExt<'mir, 'tcx> for crate::MiriInterpCx<'mir, 'tcx> {}
pub(super) trait EvalContextExt<'mir, 'tcx: 'mir>:
crate::MiriInterpCxExt<'mir, 'tcx>
{
fn emulate_x86_aesni_intrinsic(
&mut self,
link_name: Symbol,
abi: Abi,
args: &[OpTy<'tcx, Provenance>],
dest: &PlaceTy<'tcx, Provenance>,
) -> InterpResult<'tcx, EmulateByNameResult<'mir, 'tcx>> {
let this = self.eval_context_mut();
// Prefix should have already been checked.
let unprefixed_name = link_name.as_str().strip_prefix("llvm.x86.aesni.").unwrap();

match unprefixed_name {
// Used to implement the _mm_aesdec_si128, _mm256_aesdec_epi128
// and _mm512_aesdec_epi128 functions.
// Performs one round of an AES decryption on each 128-bit word of
// `state` with the corresponding 128-bit key of `key`.
"aesdec" | "aesdec.256" | "aesdec.512" => {
let [state, key] =
this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;

aes_round(this, state, key, dest, |state, key| {
// As described in
// https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_mm_aesdec_si128
let state = state.to_le_bytes();
let state = inv_shift_rows(state);
let state = inv_sub_bytes(state);
let state = inv_mix_columns(state);
let state = u128::from_le_bytes(state);
state ^ key
})?;
}
// Used to implement the _mm_aesdeclast_si128, _mm256_aesdeclast_epi128
// and _mm512_aesdeclast_epi128 functions.
// Performs last round of an AES decryption on each 128-bit word of
// `state` with the corresponding 128-bit key of `key`.
"aesdeclast" | "aesdeclast.256" | "aesdeclast.512" => {
let [state, key] =
this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;

aes_round(this, state, key, dest, |state, key| {
// As described in
// https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_mm_aesdeclast_si128
let state = state.to_le_bytes();
let state = inv_shift_rows(state);
let state = inv_sub_bytes(state);
let state = u128::from_le_bytes(state);
state ^ key
})?;
}
// Used to implement the _mm_aesenc_si128, _mm256_aesenc_epi128
// and _mm512_aesenc_epi128 functions.
// Performs one round of an AES encryption on each 128-bit word of
// `state` with the corresponding 128-bit key of `key`.
"aesenc" | "aesenc.256" | "aesenc.512" => {
let [state, key] =
this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;

aes_round(this, state, key, dest, |state, key| {
// As described in
// https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_mm_aesenc_si128
let state = state.to_le_bytes();
let state = shift_rows(state);
let state = sub_bytes(state);
let state = mix_columns(state);
let state = u128::from_le_bytes(state);
state ^ key
})?;
}
// Used to implement the _mm_aesenclast_si128, _mm256_aesenclast_epi128
// and _mm512_aesenclast_epi128 functions.
// Performs last round of an AES encryption on each 128-bit word of
// `state` with the corresponding 128-bit key of `key`.
"aesenclast" | "aesenclast.256" | "aesenclast.512" => {
let [state, key] =
this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;

aes_round(this, state, key, dest, |state, key| {
// As described in
// https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_mm_aesenclast_si128
let state = state.to_le_bytes();
let state = shift_rows(state);
let state = sub_bytes(state);
let state = u128::from_le_bytes(state);
state ^ key
})?;
}
// Used to implement the _mm_aesimc_si128 function.
// Performs the AES InvMixColumns operation on `op`
"aesimc" => {
let [op] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;

// Transmute to `u128`
let op = op.transmute(this.machine.layouts.u128, this)?;
let dest = dest.transmute(this.machine.layouts.u128, this)?;

let op = this.read_scalar(&op)?.to_u128()?;
let res = u128::from_le_bytes(inv_mix_columns(op.to_le_bytes()));

this.write_scalar(Scalar::from_u128(res), &dest)?;
}
// Used to implement the _mm_aeskeygenassist_si128 function.
// Assist in expanding the AES cipher key by computing steps
// towards generating a round key for encryption cipher using
// data from `op` and an 8-bit round constant `imm`.
"aeskeygenassist" => {
let [op, imm] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;

// Transmute to `[u32; 4]`
let u32x4_layout =
this.layout_of(Ty::new_array(this.tcx.tcx, this.tcx.types.u32, 4))?;
let op = op.transmute(u32x4_layout, this)?;
let dest = dest.transmute(u32x4_layout, this)?;

// As described in
// https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_mm_aeskeygenassist_si128
// First and third elements are unused
let x1 = this.read_scalar(&this.project_index(&op, 1)?)?.to_u32()?;
let x3 = this.read_scalar(&this.project_index(&op, 3)?)?.to_u32()?;
let imm = this.read_scalar(imm)?.to_u8()?;

let rcon = u32::from(imm);
let res0 = sub_word(x1);
let res1 = rot_word(sub_word(x1)) ^ rcon;
let res2 = sub_word(x3);
let res3 = rot_word(sub_word(x3)) ^ rcon;

this.write_scalar(Scalar::from_u32(res0), &this.project_index(&dest, 0)?)?;
this.write_scalar(Scalar::from_u32(res1), &this.project_index(&dest, 1)?)?;
this.write_scalar(Scalar::from_u32(res2), &this.project_index(&dest, 2)?)?;
this.write_scalar(Scalar::from_u32(res3), &this.project_index(&dest, 3)?)?;
}
_ => return Ok(EmulateByNameResult::NotSupported),
}
Ok(EmulateByNameResult::NeedsJumping)
}
}

// Performs an AES round (given by `f`) on each 128-bit word of
// `state` with the corresponding 128-bit key of `key`.
fn aes_round<'tcx>(
this: &mut crate::MiriInterpCx<'_, 'tcx>,
state: &OpTy<'tcx, Provenance>,
key: &OpTy<'tcx, Provenance>,
dest: &PlaceTy<'tcx, Provenance>,
f: impl Fn(u128, u128) -> u128,
) -> InterpResult<'tcx, ()> {
assert_eq!(dest.layout.size, state.layout.size);
assert_eq!(dest.layout.size, key.layout.size);

// Transmute arguments to arrays of `u128`.
assert_eq!(dest.layout.size.bytes() % 16, 0);
let len = dest.layout.size.bytes() / 16;

let u128_array_layout =
this.layout_of(Ty::new_array(this.tcx.tcx, this.tcx.types.u128, len))?;

let state = state.transmute(u128_array_layout, this)?;
let key = key.transmute(u128_array_layout, this)?;
let dest = dest.transmute(u128_array_layout, this)?;

for i in 0..len {
let state = this.read_scalar(&this.project_index(&state, i)?)?.to_u128()?;
let key = this.read_scalar(&this.project_index(&key, i)?)?.to_u128()?;
let dest = this.project_index(&dest, i)?;

let res = f(state, key);

this.write_scalar(Scalar::from_u128(res), &dest)?;
}

Ok(())
}

// AES cypher primitives. They are not optimized in any way, they are
// a direct implementation based on the descriptions from "FIPS 197, Advanced
// Encryption Standard (AES)".
// https://csrc.nist.gov/files/pubs/fips/197/final/docs/fips-197.pdf

// Primitives operate on 4x4 matrices represented with a 16-element array
// in column-major order.

/// ShiftRows - cyclically shifts the last three rows
#[rustfmt::skip]
fn shift_rows(s: [u8; 16]) -> [u8; 16] {
[
s[0], s[5], s[10], s[15],
s[4], s[9], s[14], s[3],
s[8], s[13], s[2], s[7],
s[12], s[1], s[6], s[11],
]
}

/// InvShiftRows - cyclically inverse shifts the last three rows
#[rustfmt::skip]
fn inv_shift_rows(s: [u8; 16]) -> [u8; 16] {
[
s[0], s[13], s[10], s[7],
s[4], s[1], s[14], s[11],
s[8], s[5], s[2], s[15],
s[12], s[9], s[6], s[3],
]
}

#[rustfmt::skip]
const SBOX: [u8; 256] = [
0x63, 0x7C, 0x77, 0x7B, 0xF2, 0x6B, 0x6F, 0xC5, 0x30, 0x01, 0x67, 0x2B, 0xFE, 0xD7, 0xAB, 0x76,
0xCA, 0x82, 0xC9, 0x7D, 0xFA, 0x59, 0x47, 0xF0, 0xAD, 0xD4, 0xA2, 0xAF, 0x9C, 0xA4, 0x72, 0xC0,
0xB7, 0xFD, 0x93, 0x26, 0x36, 0x3F, 0xF7, 0xCC, 0x34, 0xA5, 0xE5, 0xF1, 0x71, 0xD8, 0x31, 0x15,
0x04, 0xC7, 0x23, 0xC3, 0x18, 0x96, 0x05, 0x9A, 0x07, 0x12, 0x80, 0xE2, 0xEB, 0x27, 0xB2, 0x75,
0x09, 0x83, 0x2C, 0x1A, 0x1B, 0x6E, 0x5A, 0xA0, 0x52, 0x3B, 0xD6, 0xB3, 0x29, 0xE3, 0x2F, 0x84,
0x53, 0xD1, 0x00, 0xED, 0x20, 0xFC, 0xB1, 0x5B, 0x6A, 0xCB, 0xBE, 0x39, 0x4A, 0x4C, 0x58, 0xCF,
0xD0, 0xEF, 0xAA, 0xFB, 0x43, 0x4D, 0x33, 0x85, 0x45, 0xF9, 0x02, 0x7F, 0x50, 0x3C, 0x9F, 0xA8,
0x51, 0xA3, 0x40, 0x8F, 0x92, 0x9D, 0x38, 0xF5, 0xBC, 0xB6, 0xDA, 0x21, 0x10, 0xFF, 0xF3, 0xD2,
0xCD, 0x0C, 0x13, 0xEC, 0x5F, 0x97, 0x44, 0x17, 0xC4, 0xA7, 0x7E, 0x3D, 0x64, 0x5D, 0x19, 0x73,
0x60, 0x81, 0x4F, 0xDC, 0x22, 0x2A, 0x90, 0x88, 0x46, 0xEE, 0xB8, 0x14, 0xDE, 0x5E, 0x0B, 0xDB,
0xE0, 0x32, 0x3A, 0x0A, 0x49, 0x06, 0x24, 0x5C, 0xC2, 0xD3, 0xAC, 0x62, 0x91, 0x95, 0xE4, 0x79,
0xE7, 0xC8, 0x37, 0x6D, 0x8D, 0xD5, 0x4E, 0xA9, 0x6C, 0x56, 0xF4, 0xEA, 0x65, 0x7A, 0xAE, 0x08,
0xBA, 0x78, 0x25, 0x2E, 0x1C, 0xA6, 0xB4, 0xC6, 0xE8, 0xDD, 0x74, 0x1F, 0x4B, 0xBD, 0x8B, 0x8A,
0x70, 0x3E, 0xB5, 0x66, 0x48, 0x03, 0xF6, 0x0E, 0x61, 0x35, 0x57, 0xB9, 0x86, 0xC1, 0x1D, 0x9E,
0xE1, 0xF8, 0x98, 0x11, 0x69, 0xD9, 0x8E, 0x94, 0x9B, 0x1E, 0x87, 0xE9, 0xCE, 0x55, 0x28, 0xDF,
0x8C, 0xA1, 0x89, 0x0D, 0xBF, 0xE6, 0x42, 0x68, 0x41, 0x99, 0x2D, 0x0F, 0xB0, 0x54, 0xBB, 0x16,
];

/// SubBytes - S-box transformation
fn sub_bytes(s: [u8; 16]) -> [u8; 16] {
s.map(|byte| SBOX[usize::from(byte)])
}

/// InvSubBytes - inverse S-box transformation
fn inv_sub_bytes(s: [u8; 16]) -> [u8; 16] {
#[rustfmt::skip]
const INV_SBOX: [u8; 256] = [
0x52, 0x09, 0x6A, 0xD5, 0x30, 0x36, 0xA5, 0x38, 0xBF, 0x40, 0xA3, 0x9E, 0x81, 0xF3, 0xD7, 0xFB,
0x7C, 0xE3, 0x39, 0x82, 0x9B, 0x2F, 0xFF, 0x87, 0x34, 0x8E, 0x43, 0x44, 0xC4, 0xDE, 0xE9, 0xCB,
0x54, 0x7B, 0x94, 0x32, 0xA6, 0xC2, 0x23, 0x3D, 0xEE, 0x4C, 0x95, 0x0B, 0x42, 0xFA, 0xC3, 0x4E,
0x08, 0x2E, 0xA1, 0x66, 0x28, 0xD9, 0x24, 0xB2, 0x76, 0x5B, 0xA2, 0x49, 0x6D, 0x8B, 0xD1, 0x25,
0x72, 0xF8, 0xF6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xD4, 0xA4, 0x5C, 0xCC, 0x5D, 0x65, 0xB6, 0x92,
0x6C, 0x70, 0x48, 0x50, 0xFD, 0xED, 0xB9, 0xDA, 0x5E, 0x15, 0x46, 0x57, 0xA7, 0x8D, 0x9D, 0x84,
0x90, 0xD8, 0xAB, 0x00, 0x8C, 0xBC, 0xD3, 0x0A, 0xF7, 0xE4, 0x58, 0x05, 0xB8, 0xB3, 0x45, 0x06,
0xD0, 0x2C, 0x1E, 0x8F, 0xCA, 0x3F, 0x0F, 0x02, 0xC1, 0xAF, 0xBD, 0x03, 0x01, 0x13, 0x8A, 0x6B,
0x3A, 0x91, 0x11, 0x41, 0x4F, 0x67, 0xDC, 0xEA, 0x97, 0xF2, 0xCF, 0xCE, 0xF0, 0xB4, 0xE6, 0x73,
0x96, 0xAC, 0x74, 0x22, 0xE7, 0xAD, 0x35, 0x85, 0xE2, 0xF9, 0x37, 0xE8, 0x1C, 0x75, 0xDF, 0x6E,
0x47, 0xF1, 0x1A, 0x71, 0x1D, 0x29, 0xC5, 0x89, 0x6F, 0xB7, 0x62, 0x0E, 0xAA, 0x18, 0xBE, 0x1B,
0xFC, 0x56, 0x3E, 0x4B, 0xC6, 0xD2, 0x79, 0x20, 0x9A, 0xDB, 0xC0, 0xFE, 0x78, 0xCD, 0x5A, 0xF4,
0x1F, 0xDD, 0xA8, 0x33, 0x88, 0x07, 0xC7, 0x31, 0xB1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xEC, 0x5F,
0x60, 0x51, 0x7F, 0xA9, 0x19, 0xB5, 0x4A, 0x0D, 0x2D, 0xE5, 0x7A, 0x9F, 0x93, 0xC9, 0x9C, 0xEF,
0xA0, 0xE0, 0x3B, 0x4D, 0xAE, 0x2A, 0xF5, 0xB0, 0xC8, 0xEB, 0xBB, 0x3C, 0x83, 0x53, 0x99, 0x61,
0x17, 0x2B, 0x04, 0x7E, 0xBA, 0x77, 0xD6, 0x26, 0xE1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0C, 0x7D,
];
s.map(|byte| INV_SBOX[usize::from(byte)])
}

/// MixColumns - multiplies `MATRIX` by `s` in GF(2^8)
fn mix_columns(s: [u8; 16]) -> [u8; 16] {
#[rustfmt::skip]
const MATRIX: [u8; 16] = [
0x02, 0x01, 0x01, 0x03,
0x03, 0x02, 0x01, 0x01,
0x01, 0x03, 0x02, 0x01,
0x01, 0x01, 0x03, 0x02,
];
mul_matrix_gf2p8(MATRIX, s)
}

/// InvMixColumns - multiplies `INV_MATRIX` by `s` in GF(2^8)
fn inv_mix_columns(s: [u8; 16]) -> [u8; 16] {
#[rustfmt::skip]
const INV_MATRIX: [u8; 16] = [
0x0E, 0x09, 0x0D, 0x0B,
0x0B, 0x0E, 0x09, 0x0D,
0x0D, 0x0B, 0x0E, 0x09,
0x09, 0x0D, 0x0B, 0x0E,
];
mul_matrix_gf2p8(INV_MATRIX, s)
}

/// Matrix multiplication where each element is a GF(2^8) polynomial
fn mul_matrix_gf2p8(a: [u8; 16], b: [u8; 16]) -> [u8; 16] {
fn index(row: usize, col: usize) -> usize {
// Calculate index of element at (row,col)
// Remember that elements are arranged in column-major order.
col.checked_mul(4).unwrap().checked_add(row).unwrap()
}

let mut res = [0; 16];
for row in 0..4 {
for col in 0..4 {
let res = &mut res[index(row, col)];
*res ^= mul_gf2p8(a[index(row, 0)], b[index(0, col)]);
*res ^= mul_gf2p8(a[index(row, 1)], b[index(1, col)]);
*res ^= mul_gf2p8(a[index(row, 2)], b[index(2, col)]);
*res ^= mul_gf2p8(a[index(row, 3)], b[index(3, col)]);
}
}
res
}

/// SubWord - S-box transformation on 4 bytes
fn sub_word(w: u32) -> u32 {
u32::from_ne_bytes(w.to_ne_bytes().map(|byte| SBOX[usize::from(byte)]))
}

/// RotWord - Rotate 32-bit word 1 byte
fn rot_word(w: u32) -> u32 {
w.rotate_right(8)
}

/// Modular multiplication of GF(2^8) polynomials `a(x)` and `b(x)`.
fn mul_gf2p8(mut a: u8, mut b: u8) -> u8 {
// Irreducible polynomial defined in equation (4.1) of FIPS 197.
const M: u8 = 0b11011; // m(x) = x^8 + x^4 + x^3 + x^1 + 1

// Start with res(x) = 0
let mut res = 0;
for _ in 0..8 {
if (a & 1) == 1 {
// If the constant term of `a(x)` is 1,
// add `b(x)` to `res(x)`
res ^= b;
}
// Shift down degree of `a(x)` by 1
a >>= 1;
// Shift up degree of `b(x)` by 1 (modulo `m(x)`)
if (b & 0x80) != 0 {
b = (b << 1) ^ M;
} else {
b <<= 1;
}
}
res
}

#[cfg(test)]
mod tests {
use super::*;

// Magic values from "Appendix C.1"
const STATE_START: [u8; 16] = 0x00102030405060708090A0B0C0D0E0F0_u128.to_be_bytes();
const STATE_S_BOX: [u8; 16] = 0x63CAB7040953D051CD60E0E7BA70E18C_u128.to_be_bytes();
const STATE_S_ROW: [u8; 16] = 0x6353E08C0960E104CD70B751BACAD0E7_u128.to_be_bytes();
const STATE_M_COL: [u8; 16] = 0x5F72641557F5BC92F7BE3B291DB9F91A_u128.to_be_bytes();

#[test]
fn test_shift_rows() {
assert_eq!(shift_rows(STATE_S_BOX), STATE_S_ROW);
}

#[test]
fn test_inv_shift_rows() {
assert_eq!(inv_shift_rows(STATE_S_ROW), STATE_S_BOX);
}

#[test]
fn test_sub_bytes() {
assert_eq!(sub_bytes(STATE_START), STATE_S_BOX);
}

#[test]
fn test_inv_sub_bytes() {
assert_eq!(inv_sub_bytes(STATE_S_BOX), STATE_START);
}

#[test]
fn test_mix_columns() {
assert_eq!(mix_columns(STATE_S_ROW), STATE_M_COL);
}

#[test]
fn test_inv_mix_columns() {
assert_eq!(inv_mix_columns(STATE_M_COL), STATE_S_ROW);
}
}
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