[PATCH v5 4/8] crypto: x86/aesni-xctr: Add accelerated implementation of XCTR

Nathan Huckleberry
2022-04-27T00:38:27Z

Add hardware accelerated versions of XCTR for x86-64 CPUs with AESNI
support. These implementations are modified versions of the CTR
implementations found in aesni-intel_asm.S and aes_ctrby8_avx-x86_64.S.

More information on XCTR can be found in the HCTR2 paper:
"Length-preserving encryption with HCTR2":
https://eprint.iacr.org/2021/1441.pdf

Signed-off-by: Nathan Huckleberry <nhuck@google.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/x86/crypto/aes_ctrby8_avx-x86_64.S | 232 ++++++++++++++++--------
arch/x86/crypto/aesni-intel_glue.c | 109 +++++++++++
crypto/Kconfig | 2 +-
3 files changed, 262 insertions(+), 81 deletions(-)

diff --git a/arch/x86/crypto/aes_ctrby8_avx-x86_64.S b/arch/x86/crypto/aes_ctrby8_avx-x86_64.S
index 43852ba6e19c..6de06779b77c 100644
--- a/arch/x86/crypto/aes_ctrby8_avx-x86_64.S
+++ b/arch/x86/crypto/aes_ctrby8_avx-x86_64.S
@@ -23,6 +23,10 @@

#define VMOVDQ vmovdqu

+/* Note: the "x" prefix in these aliases means "this is an xmm register". The
+ * alias prefixes have no relation to XCTR where the "X" prefix means "XOR
+ * counter".
+ */
#define xdata0 %xmm0
#define xdata1 %xmm1
#define xdata2 %xmm2
@@ -31,8 +35,10 @@
#define xdata5 %xmm5
#define xdata6 %xmm6
#define xdata7 %xmm7
-#define xcounter %xmm8
-#define xbyteswap %xmm9
+#define xcounter %xmm8 // CTR mode only
+#define xiv %xmm8 // XCTR mode only
+#define xbyteswap %xmm9 // CTR mode only
+#define xtmp %xmm9 // XCTR mode only
#define xkey0 %xmm10
#define xkey4 %xmm11
#define xkey8 %xmm12
@@ -45,7 +51,7 @@
#define p_keys %rdx
#define p_out %rcx
#define num_bytes %r8
-
+#define counter %r9 // XCTR mode only
#define tmp %r10
#define DDQ_DATA 0
#define XDATA 1
@@ -102,7 +108,7 @@ ddq_add_8:
* do_aes num_in_par load_keys key_len
* This increments p_in, but not p_out
*/
-.macro do_aes b, k, key_len
+.macro do_aes b, k, key_len, xctr
.set by, \b
.set load_keys, \k
.set klen, \key_len
@@ -111,29 +117,48 @@ ddq_add_8:
vmovdqa 0*16(p_keys), xkey0
.endif

- vpshufb xbyteswap, xcounter, xdata0
-
- .set i, 1
- .rept (by - 1)
- club XDATA, i
- vpaddq (ddq_add_1 + 16 * (i - 1))(%rip), xcounter, var_xdata
- vptest ddq_low_msk(%rip), var_xdata
- jnz 1f
- vpaddq ddq_high_add_1(%rip), var_xdata, var_xdata
- vpaddq ddq_high_add_1(%rip), xcounter, xcounter
- 1:
- vpshufb xbyteswap, var_xdata, var_xdata
- .set i, (i +1)
- .endr
+ .if !\xctr
+ vpshufb xbyteswap, xcounter, xdata0
+ .set i, 1
+ .rept (by - 1)
+ club XDATA, i
+ vpaddq (ddq_add_1 + 16 * (i - 1))(%rip), xcounter, var_xdata
+ vptest ddq_low_msk(%rip), var_xdata
+ jnz 1f
+ vpaddq ddq_high_add_1(%rip), var_xdata, var_xdata
+ vpaddq ddq_high_add_1(%rip), xcounter, xcounter
+ 1:
+ vpshufb xbyteswap, var_xdata, var_xdata
+ .set i, (i +1)
+ .endr
+ .else
+ movq counter, xtmp
+ .set i, 0
+ .rept (by)
+ club XDATA, i
+ vpaddq (ddq_add_1 + 16 * i)(%rip), xtmp, var_xdata
+ .set i, (i +1)
+ .endr
+ .set i, 0
+ .rept (by)
+ club XDATA, i
+ vpxor xiv, var_xdata, var_xdata
+ .set i, (i +1)
+ .endr
+ .endif

vmovdqa 1*16(p_keys), xkeyA

vpxor xkey0, xdata0, xdata0
- vpaddq (ddq_add_1 + 16 * (by - 1))(%rip), xcounter, xcounter
- vptest ddq_low_msk(%rip), xcounter
- jnz 1f
- vpaddq ddq_high_add_1(%rip), xcounter, xcounter
- 1:
+ .if !\xctr
+ vpaddq (ddq_add_1 + 16 * (by - 1))(%rip), xcounter, xcounter
+ vptest ddq_low_msk(%rip), xcounter
+ jnz 1f
+ vpaddq ddq_high_add_1(%rip), xcounter, xcounter
+ 1:
+ .else
+ add $by, counter
+ .endif

.set i, 1
.rept (by - 1)
@@ -371,94 +396,100 @@ ddq_add_8:
.endr
.endm

-.macro do_aes_load val, key_len
- do_aes \val, 1, \key_len
+.macro do_aes_load val, key_len, xctr
+ do_aes \val, 1, \key_len, \xctr
.endm

-.macro do_aes_noload val, key_len
- do_aes \val, 0, \key_len
+.macro do_aes_noload val, key_len, xctr
+ do_aes \val, 0, \key_len, \xctr
.endm

/* main body of aes ctr load */

-.macro do_aes_ctrmain key_len
+.macro do_aes_ctrmain key_len, xctr
cmp $16, num_bytes
- jb .Ldo_return2\key_len
+ jb .Ldo_return2\xctr\key_len

- vmovdqa byteswap_const(%rip), xbyteswap
- vmovdqu (p_iv), xcounter
- vpshufb xbyteswap, xcounter, xcounter
+ .if !\xctr
+ vmovdqa byteswap_const(%rip), xbyteswap
+ vmovdqu (p_iv), xcounter
+ vpshufb xbyteswap, xcounter, xcounter
+ .else
+ andq $(~0xf), num_bytes
+ shr $4, counter
+ vmovdqu (p_iv), xiv
+ .endif

mov num_bytes, tmp
and $(7*16), tmp
- jz .Lmult_of_8_blks\key_len
+ jz .Lmult_of_8_blks\xctr\key_len

/* 1 <= tmp <= 7 */
cmp $(4*16), tmp
- jg .Lgt4\key_len
- je .Leq4\key_len
+ jg .Lgt4\xctr\key_len
+ je .Leq4\xctr\key_len

-.Llt4\key_len:
+.Llt4\xctr\key_len:
cmp $(2*16), tmp
- jg .Leq3\key_len
- je .Leq2\key_len
+ jg .Leq3\xctr\key_len
+ je .Leq2\xctr\key_len

-.Leq1\key_len:
- do_aes_load 1, \key_len
+.Leq1\xctr\key_len:
+ do_aes_load 1, \key_len, \xctr
add $(1*16), p_out
and $(~7*16), num_bytes
- jz .Ldo_return2\key_len
- jmp .Lmain_loop2\key_len
+ jz .Ldo_return2\xctr\key_len
+ jmp .Lmain_loop2\xctr\key_len

-.Leq2\key_len:
- do_aes_load 2, \key_len
+.Leq2\xctr\key_len:
+ do_aes_load 2, \key_len, \xctr
add $(2*16), p_out
and $(~7*16), num_bytes
- jz .Ldo_return2\key_len
- jmp .Lmain_loop2\key_len
+ jz .Ldo_return2\xctr\key_len
+ jmp .Lmain_loop2\xctr\key_len

-.Leq3\key_len:
- do_aes_load 3, \key_len
+.Leq3\xctr\key_len:
+ do_aes_load 3, \key_len, \xctr
add $(3*16), p_out
and $(~7*16), num_bytes
- jz .Ldo_return2\key_len
- jmp .Lmain_loop2\key_len
+ jz .Ldo_return2\xctr\key_len
+ jmp .Lmain_loop2\xctr\key_len

-.Leq4\key_len:
- do_aes_load 4, \key_len
+.Leq4\xctr\key_len:
+ do_aes_load 4, \key_len, \xctr
add $(4*16), p_out
and $(~7*16), num_bytes
- jz .Ldo_return2\key_len
- jmp .Lmain_loop2\key_len
+ jz .Ldo_return2\xctr\key_len
+ jmp .Lmain_loop2\xctr\key_len

-.Lgt4\key_len:
+.Lgt4\xctr\key_len:
cmp $(6*16), tmp
- jg .Leq7\key_len
- je .Leq6\key_len
+ jg .Leq7\xctr\key_len
+ je .Leq6\xctr\key_len

-.Leq5\key_len:
- do_aes_load 5, \key_len
+.Leq5\xctr\key_len:
+ do_aes_load 5, \key_len, \xctr
add $(5*16), p_out
and $(~7*16), num_bytes
- jz .Ldo_return2\key_len
- jmp .Lmain_loop2\key_len
+ jz .Ldo_return2\xctr\key_len
+ jmp .Lmain_loop2\xctr\key_len

-.Leq6\key_len:
- do_aes_load 6, \key_len
+.Leq6\xctr\key_len:
+ do_aes_load 6, \key_len, \xctr
add $(6*16), p_out
and $(~7*16), num_bytes
- jz .Ldo_return2\key_len
- jmp .Lmain_loop2\key_len
+ jz .Ldo_return2\xctr\key_len
+ jmp .Lmain_loop2\xctr\key_len

-.Leq7\key_len:
- do_aes_load 7, \key_len
+.Leq7\xctr\key_len:
+ do_aes_load 7, \key_len, \xctr
add $(7*16), p_out
and $(~7*16), num_bytes
- jz .Ldo_return2\key_len
- jmp .Lmain_loop2\key_len
+ jz .Ldo_return2\xctr\key_len
+ jmp .Lmain_loop2\xctr\key_len

-.Lmult_of_8_blks\key_len:
+.Lmult_of_8_blks\xctr\key_len:
.if (\key_len != KEY_128)
vmovdqa 0*16(p_keys), xkey0
vmovdqa 4*16(p_keys), xkey4
@@ -471,17 +502,19 @@ ddq_add_8:
vmovdqa 9*16(p_keys), xkey12
.endif
.align 16
-.Lmain_loop2\key_len:
+.Lmain_loop2\xctr\key_len:
/* num_bytes is a multiple of 8 and >0 */
- do_aes_noload 8, \key_len
+ do_aes_noload 8, \key_len, \xctr
add $(8*16), p_out
sub $(8*16), num_bytes
- jne .Lmain_loop2\key_len
+ jne .Lmain_loop2\xctr\key_len

-.Ldo_return2\key_len:
- /* return updated IV */
- vpshufb xbyteswap, xcounter, xcounter
- vmovdqu xcounter, (p_iv)
+.Ldo_return2\xctr\key_len:
+ .if !\xctr
+ /* return updated IV */
+ vpshufb xbyteswap, xcounter, xcounter
+ vmovdqu xcounter, (p_iv)
+ .endif
RET
.endm

@@ -494,7 +527,7 @@ ddq_add_8:
*/
SYM_FUNC_START(aes_ctr_enc_128_avx_by8)
/* call the aes main loop */
- do_aes_ctrmain KEY_128
+ do_aes_ctrmain KEY_128 0

SYM_FUNC_END(aes_ctr_enc_128_avx_by8)

@@ -507,7 +540,7 @@ SYM_FUNC_END(aes_ctr_enc_128_avx_by8)
*/
SYM_FUNC_START(aes_ctr_enc_192_avx_by8)
/* call the aes main loop */
- do_aes_ctrmain KEY_192
+ do_aes_ctrmain KEY_192 0

SYM_FUNC_END(aes_ctr_enc_192_avx_by8)

@@ -520,6 +553,45 @@ SYM_FUNC_END(aes_ctr_enc_192_avx_by8)
*/
SYM_FUNC_START(aes_ctr_enc_256_avx_by8)
/* call the aes main loop */
- do_aes_ctrmain KEY_256
+ do_aes_ctrmain KEY_256 0

SYM_FUNC_END(aes_ctr_enc_256_avx_by8)
+
+/*
+ * routine to do AES128 XCTR enc/decrypt "by8"
+ * XMM registers are clobbered.
+ * Saving/restoring must be done at a higher level
+ * aes_xctr_enc_128_avx_by8(const u8 *in, const u8 *iv, const void *keys,
+ * u8* out, unsigned int num_bytes, unsigned int byte_ctr)
+ */
+SYM_FUNC_START(aes_xctr_enc_128_avx_by8)
+ /* call the aes main loop */
+ do_aes_ctrmain KEY_128 1
+
+SYM_FUNC_END(aes_xctr_enc_128_avx_by8)
+
+/*
+ * routine to do AES192 XCTR enc/decrypt "by8"
+ * XMM registers are clobbered.
+ * Saving/restoring must be done at a higher level
+ * aes_xctr_enc_192_avx_by8(const u8 *in, const u8 *iv, const void *keys,
+ * u8* out, unsigned int num_bytes, unsigned int byte_ctr)
+ */
+SYM_FUNC_START(aes_xctr_enc_192_avx_by8)
+ /* call the aes main loop */
+ do_aes_ctrmain KEY_192 1
+
+SYM_FUNC_END(aes_xctr_enc_192_avx_by8)
+
+/*
+ * routine to do AES256 XCTR enc/decrypt "by8"
+ * XMM registers are clobbered.
+ * Saving/restoring must be done at a higher level
+ * aes_xctr_enc_256_avx_by8(const u8 *in, const u8 *iv, const void *keys,
+ * u8* out, unsigned int num_bytes, unsigned int byte_ctr)
+ */
+SYM_FUNC_START(aes_xctr_enc_256_avx_by8)
+ /* call the aes main loop */
+ do_aes_ctrmain KEY_256 1
+
+SYM_FUNC_END(aes_xctr_enc_256_avx_by8)
diff --git a/arch/x86/crypto/aesni-intel_glue.c b/arch/x86/crypto/aesni-intel_glue.c
index 41901ba9d3a2..f79ed168a77b 100644
--- a/arch/x86/crypto/aesni-intel_glue.c
+++ b/arch/x86/crypto/aesni-intel_glue.c
@@ -135,6 +135,20 @@ asmlinkage void aes_ctr_enc_192_avx_by8(const u8 *in, u8 *iv,
void *keys, u8 *out, unsigned int num_bytes);
asmlinkage void aes_ctr_enc_256_avx_by8(const u8 *in, u8 *iv,
void *keys, u8 *out, unsigned int num_bytes);
+
+
+asmlinkage void aes_xctr_enc_128_avx_by8(const u8 *in, const u8 *iv,
+ const void *keys, u8 *out, unsigned int num_bytes,
+ unsigned int byte_ctr);
+
+asmlinkage void aes_xctr_enc_192_avx_by8(const u8 *in, const u8 *iv,
+ const void *keys, u8 *out, unsigned int num_bytes,
+ unsigned int byte_ctr);
+
+asmlinkage void aes_xctr_enc_256_avx_by8(const u8 *in, const u8 *iv,
+ const void *keys, u8 *out, unsigned int num_bytes,
+ unsigned int byte_ctr);
+
/*
* asmlinkage void aesni_gcm_init_avx_gen2()
* gcm_data *my_ctx_data, context data
@@ -527,6 +541,59 @@ static int ctr_crypt(struct skcipher_request *req)
return err;
}

+static void aesni_xctr_enc_avx_tfm(struct crypto_aes_ctx *ctx, u8 *out,
+ const u8 *in, unsigned int len, u8 *iv,
+ unsigned int byte_ctr)
+{
+ if (ctx->key_length == AES_KEYSIZE_128)
+ aes_xctr_enc_128_avx_by8(in, iv, (void *)ctx, out, len,
+ byte_ctr);
+ else if (ctx->key_length == AES_KEYSIZE_192)
+ aes_xctr_enc_192_avx_by8(in, iv, (void *)ctx, out, len,
+ byte_ctr);
+ else
+ aes_xctr_enc_256_avx_by8(in, iv, (void *)ctx, out, len,
+ byte_ctr);
+}
+
+static int xctr_crypt(struct skcipher_request *req)
+{
+ struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
+ struct crypto_aes_ctx *ctx = aes_ctx(crypto_skcipher_ctx(tfm));
+ u8 keystream[AES_BLOCK_SIZE];
+ struct skcipher_walk walk;
+ unsigned int nbytes;
+ unsigned int byte_ctr = 0;
+ int err;
+ __le32 block[AES_BLOCK_SIZE / sizeof(__le32)];
+
+ err = skcipher_walk_virt(&walk, req, false);
+
+ while ((nbytes = walk.nbytes) > 0) {
+ kernel_fpu_begin();
+ if (nbytes & AES_BLOCK_MASK)
+ aesni_xctr_enc_avx_tfm(ctx, walk.dst.virt.addr,
+ walk.src.virt.addr, nbytes & AES_BLOCK_MASK,
+ walk.iv, byte_ctr);
+ nbytes &= ~AES_BLOCK_MASK;
+ byte_ctr += walk.nbytes - nbytes;
+
+ if (walk.nbytes == walk.total && nbytes > 0) {
+ memcpy(block, walk.iv, AES_BLOCK_SIZE);
+ block[0] ^= cpu_to_le32(1 + byte_ctr / AES_BLOCK_SIZE);
+ aesni_enc(ctx, keystream, (u8 *)block);
+ crypto_xor_cpy(walk.dst.virt.addr + walk.nbytes -
+ nbytes, walk.src.virt.addr + walk.nbytes
+ - nbytes, keystream, nbytes);
+ byte_ctr += nbytes;
+ nbytes = 0;
+ }
+ kernel_fpu_end();
+ err = skcipher_walk_done(&walk, nbytes);
+ }
+ return err;
+}
+
static int
rfc4106_set_hash_subkey(u8 *hash_subkey, const u8 *key, unsigned int key_len)
{
@@ -1050,6 +1117,33 @@ static struct skcipher_alg aesni_skciphers[] = {
static
struct simd_skcipher_alg *aesni_simd_skciphers[ARRAY_SIZE(aesni_skciphers)];

+#ifdef CONFIG_X86_64
+/*
+ * XCTR does not have a non-AVX implementation, so it must be enabled
+ * conditionally.
+ */
+static struct skcipher_alg aesni_xctr = {
+ .base = {
+ .cra_name = "__xctr(aes)",
+ .cra_driver_name = "__xctr-aes-aesni",
+ .cra_priority = 400,
+ .cra_flags = CRYPTO_ALG_INTERNAL,
+ .cra_blocksize = 1,
+ .cra_ctxsize = CRYPTO_AES_CTX_SIZE,
+ .cra_module = THIS_MODULE,
+ },
+ .min_keysize = AES_MIN_KEY_SIZE,
+ .max_keysize = AES_MAX_KEY_SIZE,
+ .ivsize = AES_BLOCK_SIZE,
+ .chunksize = AES_BLOCK_SIZE,
+ .setkey = aesni_skcipher_setkey,
+ .encrypt = xctr_crypt,
+ .decrypt = xctr_crypt,
+};
+
+static struct simd_skcipher_alg *aesni_simd_xctr;
+#endif
+
#ifdef CONFIG_X86_64
static int generic_gcmaes_set_key(struct crypto_aead *aead, const u8 *key,
unsigned int key_len)
@@ -1180,8 +1274,19 @@ static int __init aesni_init(void)
if (err)
goto unregister_skciphers;

+#ifdef CONFIG_X86_64
+ if (boot_cpu_has(X86_FEATURE_AVX))
+ err = simd_register_skciphers_compat(&aesni_xctr, 1,
+ &aesni_simd_xctr);
+ if (err)
+ goto unregister_aeads;
+#endif
+
return 0;

+unregister_aeads:
+ simd_unregister_aeads(aesni_aeads, ARRAY_SIZE(aesni_aeads),
+ aesni_simd_aeads);
unregister_skciphers:
simd_unregister_skciphers(aesni_skciphers, ARRAY_SIZE(aesni_skciphers),
aesni_simd_skciphers);
@@ -1197,6 +1302,10 @@ static void __exit aesni_exit(void)
simd_unregister_skciphers(aesni_skciphers, ARRAY_SIZE(aesni_skciphers),
aesni_simd_skciphers);
crypto_unregister_alg(&aesni_cipher_alg);
+#ifdef CONFIG_X86_64
+ if (boot_cpu_has(X86_FEATURE_AVX))
+ simd_unregister_skciphers(&aesni_xctr, 1, &aesni_simd_xctr);
+#endif
}

late_initcall(aesni_init);
diff --git a/crypto/Kconfig b/crypto/Kconfig
index 0dedba74db4a..aa06af0e0ebe 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -1161,7 +1161,7 @@ config CRYPTO_AES_NI_INTEL
In addition to AES cipher algorithm support, the acceleration
for some popular block cipher mode is supported too, including
ECB, CBC, LRW, XTS. The 64 bit version has additional
- acceleration for CTR.
+ acceleration for CTR and XCTR.

config CRYPTO_AES_SPARC64
tristate "AES cipher algorithms (SPARC64)"