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Subject[PATCH v2 4/6] crypto: x86/chacha20 - add XChaCha20 support
Date
From: Eric Biggers <ebiggers@google.com>

Add an XChaCha20 implementation that is hooked up to the x86_64 SIMD
implementations of ChaCha20. This can be used by Adiantum.

An SSSE3 implementation of single-block HChaCha20 is also added so that
XChaCha20 can use it rather than the generic implementation. This
required refactoring the ChaCha permutation into its own function.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
arch/x86/crypto/chacha20-ssse3-x86_64.S | 76 ++++++++++++-------
arch/x86/crypto/chacha20_glue.c | 99 +++++++++++++++++++------
crypto/Kconfig | 12 +--
3 files changed, 129 insertions(+), 58 deletions(-)

diff --git a/arch/x86/crypto/chacha20-ssse3-x86_64.S b/arch/x86/crypto/chacha20-ssse3-x86_64.S
index d8ac75bb448f..45e4ccdd9c98 100644
--- a/arch/x86/crypto/chacha20-ssse3-x86_64.S
+++ b/arch/x86/crypto/chacha20-ssse3-x86_64.S
@@ -23,37 +23,24 @@ CTRINC: .octa 0x00000003000000020000000100000000

.text

-ENTRY(chacha20_block_xor_ssse3)
- # %rdi: Input state matrix, s
- # %rsi: up to 1 data block output, o
- # %rdx: up to 1 data block input, i
- # %rcx: input/output length in bytes
-
- # This function encrypts one ChaCha20 block by loading the state matrix
- # in four SSE registers. It performs matrix operation on four words in
- # parallel, but requires shuffling to rearrange the words after each
- # round. 8/16-bit word rotation is done with the slightly better
- # performing SSSE3 byte shuffling, 7/12-bit word rotation uses
- # traditional shift+OR.
-
- # x0..3 = s0..3
- movdqa 0x00(%rdi),%xmm0
- movdqa 0x10(%rdi),%xmm1
- movdqa 0x20(%rdi),%xmm2
- movdqa 0x30(%rdi),%xmm3
- movdqa %xmm0,%xmm8
- movdqa %xmm1,%xmm9
- movdqa %xmm2,%xmm10
- movdqa %xmm3,%xmm11
+/*
+ * chacha20_permute - permute one block
+ *
+ * Permute one 64-byte block where the state matrix is in %xmm0-%xmm3. This
+ * function performs matrix operations on four words in parallel, but requires
+ * shuffling to rearrange the words after each round. 8/16-bit word rotation is
+ * done with the slightly better performing SSSE3 byte shuffling, 7/12-bit word
+ * rotation uses traditional shift+OR.
+ *
+ * Clobbers: %ecx, %xmm4-%xmm7
+ */
+chacha20_permute:

movdqa ROT8(%rip),%xmm4
movdqa ROT16(%rip),%xmm5
-
- mov %rcx,%rax
mov $10,%ecx

.Ldoubleround:
-
# x0 += x1, x3 = rotl32(x3 ^ x0, 16)
paddd %xmm1,%xmm0
pxor %xmm0,%xmm3
@@ -123,6 +110,28 @@ ENTRY(chacha20_block_xor_ssse3)
dec %ecx
jnz .Ldoubleround

+ ret
+ENDPROC(chacha20_permute)
+
+ENTRY(chacha20_block_xor_ssse3)
+ # %rdi: Input state matrix, s
+ # %rsi: up to 1 data block output, o
+ # %rdx: up to 1 data block input, i
+ # %rcx: input/output length in bytes
+
+ # x0..3 = s0..3
+ movdqa 0x00(%rdi),%xmm0
+ movdqa 0x10(%rdi),%xmm1
+ movdqa 0x20(%rdi),%xmm2
+ movdqa 0x30(%rdi),%xmm3
+ movdqa %xmm0,%xmm8
+ movdqa %xmm1,%xmm9
+ movdqa %xmm2,%xmm10
+ movdqa %xmm3,%xmm11
+
+ mov %rcx,%rax
+ call chacha20_permute
+
# o0 = i0 ^ (x0 + s0)
paddd %xmm8,%xmm0
cmp $0x10,%rax
@@ -189,6 +198,23 @@ ENTRY(chacha20_block_xor_ssse3)

ENDPROC(chacha20_block_xor_ssse3)

+ENTRY(hchacha20_block_ssse3)
+ # %rdi: Input state matrix, s
+ # %rsi: output (8 32-bit words)
+
+ movdqa 0x00(%rdi),%xmm0
+ movdqa 0x10(%rdi),%xmm1
+ movdqa 0x20(%rdi),%xmm2
+ movdqa 0x30(%rdi),%xmm3
+
+ call chacha20_permute
+
+ movdqu %xmm0,0x00(%rsi)
+ movdqu %xmm3,0x10(%rsi)
+
+ ret
+ENDPROC(hchacha20_block_ssse3)
+
ENTRY(chacha20_4block_xor_ssse3)
# %rdi: Input state matrix, s
# %rsi: up to 4 data blocks output, o
diff --git a/arch/x86/crypto/chacha20_glue.c b/arch/x86/crypto/chacha20_glue.c
index 036de144aab6..2bea425acb76 100644
--- a/arch/x86/crypto/chacha20_glue.c
+++ b/arch/x86/crypto/chacha20_glue.c
@@ -23,6 +23,7 @@ asmlinkage void chacha20_block_xor_ssse3(u32 *state, u8 *dst, const u8 *src,
unsigned int len);
asmlinkage void chacha20_4block_xor_ssse3(u32 *state, u8 *dst, const u8 *src,
unsigned int len);
+asmlinkage void hchacha20_block_ssse3(const u32 *state, u32 *out);
#ifdef CONFIG_AS_AVX2
asmlinkage void chacha20_2block_xor_avx2(u32 *state, u8 *dst, const u8 *src,
unsigned int len);
@@ -121,10 +122,9 @@ static void chacha20_dosimd(u32 *state, u8 *dst, const u8 *src,
}
}

-static int chacha20_simd(struct skcipher_request *req)
+static int chacha20_simd_stream_xor(struct skcipher_request *req,
+ struct chacha_ctx *ctx, u8 *iv)
{
- struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
- struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
u32 *state, state_buf[16 + 2] __aligned(8);
struct skcipher_walk walk;
int err;
@@ -132,12 +132,9 @@ static int chacha20_simd(struct skcipher_request *req)
BUILD_BUG_ON(CHACHA20_STATE_ALIGN != 16);
state = PTR_ALIGN(state_buf + 0, CHACHA20_STATE_ALIGN);

- if (req->cryptlen <= CHACHA_BLOCK_SIZE || !may_use_simd())
- return crypto_chacha_crypt(req);
-
err = skcipher_walk_virt(&walk, req, false);

- crypto_chacha_init(state, ctx, walk.iv);
+ crypto_chacha_init(state, ctx, iv);

while (walk.nbytes > 0) {
unsigned int nbytes = walk.nbytes;
@@ -156,21 +153,73 @@ static int chacha20_simd(struct skcipher_request *req)
return err;
}

-static struct skcipher_alg alg = {
- .base.cra_name = "chacha20",
- .base.cra_driver_name = "chacha20-simd",
- .base.cra_priority = 300,
- .base.cra_blocksize = 1,
- .base.cra_ctxsize = sizeof(struct chacha_ctx),
- .base.cra_module = THIS_MODULE,
-
- .min_keysize = CHACHA_KEY_SIZE,
- .max_keysize = CHACHA_KEY_SIZE,
- .ivsize = CHACHA_IV_SIZE,
- .chunksize = CHACHA_BLOCK_SIZE,
- .setkey = crypto_chacha20_setkey,
- .encrypt = chacha20_simd,
- .decrypt = chacha20_simd,
+static int chacha20_simd(struct skcipher_request *req)
+{
+ struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
+ struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
+
+ if (req->cryptlen <= CHACHA_BLOCK_SIZE || !irq_fpu_usable())
+ return crypto_chacha_crypt(req);
+
+ return chacha20_simd_stream_xor(req, ctx, req->iv);
+}
+
+static int xchacha20_simd(struct skcipher_request *req)
+{
+ struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
+ struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
+ struct chacha_ctx subctx;
+ u32 *state, state_buf[16 + 2] __aligned(8);
+ u8 real_iv[16];
+
+ if (req->cryptlen <= CHACHA_BLOCK_SIZE || !irq_fpu_usable())
+ return crypto_xchacha_crypt(req);
+
+ BUILD_BUG_ON(CHACHA20_STATE_ALIGN != 16);
+ state = PTR_ALIGN(state_buf + 0, CHACHA20_STATE_ALIGN);
+ crypto_chacha_init(state, ctx, req->iv);
+
+ kernel_fpu_begin();
+ hchacha20_block_ssse3(state, subctx.key);
+ kernel_fpu_end();
+
+ memcpy(&real_iv[0], req->iv + 24, 8);
+ memcpy(&real_iv[8], req->iv + 16, 8);
+ return chacha20_simd_stream_xor(req, &subctx, real_iv);
+}
+
+static struct skcipher_alg algs[] = {
+ {
+ .base.cra_name = "chacha20",
+ .base.cra_driver_name = "chacha20-simd",
+ .base.cra_priority = 300,
+ .base.cra_blocksize = 1,
+ .base.cra_ctxsize = sizeof(struct chacha_ctx),
+ .base.cra_module = THIS_MODULE,
+
+ .min_keysize = CHACHA_KEY_SIZE,
+ .max_keysize = CHACHA_KEY_SIZE,
+ .ivsize = CHACHA_IV_SIZE,
+ .chunksize = CHACHA_BLOCK_SIZE,
+ .setkey = crypto_chacha20_setkey,
+ .encrypt = chacha20_simd,
+ .decrypt = chacha20_simd,
+ }, {
+ .base.cra_name = "xchacha20",
+ .base.cra_driver_name = "xchacha20-simd",
+ .base.cra_priority = 300,
+ .base.cra_blocksize = 1,
+ .base.cra_ctxsize = sizeof(struct chacha_ctx),
+ .base.cra_module = THIS_MODULE,
+
+ .min_keysize = CHACHA_KEY_SIZE,
+ .max_keysize = CHACHA_KEY_SIZE,
+ .ivsize = XCHACHA_IV_SIZE,
+ .chunksize = CHACHA_BLOCK_SIZE,
+ .setkey = crypto_chacha20_setkey,
+ .encrypt = xchacha20_simd,
+ .decrypt = xchacha20_simd,
+ },
};

static int __init chacha20_simd_mod_init(void)
@@ -188,12 +237,12 @@ static int __init chacha20_simd_mod_init(void)
boot_cpu_has(X86_FEATURE_AVX512BW); /* kmovq */
#endif
#endif
- return crypto_register_skcipher(&alg);
+ return crypto_register_skciphers(algs, ARRAY_SIZE(algs));
}

static void __exit chacha20_simd_mod_fini(void)
{
- crypto_unregister_skcipher(&alg);
+ crypto_unregister_skciphers(algs, ARRAY_SIZE(algs));
}

module_init(chacha20_simd_mod_init);
@@ -204,3 +253,5 @@ MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
MODULE_DESCRIPTION("chacha20 cipher algorithm, SIMD accelerated");
MODULE_ALIAS_CRYPTO("chacha20");
MODULE_ALIAS_CRYPTO("chacha20-simd");
+MODULE_ALIAS_CRYPTO("xchacha20");
+MODULE_ALIAS_CRYPTO("xchacha20-simd");
diff --git a/crypto/Kconfig b/crypto/Kconfig
index e084e2fb6743..df466771e9bf 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -1468,19 +1468,13 @@ config CRYPTO_CHACHA20
in some performance-sensitive scenarios.

config CRYPTO_CHACHA20_X86_64
- tristate "ChaCha20 cipher algorithm (x86_64/SSSE3/AVX2)"
+ tristate "ChaCha stream cipher algorithms (x86_64/SSSE3/AVX2/AVX-512VL)"
depends on X86 && 64BIT
select CRYPTO_BLKCIPHER
select CRYPTO_CHACHA20
help
- ChaCha20 cipher algorithm, RFC7539.
-
- ChaCha20 is a 256-bit high-speed stream cipher designed by Daniel J.
- Bernstein and further specified in RFC7539 for use in IETF protocols.
- This is the x86_64 assembler implementation using SIMD instructions.
-
- See also:
- <http://cr.yp.to/chacha/chacha-20080128.pdf>
+ SSSE3, AVX2, and AVX-512VL optimized implementations of the ChaCha20
+ and XChaCha20 stream ciphers.

config CRYPTO_SEED
tristate "SEED cipher algorithm"
--
2.20.0.rc0.387.gc7a69e6b6c-goog
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