From 3ad99c22cebee84034bc53e42f5115dbc97490e8 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Tue, 10 Nov 2020 10:10:42 +0100 Subject: [PATCH] crypto: arm64/gcm - move authentication tag check to SIMD domain Instead of copying the calculated authentication tag to memory and calling crypto_memneq() to verify it, use vector bytewise compare and min across vector instructions to decide whether the tag is valid. This is more efficient, and given that the tag is only transiently held in a NEON register, it is also safer, given that calculated tags for failed decryptions should be withheld. Signed-off-by: Ard Biesheuvel Signed-off-by: Herbert Xu --- arch/arm64/crypto/ghash-ce-core.S | 15 +++++++++++++ arch/arm64/crypto/ghash-ce-glue.c | 46 ++++++++++++++++++++++++--------------- 2 files changed, 43 insertions(+), 18 deletions(-) diff --git a/arch/arm64/crypto/ghash-ce-core.S b/arch/arm64/crypto/ghash-ce-core.S index 6b958dc..7868330 100644 --- a/arch/arm64/crypto/ghash-ce-core.S +++ b/arch/arm64/crypto/ghash-ce-core.S @@ -544,7 +544,22 @@ CPU_LE( rev w8, w8 ) ext XL.16b, XL.16b, XL.16b, #8 rev64 XL.16b, XL.16b eor XL.16b, XL.16b, KS0.16b + + .if \enc == 1 st1 {XL.16b}, [x10] // store tag + .else + ldp x11, x12, [sp, #40] // load tag pointer and authsize + adr_l x17, .Lpermute_table + ld1 {KS0.16b}, [x11] // load supplied tag + add x17, x17, x12 + ld1 {KS1.16b}, [x17] // load permute vector + + cmeq XL.16b, XL.16b, KS0.16b // compare tags + mvn XL.16b, XL.16b // -1 for fail, 0 for pass + tbl XL.16b, {XL.16b}, KS1.16b // keep authsize bytes only + sminv b0, XL.16b // signed minimum across XL + smov w0, v0.b[0] // return b0 + .endif 4: ldp x29, x30, [sp], #32 ret diff --git a/arch/arm64/crypto/ghash-ce-glue.c b/arch/arm64/crypto/ghash-ce-glue.c index 2427e2f..720cd3a 100644 --- a/arch/arm64/crypto/ghash-ce-glue.c +++ b/arch/arm64/crypto/ghash-ce-glue.c @@ -55,10 +55,10 @@ asmlinkage void pmull_ghash_update_p8(int blocks, u64 dg[], const char *src, asmlinkage void pmull_gcm_encrypt(int bytes, u8 dst[], const u8 src[], u64 const h[][2], u64 dg[], u8 ctr[], u32 const rk[], int rounds, u8 tag[]); - -asmlinkage void pmull_gcm_decrypt(int bytes, u8 dst[], const u8 src[], - u64 const h[][2], u64 dg[], u8 ctr[], - u32 const rk[], int rounds, u8 tag[]); +asmlinkage int pmull_gcm_decrypt(int bytes, u8 dst[], const u8 src[], + u64 const h[][2], u64 dg[], u8 ctr[], + u32 const rk[], int rounds, const u8 l[], + const u8 tag[], u64 authsize); static int ghash_init(struct shash_desc *desc) { @@ -458,6 +458,7 @@ static int gcm_decrypt(struct aead_request *req) unsigned int authsize = crypto_aead_authsize(aead); int nrounds = num_rounds(&ctx->aes_key); struct skcipher_walk walk; + u8 otag[AES_BLOCK_SIZE]; u8 buf[AES_BLOCK_SIZE]; u8 iv[AES_BLOCK_SIZE]; u64 dg[2] = {}; @@ -474,9 +475,15 @@ static int gcm_decrypt(struct aead_request *req) memcpy(iv, req->iv, GCM_IV_SIZE); put_unaligned_be32(2, iv + GCM_IV_SIZE); + scatterwalk_map_and_copy(otag, req->src, + req->assoclen + req->cryptlen - authsize, + authsize, 0); + err = skcipher_walk_aead_decrypt(&walk, req, false); if (likely(crypto_simd_usable())) { + int ret; + do { const u8 *src = walk.src.virt.addr; u8 *dst = walk.dst.virt.addr; @@ -493,9 +500,10 @@ static int gcm_decrypt(struct aead_request *req) } kernel_neon_begin(); - pmull_gcm_decrypt(nbytes, dst, src, ctx->ghash_key.h, - dg, iv, ctx->aes_key.key_enc, nrounds, - tag); + ret = pmull_gcm_decrypt(nbytes, dst, src, + ctx->ghash_key.h, + dg, iv, ctx->aes_key.key_enc, + nrounds, tag, otag, authsize); kernel_neon_end(); if (unlikely(!nbytes)) @@ -507,6 +515,11 @@ static int gcm_decrypt(struct aead_request *req) err = skcipher_walk_done(&walk, walk.nbytes - nbytes); } while (walk.nbytes); + + if (err) + return err; + if (ret) + return -EBADMSG; } else { while (walk.nbytes >= AES_BLOCK_SIZE) { int blocks = walk.nbytes / AES_BLOCK_SIZE; @@ -548,23 +561,20 @@ static int gcm_decrypt(struct aead_request *req) err = skcipher_walk_done(&walk, 0); } + if (err) + return err; + put_unaligned_be64(dg[1], tag); put_unaligned_be64(dg[0], tag + 8); put_unaligned_be32(1, iv + GCM_IV_SIZE); aes_encrypt(&ctx->aes_key, iv, iv); crypto_xor(tag, iv, AES_BLOCK_SIZE); - } - - if (err) - return err; - /* compare calculated auth tag with the stored one */ - scatterwalk_map_and_copy(buf, req->src, - req->assoclen + req->cryptlen - authsize, - authsize, 0); - - if (crypto_memneq(tag, buf, authsize)) - return -EBADMSG; + if (crypto_memneq(tag, otag, authsize)) { + memzero_explicit(tag, AES_BLOCK_SIZE); + return -EBADMSG; + } + } return 0; } -- 2.7.4