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TLS: Favor ChaCha over AES-based ciphers on CPUs without AES support (#15034)

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On CPUs without AES support, ChaCha is always faster and safer than
software AES.

Add `crypto.core.aes.has_hardware_support` to represent whether
AES acceleration is available or not, and in `tls.Client`, favor
AES-based ciphers only if hardware support is available.

This matches what BoringSSL is doing.
This commit is contained in:
Frank Denis 2023-03-22 17:58:24 +01:00 committed by GitHub
parent 84b89d7cfe
commit d61ac0db8c
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2 changed files with 22 additions and 7 deletions
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6
lib/std/crypto/aes.zig
View File

@ -14,6 +14,12 @@ impl: {
break :impl @import("aes/soft.zig");
};
/// `true` if AES is backed by hardware (AES-NI on x86_64, ARM Crypto Extensions on AArch64).
/// Software implementations are much slower, and should be avoided if possible.
pub const has_hardware_support =
(builtin.cpu.arch == .x86_64 and has_aesni and has_avx) or
(builtin.cpu.arch == .aarch64 and has_armaes);
pub const Block = impl.Block;
pub const AesEncryptCtx = impl.AesEncryptCtx;
pub const AesDecryptCtx = impl.AesDecryptCtx;

11
lib/std/crypto/tls/Client.zig
View File

@ -1363,12 +1363,21 @@ fn limitVecs(iovecs: []std.os.iovec, len: usize) []std.os.iovec {
/// aegis-256: 461 MiB/s
/// aes128-gcm: 138 MiB/s
/// aes256-gcm: 120 MiB/s
const cipher_suites = enum_array(tls.CipherSuite, &.{
const cipher_suites = if (crypto.core.aes.has_hardware_support)
enum_array(tls.CipherSuite, &.{
.AEGIS_128L_SHA256,
.AEGIS_256_SHA384,
.AES_128_GCM_SHA256,
.AES_256_GCM_SHA384,
.CHACHA20_POLY1305_SHA256,
})
else
enum_array(tls.CipherSuite, &.{
.CHACHA20_POLY1305_SHA256,
.AEGIS_128L_SHA256,
.AEGIS_256_SHA384,
.AES_128_GCM_SHA256,
.AES_256_GCM_SHA384,
});
test {