Jakub Jelen
2020-Jan-16 10:27 UTC
[patch 1/2] use chacha20 from openssl (1.1.0+) when possible
On Fri, 2019-07-12 at 15:54 +1000, Damien Miller wrote:> On Thu, 17 Jan 2019, Yuriy M. Kaminskiy wrote: > > > On some cpu's optimized chacha implementation in openssl (1.1.0+) > > is > > notably faster (and on others it is just faster) than generic C > > implementation in openssh. > > > > Sadly, openssl's chacha20-poly1305 (EVP_chacha20_poly1305) uses > > different scheme (with padding/etc - see rfc8439) and it looks it > > is not > > possible to use in openssh. > > > > OpenSSL 1.1.1+ also exports "raw" poly1305 primitive, but I > > have not tried it yet (it was not in 1.1.0). > > > > Trivial benchmark: > > time ssh -c chacha20-poly1305 at openssh.com -S none -o Compression=no > > \ > > localhost 'dd if=/dev/zero bs=100000 count=10000' >/dev/null > > (comparing "user time" only) > > > > openssh: 7.9p1, self-compiled, based on upstream package from > > debian/unstable, > > hostkey - ecdsa/p256, pubkey auth key - ecdh/p256 > > > > Machine: pretty old amd k8 (w/ SSE2, but no SSSE3/AVX/AESNI) > > OS: linux/debian/stretch, openssl 1.1.0j-1deb9u1 > > i386: speed: +8% > > amd64: speed: +10% > > > > Machine: raspberry pi 3b+ (BCM2837B0, 4-core Cortex-A53 @1.4GHz) > > OS: raspbian/stretch > > > > baseline: armhf/raspbian: unpatched ssh-7.9p1: 30.8s > > > > with openssl 1.1.0j-1deb9u1 from raspbian (compiled for armv6 > > without neon): > > > > armhf/raspbian: 24.7 seconds, speed: +25% > > > > with openssl 1.1.0j-1deb9u1 from debian/stretch/armhf (compiled for > > armv7 with neon autodetection): > > armhf: 22.2 seconds, speed: +39% > > > > Patches against 7.9p1 (tested) and git master (untested, only > > resolved > > configure.ac conflict) attached. > > Thanks for this - it seems to work okay with OpenSSL when patched to > -current, but when I adapt it for OpenBSD/LibreSSL the encryption is > broken and the connection fails right after KEX. > > I expect that there is some difference between OpenSSL and LibreSSL > wrt > IV lengths or something. OpenSSH does need to support both, so this > will > take a little figuring out. > > One comment on the patch itself: it passes do_encrypt though in a > bunch > of places and I'm not sure the usage is correct in all of them. In > fact > I don't think it can even be made consistent for decryption, as the > ctx->main_evp has to be used in encryption mode (not decryption) to > generate the poly1305 key. > > Given this is a stream cipher and there is AFAIK no difference > between > encryption and decryption, I think it would be better just fix > do_encrypt > to 1 to avoid inconsistency.Hi Damien, do you have any update on this? Indeed, it looks like LibreSSL has the IV of 96 b [1], while OpenSSL uses 128 bits (including the 32b counter) [2]. Otherwise, I did not notice any differences. I have really no experience with OpenBSD so I do not have simple way to test my changes, but I believe something like this should address the difference: diff --git a/cipher-chachapoly.c b/cipher-chachapoly.c index a58616fb..7e6995f6 100644 --- a/cipher-chachapoly.c +++ b/cipher-chachapoly.c @@ -109,7 +109,14 @@ chachapoly_crypt(struct chachapoly_ctx *ctx, u_int seqnr, u_char *dest, const u_char *src, u_int len, u_int aadlen, u_int authlen, int do_encrypt) { #if defined(WITH_OPENSSL) && defined(HAVE_EVP_CHACHA20) +#if defined(LIBRESSL_VERSION_NUMBER) +#define CHACHA_IV_OFFSET 4 + u_char seqbuf[12]; +#else +#define CHACHA_IV_OFFSET 8 + /* OpenSSL IV contains also the counter in the first 4 bytes */ u_char seqbuf[16]; +#endif int r = SSH_ERR_LIBCRYPTO_ERROR; #else u_char seqbuf[8]; @@ -125,7 +132,7 @@ chachapoly_crypt(struct chachapoly_ctx *ctx, u_int seqnr, u_char *dest, memset(poly_key, 0, sizeof(poly_key)); #if defined(WITH_OPENSSL) && defined(HAVE_EVP_CHACHA20) memset(seqbuf + 0, 0, 8); - POKE_U64(seqbuf + 8, seqnr); + POKE_U64(seqbuf + CHACHA_IV_OFFSET, seqnr); if (!EVP_CipherInit(ctx->main_evp, NULL, NULL, seqbuf, do_encrypt)) goto out; if (EVP_Cipher(ctx->main_evp, poly_key, (u_char *)poly_key, sizeof(poly_key)) < 0) For the do_encrypt, you are right. Chacha20 is stream cipher so there is no difference between decryption and encryption but the EVP API requires this argument. For consistency, I would be for using 1 in all the cases. If you have some wip branch you used for porting to openbsd or something I can test, I guess I can try that. [1] https://man.openbsd.org/man3/EVP_EncryptInit.3 [2] https://www.openssl.org/docs/man1.1.1/man3/EVP_chacha20_poly1305.html Regards, -- Jakub Jelen Senior Software Engineer Security Technologies Red Hat, Inc.
Yuriy M. Kaminskiy
2020-Jan-16 15:55 UTC
[patch 1/2] use chacha20 from openssl (1.1.0+) when possible
On 16.01.2020 13:27, Jakub Jelen wrote:> On Fri, 2019-07-12 at 15:54 +1000, Damien Miller wrote: >> On Thu, 17 Jan 2019, Yuriy M. Kaminskiy wrote: >> >>> On some cpu's optimized chacha implementation in openssl (1.1.0+) >>> is >>> notably faster (and on others it is just faster) than generic C >>> implementation in openssh. >>> >>> Sadly, openssl's chacha20-poly1305 (EVP_chacha20_poly1305) uses >>> different scheme (with padding/etc - see rfc8439) and it looks it >>> is not >>> possible to use in openssh. >>> >>> OpenSSL 1.1.1+ also exports "raw" poly1305 primitive, but I >>> have not tried it yet (it was not in 1.1.0). >>> >>> Trivial benchmark: >>> time ssh -c chacha20-poly1305 at openssh.com -S none -o Compression=no >>> \ >>> localhost 'dd if=/dev/zero bs=100000 count=10000' >/dev/null >>> (comparing "user time" only) >>> >>> openssh: 7.9p1, self-compiled, based on upstream package from >>> debian/unstable, >>> hostkey - ecdsa/p256, pubkey auth key - ecdh/p256 >>> >>> Machine: pretty old amd k8 (w/ SSE2, but no SSSE3/AVX/AESNI) >>> OS: linux/debian/stretch, openssl 1.1.0j-1deb9u1 >>> i386: speed: +8% >>> amd64: speed: +10% >>> >>> Machine: raspberry pi 3b+ (BCM2837B0, 4-core Cortex-A53 @1.4GHz) >>> OS: raspbian/stretch >>> >>> baseline: armhf/raspbian: unpatched ssh-7.9p1: 30.8s >>> >>> with openssl 1.1.0j-1deb9u1 from raspbian (compiled for armv6 >>> without neon): >>> >>> armhf/raspbian: 24.7 seconds, speed: +25% >>> >>> with openssl 1.1.0j-1deb9u1 from debian/stretch/armhf (compiled for >>> armv7 with neon autodetection): >>> armhf: 22.2 seconds, speed: +39% >>> >>> Patches against 7.9p1 (tested) and git master (untested, only >>> resolved >>> configure.ac conflict) attached. >> >> Thanks for this - it seems to work okay with OpenSSL when patched to >> -current, but when I adapt it for OpenBSD/LibreSSL the encryption is >> broken and the connection fails right after KEX. >> >> I expect that there is some difference between OpenSSL and LibreSSL >> wrt >> IV lengths or something. OpenSSH does need to support both, so this >> will >> take a little figuring out. >> >> One comment on the patch itself: it passes do_encrypt though in a >> bunch >> of places and I'm not sure the usage is correct in all of them. In >> fact >> I don't think it can even be made consistent for decryption, as the >> ctx->main_evp has to be used in encryption mode (not decryption) to >> generate the poly1305 key. >> >> Given this is a stream cipher and there is AFAIK no difference >> between >> encryption and decryption, I think it would be better just fix >> do_encrypt >> to 1 to avoid inconsistency. > > Hi Damien, > do you have any update on this? > > Indeed, it looks like LibreSSL has the IV of 96 b [1], while OpenSSL > uses 128 bits (including the 32b counter) [2]. Otherwise, I did not > notice any differences.Given libressl contains no optimized chacha20/poly1305/{curve,ed}25519, I'd rather use openssh builtin implementation on libressl.> I have really no experience with OpenBSD so I do not have simple way to > test my changes, but I believe something like this should address the > difference: > > diff --git a/cipher-chachapoly.c b/cipher-chachapoly.c > index a58616fb..7e6995f6 100644 > --- a/cipher-chachapoly.c > +++ b/cipher-chachapoly.c > @@ -109,7 +109,14 @@ chachapoly_crypt(struct chachapoly_ctx *ctx, u_int > seqnr, u_char *dest, > const u_char *src, u_int len, u_int aadlen, u_int authlen, int > do_encrypt) > { > #if defined(WITH_OPENSSL) && defined(HAVE_EVP_CHACHA20) > +#if defined(LIBRESSL_VERSION_NUMBER) > +#define CHACHA_IV_OFFSET 4 > + u_char seqbuf[12]; > +#else > +#define CHACHA_IV_OFFSET 8 > + /* OpenSSL IV contains also the counter in the first 4 bytes */ > u_char seqbuf[16]; > +#endif... and if not, I'd use EVP_CIPHER_CTX_iv_length() rather than brittle compile-time magic numbers.> int r = SSH_ERR_LIBCRYPTO_ERROR; > #else > u_char seqbuf[8]; > @@ -125,7 +132,7 @@ chachapoly_crypt(struct chachapoly_ctx *ctx, u_int > seqnr, u_char *dest, > memset(poly_key, 0, sizeof(poly_key)); > #if defined(WITH_OPENSSL) && defined(HAVE_EVP_CHACHA20) > memset(seqbuf + 0, 0, 8);memset(seqbuf + 0, 0, CHACHA_IV_OFFSET);> - POKE_U64(seqbuf + 8, seqnr); > + POKE_U64(seqbuf + CHACHA_IV_OFFSET, seqnr); > if (!EVP_CipherInit(ctx->main_evp, NULL, NULL, seqbuf, > do_encrypt)) > goto out; > if (EVP_Cipher(ctx->main_evp, poly_key, (u_char *)poly_key, > sizeof(poly_key)) < 0) > > For the do_encrypt, you are right. Chacha20 is stream cipher so there > is no difference between decryption and encryption but the EVP API > requires this argument. For consistency, I would be for using 1 in all > the cases. > > If you have some wip branch you used for porting to openbsd or > something I can test, I guess I can try that. > > [1] https://man.openbsd.org/man3/EVP_EncryptInit.3 > [2] > https://www.openssl.org/docs/man1.1.1/man3/EVP_chacha20_poly1305.html
Damien Miller
2020-Jan-23 00:57 UTC
[patch 1/2] use chacha20 from openssl (1.1.0+) when possible
On Thu, 16 Jan 2020, Jakub Jelen wrote:> > Thanks for this - it seems to work okay with OpenSSL when patched to > > -current, but when I adapt it for OpenBSD/LibreSSL the encryption is > > broken and the connection fails right after KEX.I've worked with the LibreSSL developers and they should land a fix for EVP_chacha20 soon. Hopefully this will happen soon enough to get this committed before the looming OpenSSH release. -d
Damien Miller
2020-Jan-23 02:37 UTC
[patch 1/2] use chacha20 from openssl (1.1.0+) when possible
On Thu, 23 Jan 2020, Damien Miller wrote:> On Thu, 16 Jan 2020, Jakub Jelen wrote: > > > > Thanks for this - it seems to work okay with OpenSSL when patched to > > > -current, but when I adapt it for OpenBSD/LibreSSL the encryption is > > > broken and the connection fails right after KEX. > > I've worked with the LibreSSL developers and they should land a fix > for EVP_chacha20 soon. Hopefully this will happen soon enough to get > this committed before the looming OpenSSH release.Here's the working patches BTW. I've separated the libcrypto chacha/poly implementation to its own file for clarity. -d -------------- next part --------------