From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by inbox.dpdk.org (Postfix) with ESMTP id ECEA948884; Wed, 1 Oct 2025 20:57:04 +0200 (CEST) Received: from mails.dpdk.org (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id DAB5A40BA0; Wed, 1 Oct 2025 20:57:04 +0200 (CEST) Received: from dkmailrelay1.smartsharesystems.com (smartserver.smartsharesystems.com [77.243.40.215]) by mails.dpdk.org (Postfix) with ESMTP id C3125400D5 for ; Wed, 1 Oct 2025 20:57:03 +0200 (CEST) Received: from smartserver.smartsharesystems.com (smartserver.smartsharesys.local [192.168.4.10]) by dkmailrelay1.smartsharesystems.com (Postfix) with ESMTP id A618F209B9; Wed, 1 Oct 2025 20:57:02 +0200 (CEST) Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Subject: RE: [dpdk-dev v5 1/2] eal: introduce rte_timingsafe_memcmp() based on OpenBSD API Date: Wed, 1 Oct 2025 20:57:02 +0200 Message-ID: <98CBD80474FA8B44BF855DF32C47DC35F6548B@smartserver.smartshare.dk> In-Reply-To: <20251001153242.55987-1-kai.ji@intel.com> X-MimeOLE: Produced By Microsoft Exchange V6.5 X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [dpdk-dev v5 1/2] eal: introduce rte_timingsafe_memcmp() based on OpenBSD API Thread-Index: Adwy6KYSeY7Xv/vGRaGEd4AitL9zLAAGs04Q References: <20250929145049.153078-1-kai.ji@intel.com> <20251001153242.55987-1-kai.ji@intel.com> From: =?iso-8859-1?Q?Morten_Br=F8rup?= To: "Kai Ji" , , Cc: , , , X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org > From: Kai Ji [mailto:kai.ji@intel.com] > Sent: Wednesday, 1 October 2025 17.33 >=20 > Bugzilla ID: 1773 > https://bugs.dpdk.org/show_bug.cgi?id=3D1773 >=20 > Signed-off-by: Kai Ji > --- > lib/eal/include/rte_memory.h | 38 = ++++++++++++++++++++++++++++++++++++ > 1 file changed, 38 insertions(+) >=20 > diff --git a/lib/eal/include/rte_memory.h > b/lib/eal/include/rte_memory.h > index dcc0e69cfe..6939c1caad 100644 > --- a/lib/eal/include/rte_memory.h > +++ b/lib/eal/include/rte_memory.h > @@ -746,6 +746,44 @@ __rte_experimental > void > rte_memzero_explicit(void *dst, size_t sz); >=20 > +/** > + * @warning > + * @b EXPERIMENTAL: this API may change without prior notice. > + * > + * Constant-time memory comparison. > + * > + * This function compares two memory regions in constant time, making > it > + * resistant to timing side-channel attacks. The execution time > depends only > + * on the length parameter, not on the actual data values being > compared. > + * > + * This is particularly important for cryptographic operations where > timing > + * differences could leak information about secret keys, passwords, = or > other > + * sensitive data. > + * > + * @param a > + * Pointer to the first memory region to compare > + * @param b > + * Pointer to the second memory region to compare > + * @param n > + * Number of bytes to compare > + * @return > + * 0 if the memory regions are identical, non-zero if they differ > + */ > +__rte_experimental > +static inline int > +rte_timingsafe_memcmp(const void *a, const void *b, size_t n) > +{ > + const volatile uint8_t *pa =3D (const volatile uint8_t *)a; > + const volatile uint8_t *pb =3D (const volatile uint8_t *)b; > + uint8_t result =3D 0; > + size_t i; > + > + for (i =3D 0; i < n; i++) > + result |=3D pa[i] ^ pb[i]; > + > + return result; > +} > + > #ifdef __cplusplus > } > #endif > -- > 2.34.1 NAK. This returns (binary) non-equality only. It does not return (tri-state) = <0, 0, or >0, so it's not like memcmp or FreeBSD timingsafe_memcmp. Also, please put the function ("memeq") first in the name, and then the = extra property ("timingsafe") last, like rte_memzero_explicit. Like this: __rte_experimental static inline bool rte_memeq_timingsafe(const void *a, const void *b, size_t n) { const volatile uint8_t *pa =3D (const volatile uint8_t *)a; const volatile uint8_t *pb =3D (const volatile uint8_t *)b; uint8_t result =3D 0; size_t i; for (i =3D 0; i < n; i++) result |=3D pa[i] ^ pb[i]; return result =3D=3D UINT8_C(0); } Stephen, agree?