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[2a01:4f8:120:2468::2]) by smtp.gmail.com with ESMTPSA id i25-20020a1c5419000000b003c7084d072csm2180351wmb.28.2022.10.26.07.57.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 Oct 2022 07:57:00 -0700 (PDT) From: =?utf-8?b?w4Z2YXIgQXJuZmrDtnLDsCBCamFybWFzb24=?= To: git@vger.kernel.org Cc: Junio C Hamano , Mike Hommey , "brian m . carlson" , =?utf-8?q?Carlo_Marcelo?= =?utf-8?q?_Arenas_Bel=C3=B3n?= , Eric Sunshine , Glen Choo , Eric DeCosta , =?utf-8?b?w4Z2YXIgQXJuZmrDtnLDsCBC?= =?utf-8?b?amFybWFzb24=?= Subject: [PATCH v4 9/9] Makefile: discuss SHAttered in *_SHA{1,256} discussion Date: Wed, 26 Oct 2022 16:56:47 +0200 Message-Id: X-Mailer: git-send-email 2.38.0.1251.g3eefdfb5e7a In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Let's mention the SHAttered attack and more generally why we use the sha1collisiondetection backend by default, and note that for SHA-256 the user should feel free to pick any of the supported backends as far as hashing security is concerned. Signed-off-by: Ævar Arnfjörð Bjarmason --- Makefile | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/Makefile b/Makefile index a0ca6456b85..805e88ed5fd 100644 --- a/Makefile +++ b/Makefile @@ -481,6 +481,16 @@ include shared.mak # # === SHA-1 backend === # +# ==== Security ==== +# +# Due to the SHAttered (https://shattered.io) attack vector on SHA-1 +# it's strongly recommended to use the sha1collisiondetection +# counter-cryptanalysis library for SHA-1 hashing (DC_SHA1). +# +# If you know that you can trust the repository contents, or where +# potential SHA-1 attacks are otherwise mitigated the backends listed +# in "Other SHA-1 implementations" are faster than DC_SHA1. +# # ==== Default SHA-1 backend ==== # # If no *_SHA1 backend is picked we'll fall back on using the default. @@ -525,6 +535,11 @@ include shared.mak # # === SHA-256 backend === # +# ==== Security ==== +# +# Unlike SHA-1 the SHA-256 algorithm does not suffer from any known +# vulnerabilities, so any implementation will do. +# # ==== Default SHA-256 backend ==== # # If no *_SHA256 backend is picked we'll fall fall back on using the