From eddc77a1b1a59df4c7ba1a0705d684529b2205a1 Mon Sep 17 00:00:00 2001 From: Peter Todd Date: Wed, 1 Mar 2017 10:58:14 -0500 Subject: [PATCH] Add comment re: why SHA1 is disabled --- contrib/verify-commits/gpg.sh | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/contrib/verify-commits/gpg.sh b/contrib/verify-commits/gpg.sh index 4df8bee3b3..61e7552863 100755 --- a/contrib/verify-commits/gpg.sh +++ b/contrib/verify-commits/gpg.sh @@ -11,6 +11,15 @@ IFS=' if [ "$BITCOIN_VERIFY_COMMITS_ALLOW_SHA1" = 1 ]; then GPG_RES="$(echo "$INPUT" | gpg --trust-model always "$@" 2>/dev/null)" else + # Note how we've disabled SHA1 with the --weak-digest option, disabling + # signatures - including selfsigs - that use SHA1. While you might think that + # collision attacks shouldn't be an issue as they'd be an attack on yourself, + # in fact because what's being signed is a commit object that's + # semi-deterministically generated by untrusted input (the pull-req) in theory + # an attacker could construct a pull-req that results in a commit object that + # they've created a collision for. Not the most likely attack, but preventing + # it is pretty easy so we do so as a "belt-and-suspenders" measure. + GPG_RES="$(echo "$INPUT" | gpg --trust-model always --weak-digest sha1 "$@" 2>/dev/null)" fi for LINE in $(echo "$GPG_RES"); do