From f0f8b124f0d2332e1c0b496df5e5f9c4b3db6bc3 Mon Sep 17 00:00:00 2001 From: Werner Koch Date: Thu, 13 Aug 2020 11:19:22 +0200 Subject: [PATCH] gpg: Ignore personal_digest_prefs for ECDSA keys. * g10/sign.c (hash_for): Simplify hash algo selection for ECDSA. -- GnuPG-bug-id: 5021 Signed-off-by: Werner Koch --- g10/sign.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/g10/sign.c b/g10/sign.c index a71ceda21..4793dd137 100644 --- a/g10/sign.c +++ b/g10/sign.c @@ -534,7 +534,7 @@ openpgp_card_v1_p (PKT_public_key *pk) } - +/* Get a matching hash algorithm for DSA and ECDSA. */ static int match_dsa_hash (unsigned int qbytes) { @@ -609,9 +609,13 @@ hash_for (PKT_public_key *pk) 160-bit hash unless --enable-dsa2 is set, in which case act like a new DSA key that just happens to have a 160-bit q (i.e. allow truncation). If q is not 160, by definition it - must be a new DSA key. */ + must be a new DSA key. We ignore the personal_digest_prefs + for ECDSA because they should always macth the curve and + truncated hashes are not useful either. Even worse, + smartcards may reject non matching hash lengths for curves + (e.g. using SHA-512 with brainpooolP385r1 on a Yubikey). */ - if (opt.personal_digest_prefs) + if (pk->pubkey_algo == PUBKEY_ALGO_DSA && opt.personal_digest_prefs) { prefitem_t *prefs;