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52 lines
2.0 KiB
52 lines
2.0 KiB
From 1c6d5f6162a46bcde94e8ae9eaa0c41da1d7faa3 Mon Sep 17 00:00:00 2001
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From: Clemens Lang <cllang@redhat.com>
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Date: Tue, 1 Mar 2022 15:44:18 +0100
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Subject: [PATCH] Allow SHA1 in seclevel 2 if rh-allow-sha1-signatures = yes
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References: rhbz#2055796
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---
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doc/man5/config.pod | 7 ++++++-
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ssl/t1_lib.c | 8 ++++++++
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2 files changed, 14 insertions(+), 1 deletion(-)
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diff --git a/doc/man5/config.pod b/doc/man5/config.pod
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index aa1be5ca7f..aa69e2b844 100644
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--- a/doc/man5/config.pod
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+++ b/doc/man5/config.pod
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@@ -305,7 +305,12 @@ When set to B<no>, any attempt to create or verify a signature with a SHA1
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digest will fail. For compatibility with older versions of OpenSSL, set this
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option to B<yes>. This setting also affects TLS, where signature algorithms
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that use SHA1 as digest will no longer be supported if this option is set to
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-B<no>.
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+B<no>. Note that enabling B<rh-allow-sha1-signatures> will allow TLS signature
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+algorithms that use SHA1 in security level 2, despite the definition of
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+security level 2 of 112 bits of security, which SHA1 does not meet. Because
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+TLS 1.1 or lower use MD5-SHA1 as pseudorandom function (PRF) to derive key
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+material, disabling B<rh-allow-sha1-signatures> requires the use of TLS 1.2 or
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+newer.
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=item B<fips_mode> (deprecated)
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diff --git a/ssl/t1_lib.c b/ssl/t1_lib.c
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index 4b74ee1a34..724ded67ba 100644
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--- a/ssl/t1_lib.c
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+++ b/ssl/t1_lib.c
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@@ -2106,6 +2106,14 @@ static int tls12_sigalg_allowed(const SSL *s, int op, const SIGALG_LOOKUP *lu)
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}
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}
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+ if (lu->hash == NID_sha1
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+ && ossl_ctx_legacy_digest_signatures_allowed(s->ctx->libctx, 0)
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+ && SSL_get_security_level(s) < 3) {
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+ /* when rh-allow-sha1-signatures = yes and security level <= 2,
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+ * explicitly allow SHA1 for backwards compatibility */
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+ return 1;
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+ }
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+
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/* Finally see if security callback allows it */
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secbits = sigalg_security_bits(s->ctx, lu);
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sigalgstr[0] = (lu->sigalg >> 8) & 0xff;
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--
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2.35.1
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