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Allow SHA1 in seclevel 2 if rh-allow-sha1-signatures = yes

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We want legacy policy to be able to talk to older RHEL that only
supports SHA1 signature algorithms, so allow SHA1 signatures even in
seclevel 2 if rh-allow-sha1-signatures is set to yes.

Resolves: rhbz#2060510
Signed-off-by: Clemens Lang <cllang@redhat.com>
This commit is contained in:
Clemens Lang 2022-03-01 15:58:48 +01:00
parent ede38fcb54
commit 3c66c99bd5
2 changed files with 58 additions and 1 deletions
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51
0052-Allow-SHA1-in-seclevel-2-if-rh-allow-sha1-signatures.patch Normal file
View File

@ -0,0 +1,51 @@
From 1c6d5f6162a46bcde94e8ae9eaa0c41da1d7faa3 Mon Sep 17 00:00:00 2001
From: Clemens Lang <cllang@redhat.com>
Date: Tue, 1 Mar 2022 15:44:18 +0100
Subject: [PATCH] Allow SHA1 in seclevel 2 if rh-allow-sha1-signatures = yes
References: rhbz#2055796
---
doc/man5/config.pod | 7 ++++++-
ssl/t1_lib.c | 8 ++++++++
2 files changed, 14 insertions(+), 1 deletion(-)
diff --git a/doc/man5/config.pod b/doc/man5/config.pod
index aa1be5ca7f..aa69e2b844 100644
--- a/doc/man5/config.pod
+++ b/doc/man5/config.pod
@@ -305,7 +305,12 @@ When set to B<no>, any attempt to create or verify a signature with a SHA1
digest will fail. For compatibility with older versions of OpenSSL, set this
option to B<yes>. This setting also affects TLS, where signature algorithms
that use SHA1 as digest will no longer be supported if this option is set to
-B<no>.
+B<no>. Note that enabling B<rh-allow-sha1-signatures> will allow TLS signature
+algorithms that use SHA1 in security level 2, despite the definition of
+security level 2 of 112 bits of security, which SHA1 does not meet. Because
+TLS 1.1 or lower use MD5-SHA1 as pseudorandom function (PRF) to derive key
+material, disabling B<rh-allow-sha1-signatures> requires the use of TLS 1.2 or
+newer.
=item B<fips_mode> (deprecated)
diff --git a/ssl/t1_lib.c b/ssl/t1_lib.c
index 4b74ee1a34..724ded67ba 100644
--- a/ssl/t1_lib.c
+++ b/ssl/t1_lib.c
@@ -2106,6 +2106,14 @@ static int tls12_sigalg_allowed(const SSL *s, int op, const SIGALG_LOOKUP *lu)
}
}
+ if (lu->hash == NID_sha1
+ && ossl_ctx_legacy_digest_signatures_allowed(s->ctx->libctx, 0)
+ && SSL_get_security_level(s) < 3) {
+ /* when rh-allow-sha1-signatures = yes and security level <= 2,
+ * explicitly allow SHA1 for backwards compatibility */
+ return 1;
+ }
+
/* Finally see if security callback allows it */
secbits = sigalg_security_bits(s->ctx, lu);
sigalgstr[0] = (lu->sigalg >> 8) & 0xff;
--
2.35.1

8
openssl.spec
View File

@ -15,7 +15,7 @@
Summary: Utilities from the general purpose cryptography library with TLS implementation
Name: openssl
Version: 3.0.1
Release: 14%{?dist}
Release: 15%{?dist}
Epoch: 1
# We have to remove certain patented algorithms from the openssl source
# tarball with the hobble-openssl script which is included below.
@ -82,6 +82,8 @@ Patch49: 0049-Selectively-disallow-SHA1-signatures.patch
Patch50: 0050-FIPS-enable-pkcs12-mac.patch
# Backport of patch for RHEL for Edge rhbz #2027261
Patch51: 0051-Support-different-R_BITS-lengths-for-KBKDF.patch
# Allow SHA1 in seclevel 2 if rh-allow-sha1-signatures = yes
Patch52: 0052-Allow-SHA1-in-seclevel-2-if-rh-allow-sha1-signatures.patch
License: ASL 2.0
URL: http://www.openssl.org/
@ -412,6 +414,10 @@ install -m644 %{SOURCE9} \
%ldconfig_scriptlets libs
%changelog
* Tue Mar 01 2022 Clemens Lang <cllang@redhat.com> - 1:3.0.1-15
- Allow SHA1 in SECLEVEL 2 if rh-allow-sha1-signatures = yes
- Resolves: rhbz#2060510
* Fri Feb 25 2022 Clemens Lang <cllang@redhat.com> - 1:3.0.1-14
- Prevent use of SHA1 with ECDSA
- Resolves: rhbz#2031742