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authordjm@openbsd.org <djm@openbsd.org>2019-05-20 00:20:35 +0000
committerDamien Miller <djm@mindrot.org>2019-05-20 10:21:58 +1000
commit476e3551b2952ef73acc43d995e832539bf9bc4d (patch)
tree326f23ca0f27d7fd4242ce88892d0af9a2da2c3c
parent606077ee1e77af5908431d003fb28461ef7be092 (diff)
upstream: When signing certificates with an RSA key, default to
using the rsa-sha2-512 signature algorithm. Certificates signed by RSA keys will therefore be incompatible with OpenSSH < 7.2 unless the default is overridden. Document the ability of the ssh-keygen -t flag to override the signature algorithm when signing certificates, and the new default. ok deraadt@ OpenBSD-Commit-ID: 400c9c15013978204c2cb80f294b03ae4cfc8b95
-rw-r--r--ssh-keygen.113
-rw-r--r--sshkey.c9
2 files changed, 19 insertions, 3 deletions
diff --git a/ssh-keygen.1 b/ssh-keygen.1
index f2977424..673bf6e2 100644
--- a/ssh-keygen.1
+++ b/ssh-keygen.1
@@ -1,4 +1,4 @@
-.\" $OpenBSD: ssh-keygen.1,v 1.158 2019/04/19 05:47:44 dtucker Exp $
+.\" $OpenBSD: ssh-keygen.1,v 1.159 2019/05/20 00:20:35 djm Exp $
.\"
.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -35,7 +35,7 @@
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
-.Dd $Mdocdate: April 19 2019 $
+.Dd $Mdocdate: May 20 2019 $
.Dt SSH-KEYGEN 1
.Os
.Sh NAME
@@ -577,6 +577,15 @@ The possible values are
.Dq ed25519 ,
or
.Dq rsa .
+.Pp
+This flag may also be used to specify the desired signature type when
+signing certificates using a RSA CA key.
+The available RSA signature variants are
+.Dq ssh-rsa
+(SHA1 signatures, not recommended),
+.Dq rsa-sha2-256
+.Dq rsa-sha2-512
+(the default).
.It Fl U
When used in combination with
.Fl s ,
diff --git a/sshkey.c b/sshkey.c
index 9849cb23..379a579c 100644
--- a/sshkey.c
+++ b/sshkey.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshkey.c,v 1.74 2019/05/03 03:25:18 dtucker Exp $ */
+/* $OpenBSD: sshkey.c,v 1.75 2019/05/20 00:20:35 djm Exp $ */
/*
* Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
* Copyright (c) 2008 Alexander von Gernler. All rights reserved.
@@ -2528,6 +2528,13 @@ sshkey_certify_custom(struct sshkey *k, struct sshkey *ca, const char *alg,
strcmp(alg, k->cert->signature_type) != 0)
return SSH_ERR_INVALID_ARGUMENT;
+ /*
+ * If no signing algorithm or signature_type was specified and we're
+ * using a RSA key, then default to a good signature algorithm.
+ */
+ if (alg == NULL && ca->type == KEY_RSA)
+ alg = "rsa-sha2-512";
+
if ((ret = sshkey_to_blob(ca, &ca_blob, &ca_len)) != 0)
return SSH_ERR_KEY_CERT_INVALID_SIGN_KEY;