Blame SOURCES/openssh-8.7p1-nohostsha1proof.patch

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diff -up openssh-8.7p1/compat.c.sshrsacheck openssh-8.7p1/compat.c
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--- openssh-8.7p1/compat.c.sshrsacheck	2023-01-12 13:29:06.338710923 +0100
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+++ openssh-8.7p1/compat.c	2023-01-12 13:29:06.357711165 +0100
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@@ -43,6 +43,7 @@ void
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 compat_banner(struct ssh *ssh, const char *version)
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 {
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 	int i;
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+	int forbid_ssh_rsa = 0;
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 	static struct {
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 		char	*pat;
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 		int	bugs;
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@@ -145,16 +146,21 @@ compat_banner(struct ssh *ssh, const cha
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 	};
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 	/* process table, return first match */
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+	forbid_ssh_rsa = (ssh->compat & SSH_RH_RSASIGSHA);
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 	ssh->compat = 0;
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 	for (i = 0; check[i].pat; i++) {
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 		if (match_pattern_list(version, check[i].pat, 0) == 1) {
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 			debug_f("match: %s pat %s compat 0x%08x",
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 			    version, check[i].pat, check[i].bugs);
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 			ssh->compat = check[i].bugs;
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+	if (forbid_ssh_rsa)
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+		ssh->compat |= SSH_RH_RSASIGSHA;
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 			return;
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 		}
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 	}
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 	debug_f("no match: %s", version);
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+	if (forbid_ssh_rsa)
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+		ssh->compat |= SSH_RH_RSASIGSHA;
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 }
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 /* Always returns pointer to allocated memory, caller must free. */
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diff -up openssh-8.7p1/compat.h.sshrsacheck openssh-8.7p1/compat.h
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--- openssh-8.7p1/compat.h.sshrsacheck	2021-08-20 06:03:49.000000000 +0200
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+++ openssh-8.7p1/compat.h	2023-01-12 13:29:06.358711178 +0100
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@@ -30,7 +30,7 @@
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 #define SSH_BUG_UTF8TTYMODE	0x00000001
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 #define SSH_BUG_SIGTYPE		0x00000002
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 #define SSH_BUG_SIGTYPE74	0x00000004
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-/* #define unused		0x00000008 */
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+#define SSH_RH_RSASIGSHA	0x00000008
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 #define SSH_OLD_SESSIONID	0x00000010
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 /* #define unused		0x00000020 */
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 #define SSH_BUG_DEBUG		0x00000040
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diff -up openssh-8.7p1/serverloop.c.sshrsacheck openssh-8.7p1/serverloop.c
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--- openssh-8.7p1/serverloop.c.sshrsacheck	2023-01-12 14:57:08.118400073 +0100
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+++ openssh-8.7p1/serverloop.c	2023-01-12 14:59:17.330470518 +0100
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@@ -737,6 +737,10 @@ server_input_hostkeys_prove(struct ssh *
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 			else if (ssh->kex->flags & KEX_RSA_SHA2_256_SUPPORTED)
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 				sigalg = "rsa-sha2-256";
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 		}
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+		if (ssh->compat & SSH_RH_RSASIGSHA && sigalg == NULL) {
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+			sigalg = "rsa-sha2-512";
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+			debug3_f("SHA1 signature is not supported, falling back to %s", sigalg);
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+		}
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 		debug3_f("sign %s key (index %d) using sigalg %s",
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 		sshkey_type(key), ndx, sigalg == NULL ? "default" : sigalg);
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 		if ((r = sshbuf_put_cstring(sigbuf,
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diff -up openssh-8.7p1/sshd.c.sshrsacheck openssh-8.7p1/sshd.c
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--- openssh-8.7p1/sshd.c.sshrsacheck	2023-01-12 13:29:06.355711140 +0100
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+++ openssh-8.7p1/sshd.c	2023-01-12 13:29:06.358711178 +0100
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@@ -1640,6 +1651,7 @@ main(int ac, char **av)
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 	int keytype;
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 	Authctxt *authctxt;
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 	struct connection_info *connection_info = NULL;
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+	int forbid_ssh_rsa = 0;
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 #ifdef HAVE_SECUREWARE
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 	(void)set_auth_parameters(ac, av);
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@@ -1938,6 +1950,19 @@ main(int ac, char **av)
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 		    key = NULL;
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 		    continue;
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 		}
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+		if (key && (sshkey_type_plain(key->type) == KEY_RSA || sshkey_type_plain(key->type) == KEY_RSA_CERT)) {
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+		    size_t sign_size = 0;
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+		    u_char *tmp = NULL;
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+		    u_char data[] = "Test SHA1 vector";
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+		    int res;
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+
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+		    res = ssh_rsa_sign(key, &tmp, &sign_size, data, sizeof(data), NULL);
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+		    free(tmp);
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+		    if (res == SSH_ERR_LIBCRYPTO_ERROR) {
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+			logit_f("sshd: ssh-rsa algorithm is disabled");
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+		    	forbid_ssh_rsa = 1;
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+		    }
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+		}
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 		if (sshkey_is_sk(key) &&
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 		    key->sk_flags & SSH_SK_USER_PRESENCE_REQD) {
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 			debug("host key %s requires user presence, ignoring",
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@@ -2275,6 +2306,9 @@ main(int ac, char **av)
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 	check_ip_options(ssh);
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+	if (forbid_ssh_rsa)
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+		ssh->compat |= SSH_RH_RSASIGSHA;
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+
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 	/* Prepare the channels layer */
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 	channel_init_channels(ssh);
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 	channel_set_af(ssh, options.address_family);