Make with config keywords support which percent_expansions more consistent.

 - %C is moved into its own function and added to Match Exec.
 - move the common (global) options into a macro.  This is ugly but it's
   the least-ugly way I could come up with.
 - move IdentityAgent and ForwardAgent percent expansion to before the
   config dump to make it regression-testable.
 - document all of the above

ok jmc@ for man page bits, "makes things less terrible" djm@ for the rest.

4 files changed, 92 insertions, 88 deletions

diff --git a/usr.bin/ssh/readconf.c b/usr.bin/ssh/readconf.c
index 886ebcdcadf..dce08a7e7ad 100644
--- a/usr.bin/ssh/readconf.c
+++ b/usr.bin/ssh/readconf.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: readconf.c,v 1.326 2020/02/06 22:46:31 djm Exp $ */
+/* $OpenBSD: readconf.c,v 1.327 2020/04/03 02:27:12 dtucker Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -310,6 +310,24 @@ kex_default_pk_alg(void)
 	return kex_default_pk_alg_filtered;
 }
 
+char *
+ssh_connection_hash(const char *thishost, const char *host, const char *portstr,
+    const char *user)
+{
+	struct ssh_digest_ctx *md;
+	u_char conn_hash[SSH_DIGEST_MAX_LENGTH];
+
+	if ((md = ssh_digest_start(SSH_DIGEST_SHA1)) == NULL ||
+	    ssh_digest_update(md, thishost, strlen(thishost)) < 0 ||
+	    ssh_digest_update(md, host, strlen(host)) < 0 ||
+	    ssh_digest_update(md, portstr, strlen(portstr)) < 0 ||
+	    ssh_digest_update(md, user, strlen(user)) < 0 ||
+	    ssh_digest_final(md, conn_hash, sizeof(conn_hash)) < 0)
+		fatal("%s: mux digest failed", __func__);
+	ssh_digest_free(md);
+	return tohex(conn_hash, ssh_digest_bytes(SSH_DIGEST_SHA1));
+}
+
 /*
  * Adds a local TCP/IP port forward to options.  Never returns if there is an
  * error.
@@ -632,6 +650,8 @@ match_cfg_line(Options *options, char **condition, struct passwd *pw,
 			if (r == (negate ? 1 : 0))
 				this_result = result = 0;
 		} else if (strcasecmp(attrib, "exec") == 0) {
+			char *conn_hash_hex;
+
 			if (gethostname(thishost, sizeof(thishost)) == -1)
 				fatal("gethostname: %s", strerror(errno));
 			strlcpy(shorthost, thishost, sizeof(shorthost));
@@ -639,8 +659,11 @@ match_cfg_line(Options *options, char **condition, struct passwd *pw,
 			snprintf(portstr, sizeof(portstr), "%d", port);
 			snprintf(uidstr, sizeof(uidstr), "%llu",
 			    (unsigned long long)pw->pw_uid);
+			conn_hash_hex = ssh_connection_hash(thishost, host,
+			   portstr, pw->pw_name);
 
 			cmd = percent_expand(arg,
+			    "C", conn_hash_hex,
 			    "L", shorthost,
 			    "d", pw->pw_dir,
 			    "h", host,
@@ -651,6 +674,7 @@ match_cfg_line(Options *options, char **condition, struct passwd *pw,
 			    "u", pw->pw_name,
 			    "i", uidstr,
 			    (char *)NULL);
+			free(conn_hash_hex);
 			if (result != 1) {
 				/* skip execution if prior predicate failed */
 				debug3("%.200s line %d: skipped exec "
diff --git a/usr.bin/ssh/readconf.h b/usr.bin/ssh/readconf.h
index feedb3d202c..e143a1082ae 100644
--- a/usr.bin/ssh/readconf.h
+++ b/usr.bin/ssh/readconf.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: readconf.h,v 1.132 2020/01/23 02:46:49 dtucker Exp $ */
+/* $OpenBSD: readconf.h,v 1.133 2020/04/03 02:27:12 dtucker Exp $ */
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -200,6 +200,8 @@ typedef struct {
 #define SSH_STRICT_HOSTKEY_ASK	3
 
 const char *kex_default_pk_alg(void);
+char	*ssh_connection_hash(const char *thishost, const char *host,
+    const char *portstr, const char *user);
 void     initialize_options(Options *);
 void     fill_default_options(Options *);
 void	 fill_default_options_for_canonicalization(Options *);
diff --git a/usr.bin/ssh/ssh.c b/usr.bin/ssh/ssh.c
index 1bc5443f361..3ed4cd73342 100644
--- a/usr.bin/ssh/ssh.c
+++ b/usr.bin/ssh/ssh.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh.c,v 1.521 2020/03/06 18:20:02 markus Exp $ */
+/* $OpenBSD: ssh.c,v 1.522 2020/04/03 02:27:12 dtucker Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -76,7 +76,6 @@
 #include "canohost.h"
 #include "compat.h"
 #include "cipher.h"
-#include "digest.h"
 #include "packet.h"
 #include "sshbuf.h"
 #include "channels.h"
@@ -161,6 +160,13 @@ char *forward_agent_sock_path = NULL;
 /* Various strings used to to percent_expand() arguments */
 static char thishost[NI_MAXHOST], shorthost[NI_MAXHOST], portstr[NI_MAXSERV];
 static char uidstr[32], *host_arg, *conn_hash_hex;
+#define DEFAULT_CLIENT_PERCENT_EXPAND_ARGS \
+    "C", conn_hash_hex, \
+    "L", shorthost, \
+    "i", uidstr, \
+    "l", thishost, \
+    "n", host_arg, \
+    "p", portstr
 
 /* socket address the host resolves to */
 struct sockaddr_storage hostaddr;
@@ -585,8 +591,6 @@ main(int ac, char **av)
 	extern char *optarg;
 	struct Forward fwd;
 	struct addrinfo *addrs = NULL;
-	struct ssh_digest_ctx *md;
-	u_char conn_hash[SSH_DIGEST_MAX_LENGTH];
 	size_t n, len;
 
 	/* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
@@ -1309,15 +1313,8 @@ main(int ac, char **av)
 	snprintf(uidstr, sizeof(uidstr), "%llu",
 	    (unsigned long long)pw->pw_uid);
 
-	if ((md = ssh_digest_start(SSH_DIGEST_SHA1)) == NULL ||
-	    ssh_digest_update(md, thishost, strlen(thishost)) < 0 ||
-	    ssh_digest_update(md, host, strlen(host)) < 0 ||
-	    ssh_digest_update(md, portstr, strlen(portstr)) < 0 ||
-	    ssh_digest_update(md, options.user, strlen(options.user)) < 0 ||
-	    ssh_digest_final(md, conn_hash, sizeof(conn_hash)) < 0)
-		fatal("%s: mux digest failed", __func__);
-	ssh_digest_free(md);
-	conn_hash_hex = tohex(conn_hash, ssh_digest_bytes(SSH_DIGEST_SHA1));
+	conn_hash_hex = ssh_connection_hash(thishost, host, portstr,
+	    options.user);
 
 	/*
 	 * Expand tokens in arguments. NB. LocalCommand is expanded later,
@@ -1328,14 +1325,9 @@ main(int ac, char **av)
 		debug3("expanding RemoteCommand: %s", options.remote_command);
 		cp = options.remote_command;
 		options.remote_command = percent_expand(cp,
-		    "C", conn_hash_hex,
-		    "L", shorthost,
+		    DEFAULT_CLIENT_PERCENT_EXPAND_ARGS,
 		    "d", pw->pw_dir,
 		    "h", host,
-		    "i", uidstr,
-		    "l", thishost,
-		    "n", host_arg,
-		    "p", portstr,
 		    "r", options.user,
 		    "u", pw->pw_name,
 		    (char *)NULL);
@@ -1350,20 +1342,44 @@ main(int ac, char **av)
 		cp = tilde_expand_filename(options.control_path, getuid());
 		free(options.control_path);
 		options.control_path = percent_expand(cp,
-		    "C", conn_hash_hex,
-		    "L", shorthost,
+		    DEFAULT_CLIENT_PERCENT_EXPAND_ARGS,
+		    "d", pw->pw_dir,
 		    "h", host,
-		    "i", uidstr,
-		    "l", thishost,
-		    "n", host_arg,
-		    "p", portstr,
 		    "r", options.user,
 		    "u", pw->pw_name,
-		    "i", uidstr,
 		    (char *)NULL);
 		free(cp);
 	}
 
+	if (options.identity_agent != NULL) {
+		p = tilde_expand_filename(options.identity_agent, getuid());
+		cp = percent_expand(p,
+		    DEFAULT_CLIENT_PERCENT_EXPAND_ARGS,
+		    "d", pw->pw_dir,
+		    "h", host,
+		    "r", options.user,
+		    "u", pw->pw_name,
+		    (char *)NULL);
+		free(p);
+		free(options.identity_agent);
+		options.identity_agent = cp;
+	}
+
+	if (options.forward_agent_sock_path != NULL) {
+		p = tilde_expand_filename(options.forward_agent_sock_path,
+		    getuid());
+		cp = percent_expand(p,
+		    DEFAULT_CLIENT_PERCENT_EXPAND_ARGS,
+		    "d", pw->pw_dir,
+		    "h", host,
+		    "r", options.user,
+		    "u", pw->pw_name,
+		    (char *)NULL);
+		free(p);
+		free(options.forward_agent_sock_path);
+		options.forward_agent_sock_path = cp;
+	}
+
 	if (config_test) {
 		dump_client_config(&options, host);
 		exit(0);
@@ -1482,23 +1498,7 @@ main(int ac, char **av)
 		if (strcmp(options.identity_agent, "none") == 0) {
 			unsetenv(SSH_AUTHSOCKET_ENV_NAME);
 		} else {
-			p = tilde_expand_filename(options.identity_agent,
-			    getuid());
-			cp = percent_expand(p,
-			    "d", pw->pw_dir,
-			    "h", host,
-			    "i", uidstr,
-			    "l", thishost,
-			    "r", options.user,
-			    "u", pw->pw_name,
-			    (char *)NULL);
-			free(p);
-			/*
-			 * If identity_agent represents an environment variable
-			 * then recheck that it is valid (since processing with
-			 * percent_expand() may have changed it) and substitute
-			 * its value.
-			 */
+			cp = options.identity_agent;
 			if (cp[0] == '$') {
 				if (!valid_env_name(cp + 1)) {
 					fatal("Invalid IdentityAgent "
@@ -1512,22 +1512,10 @@ main(int ac, char **av)
 				/* identity_agent specifies a path directly */
 				setenv(SSH_AUTHSOCKET_ENV_NAME, cp, 1);
 			}
-			free(cp);
 		}
 	}
 
-	if (options.forward_agent && (options.forward_agent_sock_path != NULL)) {
-		p = tilde_expand_filename(options.forward_agent_sock_path, getuid());
-		cp = percent_expand(p,
-		    "d", pw->pw_dir,
-		    "h", host,
-		    "i", uidstr,
-		    "l", thishost,
-		    "r", options.user,
-		    "u", pw->pw_name,
-		    (char *)NULL);
-		free(p);
-
+	if (options.forward_agent && options.forward_agent_sock_path != NULL) {
 		if (cp[0] == '$') {
 			if (!valid_env_name(cp + 1)) {
 				fatal("Invalid ForwardAgent environment variable name %s", cp);
@@ -1952,14 +1940,9 @@ ssh_session2(struct ssh *ssh, struct passwd *pw)
 		debug3("expanding LocalCommand: %s", options.local_command);
 		cp = options.local_command;
 		options.local_command = percent_expand(cp,
-		    "C", conn_hash_hex,
-		    "L", shorthost,
+		    DEFAULT_CLIENT_PERCENT_EXPAND_ARGS,
 		    "d", pw->pw_dir,
 		    "h", host,
-		    "i", uidstr,
-		    "l", thishost,
-		    "n", host_arg,
-		    "p", portstr,
 		    "r", options.user,
 		    "u", pw->pw_name,
 		    "T", tun_fwd_ifname == NULL ? "NONE" : tun_fwd_ifname,
@@ -2116,9 +2099,13 @@ load_public_identity_files(struct passwd *pw)
 			continue;
 		}
 		cp = tilde_expand_filename(options.identity_files[i], getuid());
-		filename = percent_expand(cp, "d", pw->pw_dir,
-		    "u", pw->pw_name, "l", thishost, "h", host,
-		    "r", options.user, (char *)NULL);
+		filename = percent_expand(cp,
+		    DEFAULT_CLIENT_PERCENT_EXPAND_ARGS,
+		    "d", pw->pw_dir,
+		    "h", host,
+		    "r", options.user,
+		    "u", pw->pw_name,
+		    (char *)NULL);
 		free(cp);
 		check_load(sshkey_load_public(filename, &public, NULL),
 		    filename, "pubkey");
@@ -2168,10 +2155,9 @@ load_public_identity_files(struct passwd *pw)
 		cp = tilde_expand_filename(options.certificate_files[i],
 		    getuid());
 		filename = percent_expand(cp,
+		    DEFAULT_CLIENT_PERCENT_EXPAND_ARGS,
 		    "d", pw->pw_dir,
 		    "h", host,
-		    "i", uidstr,
-		    "l", thishost,
 		    "r", options.user,
 		    "u", pw->pw_name,
 		    (char *)NULL);
diff --git a/usr.bin/ssh/ssh_config.5 b/usr.bin/ssh/ssh_config.5
index 14afcdbd602..1a51b82c575 100644
--- a/usr.bin/ssh/ssh_config.5
+++ b/usr.bin/ssh/ssh_config.5
@@ -33,8 +33,8 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.\" $OpenBSD: ssh_config.5,v 1.322 2020/02/07 03:54:44 dtucker Exp $
-.Dd $Mdocdate: February 7 2020 $
+.\" $OpenBSD: ssh_config.5,v 1.323 2020/04/03 02:27:12 dtucker Exp $
+.Dd $Mdocdate: April 3 2020 $
 .Dt SSH_CONFIG 5
 .Os
 .Sh NAME
@@ -1846,31 +1846,23 @@ otherwise.
 The local username.
 .El
 .Pp
-.Cm Match exec
-accepts the tokens %%, %h, %i, %L, %l, %n, %p, %r, and %u.
-.Pp
-.Cm CertificateFile
-accepts the tokens %%, %d, %h, %i, %l, %r, and %u.
-.Pp
-.Cm ControlPath
-accepts the tokens %%, %C, %h, %i, %L, %l, %n, %p, %r, and %u.
+.Cm Match exec ,
+.Cm CertificateFile ,
+.Cm ControlPath ,
+.Cm IdentityAgent ,
+.Cm IdentityFile ,
+and
+.Cm RemoteCommand
+accept the tokens %%, %C, %d, %h, %i, %L, %l, %n, %p, %r, and %u.
 .Pp
 .Cm Hostname
 accepts the tokens %% and %h.
 .Pp
-.Cm IdentityAgent
-and
-.Cm IdentityFile
-accept the tokens %%, %d, %h, %i, %l, %r, and %u.
-.Pp
 .Cm LocalCommand
-accepts the tokens %%, %C, %d, %h, %i, %l, %n, %p, %r, %T, and %u.
+accepts all tokens.
 .Pp
 .Cm ProxyCommand
 accepts the tokens %%, %h, %n, %p, and %r.
-.Pp
-.Cm RemoteCommand
-accepts the tokens %%, %C, %d, %h, %i, %l, %n, %p, %r, and %u.
 .Sh FILES
 .Bl -tag -width Ds
 .It Pa ~/.ssh/config