[PATCH] allow wildcard matches for principals with CA certs and return all matches when calling find-principals

[Fabian Stelzer]

---
ssh-keygen -Y find-principals will fail to return any matches if a 
certificate signature is used and the allowed principals file contains a 
wildcard principal (e.g.: *@example.com). Since we need to specify the full 
princpal for -Y verify, find-principals should return the matching ones.
Instead of adjusting the heavily used function sshkey_cert_check_authority()
we instead duplicate a little bit of the cert princpal matching code into 
cert_filter_principals() and no longer have the former verify the principal.
This makes for a much simpler diff and a more constrained change.
The explicit deny on wildcards is dropped as well.

 regress/sshsig.sh | 17 +++++++++++++++++
 sshsig.c          | 24 +++++++++++++-----------
 2 files changed, 30 insertions(+), 11 deletions(-)

diff --git a/regress/sshsig.sh b/regress/sshsig.sh
index f8d85c2f..dcfd2e78 100644
--- a/regress/sshsig.sh
+++ b/regress/sshsig.sh
@@ -342,6 +342,23 @@ for t in $SIGNKEYS; do
 		-f $OBJ/allowed_signers >/dev/null 2>&1 || \
 		fail "failed find-principals for $t with ca key"
 
+	# CA with wildcard principal
+	(printf "*@example.com cert-authority " ;
+	 cat $CA_PUB) > $OBJ/allowed_signers
+	# find-principals CA with wildcard principal
+	${SSHKEYGEN} -vvv -Y find-principals -s $sigfile \
+		-Overify-time=19850101 \
+		-f $OBJ/allowed_signers 2>/dev/null | \
+		fgrep "$sig_principal" >/dev/null || \
+		fail "failed find-principals for $t with ca key using wildcard principal"
+
+	# verify CA with wildcard principal
+	${SSHKEYGEN} -vvv -Y verify -s $sigfile -n $sig_namespace \
+		-I $sig_principal -f $OBJ/allowed_signers \
+		-Overify-time=19850101 \
+		< $DATA >/dev/null 2>&1 || \
+		fail "failed signature for $t cert using wildcard principal"
+
 	# signing key listed as cert-authority
 	(printf "$sig_principal cert-authority " ;
 	 cat $pubkey) > $OBJ/allowed_signers
diff --git a/sshsig.c b/sshsig.c
index f8c63f7b..1a61bbc6 100644
--- a/sshsig.c
+++ b/sshsig.c
@@ -820,6 +820,7 @@ cert_filter_principals(const char *path, u_long linenum,
 	const char *reason;
 	struct sshbuf *nprincipals;
 	int r = SSH_ERR_INTERNAL_ERROR, success = 0;
+	u_int i;
 
 	oprincipals = principals = *principalsp;
 	*principalsp = NULL;
@@ -830,22 +831,23 @@ cert_filter_principals(const char *path, u_long linenum,
 	}
 
 	while ((cp = strsep(&principals, ",")) != NULL && *cp != '\0') {
-		if (strcspn(cp, "!?*") != strlen(cp)) {
-			debug("%s:%lu: principal \"%s\" not authorized: "
-			    "contains wildcards", path, linenum, cp);
-			continue;
-		}
-		/* Check against principals list in certificate */
+		/* Check certificate validity */
 		if ((r = sshkey_cert_check_authority(cert, 0, 1, 0,
-		    verify_time, cp, &reason)) != 0) {
+		    verify_time, NULL, &reason)) != 0) {
 			debug("%s:%lu: principal \"%s\" not authorized: %s",
 			    path, linenum, cp, reason);
 			continue;
 		}
-		if ((r = sshbuf_putf(nprincipals, "%s%s",
-		    sshbuf_len(nprincipals) != 0 ? "," : "", cp)) != 0) {
-			error_f("buffer error");
-			goto out;
+		/* Return all matching principal names from the cert */
+		for (i = 0; i < cert->cert->nprincipals; i++) {
+			if (match_pattern(cert->cert->principals[i], cp)) {
+				if ((r = sshbuf_putf(nprincipals, "%s%s",
+					sshbuf_len(nprincipals) != 0 ? "," : "",
+						cert->cert->principals[i])) != 0) {
+					error_f("buffer error");
+					goto out;
+				}
+			}
 		}
 	}
 	if (sshbuf_len(nprincipals) == 0) {
-- 
2.34.1