sshd might fail to start if given an unsupported configuration option.

Try to avoid this problem checking for some possible unsupported options,
and avoid using them in the configuration file.

diff --git a/tests/sshserver.pl b/tests/sshserver.pl
index a50bdf0..a00dbbc 100644 (file)
--- a/tests/sshserver.pl
+++ b/tests/sshserver.pl
@@ -86,6 +86,28 @@ if ($username eq "root") {
     exit 1;
 }
 
+# Support for some options might have not been built into sshd.  On some
+# platforms specifying an unsupported option prevents sshd from starting.
+# Check here for possible unsupported options, avoiding its use in sshd.
+sub sshd_supports_opt($) {
+    my ($option) = @_;
+    my $err = 1;
+    chomp($err = qx($sshd -t -o $option=no 2>&1 | grep $option 2>&1 | wc -l));
+    return !$err;
+}
+
+my $supports_UsePAM = sshd_supports_opt('UsePAM');
+my $supports_UseDNS = sshd_supports_opt('UseDNS');
+my $supports_ChReAu = sshd_supports_opt('ChallengeResponseAuthentication');
+if ($verbose) {
+    print STDERR "sshd supports UsePAM: ";
+    print STDERR $supports_UsePAM ? "yes\n" : "no\n";
+    print STDERR "sshd supports UseDNS: ";
+    print STDERR $supports_UseDNS ? "yes\n" : "no\n";
+    print STDERR "sshd supports ChallengeResponseAuthentication: ";
+    print STDERR $supports_ChReAu ? "yes\n" : "no\n";
+}
+
 if (! -e "curl_client_key.pub") {
     if ($verbose) {
         print STDERR "Generating host and client keys...\n";
@@ -96,8 +118,8 @@ if (! -e "curl_client_key.pub") {
     system "ssh-keygen -q -t dsa -f curl_client_key -C 'curl test client' -N ''" and die "Could not generate key";
 }
 
-open(FILE, ">$conffile") || die "Could not write $conffile";
-print FILE <<EOF
+open(my $FILE, ">$conffile") || die "Could not write $conffile";
+print $FILE <<EOF
 # This is a generated file!  Do not edit!
 # OpenSSH sshd configuration file for curl testing
 AllowUsers $username
@@ -127,12 +149,27 @@ UseLogin no
 X11Forwarding no
 UsePrivilegeSeparation no
 # Newer OpenSSH options
-UsePAM no
-UseDNS no
-ChallengeResponseAuthentication no
 EOF
 ;
-close FILE;
+close $FILE;
+
+sub set_sshd_option {
+    my ($string) = @_;
+    if (open(my $FILE, ">>$conffile")) {
+        print $FILE "$string\n";
+        close $FILE;
+    }
+}
+
+if ($supports_UsePAM) {
+    set_sshd_option('UsePAM no');
+}
+if ($supports_UseDNS) {
+    set_sshd_option('UseDNS no');
+}
+if ($supports_ChReAu) {
+    set_sshd_option('ChallengeResponseAuthentication no');
+}
 
 if (system "$sshd -t -q -f $conffile") {
     # This is likely due to missing support for UsePam