libssh: Fix matching user-specified MD5 hex key

Prior to this change a match would never be successful because it
was mistakenly coded to compare binary data from libssh to a
user-specified hex string (ie CURLOPT_SSH_HOST_PUBLIC_KEY_MD5).

Reported-by: fds242@users.noreply.github.com

Fixes https://github.com/curl/curl/issues/4971
Closes https://github.com/curl/curl/pull/4974

1 files changed, 24 insertions, 4 deletions

diff --git a/tests/sshserver.pl b/tests/sshserver.pl
index 197e8b872..4414ca51b 100644
--- a/tests/sshserver.pl
+++ b/tests/sshserver.pl
@@ -28,6 +28,9 @@ use strict;
 use warnings;
 use Cwd;
 use Cwd 'abs_path';
+use Digest::MD5;
+use Digest::MD5 'md5_hex';
+use MIME::Base64;
 
 #***************************************************************************
 # Variables and subs imported from sshhelp module
@@ -48,6 +51,7 @@ use sshhelp qw(
     $sftpcmds
     $hstprvkeyf
     $hstpubkeyf
+    $hstpubmd5f
     $cliprvkeyf
     $clipubkeyf
     display_sshdconfig
@@ -357,10 +361,11 @@ if((($sshid =~ /OpenSSH/) && ($sshvernum < 299)) ||
 #
 if((! -e $hstprvkeyf) || (! -s $hstprvkeyf) ||
    (! -e $hstpubkeyf) || (! -s $hstpubkeyf) ||
+   (! -e $hstpubmd5f) || (! -s $hstpubmd5f) ||
    (! -e $cliprvkeyf) || (! -s $cliprvkeyf) ||
    (! -e $clipubkeyf) || (! -s $clipubkeyf)) {
     # Make sure all files are gone so ssh-keygen doesn't complain
-    unlink($hstprvkeyf, $hstpubkeyf, $cliprvkeyf, $clipubkeyf);
+    unlink($hstprvkeyf, $hstpubkeyf, $hstpubmd5f, $cliprvkeyf, $clipubkeyf);
     logmsg 'generating host keys...' if($verbose);
     if(system "\"$sshkeygen\" -q -t rsa -f $hstprvkeyf -C 'curl test server' -N ''") {
         logmsg 'Could not generate host key';
@@ -374,6 +379,21 @@ if((! -e $hstprvkeyf) || (! -s $hstprvkeyf) ||
     # Make sure that permissions are restricted so openssh doesn't complain
     system "chmod 600 $hstprvkeyf";
     system "chmod 600 $cliprvkeyf";
+    # Save md5 hash of public host key
+    open(RSAKEYFILE, "<$hstpubkeyf");
+    my @rsahostkey = do { local $/ = ' '; <RSAKEYFILE> };
+    close(RSAKEYFILE);
+    if(!$rsahostkey[1]) {
+        logmsg 'Failed parsing base64 encoded RSA host key';
+        exit 1;
+    }
+    open(PUBMD5FILE, ">$hstpubmd5f");
+    print PUBMD5FILE md5_hex(decode_base64($rsahostkey[1]));
+    close(PUBMD5FILE);
+    if((! -e $hstpubmd5f) || (! -s $hstpubmd5f)) {
+        logmsg 'Failed writing md5 hash of RSA host key';
+        exit 1;
+    }
 }
 
 
@@ -1099,8 +1119,8 @@ elsif($verbose && ($rc >> 8)) {
 #***************************************************************************
 # Clean up once the server has stopped
 #
-unlink($hstprvkeyf, $hstpubkeyf, $cliprvkeyf, $clipubkeyf, $knownhosts);
-unlink($sshdconfig, $sshconfig, $sftpconfig);
-
+unlink($hstprvkeyf, $hstpubkeyf, $hstpubmd5f,
+       $cliprvkeyf, $clipubkeyf, $knownhosts,
+       $sshdconfig, $sshconfig, $sftpconfig);
 
 exit 0;