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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
This commit is contained in:
Jay Satiro 2020-02-23 18:37:09 -05:00
parent e54b1885d1
commit 09aa807240
9 changed files with 159 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
lib/vssh/libssh.c
View File

@ -345,13 +345,27 @@ static int myssh_is_known(struct connectdata *conn)
return rc;
if(data->set.str[STRING_SSH_HOST_PUBLIC_KEY_MD5]) {
int i;
char md5buffer[33];
const char *pubkey_md5 = data->set.str[STRING_SSH_HOST_PUBLIC_KEY_MD5];
rc = ssh_get_publickey_hash(pubkey, SSH_PUBLICKEY_HASH_MD5,
&hash, &hlen);
if(rc != SSH_OK)
if(rc != SSH_OK || hlen != 16) {
failf(data,
"Denied establishing ssh session: md5 fingerprint not available");
goto cleanup;
}
if(hlen != strlen(data->set.str[STRING_SSH_HOST_PUBLIC_KEY_MD5]) ||
memcmp(&data->set.str[STRING_SSH_HOST_PUBLIC_KEY_MD5], hash, hlen)) {
for(i = 0; i < 16; i++)
msnprintf(&md5buffer[i*2], 3, "%02x", (unsigned char)hash[i]);
infof(data, "SSH MD5 fingerprint: %s\n", md5buffer);
if(!strcasecompare(md5buffer, pubkey_md5)) {
failf(data,
"Denied establishing ssh session: mismatch md5 fingerprint. "
"Remote %s is not equal to %s", md5buffer, pubkey_md5);
rc = SSH_ERROR;
goto cleanup;
}

1
tests/.gitignore vendored
View File

@ -6,6 +6,7 @@ curl_client_key.pub
curl_client_knownhosts
curl_host_rsa_key
curl_host_rsa_key.pub
curl_host_rsa_key.pub_md5
curl_sftp_cmds
curl_sftp_config
curl_ssh_config

1
tests/FILEFORMAT
View File

@ -366,6 +366,7 @@ Available substitute variables include:
%FILE_PWD - Current directory, on windows prefixed with a slash
%RTSP6PORT - IPv6 port number of the RTSP server
%RTSPPORT - Port number of the RTSP server
%SSHSRVMD5 - MD5 of SSH server's public key
%SMTP6PORT - IPv6 port number of the SMTP server
%SMTPPORT - Port number of the SMTP server
%SOCKSPORT - Port number of the SOCKS4/5 server

2
tests/data/Makefile.inc
View File

@ -85,7 +85,7 @@ test626 test627 test628 test629 test630 test631 test632 test633 test634 \
test635 test636 test637 test638 test639 test640 test641 test642 \
test643 test644 test645 test646 test647 test648 test649 test650 test651 \
test652 test653 test654 test655 test656 test658 test659 test660 test661 \
test662 test663 \
test662 test663 test664 test665 \
\
test700 test701 test702 test703 test704 test705 test706 test707 test708 \
test709 test710 test711 test712 test713 test714 test715 test716 test717 \

44
tests/data/test664 Normal file
View File

@ -0,0 +1,44 @@
<testcase>
<info>
<keywords>
SFTP
server key check
</keywords>
</info>
#
# Server-side
<reply>
<data>
test
</data>
</reply>
#
# Client-side
<client>
<server>
sftp
</server>
<name>
SFTP correct host key
</name>
<command>
--hostpubmd5 %SSHSRVMD5 --key curl_client_key --pubkey curl_client_key.pub -u %USER: sftp://%HOSTIP:%SSHPORT%POSIX_PWD/log/file664.txt
</command>
<file name="log/file664.txt">
test
</file>
</client>
#
# Verify data after the test has been "shot"
<verify>
<errorcode>
0
</errorcode>
<valgrind>
disable
</valgrind>
</verify>
</testcase>

44
tests/data/test665 Normal file
View File

@ -0,0 +1,44 @@
<testcase>
<info>
<keywords>
SCP
server key check
</keywords>
</info>
#
# Server-side
<reply>
<data>
test
</data>
</reply>
#
# Client-side
<client>
<server>
scp
</server>
<name>
SCP correct host key
</name>
<command>
--hostpubmd5 %SSHSRVMD5 --key curl_client_key --pubkey curl_client_key.pub -u %USER: scp://%HOSTIP:%SSHPORT%POSIX_PWD/log/file665.txt
</command>
<file name="log/file665.txt">
test
</file>
</client>
#
# Verify data after the test has been "shot"
<verify>
<errorcode>
0
</errorcode>
<valgrind>
disable
</valgrind>
</verify>
</testcase>

24
tests/runtests.pl
View File

@ -152,6 +152,8 @@ my $SMBPORT; # SMB server port
my $SMBSPORT; # SMBS server port
my $NEGTELNETPORT; # TELNET server port with negotiation
my $SSHSRVMD5; # MD5 of ssh server public key
my $srcdir = $ENV{'srcdir'} || '.';
my $CURL="../src/curl".exe_ext('TOOL'); # what curl executable to run on the tests
my $VCURL=$CURL; # what curl binary to use to verify the servers with
@ -2139,6 +2141,18 @@ sub runsshserver {
return (0,0);
}
my $hstpubmd5f = "curl_host_rsa_key.pub_md5";
if(!open(PUBMD5FILE, "<", $hstpubmd5f) ||
(read(PUBMD5FILE, $SSHSRVMD5, 32) != 32) ||
!close(PUBMD5FILE) ||
($SSHSRVMD5 !~ /^[a-f0-9]{32}$/i))
{
my $msg = "Fatal: $srvrname pubkey md5 missing : \"$hstpubmd5f\" : $!";
logmsg "$msg\n";
stopservers($verbose);
die $msg;
}
if($verbose) {
logmsg "RUN: $srvrname server is now running PID $pid2\n";
}
@ -3158,6 +3172,16 @@ sub subVariables {
$$thing =~ s/%SRCDIR/$srcdir/g;
$$thing =~ s/%USER/$USER/g;
if($$thing =~ /%SSHSRVMD5/) {
if(!$SSHSRVMD5) {
my $msg = "Fatal: Missing SSH server pubkey MD5. Is server running?";
logmsg "$msg\n";
stopservers($verbose);
die $msg;
}
$$thing =~ s/%SSHSRVMD5/$SSHSRVMD5/g;
}
# The purpose of FTPTIME2 and FTPTIME3 is to provide times that can be
# used for time-out tests and that would work on most hosts as these
# adjust for the startup/check time for this particular host. We needed

3
tests/sshhelp.pm
View File

@ -50,6 +50,7 @@ use vars qw(
$sftpcmds
$hstprvkeyf
$hstpubkeyf
$hstpubmd5f
$cliprvkeyf
$clipubkeyf
@sftppath
@ -82,6 +83,7 @@ use vars qw(
$sftpcmds
$hstprvkeyf
$hstpubkeyf
$hstpubmd5f
$cliprvkeyf
$clipubkeyf
display_sshdconfig
@ -122,6 +124,7 @@ $sftpcmds = 'curl_sftp_cmds'; # sftp client commands batch file
$knownhosts = 'curl_client_knownhosts'; # ssh knownhosts file
$hstprvkeyf = 'curl_host_rsa_key'; # host private key file
$hstpubkeyf = 'curl_host_rsa_key.pub'; # host public key file
$hstpubmd5f = 'curl_host_rsa_key.pub_md5'; # md5 hash of host public key
$cliprvkeyf = 'curl_client_key'; # client private key file
$clipubkeyf = 'curl_client_key.pub'; # client public key file

28
tests/sshserver.pl
View File

@ -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;