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Support multiple keys per user

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In use cases where one user is supposed to be reachable with multiple
public keys, but where each public key should only have access to a
specific set of commands, the variable $SSH_USER_AUTH will be considered
together with colon separated username->key pairs in the configuration
to determine the set of commands to use.

Signed-off-by: Georg Pfuetzenreuter <mail@georg-pfuetzenreuter.net>
This commit is contained in:
Georg Pfuetzenreuter 2024-09-15 19:23:03 +02:00
parent 3bed7bad11
commit 194a71e968
Signed by: Georg
GPG Key ID: 1ED2F138E7E6FF57
3 changed files with 31 additions and 2 deletions
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24
authorized-exec.pl
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@ -22,6 +22,30 @@ my %config = do $configfile;
die "Couldn't run $configfile" unless %config;
my $user = $ENV{'USER'};
my $authfile = $ENV{'SSH_USER_AUTH'};
my %publickeys;
if ($authfile && -f $authfile) {
open my $fh, '<', $authfile or die "Found authentication file, but failed to read it: $!";
while (<$fh>) {
$_ =~ /^publickey (ssh-[a-z0-9]+ .*)$/;
$publickeys{$1} = 1;
}
close $fh or print STDERR "Failed to close authentication file: $!";
}
foreach my $userentry (keys %config) {
my @userelements = split(':', $userentry);
if (scalar @userelements > 1) {
my $entry_user = $userelements[0];
my $entry_key = $userelements[1];
if ($entry_user eq $user && exists($publickeys{$entry_key})) {
$user = $userentry;
last;
}
}
}
if (! exists($config{$user}) ) {
print STDERR 'Unauthorized user.';

4
authorized-exec.pod
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@ -15,10 +15,12 @@
The command line to validate is taken either from the arguments passed after the configuration file, or read from the variable $SSH_ORIGINAL_COMMAND, which is passed if used as a forced SSH command.
The application supports handling different sets of authorized commands for a single user based on the public key the session was initiated with. This utilizes the variable $SSH_USER_AUTH, which requires the OpenSSH server to be configured with "ExposeAuthInfo" enabled in sshd_config(5).
=head1 EXAMPLES
In authorized_keys, sshd(8), the following syntax can be used:
command="/usr/bin/authorized-exec.pod /etc/authorized-exec/service1.pl" ssh-ed25519 ....
command="/usr/bin/authorized-exec /etc/authorized-exec/service1.pl" ssh-ed25519 ....
=head1 AUTHOR

5
config.example.pl
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@ -1,10 +1,13 @@
# the patterns are read as regular expressions and anchored with ^ and $ by default
(
'georg' => [
'georg2:ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIFY7Pvf4Rzn7C8Ioi1ZvY/O7tJsMCv27URdQE5o1daDK' => [
'echo hi',
'true',
'printf %s [a-z0-9 ]+',
],
'georg2' => [
'echo bye',
],
'root' => [
'ls -a /root',
],