From: Fabian Grünbichler <f.gruenbichler@proxmox.com>
Date: Fri, 8 Oct 2021 08:18:21 +0000 (+0200)
Subject: support downloading alternate chains
X-Git-Url: https://git.proxmox.com/?p=proxmox-acme.git;a=commitdiff_plain;h=2307c38b59c6bc8f1e3dae4748a17d7943f4009f

support downloading alternate chains

the current default chains end with an expired root certificate for
maximum compatibility with old Android versions. this breaks some other
older clients (openssl, gnutls) which don't expect chains to contain any
expired certificates, even if they are 'above' the trust anchor.

by setting $root, it is possible to specify which root the ACME provided
certificate chain should end with, downloading alternate chains as
necessary.

Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
Reviewed-by: Stoiko Ivanov <s.ivanov@proxmox.com>
Tested-by: Stoiko Ivanov <s.ivanov@proxmox.com>
---

diff --git a/src/PVE/ACME.pm b/src/PVE/ACME.pm
index 265482d..57578d7 100644
--- a/src/PVE/ACME.pm
+++ b/src/PVE/ACME.pm
@@ -442,17 +442,50 @@ sub deactivate_authorization {
 
 # Get certificate
 # GET-as-POST to order's certificate URL
+# if $root is specified, attempts to find a matching (alternate) chain
 # Expects a '200 OK' reply
 # returns certificate chain in PEM format
 sub get_certificate {
-    my ($self, $order) = @_;
+    my ($self, $order, $root) = @_;
 
     $self->fatal("no certificate URL available (yet?)", $order)
        if !$order->{certificate};
 
+    my $check_root = sub {
+	my ($chain) = @_;
+
+	my @certs = PVE::Certificate::split_pem($chain);
+	my $root_pem = $certs[-1];
+
+	my ($file, $fh) = PVE::Tools::tempfile_contents($root_pem);
+	my $info = PVE::Certificate::get_certificate_info($file);
+
+	return defined($info->{issuer}) && $info->{issuer} =~ m/\Q$root\E/i;
+    };
+
     my $r = $self->do(POST => $order->{certificate}, '');
     my $return = eval {
+	# default chain
 	my $res = __get_result($r, 200, 1);
+	if ($root && !$check_root->($res)) {
+	    # alternate chains if requested and default didn't match
+	    $res = undef;
+	    my @links = $r->header('link');
+	    for my $link (@links) {
+		if ($link =~ /^<(.*)>;rel="alternate"$/) {
+		    my $url = $1;
+		    my $chain = eval { __get_result($self->do(POST => $url, ''), 200, 1); };
+		    die "failed to retrieve alternate chain from '$url' - $@\n" if $@;
+		    if ($check_root->($chain)) {
+			$res = $chain;
+			last;
+		    }
+		}
+	    }
+	    die "no matching alternate chain for '$root' returned by server\n"
+		if !defined($res);
+	}
+
 	if ($res =~ /^(-----BEGIN CERTIFICATE-----)(.+)(-----END CERTIFICATE-----)$/s) { # untaint
 	    return $1 . $2 . $3;
 	}