[pve-devel] [PATCH pve-cluster] fix #6701: Add keyUsage extension to root CA

[Arthur Bied-Charreton <a.bied-charreton@proxmox.com>]

Add the keyUsage[1] extension to the PVE root CA to comply with RFC
5280. Python started to enforce this as of 3.13 by defaulting to using the 
VERIFY_X509_STRICT flag, which breaks clients like Ansible.

The authorityKeyIdentifier[2] and subjectKeyIdentifier[3] extensions are
not strictly required for fixing this issue, however RFC 5280 mandates
them for conforming CAs, so adding them makes sense as well.

[1] https://www.rfc-editor.org/rfc/rfc5280#section-4.2.1.3
[2] https://www.rfc-editor.org/rfc/rfc5280#section-4.2.1.1
[3] https://www.rfc-editor.org/rfc/rfc5280#section-4.2.1.2

Signed-off-by: Arthur Bied-Charreton <a.bied-charreton@proxmox.com>
---
This fix is not required for PBS and PDM, since they only use self-signed
certificates.

You can run the script below to test the changes, should fail with
"CA cert does not include key usage extension" before applying the patch,
and succeed afterwards. 

```
#!/usr/bin/env python3

import socket
import ssl
import sys

try:
    context = ssl.create_default_context(cafile="/etc/pve/pve-root-ca.pem")
    context.check_hostname = True
    context.verify_mode = ssl.CERT_REQUIRED

    with socket.create_connection(("localhost", 8006), timeout=10) as sock:
        with context.wrap_socket(sock, server_hostname="localhost") as ssock:
            print(f"success")

except ssl.SSLCertVerificationError as e:
    print(e)
```
    
 src/PVE/Cluster/Setup.pm | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/src/PVE/Cluster/Setup.pm b/src/PVE/Cluster/Setup.pm
index 75d3507..d95a278 100644
--- a/src/PVE/Cluster/Setup.pm
+++ b/src/PVE/Cluster/Setup.pm
@@ -426,6 +426,25 @@ sub gen_pveca_cert {
     my $uuid_str;
     UUID::unparse($uuid, $uuid_str);
 
+    my $sslconf = <<__EOD;
+[req]
+distinguished_name = req_distinguished_name
+x509_extensions = v3_ca
+
+[ req_distinguished_name ]
+
+[ v3_ca ]
+basicConstraints = critical,CA:TRUE
+keyUsage = critical,keyCertSign,cRLSign
+authorityKeyIdentifier = keyid:always,issuer
+subjectKeyIdentifier = hash
+__EOD
+
+    my $cfgfn = "/tmp/pvesslconf-$$.tmp";
+    my $fh = IO::File->new($cfgfn, "w");
+    print $fh $sslconf;
+    close($fh);
+
     eval {
         # wrap openssl with faketime to prevent bug #904
         run_silent_cmd([
@@ -439,6 +458,8 @@ sub gen_pveca_cert {
             '-new',
             '-x509',
             '-nodes',
+            '-config',
+            $cfgfn,
             '-key',
             $pveca_key_fn,
             '-out',
@@ -448,6 +469,8 @@ sub gen_pveca_cert {
         ]);
     };
 
+    unlink $cfgfn;
+
     die "generating pve root certificate failed:\n$@" if $@;
 
     return 1;
-- 
2.47.3


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