KVM direct download: http:// URL redirecting to HTTPS fails with PKIX error because HttpDirectTemplateDownloader ignores the JRE cacerts

Start by reading HttpDirectTemplateDownloader and HttpsDirectTemplateDownloader, then trace how LibvirtComputingResource.enableSSLForKvmAgent() configures the trust store. Compare the HTTP redirect path with the HTTPS downloader’s trust handling and check existing downloader tests. Done means an HTTP URL that redirects to HTTPS validates with both the JRE cacerts and CloudStack trust material, including when cloud.jks cannot be loaded.

problem

When a Direct Download template/ISO is registered with an http:// URL that redirects to https://

http://download.cirros-cloud.net/0.6.2/cirros-0.6.2-x86_64-disk.img > https://github.com/cirros-dev/cirros/releases/download/0.6.2/cirros-0.6.2-x86_64-disk.img

curl -sI http://download.cirros-cloud.net/0.6.2/cirros-0.6.2-x86_64-disk.img
HTTP/1.1 302 Found
Date: Tue, 27 Oct 2026 12:37:30 GMT
Server: Apache
Location: https://github.com/cirros-dev/cirros/releases/download/0.6.2/cirros-0.6.2-x86_64-disk.img
Cache-Control: max-age=600
Expires: Tue, 27 Oct 2026 12:47:30 GMT
Content-Type: text/html; charset=iso-8859-1

host fails with a TLS error, even when the target's root CA is present in the JRE trust store (cacerts):

    ERROR [direct.download.HttpDirectTemplateDownloader] Cannot reach URL: http://download.cirros-cloud.net/0.6.2/cirros-0.6.2-x86_64-disk.img
    due to: (certificate_unknown) PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException:
    unable to find valid certification path to requested target
        ...
        at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:323)
        at org.apache.cloudstack.direct.download.HttpDirectTemplateDownloader.checkUrl(HttpDirectTemplateDownloader.java:120)
        at org.apache.cloudstack.direct.download.DirectDownloadHelper.checkUrlExistence(DirectDownloadHelper.java:75)
        at com.cloud.hypervisor.kvm.resource.wrapper.LibvirtCheckUrlCommand.execute(LibvirtCheckUrlCommand.java:43)

Related: #12878 (same trust-store root cause for the https:// Let's Encrypt case).

versions

ACS 4.22.x and 4.23
Hypervisor: KVM, OpenJDK 17

The steps to reproduce the bug

1. Set store.download.follow.redirects to true.
2. On the kvm host make sure latest ca certificate is present

 dnf update -y ca-certificates
 update-ca-trust extract

2. Make sure the KVM host's JRE cacerts trusts the target CAs

[root@ref-trl-12464-k-Mol8-kiran-chavala-kvm1 ~]# keytool -list -cacerts -storepass changeit 2>/dev/null | grep -iE 'sectigo|isrg'
isrgrootx1, 27 Oct 2026, trustedCertEntry,
isrgrootx2, 27 Oct 2026, trustedCertEntry,
sectigopublicserverauthenticationroote46, 27 Oct 2026, trustedCertEntry,
sectigopublicserverauthenticationrootr46, 27 Oct 2026, trustedCertEntry,

These certs are not present in /etc/cloudstack/agent/cloud.jks

3. Register a direct download template:

       cmk register template name=cirros-http displaytext=cirros format=QCOW2 hypervisor=KVM \
         url=http://download.cirros-cloud.net/0.6.2/cirros-0.6.2-x86_64-disk.img \
         ostypeid=<id> zoneid=<id> directdownload=true

4. Registration fails with URL: ... validation failed on host ...; the agent log shows the PKIX error above.

    ERROR [direct.download.HttpDirectTemplateDownloader] Cannot reach URL: http://download.cirros-cloud.net/0.6.2/cirros-0.6.2-x86_64-disk.img
    due to: (certificate_unknown) PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException:
    unable to find valid certification path to requested target
        ...
        at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:323)
        at org.apache.cloudstack.direct.download.HttpDirectTemplateDownloader.checkUrl(HttpDirectTemplateDownloader.java:120)
        at org.apache.cloudstack.direct.download.DirectDownloadHelper.checkUrlExistence(DirectDownloadHelper.java:75)
        at com.cloud.hypervisor.kvm.resource.wrapper.LibvirtCheckUrlCommand.execute(LibvirtCheckUrlCommand.java:43)

5. Registering the equivalent https://github.com/cirros-dev/cirros/releases/download/0.6.2/cirros-0.6.2-x86_64-disk.img URL succeeds for the HEAD check, showing that only the HTTP downloader path is affected.

Workaround

is to upload every public root in the redirect chain via uploadTemplateDirectDownloadCertificate, which is meant for private CAs.

keytool -exportcert -rfc -cacerts -storepass changeit   -alias sectigopublicserverauthenticationroote46 -file /root/sectigo-e46.pem
keytool -exportcert -rfc -cacerts -storepass changeit -alias isrgrootx1 -file /root/isrg-root-x1.pem

cmk upload templatedirectdownloadcertificate hypervisor=KVM name=sectigo-e46 zoneid=7ddb0067-e94b-4320-a08d-2b0019b83a20 certificate="$(cat /root/sectigo-e46.pem)"

cmk upload templatedirectdownloadcertificate hypervisor=KVM name=isrg-root-x1 zoneid=7ddb0067-e94b-4320-a08d-2b0019b83a20 certificate="$(cat /root/isrg-root-x1.pem)"

On kvm host 

 PASS=$(sed -n 's/^keystore.passphrase=//p' /etc/cloudstack/agent/agent.properties)
  keytool -list -keystore /etc/cloudstack/agent/cloud.jks -storepass "$PASS" | grep -i sectigo

What to do about it?

Root case form Claude ai

- `LibvirtComputingResource.enableSSLForKvmAgent()` sets the JVM-wide `javax.net.ssl.trustStore` to
  `/etc/cloudstack/agent/cloud.jks`, which normally contains only the CloudStack CA.
- `HttpsDirectTemplateDownloader` builds its own SSLContext that merges `cloud.jks` **and** the JRE `cacerts`,
  so `https://` URLs validate correctly.
- `HttpDirectTemplateDownloader` (used for `http://` URLs) uses commons-httpclient 3.x, whose `https`
  protocol handler uses the JVM default SSL socket factory. When the redirect is followed to HTTPS, the
  certificate is checked against `cloud.jks` only, and public CAs (Let's Encrypt, Sectigo, DigiCert, ...)
  are rejected.

Fix

- Migrate `HttpDirectTemplateDownloader` from commons-httpclient 3.x to Apache HttpClient 4.x (as
  `HttpsDirectTemplateDownloader` already uses), configured with an `SSLConnectionSocketFactory` built from
  the merged `cloud.jks` + JRE `cacerts` trust material, so redirects to HTTPS are validated the same way as
  direct `https://` URLs.
- Factor the trust-store merging logic out of `HttpsDirectTemplateDownloader.getSSLContext()` into a shared
  helper so both downloaders (and `getRemoteFileSize`) use one context. If `cloud.jks` can't be loaded, the
  helper should still load `cacerts` rather than falling back to `SSLContext.getDefault()`, which is `cloud.jks`-only.