Packer Proxmox Plugin SSL Certificate Verification Error - insecure_skip_tls_verify Ignored

Packer
1

Hello,

I’m trying to use HashiCorp Packer with the official Proxmox plugin to build VM templates, but I’m encountering a persistent SSL certificate verification error that seems to be a bug in the plugin.

Environment:

  • Packer: Latest version
  • Packer Proxmox Plugin: v1.2.2 (latest)
  • Proxmox VE: 3-node cluster, targeting one specific node
  • Certificate: Valid Let’s Encrypt certificate

Despite setting insecure_skip_tls_verify = true in my Packer configuration, I consistently get this error:
Error creating VM: 596 error:0A000086:SSL routines::certificate verify failed

What i have trid so far:

  • The Let’s Encrypt certificate is valid and matches the hostname exactly
  • PowerShell can verify the certificate successfully
  • The Proxmox API is accessible via browser and other tools
  • API token has Administrator privileges with no privilege separation
  • Tried both HTTPS and HTTP URLs
  • Tested with hardcoded values (no variables)
  • Tried multiple plugin versions (1.1.3, 1.2.2)
packer {
  required_plugins {
    proxmox = {
      version = ">= 1.2.2"
      source  = "github.com/hashicorp/proxmox"
    }
  }
}

source "proxmox-iso" "ubuntu-server" {
  proxmox_url              = "https://my-proxmox.example.com:8006/api2/json"
  username                 = "root@pam!packer"
  token                    = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
  insecure_skip_tls_verify = true
  
  node                 = "my-proxmox-node"
  vm_name              = "ubuntu-server-template"
  template_description = "Ubuntu Server 24.04 template built with Packer"
  
  boot_iso {
    iso_file         = "local:iso/ubuntu-24.04.1-live-server-amd64.iso"
    iso_storage_pool = "local"
    unmount          = true
  }
  
  qemu_agent = true
  
  scsi_controller = "virtio-scsi-pci"
  
  disks {
    disk_size    = "20G"
    storage_pool = "local-perf-dir01"
    type         = "scsi"
  }
  
  cores  = 2
  memory = 2048
  
  network_adapters {
    model  = "virtio"
    bridge = "vmbr0"
  }
  
  cloud_init              = true
  cloud_init_storage_pool = "local-perf-dir01"
  
  boot_command = [
    "<esc><wait>",
    "e<wait>",
    "<down><down><down><end>",
    "<bs><bs><bs><bs><wait>",
    "autoinstall ds=nocloud-net\\;s=http://{{ .HTTPIP }}:{{ .HTTPPort }}/ ---<wait>",
    "<f10><wait>"
  ]
  
  boot      = "c"
  boot_wait = "5s"
  
  http_directory = "http"
  
  ssh_username = "ubuntu"
  ssh_password = "ubuntu"
  ssh_timeout  = "20m"
}

build {
  name = "ubuntu-server"
  sources = [
    "source.proxmox-iso.ubuntu-server"
  ]
  
  provisioner "shell" {
    inline = [
      "echo 'Template build complete!'"
    ]
  }
}

Is there a known workaround for this issue, or should this be reported as a bug to the HashiCorp Packer plugin repository?