SSH communicator fails when ssh_password contains "#"

[hc-github-team-packer]

This issue was originally opened by @digitalqualms in hashicorp/packer#12904 and has been migrated to this repository. The original issue description is below.

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Overview of the Issue

When using the proxmox-iso, I was encountering SSH handshake error. It turned out that because my ssh_password value I was using contained the pound/hash symbol "#". It looks like this value isn't escaped properly.

Reproduction Steps

Create an HCL template that uses the ssh communicator. Set the ssh_password value to something that contain "#". Build fails with:

Packer version

1.9.4

Simplified Packer Template

source "proxmox-iso" "ubuntu22-04" {
  // Proxmox config
  iso_file       = "local:iso/ubuntu-22.04.2-live-server-amd64.iso"
  iso_checksum   = "none"
  proxmox_url    = "https:/proxmox:8006/api2/json"
  username       = ${var.pve_username
  token          = var.pve_token
  node           = "pve1"
  http_directory = "config"

  onboot             = true
  memory             = 8192
  ballooning_minimum = 4096
  cores              = 2
  cpu_type           = "host"
  os                 = "l26"
  bios               = "ovmf"
  scsi_controller    = "virtio-scsi-single"
  efi_config {
    efi_storage_pool  = "local-thin"
    efi_type          = "4m"
    pre_enrolled_keys = true
  }
  disks {
    disk_size    = "50G"
    storage_pool = "local-thin"
    type         = "scsi"
  }
  network_adapters {
    bridge   = "vmbr0"
    model    = "virtio"
    firewall = true
  }
  boot_command = [
    "c",
    "linux /casper/vmlinuz --- pv6.disable=1 autoinstall ds='nocloud-net;s=http://{{ .HTTPIP }}:{{ .HTTPPort }}/'",
    "<enter><wait>",
    "initrd /casper/initrd<enter><wait>",
    "boot<enter>"
  ]
  boot_wait            = "10s"
  ssh_username         = "myuser"
  ssh_password         = "abc-def#"
  ssh_timeout          = "120m"
  ssh_handshake_attempts = 10
  template_description = "Ubuntu 22.04, generated on ${timestamp()}"
  template_name        = "ubuntu-22.04"
  unmount_iso          = true
}

build {
  sources = ["source.proxmox-iso.ubuntu22-04"]
  provisioner "shell" {
    inline = [
      "while [ ! -f /var/lib/cloud/instance/boot-finished ]; do echo 'Waiting for cloud-init...'; sleep 1; done"
    ]
  }
}

Operating system and Environment details

Packer run from macOS 14.4.1 (23E224), arm64
Proxmox plugin: v1.1.7_x5.0_darwin_arm64
Connecting to Ubuntu 22.04

Log Fragments and crash.log files

02 19:50:12 [INFO] Attempting SSH connection to 192.168.0.97:22...
2024/04/02 19:50:12 packer-plugin-proxmox_v1.1.7_x5.0_darwin_arm64 plugin: 2024/04/02 19:50:12 [DEBUG] reconnecting to TCP connection for SSH
2024/04/02 19:50:12 packer-plugin-proxmox_v1.1.7_x5.0_darwin_arm64 plugin: 2024/04/02 19:50:12 [DEBUG] handshaking with SSH
2024/04/02 19:50:14 packer-plugin-proxmox_v1.1.7_x5.0_darwin_arm64 plugin: 2024/04/02 19:50:14 [DEBUG] SSH handshake err: ssh: handshake failed: ssh: unable to authenticate, attempted methods [none password], no supported methods remain
2024/04/02 19:50:14 packer-plugin-proxmox_v1.1.7_x5.0_darwin_arm64 plugin: 2024/04/02 19:50:14 [DEBUG] Detected authentication error. Increasing handshake attempts.
2024/04/02 19:50:21 packer-plugin-proxmox_v1.1.7_x5.0_darwin_arm64 plugin: 2024/04/
==> proxmox-iso.ubuntu22-04: Error waiting for SSH: Packer experienced an authentication error when trying to connect via SSH. This can happen if your username/password are wrong. You may want to double-check your credentials as part of your debugging process. original error: ssh: handshake failed: ssh: unable to authenticate, attempted methods [none password], no supported methods remain

[lbajolet-hashicorp]

Too early to tell this is the root cause of the problem, I mislabeled the original issue, hence why this was automatically created.