Read an ACL policy that do not exists using CLI results in panic

[livioribeiro]

Overview of the Issue

When reading an ACL policy that does not exist using the CLI, it results in a panic.

However, when using the flag -format=json, the panic does not occur and it returns the string null

---

Reproduction Steps

With ACL initialized, execute in a server agent consul acl policy read -token=<consul token> -name does-not-exist

Consul info for both Client and Server

Server info

agent:
	check_monitors = 0
	check_ttls = 0
	checks = 0
	services = 0
build:
	prerelease = 
	revision = 53f65dc3
	version = 1.15.0
	version_metadata = 
consul:
	acl = enabled
	bootstrap = false
	known_datacenters = 1
	leader = false
	leader_addr = 10.99.0.13:8300
	server = true
raft:
	applied_index = 269
	commit_index = 269
	fsm_pending = 0
	last_contact = 29.57435ms
	last_log_index = 269
	last_log_term = 3
	last_snapshot_index = 0
	last_snapshot_term = 0
	latest_configuration = [{Suffrage:Voter ID:3239f2d0-0c18-f1ad-9879-f3cc68196fff Address:10.99.0.11:8300} {Suffrage:Voter ID:a9074442-03f0-ec2c-7138-13da2bd0f7ba Address:10.99.0.12:8300} {Suffrage:Voter ID:db2e41cc-8b21-6ffa-401d-429c5ba13707 Address:10.99.0.13:8300}]
	latest_configuration_index = 0
	num_peers = 2
	protocol_version = 3
	protocol_version_max = 3
	protocol_version_min = 0
	snapshot_version_max = 1
	snapshot_version_min = 0
	state = Follower
	term = 3
runtime:
	arch = amd64
	cpu_count = 8
	goroutines = 145
	max_procs = 8
	os = linux
	version = go1.20.1
serf_lan:
	coordinate_resets = 0
	encrypted = true
	event_queue = 0
	event_time = 3
	failed = 0
	health_score = 0
	intent_queue = 0
	left = 0
	member_time = 5
	members = 3
	query_queue = 0
	query_time = 1
serf_wan:
	coordinate_resets = 0
	encrypted = true
	event_queue = 0
	event_time = 1
	failed = 0
	health_score = 0
	intent_queue = 0
	left = 0
	member_time = 3
	members = 3
	query_queue = 0
	query_time = 1

data_dir       = "/opt/consul"
server         = true
advertise_addr = "{{ GetInterfaceIP \"eth0\" }}"
client_addr    = "127.0.0.1 {{ GetInterfaceIP \"eth0\" }}"
primary_datacenter = "dc1"

bootstrap_expect = 3
retry_join = [
  "10.99.0.11",
  "10.99.0.12",
  "10.99.0.13",
]

tls {
  defaults {
    ca_file         = "/etc/certs.d/ca.pem"
    cert_file       = "/etc/certs.d/cert.pem"
    key_file        = "/etc/certs.d/private_key.pem"

    verify_incoming = true
    verify_outgoing = true
  }

  internal_rpc {
    verify_server_hostname = true
  }
}

auto_encrypt {
  allow_tls = true
}

encrypt = "redacted"

ports {
  https    = 8501
  grpc     = 8502
  grpc_tls = 8503
}

connect {
  enabled = true
}

acl {
  enabled                  = true
  default_policy           = "deny"
  enable_token_persistence = true

  tokens {
    initial_management = "redacted"
    agent              = "redacted"
  }
}

ui_config {
  enabled          = true
}

telemetry {
  prometheus_retention_time = "10s"
  disable_hostname          = true
}

Operating system and Environment details

OS: Ubuntu 22.04
Arch: Amd64
Platform: LXD Container

Log Fragments

The output of the panic:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0xe47c9a]

goroutine 1 [running]:
github.com/hashicorp/consul/command/acl/policy.(*prettyFormatter).FormatPolicy(0xc000212000, 0x0)
	github.com/hashicorp/consul/command/acl/policy/formatter.go:53 +0x3a
github.com/hashicorp/consul/command/acl/policy/read.(*cmd).Run(0xc0002351f0, {0xc000138040?, 0xffffffffffffffff?, 0x0?})
	github.com/hashicorp/consul/command/acl/policy/read/policy_read.go:100 +0x397
github.com/mitchellh/cli.(*CLI).Run(0xc0008d1900)
	github.com/mitchellh/cli@v1.1.0/cli.go:260 +0x5f8
main.realMain()
	github.com/hashicorp/consul/main.go:48 +0x40f
main.main()
	github.com/hashicorp/consul/main.go:18 +0x19