Segfault on --help with --tlsverify if no ca certificate is present

[pvanagtmaal]

BUG REPORT INFORMATION

Description

Docker segfaults when trying to list view the helptext (--help) when using tls verification without a CA certificate.

Steps to reproduce the issue:

1. Make sure there is no ca.pem in $HOME/.docker/
2. Execute docker --tlsverify --help

Describe the results you received:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x60 pc=0x8d8605]

goroutine 1 [running]:
github.com/docker/cli/vendor/github.com/docker/docker/client.(*Client).ClientVersion(0x0, 0x2507800, 0x0)
	/go/src/github.com/docker/cli/vendor/github.com/docker/docker/client/client.go:321 +0x5
main.areSubcommandsSupported(0xc42058a240, 0x24dc060, 0xc420101b80, 0x24ca720, 0xc4204b9440)
	/go/src/github.com/docker/cli/cmd/docker/docker.go:309 +0x60
main.isSupported(0xc42058a240, 0x24dc060, 0xc420101b80, 0x7ffe6135d7d0, 0x24ba280)
	/go/src/github.com/docker/cli/cmd/docker/docker.go:260 +0x43
main.setHelpFunc.func1(0xc42058a240, 0xc4200100a0, 0x2, 0x2)
	/go/src/github.com/docker/cli/cmd/docker/docker.go:90 +0x72
github.com/docker/cli/vendor/github.com/spf13/cobra.(*Command).ExecuteC(0xc42058a240, 0xc420455470, 0xc420455410, 0xc42000e200)
	/go/src/github.com/docker/cli/vendor/github.com/spf13/cobra/command.go:790 +0x5bb
github.com/docker/cli/vendor/github.com/spf13/cobra.(*Command).Execute(0xc42058a240, 0xc42058a240, 0x24cef20)
	/go/src/github.com/docker/cli/vendor/github.com/spf13/cobra/command.go:738 +0x2b
main.main()
	/go/src/github.com/docker/cli/cmd/docker/docker.go:162 +0xd0

Describe the results you expected:
The same warning you get when executing for example docker --tlsverify info without a ca.pem in $HOME/.docker/: could not read CA certificate "$HOME/.docker/ca.pem": open $HOME/.docker/ca.pem: no such file or directory

Additional information you deem important (e.g. issue happens only occasionally):
Tested on both Arch Linux and Debian Stretch

Output of docker version:
Arch Linux:

Client:
 Version:      18.05.0-ce
 API version:  1.37
 Go version:   go1.10.2
 Git commit:   f150324782
 Built:        Wed May 16 22:27:45 2018
 OS/Arch:      linux/amd64
 Experimental: false
 Orchestrator: swarm

Server:
 Engine:
  Version:      18.05.0-ce
  API version:  1.37 (minimum version 1.12)
  Go version:   go1.10.2
  Git commit:   f150324782
  Built:        Wed May 16 22:28:17 2018
  OS/Arch:      linux/amd64
  Experimental: false

Debian Stretch:

Client:
 Version:      18.03.1-ce
 API version:  1.37
 Go version:   go1.9.5
 Git commit:   9ee9f40
 Built:        Thu Apr 26 07:17:14 2018
 OS/Arch:      linux/amd64
 Experimental: false
 Orchestrator: swarm

Server:
 Engine:
  Version:      18.03.1-ce
  API version:  1.37 (minimum version 1.12)
  Go version:   go1.9.5
  Git commit:   9ee9f40
  Built:        Thu Apr 26 07:15:24 2018
  OS/Arch:      linux/amd64
  Experimental: false

Output of docker info:

Arch Linux:

Containers: 0
 Running: 0
 Paused: 0
 Stopped: 0
Images: 33
Server Version: 18.05.0-ce
Storage Driver: overlay2
 Backing Filesystem: extfs
 Supports d_type: true
 Native Overlay Diff: false
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
 Volume: local
 Network: bridge host macvlan null overlay
 Log: awslogs fluentd gcplogs gelf journald json-file logentries splunk syslog
Swarm: inactive
Runtimes: runc
Default Runtime: runc
Init Binary: docker-init
containerd version: 773c489c9c1b21a6d78b5c538cd395416ec50f88
runc version: 4fc53a81fb7c994640722ac585fa9ca548971871
init version: 949e6fa
Security Options:
 seccomp
  Profile: default
Kernel Version: 4.16.13-1-ARCH
Operating System: Arch Linux
OSType: linux
Architecture: x86_64
CPUs: 4
Total Memory: 7.698GiB
Name: <left out>
ID: DHWN:5OLZ:O6NU:FBTD:3XTA:PI2N:E3ON:N4NT:AI2Z:BSSV:JJS3:ETLW
Docker Root Dir: /var/lib/docker
Debug Mode (client): false
Debug Mode (server): false
Registry: https://index.docker.io/v1/
Labels:
Experimental: false
Insecure Registries:
 127.0.0.0/8
Live Restore Enabled: false

Debian Stretch:

Containers: 0
 Running: 0
 Paused: 0
 Stopped: 0
Images: 0
Server Version: 18.03.1-ce
Storage Driver: overlay2
 Backing Filesystem: extfs
 Supports d_type: true
 Native Overlay Diff: true
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
 Volume: local
 Network: bridge host macvlan null overlay
 Log: awslogs fluentd gcplogs gelf journald json-file logentries splunk syslog
Swarm: inactive
Runtimes: runc
Default Runtime: runc
Init Binary: docker-init
containerd version: 773c489c9c1b21a6d78b5c538cd395416ec50f88
runc version: 4fc53a81fb7c994640722ac585fa9ca548971871
init version: 949e6fa
Security Options:
 seccomp
  Profile: default
Kernel Version: 4.9.0-6-amd64
Operating System: Debian GNU/Linux 9 (stretch)
OSType: linux
Architecture: x86_64
CPUs: 1
Total Memory: 996.4MiB
Name: <left out>
ID: ABAF:EW3C:EAZP:LFMA:2KRF:4L2P:42U2:6TWF:ZN2D:NVQZ:SHVA:UH75
Docker Root Dir: /var/lib/docker
Debug Mode (client): false
Debug Mode (server): false
Registry: https://index.docker.io/v1/
Labels:
Experimental: false
Insecure Registries:
 127.0.0.0/8
Live Restore Enabled: false

WARNING: No swap limit support

Additional environment details (AWS, VirtualBox, physical, etc.):
Arch Linux on a physical device
Debian Stretch on a VPS

[silvin-lubecki]

Thank you @pvanagtmaal for filling this bug report!
I can reproduce it on master.

[pvanagtmaal]

Thanks 👍

P.S. I discovered the same happens with the --verbose flag as well, so docker --tlsverify --verbose.

[silvin-lubecki]

Yep I spotted it too thank you 👍
They follow the same code path, so same result...