Incorrect backend config path causes crash

[alanplatt]

Terraform Version

v0.13.0

Terraform Configuration Files

terraform {
  required_providers {
    google = {
      version = "~> 3.33.0"
    }
    kubernetes = {
      version = "~> 1.12.0"
    }
    random = {
      version = "~> 2.3.0"
    }
  }
}

Debug Output

▶ TF_LOG=trace terraform init --backend-config="tier/locals/backend.tfvars"                                                                                                (⎈ v2-verify:aptest)
2020/08/12 15:41:08 [INFO] Terraform version: 0.13.0  
2020/08/12 15:41:08 [INFO] Go runtime version: go1.14.2
2020/08/12 15:41:08 [INFO] CLI args: []string{"/usr/local/Cellar/tfenv/2.0.0/versions/0.13.0/terraform", "init", "--backend-config=tier/locals/backend.tfvars"}
2020/08/12 15:41:08 [DEBUG] Attempting to open CLI config file: /Users/alanplatt/.terraformrc
2020/08/12 15:41:08 [DEBUG] File doesn't exist, but doesn't need to. Ignoring.
2020/08/12 15:41:08 [DEBUG] ignoring non-existing provider search directory terraform.d/plugins
2020/08/12 15:41:08 [DEBUG] ignoring non-existing provider search directory /Users/alanplatt/.terraform.d/plugins
2020/08/12 15:41:08 [DEBUG] ignoring non-existing provider search directory /Users/alanplatt/Library/Application Support/io.terraform/plugins
2020/08/12 15:41:08 [DEBUG] ignoring non-existing provider search directory /Library/Application Support/io.terraform/plugins
2020/08/12 15:41:08 [INFO] CLI command args: []string{"init", "--backend-config=tier/locals/backend.tfvars"}
Initializing modules...
2020/08/12 15:41:08 [TRACE] ModuleInstaller: installing child modules for . into .terraform/modules
2020/08/12 15:41:08 [DEBUG] Module installer: begin jubilee-house
2020/08/12 15:41:08 [TRACE] ModuleInstaller: Module installer: jubilee-house <nil> already installed in modules/datacentre-certs
2020/08/12 15:41:08 [DEBUG] Module installer: begin woking
2020/08/12 15:41:08 [TRACE] ModuleInstaller: Module installer: woking <nil> already installed in modules/datacentre-certs
2020/08/12 15:41:08 [TRACE] modsdir: writing modules manifest to .terraform/modules/modules.json

Initializing the backend...
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x20 pc=0x2bfc425]

goroutine 1 [running]:
github.com/hashicorp/terraform/command.(*InitCommand).backendConfigOverrideBody(0xc00067e700, 0x32d6888, 0xf, 0xc000592380, 0xc000687d10, 0xc00059cff0, 0x29, 0x0, 0x0, 0x17762fa700000000)
        /home/circleci/project/project/command/init.go:862 +0x8b5
github.com/hashicorp/terraform/command.(*InitCommand).initBackend(0xc00067e700, 0xc0004537a0, 0x32d6888, 0xf, 0xc000592380, 0x1, 0x0, 0x0, 0x0, 0xc0000b9750, ...)
        /home/circleci/project/project/command/init.go:374 +0x4a6
github.com/hashicorp/terraform/command.(*InitCommand).Run(0xc00067e700, 0xc00004c1d0, 0x1, 0x1, 0xc0006440d0)
        /home/circleci/project/project/command/init.go:227 +0xeb1
github.com/mitchellh/cli.(*CLI).Run(0xc000652280, 0xc000652280, 0xc00063fd48, 0x1)
        /home/circleci/project/project/vendor/github.com/mitchellh/cli/cli.go:255 +0x1da
main.wrappedMain(0x0)
        /home/circleci/project/project/main.go:275 +0xc90
main.realMain(0x0)
        /home/circleci/project/project/main.go:106 +0xde
main.main()
        /home/circleci/project/project/main.go:42 +0x3a
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x20 pc=0x2bfc425]

goroutine 1 [running]:
github.com/hashicorp/terraform/command.(*InitCommand).backendConfigOverrideBody(0xc00067e700, 0x32d6888, 0xf, 0xc000592380, 0xc000687d10, 0xc00059cff0, 0x29, 0x0, 0x0, 0x17762fa700000000)
        /home/circleci/project/project/command/init.go:862 +0x8b5
github.com/hashicorp/terraform/command.(*InitCommand).initBackend(0xc00067e700, 0xc0004537a0, 0x32d6888, 0xf, 0xc000592380, 0x1, 0x0, 0x0, 0x0, 0xc0000b9750, ...)
        /home/circleci/project/project/command/init.go:374 +0x4a6
github.com/hashicorp/terraform/command.(*InitCommand).Run(0xc00067e700, 0xc00004c1d0, 0x1, 0x1, 0xc0006440d0)
        /home/circleci/project/project/command/init.go:227 +0xeb1
github.com/mitchellh/cli.(*CLI).Run(0xc000652280, 0xc000652280, 0xc00063fd48, 0x1)
        /home/circleci/project/project/vendor/github.com/mitchellh/cli/cli.go:255 +0x1da
main.wrappedMain(0x0)
        /home/circleci/project/project/main.go:275 +0xc90
main.realMain(0x0)
        /home/circleci/project/project/main.go:106 +0xde
main.main()
        /home/circleci/project/project/main.go:42 +0x3a



!!!!!!!!!!!!!!!!!!!!!!!!!!! TERRAFORM CRASH !!!!!!!!!!!!!!!!!!!!!!!!!!!!

Terraform crashed! This is always indicative of a bug within Terraform.
A crash log has been placed at "crash.log" relative to your current
working directory. It would be immensely helpful if you could please
report the crash with Terraform[1] so that we can fix this.

When reporting bugs, please include your terraform version. That
information is available on the first line of crash.log. You can also
get it by running 'terraform --version' on the command line.

SECURITY WARNING: the "crash.log" file that was created may contain 
sensitive information that must be redacted before it is safe to share 
on the issue tracker.

[1]: https://github.com/hashicorp/terraform/issues

!!!!!!!!!!!!!!!!!!!!!!!!!!! TERRAFORM CRASH !!!!!!!!!!!!!!!!!!!!!!!!!!!!

Crash Output

▶ cat crash.log                                                                                                                                                            (⎈ v2-verify:aptest)
2020/08/12 15:41:08 [INFO] Terraform version: 0.13.0  
2020/08/12 15:41:08 [INFO] Go runtime version: go1.14.2
2020/08/12 15:41:08 [INFO] CLI args: []string{"/usr/local/Cellar/tfenv/2.0.0/versions/0.13.0/terraform", "init", "--backend-config=tier/locals/backend.tfvars"}
2020/08/12 15:41:08 [DEBUG] Attempting to open CLI config file: /Users/alanplatt/.terraformrc
2020/08/12 15:41:08 [DEBUG] File doesn't exist, but doesn't need to. Ignoring.
2020/08/12 15:41:08 [DEBUG] ignoring non-existing provider search directory terraform.d/plugins
2020/08/12 15:41:08 [DEBUG] ignoring non-existing provider search directory /Users/alanplatt/.terraform.d/plugins
2020/08/12 15:41:08 [DEBUG] ignoring non-existing provider search directory /Users/alanplatt/Library/Application Support/io.terraform/plugins
2020/08/12 15:41:08 [DEBUG] ignoring non-existing provider search directory /Library/Application Support/io.terraform/plugins
2020/08/12 15:41:08 [INFO] CLI command args: []string{"init", "--backend-config=tier/locals/backend.tfvars"}
2020/08/12 15:41:08 [TRACE] ModuleInstaller: installing child modules for . into .terraform/modules
2020/08/12 15:41:08 [DEBUG] Module installer: begin jubilee-house
2020/08/12 15:41:08 [TRACE] ModuleInstaller: Module installer: jubilee-house <nil> already installed in modules/datacentre-certs
2020/08/12 15:41:08 [DEBUG] Module installer: begin woking
2020/08/12 15:41:08 [TRACE] ModuleInstaller: Module installer: woking <nil> already installed in modules/datacentre-certs
2020/08/12 15:41:08 [TRACE] modsdir: writing modules manifest to .terraform/modules/modules.json
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x20 pc=0x2bfc425]

goroutine 1 [running]:
github.com/hashicorp/terraform/command.(*InitCommand).backendConfigOverrideBody(0xc00067e700, 0x32d6888, 0xf, 0xc000592380, 0xc000687d10, 0xc00059cff0, 0x29, 0x0, 0x0, 0x17762fa700000000)
        /home/circleci/project/project/command/init.go:862 +0x8b5
github.com/hashicorp/terraform/command.(*InitCommand).initBackend(0xc00067e700, 0xc0004537a0, 0x32d6888, 0xf, 0xc000592380, 0x1, 0x0, 0x0, 0x0, 0xc0000b9750, ...)
        /home/circleci/project/project/command/init.go:374 +0x4a6
github.com/hashicorp/terraform/command.(*InitCommand).Run(0xc00067e700, 0xc00004c1d0, 0x1, 0x1, 0xc0006440d0)
        /home/circleci/project/project/command/init.go:227 +0xeb1
github.com/mitchellh/cli.(*CLI).Run(0xc000652280, 0xc000652280, 0xc00063fd48, 0x1)
        /home/circleci/project/project/vendor/github.com/mitchellh/cli/cli.go:255 +0x1da
main.wrappedMain(0x0)
        /home/circleci/project/project/main.go:275 +0xc90
main.realMain(0x0)
        /home/circleci/project/project/main.go:106 +0xde
main.main()
        /home/circleci/project/project/main.go:42 +0x3a

Expected Behavior

When i pass the backend config, if the file path is incorrect it should say 'file not found'

Actual Behavior

terraform crashed

Steps to Reproduce

File path does not exists:

1. `terraform init --backend-config="tier/locals/backend.tfvars"

[danieldreier]

Hi @alanplatt! Thanks for reporting this! I was able to reproduce it. I created a trivial github reproduction case at https://github.com/danieldreier/terraform-issue-reproductions/tree/master/25822 to show it. When I ran yours as stated without a backend block in the HCL, it didn't crash, but it crashes just as you describe with a local backend configured.

[mildwonkey]

There is an open PR that will fix this, #25804! I've already confirmed that PR fixes this issue. This is technically a breaking change, as previously users could specify a non-extant file as a shorthand for "empty out the backend config", so it should wait for 0.14.

If we wanted to fix the panic in 0.13 without breaking the current function, we could modify init to check if the file exists first, and if not treat that as an empty backend config file, around these lines:

terraform/command/init.go

Lines 857 to 858 in f5c8ef1

	newBody, fileDiags := c.loadHCLFile(item.Value)
	diags = diags.Append(fileDiags)

[mildwonkey]

This was merged for v0.13.1, so I am going to close this issue - thanks, and sorry again!

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.