Add --env-prefix to encrypt-file command

[mlocati]

When running the encrypt-file command, the travis client adds two encrypted environment variables to the project configuration (for example: encrypted_123456789ab_key and encrypted_123456789ab_iv).

The prefix of the name of these two variables is randomly generated.

In order to specify this prefix we can now use this new --env-prefix option.

For example:

travis encrypt-file --env-prefix myprefix

will generate two variables named myprefix_key and myprefix_iv

[BanzaiMan]

Hello, there. Thanks for the PR.

I have a couple of questions:

1. What does this do that the existing --key and --iv flags do not?
2. The code defines the variable, but it doesn't actually do anything. Did I miss something?

[mlocati]

I'd need to know the names of the two variables in advance.
At the moment, what we have before _key and _iv is really hard to be determined before running the command (their prefix is determined here).

If we let users specify this --env-prefix option, the env_prefix variable will be set to the value of it, and

@env_prefix ||= "encrypted_#{Digest.hexencode(Digest::SHA1.digest(input_path)[0..5])}"

won't do anything (since env_prefix is already defined, it won't be assigned the value of what we have after the =).

[mlocati]

@BanzaiMan Is there something unclear with my answer?

[BanzaiMan]

No, there isn't. I understand the intent now. One thing still a little uneasy is the name. env_prefix seems a little vague. Maybe arg_prefix, env_var_prefix or something like that. Maybe a short flag name would help as well.

Additionally, the help text should indicate how this would interact with -K/--key and --iv.

[mlocati]

One thing still a little uneasy is the name. env_prefix seems a little vague. Maybe arg_prefix, env_var_prefix or something like that.

• if users don't specify this new parameter, the name of the two variables containing the IV/key pair will be prefixed by encrypted_ followed by a SHA-1 hash (for example: encrypted_abcdef012345_iv / encrypted_abcdef012345_key)
• if users use this new parameter, they'll be able to specify what should be used instead of encrypted_abcdef012345.

So, what about enc_var_prefix ?

Maybe a short flag name would help as well.

Well, I think it'll be a rarely used argument, I don't know if it's worth reserving a short flag just for this tiny feature.

Additionally, the help text should indicate how this would interact with -K/--key and --iv.

Well, there's no interaction with the value of the generated variables, just with their names.
And to me the current text is quite clear about that:
prefix of the names of the encryption key/IV environment variables (randomly generated otherwise)
Do you have a better alternative to it?

[BanzaiMan]

enc_var_prefix seems acceptable.

By "interaction", I mean "what would happen if both -K and this new flag is given?" (as strange as it may sound). I believe this flag overrides --key and --iv, and that should be stated.

[mlocati]

• the --key (aka -K) sets the value of the encryption key
• the --iv sets the value of the encryption IV
• this --enc-var-prefix sets the prefix of the names of the two above values

Examples:

• travis encrypt-file file.txt
  generates two environment variables:
  • encrypted_abcdef012345_iv with a value generated automatically
  • encrypted_abcdef012345_key with a value generated automatically
• travis encrypt-file --enc-var-prefix myprefix file.txt
  generates two environment variables:
  • myprefix_iv with a value generated automatically
  • myprefix_key with a value generated automatically
• travis encrypt-file --iv myiv --key mykey file.txt
  generates two environment variables:
  • encrypted_abcdef012345_iv with the "myiv" value
  • encrypted_abcdef012345_key with the "mykey" value
• travis encrypt-file --enc-var-prefix myprefix --iv myiv --key mykey file.txt
  generates two environment variables:
  • myprefix_iv with the "myiv" value
  • myprefix_key with the "mykey" value

As you can see, there's no interaction between --key/-K/--iv and --enc-var-prefix.

And that's quite clear to me from the description of the options:

• --key: encryption key to be used (randomly generated otherwise)
• --iv: encryption IV to be used (randomly generated otherwise)
• --enc-var-prefix: prefix of the names of the encryption key/IV environment variables (randomly generated otherwise)

[mlocati]

Is this PR so hard to review? One year...