authentication failure when the password contains the $ symbol

[samuraikillers]

While using "$" symbol in the exporter password we get error message, similar like the #933

level=ERROR source=exporter.go:131 msg="Error opening connection to database" err="Error 1045 (28000): Access denied for user 'xxx'@'10.x.x.x' (using password: YES)"

[morawskim]

I have the same issue.

The problem occurs when the password contains a $ character and the following character is a letter (e.g. $a, $b, etc.).
In this case, the password is incorrectly interpreted and causes a failure.

Looking at the code here:

mysqld_exporter/config/config.go

Line 126 in 3c67462

cfg.ValueMapper = os.ExpandEnv

Because ExpandEnv treats $<letter> as an environment variable reference, parts of the password are unexpectedly expanded or removed.

As a workaround:
If you have a password abc$foo create env variable foo with value $foo.
This is not ideal, but it works.

Alternatively, store the password itself in an environment variable and reference that variable in the configuration instead of using the raw password value.

[samuraikillers]

@morawskim yes it's because of expanenv variable.

But should we not fix this issue?

@SuperQ do you agree on fixing this issue? Can I work on this issue?

[morawskim]

I have prepared PR - #1005

In my opinion, we should not substitute environment variables when the $ character appears inside the value.
Environment variable substitution should only happen when the value starts with the $ symbol.

If a password itself starts with $, we should use $$ to avoid unintended environment variable substitution.

[morawskim]

Hello @SuperQ

Had you time to look at this PR #1005 which resolve this issue?