Make the `password_cmd` config setting work

Given a string from `password_cmd`, we should execute it as a shell
command and assume the result is a password. That password then gets
submitted to TimeTask's login form for authentication.

Had to do a bit of wrangling to get the command to execute by
`exec.Command()`, but managed to get it working in a bit of a roundabout
way.

Found these resources in my searches:
- https://stackoverflow.com/questions/39930109/golang-execute-command#39930127
https://stackoverflow.com/questions/28783637/how-to-make-golang-execute-a-string
- https://stackoverflow.com/questions/20437336/how-to-execute-system-command-in-golang-with-unknown-arguments
- https://github.com/codeskyblue/go-sh

1 files changed, 22 insertions, 0 deletions

diff --git a/password_cmd.go b/password_cmd.go
new file mode 100644
index 0000000..821c8f6
--- /dev/null
+++ b/password_cmd.go
@@ -0,0 +1,22 @@
+package main
+
+import (
+	"os"
+	"os/exec"
+)
+
+// Execute the given string as a shell command and return the resulting output
+func passwordCmd(password_cmd string) (password string, err error) {
+	shell := os.Getenv("SHELL")
+
+	// `Command` requires us to pass shell arguments as parameters to the
+	// function, but we don't know what the arguments are because
+	// `password_cmd` is an arbitrary command. To get around this, we pass the
+	// password command to the current shell to execute.
+	output, err := exec.Command(shell, "-c", password_cmd).Output()
+	if err != nil {
+		return "", err
+	}
+
+	return string(output), nil
+}