readpassword: create internal package for password reading

* Supports stdin
* Add tests for extpass and stdin

As per user request at https://github.com/rfjakob/gocryptfs/issues/30

1 files changed, 133 insertions, 0 deletions

diff --git a/internal/readpassword/read.go b/internal/readpassword/read.go
new file mode 100644
index 0000000..f316846
--- /dev/null
+++ b/internal/readpassword/read.go
@@ -0,0 +1,133 @@
+package readpassword
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"strings"
+
+	"golang.org/x/crypto/ssh/terminal"
+
+	"github.com/rfjakob/gocryptfs/internal/toggledlog"
+)
+
+const (
+	exitCode = 9
+)
+
+// TODO
+var colorReset, colorRed string
+
+// Once() tries to get a password from the user, either from the terminal,
+// extpass or stdin.
+func Once(extpass string) string {
+	if extpass != "" {
+		return readPasswordExtpass(extpass)
+	}
+	if !terminal.IsTerminal(int(os.Stdin.Fd())) {
+		return readPasswordStdin()
+	}
+	return readPasswordTerminal("Password: ")
+}
+
+// Twice() is the same as Once but will prompt twice if we get
+// the password from the terminal.
+func Twice(extpass string) string {
+	if extpass != "" {
+		return readPasswordExtpass(extpass)
+	}
+	if !terminal.IsTerminal(int(os.Stdin.Fd())) {
+		return readPasswordStdin()
+	}
+	p1 := readPasswordTerminal("Password: ")
+	p2 := readPasswordTerminal("Repeat: ")
+	if p1 != p2 {
+		toggledlog.Fatal.Println(colorRed + "Passwords do not match" + colorReset)
+		os.Exit(exitCode)
+	}
+	return p1
+}
+
+// readPasswordTerminal reads a line from the terminal.
+// Exits on read error or empty result.
+func readPasswordTerminal(prompt string) string {
+	fd := int(os.Stdin.Fd())
+	fmt.Fprintf(os.Stderr, prompt)
+	// terminal.ReadPassword removes the trailing newline
+	p, err := terminal.ReadPassword(fd)
+	if err != nil {
+		toggledlog.Fatal.Printf(colorRed+"Could not read password from terminal: %v\n"+colorReset, err)
+		os.Exit(exitCode)
+	}
+	fmt.Fprintf(os.Stderr, "\n")
+	if len(p) == 0 {
+		toggledlog.Fatal.Println(colorRed + "Password is empty" + colorReset)
+		os.Exit(exitCode)
+	}
+	return string(p)
+}
+
+// readPasswordStdin reads a line from stdin
+// Exits on read error or empty result.
+func readPasswordStdin() string {
+	toggledlog.Info.Println("Reading password from stdin")
+	p := readLineUnbuffered(os.Stdin)
+	if len(p) == 0 {
+		fmt.Fprintf(os.Stderr, "FOOOOOO\n")
+		toggledlog.Fatal.Println(colorRed + "Got empty password from stdin" + colorReset)
+		os.Exit(exitCode)
+	}
+	return p
+}
+
+// readPasswordExtpass executes the "extpass" program and returns the first line
+// of the output.
+// Exits on read error or empty result.
+func readPasswordExtpass(extpass string) string {
+	toggledlog.Info.Println("Reading password from extpass program")
+	parts := strings.Split(extpass, " ")
+	cmd := exec.Command(parts[0], parts[1:]...)
+	cmd.Stderr = os.Stderr
+	pipe, err := cmd.StdoutPipe()
+	if err != nil {
+		toggledlog.Fatal.Printf(colorRed+"extpass pipe setup failed: %v\n"+colorReset, err)
+		os.Exit(exitCode)
+	}
+	err = cmd.Start()
+	if err != nil {
+		toggledlog.Fatal.Printf(colorRed+"extpass cmd start failed: %v\n"+colorReset, err)
+		os.Exit(exitCode)
+	}
+	p := readLineUnbuffered(pipe)
+	pipe.Close()
+	cmd.Wait()
+	if len(p) == 0 {
+		toggledlog.Fatal.Println(colorRed + "extpass: password is empty" + colorReset)
+		os.Exit(exitCode)
+	}
+	return p
+}
+
+// readLineUnbuffered reads single bytes from "r" util it gets "\n" or EOF.
+// The returned string does NOT contain the trailing "\n".
+func readLineUnbuffered(r io.Reader) (l string) {
+	b := make([]byte, 1)
+	for {
+		n, err := r.Read(b)
+		if err == io.EOF {
+			return l
+		}
+		if err != nil {
+			toggledlog.Fatal.Printf(colorRed+"readLineUnbuffered: %v\n"+colorReset, err)
+			os.Exit(exitCode)
+		}
+		if n == 0 {
+			continue
+		}
+		if b[0] == '\n' {
+			return l
+		}
+		l = l + string(b)
+	}
+}