os: add input_password(prompt) and unit tests (#15507)

.github/workflows/ci.yml

@@ -29,6 +29,7 @@ jobs:
           ## The following is needed for examples/wkhtmltopdf.v
           wget https://github.com/wkhtmltopdf/packaging/releases/download/0.12.6-1/wkhtmltox_0.12.6-1.focal_amd64.deb
           sudo apt-get install --quiet -y xfonts-75dpi xfonts-base
+          sudo apt-get install --quiet -y expect
           sudo dpkg -i wkhtmltox_0.12.6-1.focal_amd64.deb
       - name: Build v
         run: |
@@ -92,6 +93,11 @@ jobs:
           ./v2 -o v3 -usecache cmd/v
           ./v3 version
           ./v3 -o tetris  -usecache examples/tetris/tetris.v
+      - name: Test password input
+        run: |
+          ./v examples/password
+          ./v examples/password/password_ci.vsh
+
 
   ubuntu-tcc-boehm-gc:
     runs-on: ubuntu-20.04
@@ -239,6 +245,10 @@ jobs:
           ./v2 -o v3 -usecache cmd/v
           ./v3 version
           ./v3 -o tetris  -usecache examples/tetris/tetris.v
+      - name: Test password input
+        run: |
+          ./v examples/password
+          ./v examples/password/password_ci.vsh
 
   ubuntu:
     runs-on: ubuntu-20.04

examples/password/correct.expect

@@ -0,0 +1,8 @@
+#!/usr/bin/expect
+spawn ./password
+expect "Enter your password : "
+send "Sample\r"
+expect "Confirm password : "
+send "Sample\r"
+expect "Password confirmed! You entered: Sample ."
+expect eof

examples/password/incorrect.expect

@@ -0,0 +1,8 @@
+#!/usr/bin/expect
+spawn ./password
+expect "Enter your password : "
+send "Sample123\r"
+expect "Confirm password : "
+send "Sample234\r"
+expect "Passwords do not match ."
+expect eof

examples/password/password.v

@@ -0,0 +1,14 @@
+module main
+
+import os
+
+fn main() {
+	original_password := os.input_password('Enter your password : ')!
+	repeated_password := os.input_password('Confirm password : ')!
+
+	if original_password == repeated_password {
+		println('Password confirmed! You entered: $original_password .')
+	} else {
+		println('Passwords do not match .')
+	}
+}

examples/password/password_ci.vsh

@@ -0,0 +1,3 @@
+chdir('examples/password')?
+assert execute('./correct.expect').exit_code == 0
+assert execute('./incorrect.expect').exit_code == 0

vlib/os/password_nix.c.v

@@ -0,0 +1,42 @@
+module os
+
+#include <termios.h>
+
+pub struct C.termios {
+mut:
+	c_iflag int
+	c_oflag int
+	c_cflag int
+	c_lflag int
+	c_cc    [20]u8
+}
+
+fn C.tcgetattr(fd int, ptr &C.termios) int
+
+fn C.tcsetattr(fd int, action int, const_ptr &C.termios)
+
+// input_password prompts the user for a password-like secret. It disables
+// the terminal echo during user input and resets it back to normal when done.
+pub fn input_password(prompt string) !string {
+	if is_atty(1) <= 0 || getenv('TERM') == 'dumb' {
+		return error('Could not obtain password discretely.')
+	}
+
+	old_state := C.termios{}
+	if unsafe { C.tcgetattr(0, &old_state) } != 0 {
+		return last_error()
+	}
+	defer {
+		unsafe { C.tcsetattr(0, C.TCSANOW, &old_state) }
+		println('')
+	}
+
+	mut new_state := old_state
+
+	new_state.c_lflag &= int(~u32(C.ECHO)) // Disable echoing of characters
+	unsafe { C.tcsetattr(0, C.TCSANOW, &new_state) }
+
+	password := input_opt(prompt) or { return error('Failed to read password') }
+
+	return password
+}

vlib/os/password_windows.c.v

@@ -0,0 +1,26 @@
+module os
+
+#include <windows.h>
+
+// input_password prompts the user for a password-like secret. It disables
+// the terminal echo during user input and resets it back to normal when done.
+pub fn input_password(prompt string) !string {
+	if is_atty(1) <= 0 || getenv('TERM') == 'dumb' {
+		return error('Could not obtain password discretely.')
+	}
+
+	std_handle := C.GetStdHandle(C.STD_INPUT_HANDLE)
+	mut mode := u32(0)
+
+	unsafe { C.GetConsoleMode(std_handle, &mode) }
+	unsafe { C.SetConsoleMode(std_handle, mode & (~u32(C.ENABLE_ECHO_INPUT))) }
+
+	defer {
+		unsafe { C.SetConsoleMode(std_handle, &mode) }
+		println('')
+	}
+
+	password := input_opt(prompt) or { return error('Failed to read password') }
+
+	return password
+}