Update MentOs code to the latest development version.

programs/login.c

@@ -0,0 +1,193 @@
+/////                MentOS, The Mentoring Operating system project
+/// @file login.c
+/// @brief Functions used to manage login.
+/// @copyright (c) 2014-2021 This file is distributed under the MIT License.
+/// See LICENSE.md for details.
+
+/// Maximum length of credentials.
+#include <string.h>
+#include <stdbool.h>
+#include <sys/unistd.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <limits.h>
+#include <termios.h>
+#include <bits/ioctls.h>
+#include <pwd.h>
+#include <strerror.h>
+#include <stdlib.h>
+
+#define CREDENTIALS_LENGTH 50
+
+#define FG_BLACK "\033[30m"
+#define FG_WHITE "\033[37m"
+#define FG_RED   "\033[31m"
+#define BG_WHITE "\033[47m"
+#define BG_BLACK "\033[40m"
+
+void set_echo(bool_t active)
+{
+    struct termios _termios;
+    tcgetattr(STDIN_FILENO, &_termios);
+    if (active)
+        _termios.c_lflag |= (ICANON | ECHO);
+    else
+        _termios.c_lflag &= ~(ICANON | ECHO);
+    tcsetattr(STDIN_FILENO, 0, &_termios);
+}
+
+void set_erase(bool_t active)
+{
+    struct termios _termios;
+    tcgetattr(STDIN_FILENO, &_termios);
+    if (active)
+        _termios.c_lflag |= ECHOE;
+    else
+        _termios.c_lflag &= ~ECHOE;
+    tcsetattr(STDIN_FILENO, 0, &_termios);
+}
+
+/// @brief Gets the inserted command.
+static bool_t get_input(char *input, size_t max_len, bool_t hide)
+{
+    size_t index = 0;
+    int c;
+    bool_t result = false;
+
+    set_erase(false);
+    if (hide) {
+        set_echo(false);
+    }
+
+    memset(input, 0, max_len);
+    do {
+        c = getchar();
+        // Return Key
+        if (c == '\n') {
+            input[index] = 0;
+            result       = true;
+            break;
+        } else if (c == '\033') {
+            c = getchar();
+            if (c == '[') {
+                c = getchar(); // Get the char, and ignore it.
+            } else if (c == '^') {
+                c = getchar(); // Get the char.
+                if (c == 'C') {
+                    // However, the ISR of the keyboard has already put the char.
+                    // Thus, delete it by using backspace.
+                    if (!hide) {
+                        putchar('\b');
+                        putchar('\b');
+                        putchar('\n');
+                    }
+                    result = false;
+                    break;
+                } else if (c == 'U') {
+                    if (!hide) {
+                        // However, the ISR of the keyboard has already put the char.
+                        // Thus, delete it by using backspace.
+                        putchar('\b');
+                        putchar('\b');
+                        // Clear the current command.
+                        for (size_t it = 0; it < index; ++it) {
+                            putchar('\b');
+                        }
+                    }
+                    index = 0;
+                }
+            }
+        } else if (c == '\b') {
+            if (index > 0) {
+                if (!hide) {
+                    putchar('\b');
+                }
+                --index;
+            }
+        } else {
+            input[index++] = c;
+            if (index == (max_len - 1)) {
+                input[index] = 0;
+                result       = true;
+                break;
+            }
+        }
+    } while (index < max_len);
+
+    set_erase(true);
+    if (hide) {
+        set_echo(true);
+        putchar('\n');
+    }
+
+    return result;
+}
+
+static inline int setup_env(passwd_t *pwd)
+{
+    // Set the HOME.
+    char env_buffer[BUFSIZ];
+    // Set the USER.
+    if (setenv("USER", pwd->pw_name, 0) == -1) {
+        printf( "Failed to set env: `USER`\n");
+        return 0;
+    }
+    // Set the SHELL.
+    if (setenv("SHELL", pwd->pw_shell, 0) == -1) {
+        printf( "Failed to set env: `SHELL`\n");
+        return 0;
+    }
+    sprintf(env_buffer, "/home/%s", pwd->pw_name);
+    if (setenv("HOME", env_buffer, 0) == -1) {
+        printf("Failed to set env: `HOME`\n");
+        return 0;
+    }
+    return 1;
+}
+
+int main(int argc, char **argv)
+{
+    passwd_t *pwd;
+    char username[50], password[50];
+    do {
+        // Get the username.
+        do {
+            printf("Username :");
+        } while (!get_input(username, 50, false));
+        do {
+            printf("Password :");
+        } while (!get_input(password, 50, true));
+        if ((pwd = getpwnam(username)) == NULL) {
+            if (errno == ENOENT) {
+                printf("The given name was not found.\n");
+            } else if (errno == 0) {
+                printf("Cannot access passwd file.\n");
+            } else {
+                printf("Unknown error (%s).\n", strerror(errno));
+            }
+            continue;
+        }
+        if (strcmp(pwd->pw_passwd, password) != 0) {
+            printf("Wrong password.\n");
+            continue;
+        }
+        break;
+    } while (true);
+    if (pwd->pw_shell == NULL) {
+        printf("%s: There is no shell set for the user `%s`.\n", argv[0], pwd->pw_name);
+        return 1;
+    }
+
+    if (!setup_env(pwd)) {
+        printf("%s: Failed to setup the environmental variables.\n", argv[0]);
+        return 1;
+    }
+
+    char *_argv[] = { pwd->pw_shell, (char *)NULL };
+    if (execv(pwd->pw_shell, _argv) == -1) {
+        printf("%s: Failed to execute the shell.\n", argv[0]);
+        printf("%s: %s.\n", argv[0], strerror(errno));
+        return 1;
+    }
+    return 0;
+}