yep.c

/**
 * @mainpage Yep Utility.
 *
 * Software for encryption/decryption of private text data.\n
 * System requirements:
 * - Compiler: cc/gcc
 * - Compile options: -ansi -std=c99
 *
 * Copyright (c) 2012 valsorym <[email protected]>. All rights reserved.
 */

#include <err.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <termios.h>
#include <sys/time.h>
#include <unistd.h>

/* DEFINES */
/*---------------------------------------------------------------------------*/
/**
 * @def DEFAULT_HOOKWORD
 * @brief Protection word by default. Use if not specified arguments
 * are \a ARGV_HOOKWORD.
 *
 * @def DEFAULT_TEMPDIR
 * @brief Directory for storing temporary files by default. Use if not
 * specified arguments are \a ARGV_TEMPDIR.
 */
#define DEFAULT_HOOKWORD  "howdy"
#define DEFAULT_TEMPDIR   "/tmp/yep"

/**
 * @def MAXLEN_BUF
 * @brief The maximum length of text buffer. The buffer used to read lines
 * from a file, encode/decode strings.
 *
 * @def MAXLEN_PATH
 * @brief The maximum permissible length of the path to the file  including
 * the file name.
 *
 * @def MAXLEN_SYSKEY
 * @brief Maximum length of keywords: passwords, hookword.
 *
 * @def MAXLEN_TEMPNAME
 * @brief The maximum permissible length of the temporary file name.
 */
#define MAXLEN_BUF    4096
#define MAXLEN_PATH   255
#define MAXLEN_SYSKEY 15

/* NEWTYPES */
/*---------------------------------------------------------------------------*/
/**
 * @enum bool
 * @brief Boolean data type. etc. \e c99 _Bool.
 */
typedef enum {
    false=0,    /**< True value. */
    true        /**< False value. */
} bool;

/**
 * @enum cmethod
 * @brief Direction of encryption: encrypt, decrypt.
 */
typedef enum {
    encode=1,   /**< Encrypt a file. */
    decode=-1   /**< Decrypt a file. */
} cmethod;

/**
 * @enum cstatus
 * @brief The status of the encrypting/decrypting the file.
 */
typedef enum {
    no_err=0,        /**< Encryption/decryption is successful. */
    err_hookword=33, /**< Decrypted file can not be obtained because of
                      * not correct password/hookword. */
    o_err_read,      /**< Can not open for reading the original file. */
    t_err_read,      /**< Can not open for reading the temp file. */
    o_err_write,     /**< Can not open for writing the original file. */
    t_err_write,     /**< Can not open for writing the temp file. */
    o_err_save,      /**< Can not save the original file.
                      * Error function fclose(). */
    t_err_save,      /**< Can not save the temp file.
                      * Error function fclose(). */
    o_err_create,    /**< Can not create the original file.
                      * Error function createyep(). */
    t_err_create,    /**< Can not create the temp file.
                      * Error function createyep(). */
    decode_problem,  /**< Unable to decode the file. */
    encode_problem   /**< Unable to encode the file. */
} cstatus;

/**
 * @enum maintype
 * @brief The way to open the file.
 */
typedef enum {
    editfile,   /**< The file is open to change/read. */
    changepass  /**< The file is opened to change the password. */
} maintype;

/* SYSTEM FUNCTIONS */
/*---------------------------------------------------------------------------*/
extern char *geths(char [], int );
extern char csymbol(const char , int );
extern bool cstr(char [], int , const char *, const char *, cmethod );
extern bool createyep(const char *, const char *, const char *);
extern cstatus decodingfile(const char *, const char *,
    const char *, const char *);
extern cstatus encodingfile(const char *, const char *,
    const char *, const char *);
extern int terminal(const char *, ...);

/* SCREEN FUNCTIONS */
/*---------------------------------------------------------------------------*/
extern void s_help(void);
extern void s_main(const char *, const char *, const char *,
    const char *, maintype );

/* VIRTUAL SCREEN FUNCTIONS */
/*---------------------------------------------------------------------------*/
extern void vs_newpass(char [], char [], const char *);

/* MAIN */
/*---------------------------------------------------------------------------*/
/**
 * @brief Yep main function.
 *
 * @param argc Count of arguments passed.
 * @param argv The list of arguments.
 *
 * @return Returns zero on success of the program.
 */ //*
int
main(int argc, char **argv)
{
    // `curopt` - found the argument.
    // `editor` - text editor software.
    // `tempdir` - store temporary files.
    // `hookword` - indicator for file recovery.
    // `optstr` - options:
    //    -w: the argument to specify the protection word.
    //    -d: the argument to specify a directory for storing temporary files.
    //    -p: the argument to change the password on the specified file.
    //    -h, -i: the list of arguments to display help information.
    int  curopt = 0;
    char *editor = NULL,
         *tempdir = NULL,
         *hookword = NULL,
         *optstr = "w:d:p:h?";

    // Global variables `getopt`  function (unistd.h):
    // `optarg` - pointer to the current argument, if any.
    // `optopt` - the last of the known parameters.
    // `optind` - The index of the next pointer argv, which will be processed
    // the next call to getopt().
    extern char *optarg;
    extern int   optind;

    // The program requires access to the UNIX shell.
    if (!system(NULL))
        errx(1, "The UNIX shell is not available.\n");

    // Must be at least one external argument.
    if (argc < 2)
        errx(2, "See the help page on the program.\n");

    // Read the arguments list.
    while ((curopt = getopt(argc, argv, optstr)) != -1)
        switch (curopt) {
            case 'i':
            case 'h': // Show help screen.
                s_help();
                break;
            case 'w': // Read hookword.
                if (*optarg != '-')
                    hookword = optarg;
                else
                    errx(3, "Hookword parameter is not specified.\n");
                break;
            case 'd': // Read tempdir.
                if (*optarg != '-')
                    tempdir = optarg;
                else
                    errx(4, "Tempdir parameter is not specified.\n");
                break;
            case 'p': // Set new password on file.
                if (*optarg != '-')
                    s_main(hookword, editor, optarg, tempdir, changepass);
                else
                    errx(5, "Don't specify a file for change the password.\n");
                break;
            default: break;
        } // end switch ().

    // Recent arguments <EDITOR> <FILE>.
    if (argc - optind == 2) {
        // ... hookword, editor, file, tempdir,  editfile);
        s_main(hookword, argv[argc - 2], argv[argc - 1], tempdir, editfile);
    } else
        errx(6, "Wrong number of arguments.\n");

    return 0;
} // end main(). */

/* SYSTEM FUNCTIONS */
/*---------------------------------------------------------------------------*/
/**
 * @brief Read from standard input hidden line.
 *
 * @param buf The buffer where written to a string from stdin.
 * @param bufsize The size of the buffer.
 *
 * @return Returns a pointer to the line of input that is placed in the
 * buffer \a buf.
 */ //*
char
*geths(char buf[], int bufsize)
{
    int     ch,
            i = 0,
            max = bufsize - 1;
    struct
    termios term,
            oldterm;

    // Do not display the characters as you type.
    tcgetattr(0, &term);
    oldterm = term;
    term.c_lflag &= ~ECHO;          // Does not display the characters.
    term.c_lflag &= ~ICANON;        // Do not expect the press enter.
    tcsetattr(0, TCSANOW, &term);

    // Read the hidden characters.
    while ((ch = getchar()) != EOF && ch != '\n')
        if (ch == 127 || ch == 8 || ch == '\b') {
            if (i > 0) i--;
        } else if (i < max)
            buf[i++] = ch;

    buf[i++] = '\0';

    // Restore the old display options.
    term = oldterm;
    tcsetattr(0, TCSANOW, &term);

    return buf;
} // end geths(). */

/**
 * @brief Encode a character offset.
 *
 * @param ch The symbol to encode.
 * @param seek The shift to encode.
 *
 * @return Returns the encoded (If  \a seek variable  > = 0)/decoded (If
 * \a seek variable <0) symbol. If symbol failed to encode/decode, returns the
 * character \a ch variable .
 *
 * @see cstr().
 */ //*
char
csymbol(const char ch, int seek)
{
    char result = ch;
    char *alphabet = "QWERTYUIOPASDFGHJKLZXCVBNM"
                     "qwertyuiopasdfghjklzxcvbnm"
                     "1234567890 !@#$%^&*()_-+{}:";
    int alphsize = strlen(alphabet);

    // Determine the symbol.
    for (int i=0; i < alphsize; ++i)
        if (ch == *(alphabet + i)) {
            seek += i;

            while (seek >= alphsize)
                seek -= alphsize;

            while (seek < 0)
                seek += alphsize;

            if (seek >= 0 && seek < alphsize)
                result = *(alphabet + seek);

            break;
        } // end if ().

    return result;
} // end csymbol(). */

/**
 * @brief Cryptography string.
 *
 * @param buf Encoded string is placed in the buffer.
 * @param bufsize The size of the buffer.
 * @param str The string to encode.
 * @param pass Password to encrypt the string.
 * @param method Method: encode/decode.
 *
 * @return
 * - true - If the string \a str has been successfully encoded/decoded
 *   and placed in buffer \a buf.
 * - false - If you encode/decode the string is impossible.
 *
 * @see csymbol().
 */ //*
bool
cstr(char buf[], int bufsize, const char *str, const char *pass,
     cmethod method)
{
    int  len = strlen(pass),
         seek = 0;

    // Determine the offset.
    for (int i = 0; i < len; ++i)
        seek = seek + ((int)*(pass + i)) * i;

    buf[0] = '\0';

    // Can I put the original in the buffer?
    // Determine the count of processed symbols.
    len = strlen(str);
    if (len > bufsize - 1)
        return false;

    // encode || decode str.
    for (int i = 0; i < len; ++i)
        buf[i] = csymbol(*(str+i), (seek + i) * method);
    buf[len] = '\0';

    return true;
} // end cstr(). */

/**
 * @brief Creates an empty yep-file recording it encoded a keyword (hookword).
 *
 * @param hookword Word of the key.
 * @param pass Password.
 * @param file The file to be created.
 *
 * @return
 * - true - If the file is successfully created.
 * - false - An error occurred while creating the file.
 */ //*
bool
createyep(const char *hookword, const char *pass,
    const char *file)
{
    FILE *f_file;
    char buf[MAXLEN_BUF];
    bool result = false;

    if (!(f_file = fopen(file, "w")))
        return false;

    // Write a hookword in new  yepfile.
    if (cstr(buf, MAXLEN_BUF - 1, hookword, pass, encode)) {
        strncat(buf, "\n", MAXLEN_BUF);
        fputs(buf, f_file);
        result = true;
    } // end if ().

    if(fclose(f_file))
        return false;

    return result;
} // end createyep(). */

/**
 * @brief Вуcode file.
 *
 * @param hookword Word of the key.
 * @param pass Password.
 * @param file File for decoding.
 * @param tempfile The temporary file.
 *
 * @return
 * - no_err - If the operation is executed without error.
 * - o_err_read - Can not open file \a file for reading.
 * - t_err_write - Can not open file \a tempfile for writing.
 * - err_hookword - Wrong password or secret word.
 * - o_err_save - Unable to save file \a file.
 * - t_err_save - Unable to save file \a tempfile.
 * - decode_problem - Unable to decode the file \a file.
 *
 * @see encodingfile().
 */ //*
cstatus
decodingfile(const char *hookword, const char *pass, const char *file,
    const char *tempfile)
{
    FILE *f_file, *f_tempfile;
    char buf[MAXLEN_BUF],
         str[MAXLEN_BUF];
    bool hw_tested = false,
         result = no_err;

    if (!(f_file = fopen(file, "r")))
        return o_err_read;

    if (!(f_tempfile = fopen(tempfile, "w"))) {
        fclose(f_file);
        return t_err_write;
    } // end if ().

    // Encoding file.
    while(!feof(f_file)) {
        if (!hw_tested) {
            // Read hookword.
            hw_tested = true;

            if(fgets(buf, MAXLEN_BUF, f_file)) {
                buf[strlen(buf) - 1] = '\0'; // Remove "\n" symbol.
                if (!cstr(str, MAXLEN_BUF, buf, pass, decode))
                    return decode_problem;

                if (strcmp(str, hookword)) {
                    result = err_hookword;
                    break;
                } // end if ().
            } else {
                result = err_hookword;
                break;
            }
        } else {
            // Read body.
            if(fgets(buf, MAXLEN_BUF, f_file)) {
                if (cstr(str, MAXLEN_BUF, buf, pass, decode))
                    fputs(str, f_tempfile);
                else
                    return decode_problem;
            } // end if ().
        } // end if ().
    } // end while ().

    if(fclose(f_file)) {
        fclose(f_tempfile);
        return o_err_save;
    } // end if ().

    if(fclose(f_tempfile))
        return t_err_save;

    return result;
} // end decodingfile(). */

/**
 * @brief Encode file.
 *
 * @param hookword Word of the key.
 * @param pass Password.
 * @param file File for decoding.
 * @param tempfile The temporary file.
 *
 * @return
 * - no_err - If the operation is executed without error.
 * - o_err_create - If the function createyep() caused the error,
 *   etc. can not create file \a file.
 * - o_err_write - Can not open file for writing \a file.
 * - t_err_read - Can not open file for reading \a tempfile.
 * - o_err_save - Unable to close file \a file.
 * - t_err_save - Unable to close file \a tempfile.
 * - encode_problem - Unable to encode the file \a tempfile.
 *
 * @see decodingfile().
 */ //*
cstatus
encodingfile(const char *hookword, const char *pass, const char *file,
    const char *tempfile)
{
    FILE *f_file,
         *f_tempfile;
    char buf[MAXLEN_BUF],
         str[MAXLEN_BUF];
    bool result = no_err;

    if (!createyep(hookword, pass, file))
        return o_err_create;

    if (!(f_file = fopen(file, "a")))
        return o_err_write;

    if (!(f_tempfile = fopen(tempfile, "r"))) {
        fclose(f_file);
        return t_err_read;
    } // end if ().

    // Decoding file.
    while(!feof(f_tempfile)) {
        // Write body.
        if(fgets(buf, MAXLEN_BUF, f_tempfile)) {
            if (cstr(str, MAXLEN_BUF, buf, pass, encode))
                fputs(str, f_file);
            else
                return encode_problem;
        } // end if ().
    } // end while ().

    if(fclose(f_file)) {
        fclose(f_tempfile);
        return o_err_save;
    } // end if ();

    if(fclose(f_tempfile))
        return t_err_save;

    return result;
} // end encodingfile(). */

/**
 * @brief Executing shell commands.
 *
 * @detailed This function takes cover those arguments as printf() function
 * from the C standard library.
 *
 * @param format Command for the terminal.
 * @param ... Formatting options.
 *
 * @return Returns integer - the result of a shell command.
 */ //*
int
terminal(const char *format, ...)
{
    va_list ptr;
    char    buf[MAXLEN_BUF];

    va_start(ptr, format);
    vsnprintf(buf, MAXLEN_BUF, format, ptr);
    va_end(ptr);

    return system(buf);
} // end terminal(). */

/* SCREEN FUNCTIONS */
/*---------------------------------------------------------------------------*/
/**
 * @brief Show help page.
 *
 * @return No data is returned.
 */ //*
void
s_help(void)
{
    puts("\nNAME\n"
        "\tyep - encrypted text files.\n\n"
        "SYNOPSIS\n"
        "\tyep [-w hookword] [-d tempdir] editor file\n"
        "\tyep [-h | -i]\n"
        "\tyep [-w hookword] [-d tempdir] -p file\n\n"
        "DESCRIPTION\n"
        "\tyep program allows you to encrypt text files using the "
        "public key.\n\n"
        "OPTIONS\n"
        "\t-w hookword\n"
        "\t\tEstablishes additional protection for the word file. This \n"
        "\t\tword should be that you could safely recover an encrypted \n"
        "\t\tfile. If the word is not specified - the word will be used \n"
        "\t\tby default.\n"
        "\t-p file\n"
        "\t\tThe flag allows you to change the previously set password,\n"
        "\t\tand the protection word (hookword).\n"
        "\t-d tempdir\n"
        "\t\tSets the directory for storing temporary files.\n"
        "\t-h, -i\n"
        "\t\tDisplay help information about the program.\n"
        "\teditor\n"
        "\t\tSpecify a text editor synchronous: vi, vim, ee ... Use \n"
        "\t\tasynchronous editors (geany &, emacs & ...) - is impossible.\n"
        "\tfile\n"
        "\t\tThe file to be encrypted / decrypted. If the file does not \n"
        "\t\texist - it is created.\n\n"
        "BUGS\n"
        "\tEmail  bug  reports  to  [email protected].  Be sure to include \n"
        "\tthe word \"yep bugs\" somewhere in the \"Subject:\" field.\n");

    exit(0);
} // end help(). */

/**
 * @brief The main function of encoding, decoding, and change the
 * password on file.
 *
 * @param hookword Secret word.
 * @param editor Synchronous text editor.
 * @param file File manipulation.
 * @param tempdir The directory for storing temporary files.
 * @param type The method of handling file: encoding/decoding or change
 * your password.
 *
 * @return No data is returned.
 */ //*
void
s_main(const char *hookword, const char *editor, const char *file,
    const char *tempdir, maintype type)
{
    char newhookword[MAXLEN_SYSKEY],
         passagain[MAXLEN_SYSKEY],
         pass[MAXLEN_SYSKEY];
    bool existfile = false,
         existeditor = false;
    char tempname[] = "XXXXXXX",
         tempfile[MAXLEN_PATH];
//    int  len = 0;

    // Standard data.
    if (!hookword)
        hookword = DEFAULT_HOOKWORD;

    if (!tempdir)
        tempdir = DEFAULT_TEMPDIR;

    // Create a YEP temporary directory.
    if (terminal("ls -l -d %s | grep ^d", tempdir))
        if (terminal("mkdir -p %s", tempdir))
            errx(7, "Can not create a directory for storing "
                "temporary files.\n");

    // Create a random filename for a temporary file.
    if (strlen(tempdir) + strlen(tempname) >= MAXLEN_PATH)
        errx(8, "A very long name for a temporary file.\n");

    snprintf(tempfile, MAXLEN_PATH, "%s/%s", tempdir, tempname);
    if (mkstemp(tempfile) == -1)
        errx(9, "There exists a directory with that name: %s.\n", file);

    // Check for the file.
    if (!(existfile = !terminal("ls -l -d %s | grep ^-", file)))
        if (!terminal("ls -l -d %s | grep ^d", file)) {
            // There exists a directory with that name: filename.
            terminal("clear");
            errx(10, "There exists a directory with that name: %s.\n", file);
        } // end if ().

    // Checking the editor.
    existeditor = !terminal("which %s", editor);
    terminal("clear");

    // Create interface.
    printf("This will open the file with the following parameters:\n");
    printf("    Filename%s:\t%s\n",
        (existfile ? "" : " (file not exist)"), file);

    if (type == editfile)
        printf("    Editor%s:\t%s\n",
            (existeditor ? "" : " (editor is not installed)"), editor);

    printf("    Hookword%s:\t%s\n\n", (!strcmp(DEFAULT_HOOKWORD, hookword) ?
        " (default word protection)" : ""), hookword);

    if (type == editfile) {
        // Just open file.
        if (!existeditor)
            errx(11, "Editor is not installed: %s.\n", editor);
    } else if (type == changepass) {
        // Change password.
        if (!existfile)
            errx(12, "Сan not change the password on this file: %s.\n", file);
    } else
        // Bad type parameter.
        errx(13, "Is not valid action.\n");
    // end if ().

    // Read the password.
    printf("\nTo exit, press Ctrl+C.\n");
    while (true) {
        printf("\nPassword: ");
        geths(pass, MAXLEN_SYSKEY);

        if (!existfile) {
            printf("\nEnter password again: ");
            geths(passagain, MAXLEN_SYSKEY);

            if (strcmp(pass, passagain))
                printf("\nPasswords do not match. Please, enter again.\n");
            else {
                // Need create file.
                if (!createyep(hookword, pass, file))
                    errx(14, "The file can not be created: %s.\n", file);
                break;
            }
        } else
            break;
        // end if ().
    } // end while ().
    printf("\n");

    // Decoding.
    switch ((int)decodingfile(hookword, pass, file, tempfile)) {
        case o_err_read:
            errx(o_err_read, "Can not open file: %s.\n", file);
            break;
        case t_err_write:
            errx(t_err_write, "Unable to open temporary file for "
                "writing: %s.\n", tempfile);
            break;
        case err_hookword:
            errx(err_hookword, "Hookword was not recognized.\n");
            break;
        case o_err_save:
            errx(o_err_save, "Unable to close file: %s.\n", file);
            break;
        case t_err_save:
            errx(t_err_save, "Unable to close file: %s.\n", tempfile);
            break;
        case decode_problem:
            errx(decode_problem, "Unable to decode the file: %s.\n", file);
            break;
        default: break;
    } // end switch ().

    // Open the file: read/write or change the password.
    if (type == editfile) {
        // Open editor.
        if (terminal("%s %s", editor, tempfile))
            errx(15, "Can not open file: %s.\n", tempfile);
    } else if (type == changepass) {
        // Change password.
        snprintf(newhookword, MAXLEN_SYSKEY, "%s", hookword);
        vs_newpass(newhookword, pass, file);
        hookword = newhookword;
    } // end if ().

    // Encoding again.
    switch ((int)encodingfile(hookword, pass, file, tempfile)) {
        case o_err_create:
            errx(o_err_create, "Can not create file: %s.\n", file);
            break;
        case o_err_write:
            errx(o_err_write, "Unable to write data to file: %s.\n", file);
            break;
        case t_err_read:
            errx(t_err_read, "Unable to read data from the "
                "temfile: %s.\n", tempfile);
            break;
        case o_err_save:
            errx(o_err_save, "Can not save the file: %s.\n", file);
            break;
        case t_err_save:
            errx(t_err_save, "Can not save the file: %s.\n", tempfile);
            break;
        case encode_problem:
            errx(encode_problem, "Unable to encode the file: %s.\n", tempfile);
            break;
        default: break;
    } // end switch ().

    if (terminal("rm -f -P %s", tempfile))
        printf("\nThe temporary file was not deleted: %s.\n", tempfile);

    exit(0);
} // end s_main(). */

/**
 * @brief Function-interface to change password.
 *
 * @param hookword Buffer storage keyword.
 * @param pass Buffer storage password.
 * @param file The file to change the password.
 *
 * @return No data is returned.
 */ //*
void
vs_newpass(char hookword[], char pass[], const char *file)
{
    char passagain[MAXLEN_SYSKEY],
         passcode[MAXLEN_SYSKEY],
         cmd;
    int  i;

    // Go-go-go!!!
    while (true) {
        for (i = 0; i < strlen(passagain); ++i)
            passcode[i] = '*';
        passcode[i + 1] = '\0';

        terminal("clear");
        printf("You are trying to change the system "
               "data to a file: %s.\n", file);
        printf("Choose one of the actions:\n");
        printf("    1. Change password (%s).\n", passcode);
        printf("    2. Change hookword (%s).\n", hookword);
        printf("    3. Save and exit.");
        printf("\nTo exit, press Ctrl+C.\n");

        printf("\nYour choice: ");
        scanf("%c", &cmd);
        while (getchar() != '\n'); // Clear stdin buffer. Bad method. :(

        if (cmd == '1') {
            // Change password.
            while (true) {
                printf("\nEnter new password: ");
                geths(pass, MAXLEN_SYSKEY);

                printf("\nEnter password again: ");
                geths(passagain, MAXLEN_SYSKEY);

                if (strcmp(pass, passagain))
                    printf("\nPasswords do not match. Please, enter again.\n");
                else
                    break;
            } // end while ().
        } else if (cmd == '2') {
            // Change hookword.
            char hwformat[15];
            snprintf(hwformat, MAXLEN_SYSKEY, "%%%ds", MAXLEN_SYSKEY-1);
            printf("\nEnter new hookword: ");
            scanf(hwformat, hookword);
            while (getchar() != '\n'); // Clear stdin buffer. Bad method. :(
        } else if (cmd == '3') {
            // Save and exit;
            terminal("clear");
            printf("\nThe changes take effect.\n");
            return;
        } // end if ().
    } // end while ().

    exit(0);
} // end vs_newpass(). */

/* The End. */