rdo/readpassphrase.h

#include <stdio.h>
#include <unistd.h>
#include <termios.h>
#include <fcntl.h>

char* readpassphrase(const char* prompt, char* buf, size_t bufsz, int read_pw_from_stdin) {
    int n;
    int is_tty = !read_pw_from_stdin;
    int infd;
    int outfd;

    struct termios term;

    if (read_pw_from_stdin) {
        infd = 0;
        outfd = 1;
        is_tty = tcgetattr(outfd, &term) == 0;
    } else {
        infd = outfd = open("/dev/tty", O_RDWR);
        if (!(infd >= 0 && tcgetattr(outfd, &term) == 0))
            return NULL;
    }

    if (infd < 0)
        return NULL;

    if (is_tty) {
        term.c_lflag &= ~ECHO;
        tcsetattr(outfd, 0, &term);
        term.c_lflag |= ECHO;
    }

    if (write(outfd, prompt, strlen(prompt)) < 0) {
        if (is_tty)
            tcsetattr(outfd, 0, &term);
        return NULL;
    }

    n = read(infd, buf, bufsz);
    if (n < 0) {
        if (is_tty)
            tcsetattr(outfd, 0, &term);
        n = write(outfd, "\n", 1);
        return NULL;
    }

    buf[n-1] = '\0';

    // NOTE: As we disabled echo, the enter sent by the user isn't displayed, so we resend it.
    n = write(outfd, "\n", 1);

    if (is_tty)
        tcsetattr(outfd, 0, &term);

    return buf;
}