/* Initialize and serve a login terminal * * Copyright (c) 2016 Joachim Nilsson * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN * THE SOFTWARE. */ #include #include #include #include #include #include #include #include /* Not included by default in musl libc */ #include #include "finit.h" #include "helpers.h" #include "sig.h" #include "utmp-api.h" #ifndef _PATH_LOGIN #define _PATH_LOGIN "/bin/login" #endif #define CTL(x) ((x) ^ 0100) #define print(s) (void)write(STDOUT_FILENO, s, strlen(s)) /* * Read one character from stdin. */ static int readch(char *tty) { int st; char ch1; st = read(STDIN_FILENO, &ch1, 1); if (st == 0) { print("\n"); _exit(0); } if (st < 0) errx(1, "getty: %s: read error", tty); return ch1 & 0xFF; } /* * Parse and display a line from /etc/issue */ static void do_parse(char *line, struct utsname *uts, char *tty) { char *s, *s0; s0 = line; for (s = line; *s != 0; s++) { if (*s == '\\') { (void)write(1, s0, s - s0); s0 = s + 2; switch (*++s) { case 'l': print(tty); break; case 'm': print(uts->machine); break; case 'n': print(uts->nodename); break; #ifdef _GNU_SOURCE case 'o': print(uts->domainname); break; #endif case 'r': print(uts->release); break; case 's': print(uts->sysname); break; case 'v': print(uts->version); break; case 0: goto leave; default: s0 = s - 1; } } } leave: (void)write(1, s0, s - s0); } /* * Parse and display /etc/issue */ static void do_issue(char *tty) { FILE *fp; char buf[BUFSIZ] = "Welcome to \\s \\v \\n \\l\n\n"; struct utsname uts; /* * Get data about this machine. */ uname(&uts); fp = fopen("/etc/issue", "r"); if (fp) { while (fgets(buf, sizeof(buf), fp)) do_parse(buf, &uts, tty); fclose(fp); } else { do_parse(buf, &uts, tty); } do_parse("\\n login: ", &uts, tty); } /* * Handle the process of a GETTY. */ static void do_getty(char *tty, char *name, size_t len) { int ch; char *np; /* * Clean up tty name. */ if (!strncmp(tty, _PATH_DEV, strlen(_PATH_DEV))) tty += 5; /* * Display prompt. */ ch = ' '; *name = '\0'; while (ch != '\n') { do_issue(tty); np = name; while ((ch = readch(tty)) != '\n') { if (ch == CTL('U')) { while (np > name) { (void)write(1, "\b \b", 3); np--; } continue; } if (np < name + len) *np++ = ch; } *np = '\0'; if (*name == '\0') ch = ' '; /* blank line typed! */ } name[len - 1] = 0; } /* * Execute the login(1) command with the current * username as its argument. It will reply to the * calling user by typing "Password: "... */ static int do_login(char *name) { struct stat st; execl(_PATH_LOGIN, _PATH_LOGIN, name, NULL); /* * Failed to exec login, should be impossible. Try a starting a * fallback shell instead. * * Note: Add /etc/securetty handling. */ warnx("Failed exec %s, attempting fallback to %s ...", _PATH_LOGIN, _PATH_BSHELL); if (fstat(0, &st) == 0 && S_ISCHR(st.st_mode)) execl(_PATH_BSHELL, _PATH_BSHELL, NULL); return 1; /* We shouldn't get here ... */ } int getty(char *tty, speed_t speed, char *term, char *user) { int fd; char name[30]; /* Detach from initial controlling TTY */ vhangup(); fd = open(tty, O_RDWR); if (fd < 0) err(1, "Failed opening %s", tty); dup2(fd, STDIN_FILENO); dup2(fd, STDOUT_FILENO); dup2(fd, STDERR_FILENO); if (ioctl(STDIN_FILENO, TIOCSCTTY, 1) < 0) warn("Failed TIOCSCTTY"); /* The getty process is responsible for the UTMP login record */ utmp_set_login(tty, NULL); if (!user) do_getty(tty, name, sizeof(name)); else strlcpy(name, user, sizeof(name)); /* Set up TTY, re-enabling ISIG et al. */ stty(fd, speed); close(fd); if (term && term[0]) setenv("TERM", term, 1); return do_login(name); } int sh(char *tty) { int fd; char *arg0; char *args[2] = { NULL, NULL }; size_t len; struct termios term; /* Detach from initial controlling TTY */ vhangup(); fd = open(tty, O_RDWR); if (fd < 0) err(1, "Failed opening %s", tty); dup2(fd, STDIN_FILENO); dup2(fd, STDOUT_FILENO); dup2(fd, STDERR_FILENO); if (ioctl(STDIN_FILENO, TIOCSCTTY, 1) < 0) warn("Failed TIOCSCTTY"); /* The getty process is usually responsible for the UTMP login record */ utmp_set_login(tty, NULL); /* Set up TTY, re-enabling ISIG et al. */ stty(fd, B0); close(fd); /* Start /bin/sh as a login shell, i.e. with a prefix '-' */ len = strlen(_PATH_BSHELL) + 2; arg0 = malloc(len); if (!arg0) err(1, "Failed allocating memory"); snprintf(arg0, len, "-%s", _PATH_BSHELL); args[0] = arg0; /* Reenable Ctrl-D and Ctrl-C, and ... */ if (!tcgetattr(STDIN_FILENO, &term)) { term.c_lflag |= ISIG; term.c_cc[VEOF] = CTL('D'); term.c_cc[VINTR] = CTL('C'); tcsetattr(STDIN_FILENO, TCSANOW, &term); } /* ... unblock signals in general */ sig_unblock(); return execv(_PATH_BSHELL, args); } /** * Local Variables: * indent-tabs-mode: t * c-file-style: "linux" * End: */