ULOG_LOGIN(3)

ULOG_LOGIN(3) is a page from the Library Functions Manual, bestie — and it’s all about the User Login Record Library. Login-record lore, but make it make sense 💅

🎀 NAME 🎀

ulog_login, ulog_login_pseudo, ulog_logout, ulog_logout_pseudo — manage user login records

📚 LIBRARY 📚

User Login Record Library (libulog, -lulog)

✨ SYNOPSIS ✨

#include <ulog.h>

void
ulog_login(const char *line, const char *user, const char *host);

void
ulog_login_pseudo(int fd, const char *host);

void
ulog_logout(const char *line);

void
ulog_logout_pseudo(int fd);

💖 DESCRIPTION 💖

Okay so here’s the login-record tea:

• ulog_login() and ulog_login_pseudo() register a login session on a TTY. Iconic behavior.
• ulog_login() adds an entry for TTY line and username user. Simple, slay.
• ulog_login_pseudo() uses file descriptor to a pseudo-terminal master device fd to determine the TTY name, while using the username belonging to the real user ID of the calling process. It’s giving “let the system handle the identity situation” 🫶
• The optional host argument denotes a remote hostname, in case the login session is provided by a network service. So if the login came from the network, host can carry that info.
• ulog_logout() and ulog_logout_pseudo() mark the previously registered login session as being terminated. Bye bestie 👋

Now the spicy security bit:

Because the line and user arguments of ulog_login() and ulog_logout() cannot be trusted, these functions require administrative privileges. No cap. 🔥

The ulog_login_pseudo() and ulog_logout_pseudo() functions spawn a privileged process to perform the actual logging. They do not just do the privileged work themselves — they spawn a privileged process to perform the actual logging. Periodt.

👀 SEE ALSO 👀

• getuid(2)
• posix_openpt(2)
• ptsname(3)
• pututxline(3)

🕰️ HISTORY 🕰️

These functions appeared in FreeBSD 9.0. Vintage but still cute.

Okay bye bestie, this page is from Debian, dated October 11, 2010, and it’s the ULOG_LOGIN(3) manual page — mwah 💋🫶