PAM_XAUTH_DATA(3)

💅 pam_xauth_data — the X auth data struct, explained by your favorite Unix bestie 🎀

ok so this is a Linux-PAM manual page, section 3 (that's the library-functions girlies ✨), and today we're talking about pam_xauth_data — the structure that's literally carrying your X authentication data around. iykyk 💖

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✨ NAME ✨

pam_xauth_data — the structure containing X authentication data. that's it, that's the vibe. 👑

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🦋 SYNOPSIS 🦋

ok bestie, here's the exact shape of it, copy it character for character please:

#include <security/pam_appl.h>

struct pam_xauth_data {
    int namelen;
    char *name;
    int datalen;
    char *data;
};

like... four fields, no notes, slay. 🫶

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🌸 DESCRIPTION 🌸

so the pam_xauth_data structure contains X authentication data — and that data is what you use to make a connection to an X display. highkey iconic behavior.

using this mechanism, an application can communicate X authentication data to PAM service modules. why do we care? because it lets modules make a connection to the user's X display in order to:

• label the user's session on login 🏷️
• display visual feedback 👀
• or do other purposes (the manpage says "other purposes", so like... whatever else, bestie) ✨

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🎀 the fields, one by one 🎀

• name — this field contains the name of the authentication method, such as "MIT-MAGIC-COOKIE-1". literally the label of the method, no cap.
• namelen — this field contains the length of that string, and not including the trailing NUL character. yes, not including it. important. 🙈
• data — this field contains the authentication method-specific data corresponding to the specified name. it's giving "the actual payload" energy.
• datalen — this field contains its length in bytes. bytes, bestie, bytes. 💅

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🧚 how to get and set it 🧚

the X authentication data can be changed with the PAM_XAUTH_DATA item. yup, that's the item name, write it down.

it can be queried and set with pam_get_item(3) and pam_set_item (3) respectively — querying with the first one, setting with the second one, in that order, respectively, periodt.

heads up bestie: the value used to set it should be a pointer to a pam_xauth_data structure. and plot twist — an internal copy of both the structure itself and its fields is made by PAM when setting the item. so don't go thinking you can mess with your own copy afterwards and have it stick. PAM already made its own copy, she's independent now. 💀

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🔥 SEE ALSO 🔥

• pam_start(3)
• pam_get_item(3)

(that trailing comma in the original list? iconic, kept it, you're welcome. 💜)

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🌈 STANDARDS 🌈

the pam_xauth_data structure and the PAM_XAUTH_DATA item are Linux-PAM extensions. so like, this is a Linux-PAM thing, not a universal standard — no cap, that's literally what it says. ⭐

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👑 sign-off 👑

and that's the whole page, bestie — this one came from the Linux-PAM Manual, dated 07/08/2026, and it's the PAM_XAUTH_DATA(3) page, living in section 3. go forth and auth your X displays correctly, you absolute main character. 💖🦋🎀