tpm_buf_fill_hmac_session(9)

💖 tpm_buf_fill_hmac_session (9) — Kernel API Manual 💖

okay so bestie, welcome to the <pink>Kernel API Manual</pink> entry for tpm_buf_fill_hmac_session(9) — literally the glow-up moment where your session HMAC gets finalized. she's the last step, the finishing touch, the setting spray of your TPM command buffer. ✨

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🌸 NAME 🌸

tpm_buf_fill_hmac_session — finalize the session HMAC 🫶

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🎀 SYNOPSIS 🎀

int tpm_buf_fill_hmac_session (struct tpm_chip *chip , struct tpm_buf
*buf );

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🦋 ARGUMENTS 🦋

• chip — the TPM chip structure. your main character, your TPM chip 💅
• buf — The buffer to be appended. yes, this one. the buffer we're appending to, no cap.

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🔥 DESCRIPTION 🔥

okay so here's the vibe check, and it's important:

This command must not be called until all of the parameters have been appended to buf — otherwise the computed HMAC will be incorrect. 😭 like, fr fr, do not jump the gun here.

This function computes and fills in the session HMAC using the session key and, if TPM2_SA_DECRYPT was specified, computes the encryption key and encrypts the first parameter of the command buffer with it. 🔐✨

Ends the authorization session on failure. 💀 lowkey dramatic but that's the rule.

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👑 SEE ALSO 👑

Kernel file ./drivers/char/tpm/tpm2-sessions.c, plus the whole friend group:

• tpm_buf_append_name(9)
• tpm_buf_append_hmac_session(9)
• tpm_buf_check_hmac_response(9)
• tpm2_end_auth_session(9)
• tpm2_start_auth_session(9)
• tpm2_parse_create_primary(9)
• tpm2_create_primary(9)
• tpm2_sessions_init(9)

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🌈 ok that's the whole page bestie, mwah 💋 — this one's from ./drivers/char/tpm, dated October 2026, and it's the tpm_buf_fill_hmac_session(9) manual page, slay. 🎀✨💜