From: Mimi Zohar <zohar@xxxxxxxxxxxxx> The initial encrypted HMAC session feature added TPM bus encryption to various in-kernel TPM operations. This can cause performance bottlenecks with IMA, as it heavily utilizes PCR extend operations. In order to address this performance issue, introduce disable_encrypt_pcrs kernel command-line parameter to the TPM driver. Cc: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> Link: https://lore.kernel.org/linux-integrity/20241015193916.59964-1-zohar@xxxxxxxxxxxxx/ Fixes: 6519fea6fd37 ("tpm: add hmac checks to tpm2_pcr_extend()") Co-developed-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx> Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx> Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxx> Co-developed-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx> Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx> --- v1: - Derived from the earlier RFC patch with a different parameter scope, cleaner commit message and some other tweaks. I decided to create something because I did not noticed any progress. Note only compile tested as I wanted to get something quickly out. --- .../admin-guide/kernel-parameters.txt | 10 ++++ drivers/char/tpm/tpm2-cmd.c | 33 ++++++++--- drivers/char/tpm/tpm2-sessions.c | 59 +++++++++++-------- include/linux/tpm.h | 4 ++ 4 files changed, 74 insertions(+), 32 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 1518343bbe22..e27517e1a26f 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -6727,6 +6727,16 @@ torture.verbose_sleep_duration= [KNL] Duration of each verbose-printk() sleep in jiffies. + tpm.disable_encrypt_pcrs= [HW,TPM] + Do not protect PCR registers from unintended physical + access, or interposers in the bus by the means of + having an encrypted and integrity protected session + wrapped around TPM2_PCR_Extend command. Consider this + in a situation where TPM is heavily utilized by + IMA, thus protection causing a major performance hit, + and the space where machines are deployed is by other + means guarded. + tpm_suspend_pcr=[HW,TPM] Format: integer pcr id Specify that at suspend time, the tpm driver diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c index 1e856259219e..6ec307b1cb99 100644 --- a/drivers/char/tpm/tpm2-cmd.c +++ b/drivers/char/tpm/tpm2-cmd.c @@ -14,6 +14,10 @@ #include "tpm.h" #include <crypto/hash_info.h> +static bool disable_encrypt_pcrs; +module_param(disable_encrypt_pcrs, bool, 0444); +MODULE_PARM_DESC(disable_encrypt_pcrs, "Disable TPM2_PCR_Extend encryption"); + static struct tpm2_hash tpm2_hash_map[] = { {HASH_ALGO_SHA1, TPM_ALG_SHA1}, {HASH_ALGO_SHA256, TPM_ALG_SHA256}, @@ -232,18 +236,26 @@ int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, int rc; int i; - rc = tpm2_start_auth_session(chip); - if (rc) - return rc; + if (!disable_encrypt_pcrs) { + rc = tpm2_start_auth_session(chip); + if (rc) + return rc; + } rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_PCR_EXTEND); if (rc) { - tpm2_end_auth_session(chip); + if (!disable_encrypt_pcrs) + tpm2_end_auth_session(chip); return rc; } - tpm_buf_append_name(chip, &buf, pcr_idx, NULL); - tpm_buf_append_hmac_session(chip, &buf, 0, NULL, 0); + if (!disable_encrypt_pcrs) { + tpm_buf_append_name(chip, &buf, pcr_idx, NULL); + tpm_buf_append_hmac_session(chip, &buf, 0, NULL, 0); + } else { + tpm_buf_append_handle(chip, &buf, pcr_idx, NULL); + tpm_buf_append_auth(chip, &buf, 0, NULL, 0); + } tpm_buf_append_u32(&buf, chip->nr_allocated_banks); @@ -253,9 +265,12 @@ int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, chip->allocated_banks[i].digest_size); } - tpm_buf_fill_hmac_session(chip, &buf); - rc = tpm_transmit_cmd(chip, &buf, 0, "attempting extend a PCR value"); - rc = tpm_buf_check_hmac_response(chip, &buf, rc); + if (!disable_encrypt_pcrs) + tpm_buf_fill_hmac_session(chip, &buf); + rc = tpm_transmit_cmd(chip, &buf, 0, + "attempting extend a PCR value"); + if (!disable_encrypt_pcrs) + rc = tpm_buf_check_hmac_response(chip, &buf, rc); tpm_buf_destroy(&buf); diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c index 42df980168b6..02897debc3fa 100644 --- a/drivers/char/tpm/tpm2-sessions.c +++ b/drivers/char/tpm/tpm2-sessions.c @@ -205,6 +205,14 @@ static int tpm2_read_public(struct tpm_chip *chip, u32 handle, char *name) } #endif /* CONFIG_TCG_TPM2_HMAC */ +void tpm_buf_append_handle(struct tpm_chip *chip, struct tpm_buf *buf, + u32 handle, u8 *name) +{ + tpm_buf_append_u32(buf, handle); + /* count the number of handles in the upper bits of flags */ + buf->handles++; +} + /** * tpm_buf_append_name() - add a handle area to the buffer * @chip: the TPM chip structure @@ -237,9 +245,7 @@ void tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf, #endif if (!tpm2_chip_auth(chip)) { - tpm_buf_append_u32(buf, handle); - /* count the number of handles in the upper bits of flags */ - buf->handles++; + tpm_buf_append_handle(chip, buf, handle, name); return; } @@ -272,6 +278,31 @@ void tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf, } EXPORT_SYMBOL_GPL(tpm_buf_append_name); +void tpm_buf_append_auth(struct tpm_chip *chip, struct tpm_buf *buf, + u8 attributes, u8 *passphrase, int passphrase_len) +{ + /* offset tells us where the sessions area begins */ + int offset = buf->handles * 4 + TPM_HEADER_SIZE; + u32 len = 9 + passphrase_len; + + if (tpm_buf_length(buf) != offset) { + /* not the first session so update the existing length */ + len += get_unaligned_be32(&buf->data[offset]); + put_unaligned_be32(len, &buf->data[offset]); + } else { + tpm_buf_append_u32(buf, len); + } + /* auth handle */ + tpm_buf_append_u32(buf, TPM2_RS_PW); + /* nonce */ + tpm_buf_append_u16(buf, 0); + /* attributes */ + tpm_buf_append_u8(buf, 0); + /* passphrase */ + tpm_buf_append_u16(buf, passphrase_len); + tpm_buf_append(buf, passphrase, passphrase_len); +} + /** * tpm_buf_append_hmac_session() - Append a TPM session element * @chip: the TPM chip structure @@ -309,26 +340,8 @@ void tpm_buf_append_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf, #endif if (!tpm2_chip_auth(chip)) { - /* offset tells us where the sessions area begins */ - int offset = buf->handles * 4 + TPM_HEADER_SIZE; - u32 len = 9 + passphrase_len; - - if (tpm_buf_length(buf) != offset) { - /* not the first session so update the existing length */ - len += get_unaligned_be32(&buf->data[offset]); - put_unaligned_be32(len, &buf->data[offset]); - } else { - tpm_buf_append_u32(buf, len); - } - /* auth handle */ - tpm_buf_append_u32(buf, TPM2_RS_PW); - /* nonce */ - tpm_buf_append_u16(buf, 0); - /* attributes */ - tpm_buf_append_u8(buf, 0); - /* passphrase */ - tpm_buf_append_u16(buf, passphrase_len); - tpm_buf_append(buf, passphrase, passphrase_len); + tpm_buf_append_auth(chip, buf, attributes, passphrase, + passphrase_len); return; } diff --git a/include/linux/tpm.h b/include/linux/tpm.h index 587b96b4418e..4892cd004530 100644 --- a/include/linux/tpm.h +++ b/include/linux/tpm.h @@ -502,9 +502,13 @@ static inline struct tpm2_auth *tpm2_chip_auth(struct tpm_chip *chip) void tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf, u32 handle, u8 *name); +void tpm_buf_append_handle(struct tpm_chip *chip, struct tpm_buf *buf, + u32 handle, u8 *name); void tpm_buf_append_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf, u8 attributes, u8 *passphrase, int passphraselen); +void tpm_buf_append_auth(struct tpm_chip *chip, struct tpm_buf *buf, + u8 attributes, u8 *passphrase, int passphraselen); static inline void tpm_buf_append_hmac_session_opt(struct tpm_chip *chip, struct tpm_buf *buf, u8 attributes, -- 2.47.0
