On Thu Nov 7, 2024 at 2:47 AM EET, Jarkko Sakkinen wrote: > 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. > --- Noticed a couple of things I missed after sending this (see below). > .../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"); Should be in a single line in order to minimize the diff. > + 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); This is declared in wrong place as it has no outside callers. So I will move it to drivers/char/tpm/tpm.h instead. Please correct if I'm overlooking something. > static inline void tpm_buf_append_hmac_session_opt(struct tpm_chip *chip, > struct tpm_buf *buf, > u8 attributes, BR, Jarkko
