On Thu, 2024-11-07 at 02:51 +0200, Jarkko Sakkinen wrote: > On Thu Nov 7, 2024 at 2:47 AM EET, Jarkko Sakkinen wrote: > > From: Mimi Zohar <zo...@linux.ibm.com> > > > > 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.
The patch Subject line and problem description aren't quite right. In the case of TPM pcr_extend, the session isn't being encrypted, only HMAC'ed. According to James, it's the HMAC itself that is causing the performance degradation. I would remove the word "encrypted" throughout. > > > > In order to address this performance issue, introduce disable_encrypt_pcrs > > kernel command-line parameter to the TPM driver. > > > > Cc: James Bottomley <james.bottom...@hansenpartnership.com> > > Link: > > https://lore.kernel.org/linux-integrity/20241015193916.59964-1-zo...@linux.ibm.com/ > > Fixes: 6519fea6fd37 ("tpm: add hmac checks to tpm2_pcr_extend()") > > Co-developed-by: Roberto Sassu <roberto.sa...@huawei.com> > > Signed-off-by: Roberto Sassu <roberto.sa...@huawei.com> > > Signed-off-by: Mimi Zohar <zo...@linux.ibm.com> > > Co-developed-by: Jarkko Sakkinen <jar...@kernel.org> > > Signed-off-by: Jarkko Sakkinen <jar...@kernel.org> > > --- > > 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. Thanks, Jarkko. Does "parameter scope" refer to using module_param instead of __setup? > > --- > > 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. Remove the word "encrypted". > > + > > 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); The variable should probably be named something like disable_pcr_hmac_session. > > +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. Sure > > > static inline void tpm_buf_append_hmac_session_opt(struct tpm_chip *chip, > > struct tpm_buf *buf, > > u8 attributes, > > > BR, Jarkko >
