The initial HMAC session feature added TPM bus encryption and/or integrity protection to various in-kernel TPM operations. This can cause performance bottlenecks with IMA, as it heavily utilizes PCR extend operations.
In order to mitigate this performance issue, introduce a kernel command-line parameter to the TPM driver for disabling the integrity protection for PCR extension. 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> Co-developed-by: Mimi Zohar <zo...@linux.ibm.com> Signed-off-by: Mimi Zohar <zo...@linux.ibm.com> Signed-off-by: Jarkko Sakkinen <jar...@kernel.org> --- v2: - Move tpm_buf_append_handle() to the correct file, remove spurious parameter (name), include error on TPM2B and add documentation. Keep the declaration in linux/tpm.h despite not exported as it is easiest to maintain tpm_buf_* in a single header. - Rename kernel command-line option as "disable_pcr_integrity_protection", as Mimi pointed out it does not carry SA_ENCRYPT flag. 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/tpm-buf.c | 20 ++++++++ drivers/char/tpm/tpm2-cmd.c | 30 ++++++++--- drivers/char/tpm/tpm2-sessions.c | 51 ++++++++++--------- include/linux/tpm.h | 3 ++ 5 files changed, 83 insertions(+), 31 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 1518343bbe22..9fc406b20a74 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_pcr_integrity_protection= [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/tpm-buf.c b/drivers/char/tpm/tpm-buf.c index cad0048bcc3c..e49a19fea3bd 100644 --- a/drivers/char/tpm/tpm-buf.c +++ b/drivers/char/tpm/tpm-buf.c @@ -146,6 +146,26 @@ void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value) } EXPORT_SYMBOL_GPL(tpm_buf_append_u32); +/** + * tpm_buf_append_handle() - Add a handle + * @chip: &tpm_chip instance + * @buf: &tpm_buf instance + * @handle: a TPM object handle + * + * Add a handle to the buffer, and increase the count tracking the number of + * handles in the command buffer. Works only for command buffers. + */ +void tpm_buf_append_handle(struct tpm_chip *chip, struct tpm_buf *buf, u32 handle) +{ + if (buf->flags & TPM_BUF_TPM2B) { + dev_err(&chip->dev, "Invalid buffer type (TPM2B)\n"); + return; + } + + tpm_buf_append_u32(buf, handle); + buf->handles++; +} + /** * tpm_buf_read() - Read from a TPM buffer * @buf: &tpm_buf instance diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c index 1e856259219e..cc443bcf15e8 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_pcr_integrity_protection; +module_param(disable_pcr_integrity_protection, bool, 0444); +MODULE_PARM_DESC(disable_pcr_integrity_protection, "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_pcr_integrity_protection) { + 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_pcr_integrity_protection) + 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_pcr_integrity_protection) { + tpm_buf_append_name(chip, &buf, pcr_idx); + tpm_buf_append_hmac_session(chip, &buf, 0, NULL, 0); + } else { + tpm_buf_append_handle(chip, &buf, pcr_idx); + tpm_buf_append_auth(chip, &buf, 0, NULL, 0); + } tpm_buf_append_u32(&buf, chip->nr_allocated_banks); @@ -253,9 +265,11 @@ int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, chip->allocated_banks[i].digest_size); } - tpm_buf_fill_hmac_session(chip, &buf); + if (!disable_pcr_integrity_protection) + 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_pcr_integrity_protection) + 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..a7c1b162251b 100644 --- a/drivers/char/tpm/tpm2-sessions.c +++ b/drivers/char/tpm/tpm2-sessions.c @@ -237,9 +237,7 @@ 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); return; } @@ -272,6 +270,31 @@ 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 +332,8 @@ 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..20a40ade8030 100644 --- a/include/linux/tpm.h +++ b/include/linux/tpm.h @@ -421,6 +421,7 @@ void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value); u8 tpm_buf_read_u8(struct tpm_buf *buf, off_t *offset); u16 tpm_buf_read_u16(struct tpm_buf *buf, off_t *offset); u32 tpm_buf_read_u32(struct tpm_buf *buf, off_t *offset); +void tpm_buf_append_handle(struct tpm_chip *chip, struct tpm_buf *buf, u32 handle); /* * Check if TPM device is in the firmware upgrade mode. @@ -505,6 +506,8 @@ void tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf, 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
