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tpm: Address !chip->auth in tpm_buf_append_hmac_session*()

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Unless tpm_chip_bootstrap() was called by the driver, !chip->auth can
cause a null derefence in tpm_buf_hmac_session*().  Thus, address
!chip->auth in tpm_buf_hmac_session*() and remove the fallback
implementation for !TCG_TPM2_HMAC.

Cc: stable@vger.kernel.org # v6.9+
Reported-by: Stefan Berger <stefanb@linux.ibm.com>
Closes: https://lore.kernel.org/linux-integrity/20240617193408.1234365-1-stefanb@linux.ibm.com/
Fixes: 1085b8276b ("tpm: Add the rest of the session HMAC API")
Tested-by: Michael Ellerman <mpe@ellerman.id.au> # ppc
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
This commit is contained in:
Jarkko Sakkinen 2024-07-03 18:47:46 +03:00 committed by Jarkko Sakkinen
parent a61809a332
commit 7ca110f267
2 changed files with 130 additions and 124 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

186
drivers/char/tpm/tpm2-sessions.c
View File

@ -272,6 +272,110 @@ void tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
}
EXPORT_SYMBOL_GPL(tpm_buf_append_name);
/**
* tpm_buf_append_hmac_session() - Append a TPM session element
* @chip: the TPM chip structure
* @buf: The buffer to be appended
* @attributes: The session attributes
* @passphrase: The session authority (NULL if none)
* @passphrase_len: The length of the session authority (0 if none)
*
* This fills in a session structure in the TPM command buffer, except
* for the HMAC which cannot be computed until the command buffer is
* complete. The type of session is controlled by the @attributes,
* the main ones of which are TPM2_SA_CONTINUE_SESSION which means the
* session won't terminate after tpm_buf_check_hmac_response(),
* TPM2_SA_DECRYPT which means this buffers first parameter should be
* encrypted with a session key and TPM2_SA_ENCRYPT, which means the
* response buffer's first parameter needs to be decrypted (confusing,
* but the defines are written from the point of view of the TPM).
*
* Any session appended by this command must be finalized by calling
* tpm_buf_fill_hmac_session() otherwise the HMAC will be incorrect
* and the TPM will reject the command.
*
* As with most tpm_buf operations, success is assumed because failure
* will be caused by an incorrect programming model and indicated by a
* kernel message.
*/
void tpm_buf_append_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf,
u8 attributes, u8 *passphrase,
int passphrase_len)
{
#ifdef CONFIG_TCG_TPM2_HMAC
u8 nonce[SHA256_DIGEST_SIZE];
struct tpm2_auth *auth;
u32 len;
#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);
return;
}
#ifdef CONFIG_TCG_TPM2_HMAC
/*
* The Architecture Guide requires us to strip trailing zeros
* before computing the HMAC
*/
while (passphrase && passphrase_len > 0 && passphrase[passphrase_len - 1] == '\0')
passphrase_len--;
auth = chip->auth;
auth->attrs = attributes;
auth->passphrase_len = passphrase_len;
if (passphrase_len)
memcpy(auth->passphrase, passphrase, passphrase_len);
if (auth->session != tpm_buf_length(buf)) {
/* we're not the first session */
len = get_unaligned_be32(&buf->data[auth->session]);
if (4 + len + auth->session != tpm_buf_length(buf)) {
WARN(1, "session length mismatch, cannot append");
return;
}
/* add our new session */
len += 9 + 2 * SHA256_DIGEST_SIZE;
put_unaligned_be32(len, &buf->data[auth->session]);
} else {
tpm_buf_append_u32(buf, 9 + 2 * SHA256_DIGEST_SIZE);
}
/* random number for our nonce */
get_random_bytes(nonce, sizeof(nonce));
memcpy(auth->our_nonce, nonce, sizeof(nonce));
tpm_buf_append_u32(buf, auth->handle);
/* our new nonce */
tpm_buf_append_u16(buf, SHA256_DIGEST_SIZE);
tpm_buf_append(buf, nonce, SHA256_DIGEST_SIZE);
tpm_buf_append_u8(buf, auth->attrs);
/* and put a placeholder for the hmac */
tpm_buf_append_u16(buf, SHA256_DIGEST_SIZE);
tpm_buf_append(buf, nonce, SHA256_DIGEST_SIZE);
#endif
}
EXPORT_SYMBOL_GPL(tpm_buf_append_hmac_session);
#ifdef CONFIG_TCG_TPM2_HMAC
static int tpm2_create_primary(struct tpm_chip *chip, u32 hierarchy,
@ -457,82 +561,6 @@ static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip)
crypto_free_kpp(kpp);
}
/**
* tpm_buf_append_hmac_session() - Append a TPM session element
* @chip: the TPM chip structure
* @buf: The buffer to be appended
* @attributes: The session attributes
* @passphrase: The session authority (NULL if none)
* @passphrase_len: The length of the session authority (0 if none)
*
* This fills in a session structure in the TPM command buffer, except
* for the HMAC which cannot be computed until the command buffer is
* complete. The type of session is controlled by the @attributes,
* the main ones of which are TPM2_SA_CONTINUE_SESSION which means the
* session won't terminate after tpm_buf_check_hmac_response(),
* TPM2_SA_DECRYPT which means this buffers first parameter should be
* encrypted with a session key and TPM2_SA_ENCRYPT, which means the
* response buffer's first parameter needs to be decrypted (confusing,
* but the defines are written from the point of view of the TPM).
*
* Any session appended by this command must be finalized by calling
* tpm_buf_fill_hmac_session() otherwise the HMAC will be incorrect
* and the TPM will reject the command.
*
* As with most tpm_buf operations, success is assumed because failure
* will be caused by an incorrect programming model and indicated by a
* kernel message.
*/
void tpm_buf_append_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf,
u8 attributes, u8 *passphrase,
int passphrase_len)
{
u8 nonce[SHA256_DIGEST_SIZE];
u32 len;
struct tpm2_auth *auth = chip->auth;
/*
* The Architecture Guide requires us to strip trailing zeros
* before computing the HMAC
*/
while (passphrase && passphrase_len > 0
&& passphrase[passphrase_len - 1] == '\0')
passphrase_len--;
auth->attrs = attributes;
auth->passphrase_len = passphrase_len;
if (passphrase_len)
memcpy(auth->passphrase, passphrase, passphrase_len);
if (auth->session != tpm_buf_length(buf)) {
/* we're not the first session */
len = get_unaligned_be32(&buf->data[auth->session]);
if (4 + len + auth->session != tpm_buf_length(buf)) {
WARN(1, "session length mismatch, cannot append");
return;
}
/* add our new session */
len += 9 + 2 * SHA256_DIGEST_SIZE;
put_unaligned_be32(len, &buf->data[auth->session]);
} else {
tpm_buf_append_u32(buf, 9 + 2 * SHA256_DIGEST_SIZE);
}
/* random number for our nonce */
get_random_bytes(nonce, sizeof(nonce));
memcpy(auth->our_nonce, nonce, sizeof(nonce));
tpm_buf_append_u32(buf, auth->handle);
/* our new nonce */
tpm_buf_append_u16(buf, SHA256_DIGEST_SIZE);
tpm_buf_append(buf, nonce, SHA256_DIGEST_SIZE);
tpm_buf_append_u8(buf, auth->attrs);
/* and put a placeholder for the hmac */
tpm_buf_append_u16(buf, SHA256_DIGEST_SIZE);
tpm_buf_append(buf, nonce, SHA256_DIGEST_SIZE);
}
EXPORT_SYMBOL(tpm_buf_append_hmac_session);
/**
* tpm_buf_fill_hmac_session() - finalize the session HMAC
* @chip: the TPM chip structure
@ -563,6 +591,9 @@ void tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf)
u8 cphash[SHA256_DIGEST_SIZE];
struct sha256_state sctx;
if (!auth)
return;
/* save the command code in BE format */
auth->ordinal = head->ordinal;
@ -721,6 +752,9 @@ int tpm_buf_check_hmac_response(struct tpm_chip *chip, struct tpm_buf *buf,
u32 cc = be32_to_cpu(auth->ordinal);
int parm_len, len, i, handles;
if (!auth)
return rc;
if (auth->session >= TPM_HEADER_SIZE) {
WARN(1, "tpm session not filled correctly\n");
goto out;

68
include/linux/tpm.h
View File

@ -502,10 +502,6 @@ 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);
#ifdef CONFIG_TCG_TPM2_HMAC
int tpm2_start_auth_session(struct tpm_chip *chip);
void tpm_buf_append_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf,
u8 attributes, u8 *passphrase,
int passphraselen);
@ -515,9 +511,27 @@ static inline void tpm_buf_append_hmac_session_opt(struct tpm_chip *chip,
u8 *passphrase,
int passphraselen)
{
tpm_buf_append_hmac_session(chip, buf, attributes, passphrase,
passphraselen);
struct tpm_header *head;
int offset;
if (tpm2_chip_auth(chip)) {
tpm_buf_append_hmac_session(chip, buf, attributes, passphrase, passphraselen);
} else {
offset = buf->handles * 4 + TPM_HEADER_SIZE;
head = (struct tpm_header *)buf->data;
/*
* If the only sessions are optional, the command tag must change to
* TPM2_ST_NO_SESSIONS.
*/
if (tpm_buf_length(buf) == offset)
head->tag = cpu_to_be16(TPM2_ST_NO_SESSIONS);
}
}
#ifdef CONFIG_TCG_TPM2_HMAC
int tpm2_start_auth_session(struct tpm_chip *chip);
void tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf);
int tpm_buf_check_hmac_response(struct tpm_chip *chip, struct tpm_buf *buf,
int rc);
@ -532,48 +546,6 @@ static inline int tpm2_start_auth_session(struct tpm_chip *chip)
static inline void tpm2_end_auth_session(struct tpm_chip *chip)
{
}
static inline void tpm_buf_append_hmac_session(struct tpm_chip *chip,
struct tpm_buf *buf,
u8 attributes, u8 *passphrase,
int passphraselen)
{
/* offset tells us where the sessions area begins */
int offset = buf->handles * 4 + TPM_HEADER_SIZE;
u32 len = 9 + passphraselen;
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, passphraselen);
tpm_buf_append(buf, passphrase, passphraselen);
}
static inline void tpm_buf_append_hmac_session_opt(struct tpm_chip *chip,
struct tpm_buf *buf,
u8 attributes,
u8 *passphrase,
int passphraselen)
{
int offset = buf->handles * 4 + TPM_HEADER_SIZE;
struct tpm_header *head = (struct tpm_header *) buf->data;
/*
* if the only sessions are optional, the command tag
* must change to TPM2_ST_NO_SESSIONS
*/
if (tpm_buf_length(buf) == offset)
head->tag = cpu_to_be16(TPM2_ST_NO_SESSIONS);
}
static inline void tpm_buf_fill_hmac_session(struct tpm_chip *chip,
struct tpm_buf *buf)
{