On Wed, Aug 26, 2026 at 05:07:00PM +0000, Sanket Sharma wrote: > TSS_checkhmac1() and TSS_checkhmac2() silently return success when the > response tag is TPM_TAG_RSP_COMMAND (0x00c4), bypassing HMAC > verification entirely. A forged TPM response with this unauthenticated > tag allows an attacker to skip integrity checks on TPM responses.
I don't think we need threat scenario role play here. > > Reject TPM_TAG_RSP_COMMAND with -EINVAL in both functions, requiring > all responses to carry a proper authenticated tag. > > Signed-off-by: Sanket Sharma <[email protected]> > --- > security/keys/trusted-keys/trusted_tpm1.c | 4 ---- > 1 file changed, 4 deletions(-) > > diff --git a/security/keys/trusted-keys/trusted_tpm1.c > b/security/keys/trusted-keys/trusted_tpm1.c > index d47cb7108..6dbbf4546 100644 > --- a/security/keys/trusted-keys/trusted_tpm1.c > +++ b/security/keys/trusted-keys/trusted_tpm1.c > @@ -201,8 +201,6 @@ static int TSS_checkhmac1(unsigned char *buffer, > tag = LOAD16(buffer, 0); > ordinal = command; > result = LOAD32N(buffer, TPM_RETURN_OFFSET); > - if (tag == TPM_TAG_RSP_COMMAND) > - return 0; > if (tag != TPM_TAG_RSP_AUTH1_COMMAND) > return -EINVAL; > authdata = buffer + bufsize - SHA1_DIGEST_SIZE; > @@ -269,8 +267,6 @@ static int TSS_checkhmac2(unsigned char *buffer, > ordinal = command; > result = LOAD32N(buffer, TPM_RETURN_OFFSET); > > - if (tag == TPM_TAG_RSP_COMMAND) > - return 0; > if (tag != TPM_TAG_RSP_AUTH2_COMMAND) > return -EINVAL; > authdata1 = buffer + bufsize - (SHA1_DIGEST_SIZE + 1 > -- > 2.53.0 > BR, Jarkko
