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Tue, 25 Aug 2026 11:29:42 -0700 (PDT) From: sn0x-sharma To: jarkko@kernel.org Cc: James.Bottomley@HansenPartnership.com, zohar@linux.ibm.com, dhowells@redhat.com, linux-integrity@vger.kernel.org, keyrings@vger.kernel.org, linux-kernel@vger.kernel.org, security@kernel.org, w@1wt.eu, sn0x-sharma Subject: [PATCH 2/2] keys: trusted: tpm1: reject unauthenticated response tag in TSS_checkhmac1/2 Date: Tue, 25 Aug 2026 18:29:19 +0000 Message-ID: <20260825182919.15943-2-sanketsharmacsec@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260825182919.15943-1-sanketsharmacsec@gmail.com> References: <20260825182919.15943-1-sanketsharmacsec@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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. Reject TPM_TAG_RSP_COMMAND with -EINVAL in both functions, requiring all responses to carry a proper authenticated tag. Reported-by: sn0x-sharma Link: https://lore.kernel.org/linux-integrity/ Signed-off-by: sn0x-sharma --- security/keys/trusted-keys/trusted_tpm1.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c index d47cb7108..c89fc6cfe 100644 --- a/security/keys/trusted-keys/trusted_tpm1.c +++ b/security/keys/trusted-keys/trusted_tpm1.c @@ -202,7 +202,7 @@ static int TSS_checkhmac1(unsigned char *buffer, ordinal = command; result = LOAD32N(buffer, TPM_RETURN_OFFSET); if (tag == TPM_TAG_RSP_COMMAND) - return 0; + return -EINVAL; if (tag != TPM_TAG_RSP_AUTH1_COMMAND) return -EINVAL; authdata = buffer + bufsize - SHA1_DIGEST_SIZE; @@ -270,7 +270,7 @@ static int TSS_checkhmac2(unsigned char *buffer, result = LOAD32N(buffer, TPM_RETURN_OFFSET); if (tag == TPM_TAG_RSP_COMMAND) - return 0; + return -EINVAL; if (tag != TPM_TAG_RSP_AUTH2_COMMAND) return -EINVAL; authdata1 = buffer + bufsize - (SHA1_DIGEST_SIZE + 1 -- 2.53.0