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Wed, 26 Aug 2026 16:48:03 +0000 (GMT) Received: from smtpclient.apple (unknown [9.124.213.3]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTPS; Wed, 26 Aug 2026 16:48:03 +0000 (GMT) Content-Type: text/plain; charset=utf-8 Precedence: bulk X-Mailing-List: keyrings@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3864.700.51.1.1\)) Subject: Re: [PATCH v2 2/2] keys: trusted: tpm1: reject unauthenticated response tag in TSS_checkhmac1/2 From: Sudhakar Kuppusamy In-Reply-To: <20260826080405.255083-2-sanketsharmacsec@gmail.com> Date: Wed, 26 Aug 2026 22:17:51 +0530 Cc: jarkko@kernel.org, gregkh@linuxfoundation.org, "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 Content-Transfer-Encoding: quoted-printable Message-Id: References: <20260825182919.15943-1-sanketsharmacsec@gmail.com> <20260826080405.255083-1-sanketsharmacsec@gmail.com> <20260826080405.255083-2-sanketsharmacsec@gmail.com> To: Sanket Sharma X-Mailer: Apple Mail (2.3864.700.51.1.1) X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-ORIG-GUID: wmWzGIHluAZXJb3idDoRZO9sixnTeQx5 X-Proofpoint-Spam-Info: AW1haW4tMjYwODI2MDEzOCBTYWx0ZWRfX6fEsw9DyckDf xpPPMmxcUtHOYjwKDPhQiXUqRCvvoo3eEtZlpOyrtOJr3XKX2CeIyMhJdMedc+5Xpn3blQTmXCH 6pdt2TYrLPfkdcRikuLWt1OyWP9eoVQ= X-Proofpoint-GUID: BM2COZajFAbUGG38GdJR3Uzj-vDUP2oN X-Authority-Analysis: v=2.4 cv=JZyMa0KV c=1 sm=1 tr=0 ts=6a8f18ca cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=pGLkceISAAAA:8 a=NrVHMxhdPDTnOdUCm4oA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODI2MDEzOCBTYWx0ZWRfXwZDTbjQ3YzDu 4UPOlWuO1Zj4KJsUkXGpE0tFDfhqEK0YYsYzGjRRpBx4xImi0RQx2hT/FSBPxe1/7vSbmFAjfBd rZFRtutCsiT4m5ArKaTYYXLYDoQq9oEzfxTjqSuSj17uPMVkYFRXD3a64pJIQpYcLACvSSFgKsR MomantNl3tB8SOZkgboj9FQ6caQ9fK7uAieokvGJfveGB1Z53drPMJwxbT0VE6KjPhr17I7XlMa +HZaf5X3lO8b6Xkc9cBRrWmtETD/FCxy0hF9RLQ3UL7MHyE0uFHFJksF0Y4+UlY6xwNbMuhJ4qf XY40mQg+rC2ickmiDl0Gh3o2/A2cTg77tALtvXkR4QmjPXUq7SvcF49/Ykx//zluV8lu8CnFQZQ z1+Sp5L2ktLjJw0O7V+Eec0fsmRL34QaCT9BUHCNbhu4n7McPTUXycfQq8Rx5zyNu+2QDhNd/r/ U27zhU5Z1Xc/zhL8z1A== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-26_04,2026-08-26_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 clxscore=1015 adultscore=0 priorityscore=1501 impostorscore=0 malwarescore=0 bulkscore=0 lowpriorityscore=0 suspectscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608260138 > On 26 Aug 2026, at 1:34=E2=80=AFPM, Sanket Sharma = wrote: >=20 > 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. >=20 > Reject TPM_TAG_RSP_COMMAND with -EINVAL in both functions, requiring > all responses to carry a proper authenticated tag. >=20 > Signed-off-by: Sanket Sharma > --- > security/keys/trusted-keys/trusted_tpm1.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) >=20 > 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 =3D command; > result =3D LOAD32N(buffer, TPM_RETURN_OFFSET); > if (tag =3D=3D TPM_TAG_RSP_COMMAND) > - return 0; > + return -EINVAL; Hi Sanket Sharma, Instead of changing the return value to -EINVAL inside the = TPM_TAG_RSP_COMMAND check, we can simplify the control flow by removing that block entirely.Since = TPM_TAG_RSP_COMMAND is inherently not equal to TPM_TAG_RSP_AUTH1_COMMAND, the subsequent = mismatch check will naturally catch it and return -EINVAL.=20 Thanks, Sudhakar > if (tag !=3D TPM_TAG_RSP_AUTH1_COMMAND) > return -EINVAL; > authdata =3D buffer + bufsize - SHA1_DIGEST_SIZE; > @@ -270,7 +270,7 @@ static int TSS_checkhmac2(unsigned char *buffer, > result =3D LOAD32N(buffer, TPM_RETURN_OFFSET); >=20 > if (tag =3D=3D TPM_TAG_RSP_COMMAND) > - return 0; > + return -EINVAL; > if (tag !=3D TPM_TAG_RSP_AUTH2_COMMAND) > return -EINVAL; > authdata1 =3D buffer + bufsize - (SHA1_DIGEST_SIZE + 1 > --=20 > 2.53.0 >=20 >=20