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Miller" Cc: Jarkko Sakkinen , keyrings@vger.kernel.org, linux-crypto@vger.kernel.org, Xiang Mei , Weiming Shi Subject: [PATCH v2] asymmetric_keys: check asymmetric_key_ids() for NULL before dereference Date: Sat, 2 May 2026 09:33:29 -0700 Message-ID: <20260502163328.696098-2-bestswngs@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: keyrings@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit asymmetric_key_ids() returns key->payload.data[asym_key_ids], which can be NULL for keys parsed by the PKCS#8 parser (pkcs8_parser.c explicitly stores NULL in prep->payload.data[asym_key_ids]). key_or_keyring_common() in restrict.c and find_asymmetric_key() in asymmetric_type.c both dereference this return value without checking for NULL. An unprivileged user can trigger a NULL pointer dereference in key_or_keyring_common() by creating a PKCS#8 key, restricting a keyring with key_or_keyring:, and adding an X.509 cert to the restricted keyring. CONFIG_PKCS8_PRIVATE_KEY_PARSER=y is required. The following bash script can reproduce the issue: #!/bin/bash modprobe pkcs8_key_parser 2>/dev/null openssl genpkey -algorithm RSA -pkeyopt rsa_keygen_bits:1024 \ -out /tmp/poc.pem 2>/dev/null openssl pkcs8 -topk8 -nocrypt -in /tmp/poc.pem \ -outform DER -out /tmp/poc.p8 openssl req -new -x509 -key /tmp/poc.pem -outform DER \ -out /tmp/poc.der -days 365 -subj "/CN=Test" \ -addext "subjectKeyIdentifier=hash" \ -addext "authorityKeyIdentifier=keyid:always" 2>/dev/null PKCS8_ID=$(keyctl padd asymmetric pkcs8key @s < /tmp/poc.p8) KR=$(keyctl newring test_kr @s) keyctl restrict_keyring $KR asymmetric "key_or_keyring:$PKCS8_ID" keyctl padd asymmetric trigger $KR < /tmp/poc.der rm -f /tmp/poc.pem /tmp/poc.p8 /tmp/poc.der Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000 KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: 0010:key_or_keyring_common (crypto/asymmetric_keys/restrict.c:205 crypto/asymmetric_keys/restrict.c:279) Call Trace: __key_create_or_update (security/keys/key.c:884) key_create_or_update (security/keys/key.c:1021) __do_sys_add_key (security/keys/keyctl.c:134) do_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) Kernel panic - not syncing: Fatal exception Add a NULL check in find_asymmetric_key(), mirroring the existing pattern in asymmetric_match_key_ids() and asymmetric_key_describe(). In key_or_keyring_common(), skip the trusted key matching when it has no key IDs and fall through to the check_dest path. Fixes: 7d30198ee24f ("keys: X.509 public key issuer lookup without AKID") Reported-by: Xiang Mei Signed-off-by: Weiming Shi --- v2: add bash reproducer to commit message (Ignat) crypto/asymmetric_keys/asymmetric_type.c | 2 ++ crypto/asymmetric_keys/restrict.c | 9 +++++++-- 2 files changed, 9 insertions(+), 2 deletions(-) diff --git a/crypto/asymmetric_keys/asymmetric_type.c b/crypto/asymmetric_keys/asymmetric_type.c index 16a7ae16593c..22f04656d529 100644 --- a/crypto/asymmetric_keys/asymmetric_type.c +++ b/crypto/asymmetric_keys/asymmetric_type.c @@ -109,6 +109,8 @@ struct key *find_asymmetric_key(struct key *keyring, if (id_0 && id_1) { const struct asymmetric_key_ids *kids = asymmetric_key_ids(key); + if (!kids) + goto reject; if (!kids->id[1]) { pr_debug("First ID matches, but second is missing\n"); goto reject; diff --git a/crypto/asymmetric_keys/restrict.c b/crypto/asymmetric_keys/restrict.c index 86292965f493..ccf1084f720e 100644 --- a/crypto/asymmetric_keys/restrict.c +++ b/crypto/asymmetric_keys/restrict.c @@ -243,10 +243,14 @@ static int key_or_keyring_common(struct key *dest_keyring, if (IS_ERR(key)) key = NULL; } else if (trusted->type == &key_type_asymmetric) { + const struct asymmetric_key_ids *kids; const struct asymmetric_key_id **signer_ids; - signer_ids = (const struct asymmetric_key_id **) - asymmetric_key_ids(trusted)->id; + kids = asymmetric_key_ids(trusted); + if (!kids) + goto skip_trusted; + + signer_ids = (const struct asymmetric_key_id **)kids->id; /* * The auth_ids come from the candidate key (the @@ -290,6 +294,7 @@ static int key_or_keyring_common(struct key *dest_keyring, } } +skip_trusted: if (check_dest && !key) { /* See if the destination has a key that signed this one. */ key = find_asymmetric_key(dest_keyring, sig->auth_ids[0], -- 2.43.0