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a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1793360839; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=lWNdsNy/vLrG1u0INeqgX/LM/u41ZytNbZBTbjO0TYQ=; b=DFcKq24ZrN3jaUlhvvmabucEh3U3xjv9WsUR6Qhw6+PBiAuhTHOZbcgy5BmnvY8aE14twg LcS3zTW5BnGSO31VaY+0025mVyA8FH4nSAIDrMKQg8d1gKE63G84SI6bmmod/4vgaiw/od aOh0cbqjtmxn7f8KENdpKYLC8oIn3j4= X-MC-Unique: CwPkq48DOQihv5so2nWOuQ-1 X-Mimecast-MFC-AGG-ID: CwPkq48DOQihv5so2nWOuQ_1793360837 To: devel@lists.libvirt.org Subject: [PATCH v2] rpc: Deny REMOTE_PROC_AUTH_SASL_STEP without REMOTE_PROC_AUTH_SASL_START Date: Fri, 30 Oct 2026 12:47:11 +0100 Message-ID: <4a5588d071f708a9ac3c870d127137d95f81f082.1793360686.git.mprivozn@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.6 on 10.30.177.95 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: wG89o45fUxpn70FoehWO3QoZcd_f-EneMC07euXBlw8_1793360837 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Message-ID-Hash: QOCHLXRHRJD6NMVQMGCXSVYGYDUK2BJ5 X-Message-ID-Hash: QOCHLXRHRJD6NMVQMGCXSVYGYDUK2BJ5 X-MailFrom: mprivozn@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; loop; banned-address; header-match-devel.lists.libvirt.org-0; emergency; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.10 Precedence: list List-Id: Development discussions about the libvirt library & tools Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: From: Michal Privoznik via Devel Reply-To: Michal Privoznik X-ZohoMail-DKIM: fail (Header signature does not verify) X-ZM-MESSAGEID: 1793360923661158500 Content-Type: text/plain; charset="utf-8"; x-default="true" From: Michal Privoznik The usual flow of SASL is REMOTE_PROC_AUTH_SASL_INIT followed by REMOTE_PROC_AUTH_SASL_START which can either complete authentication or require further steps which are then done by calling REMOTE_PROC_AUTH_SASL_STEP (multiple times even). But if a malicious client skips the SASL_START step and calls SASL_INIT followed by SASL_STEP then the 'sasl->conn' structure inside of virNetSASLSessionServerStep() is not fully allocated (most notably the list of auth mechanisms 'mech' is NULL). But then sasl_server_step() dereferences that pointer leading to a crash. Fix this by disallowing SASL_STEP until SASL_START completed successfully. Fixes: CVE-2026-119151 Resolves: https://gitlab.com/libvirt/libvirt/-/work_items/940 Signed-off-by: Michal Privoznik --- v2 of: https://lists.libvirt.org/archives/list/devel@lists.libvirt.org/thread/3R2J= C6KASBO45SAC7HYFD6QGLZWWYLWJ/ diff to v1: - Implement a state machine to allow just INIT -> START [-> STEP [-> STEP ...]] and nothing else, - Drop checks additional from remote_daemon_dispatch.c (they were only there to report a nicer error message anyways). src/remote/remote_daemon_dispatch.c | 2 +- src/rpc/virnetsaslcontext.c | 31 +++++++++++++++++++++++++++++ 2 files changed, 32 insertions(+), 1 deletion(-) diff --git a/src/remote/remote_daemon_dispatch.c b/src/remote/remote_daemon= _dispatch.c index e548438250..2f1861f5bb 100644 --- a/src/remote/remote_daemon_dispatch.c +++ b/src/remote/remote_daemon_dispatch.c @@ -4034,7 +4034,7 @@ remoteDispatchAuthSaslStep(virNetServer *server, VIR_DEBUG("Step SASL auth %d", virNetServerClientGetFD(client)); if (virNetServerClientGetAuth(client) !=3D VIR_NET_SERVER_SERVICE_AUTH= _SASL || priv->sasl =3D=3D NULL) { - VIR_ERROR(_("client tried invalid SASL start request")); + VIR_ERROR(_("client tried invalid SASL step request")); goto authfail; } =20 diff --git a/src/rpc/virnetsaslcontext.c b/src/rpc/virnetsaslcontext.c index 8692703117..325ebd915e 100644 --- a/src/rpc/virnetsaslcontext.c +++ b/src/rpc/virnetsaslcontext.c @@ -37,12 +37,20 @@ struct _virNetSASLContext { unsigned int tcpMinSSF; }; =20 +typedef enum virNetSASLSessionState virNetSASLSessionState; +enum virNetSASLSessionState { + VIR_NET_SASL_SESSION_STATE_INIT, + VIR_NET_SASL_SESSION_STATE_START, + VIR_NET_SASL_SESSION_STATE_STEP +}; + struct _virNetSASLSession { virObjectLockable parent; =20 sasl_conn_t *conn; size_t maxbufsize; sasl_callback_t *callbacks; + virNetSASLSessionState state; }; =20 =20 @@ -248,6 +256,8 @@ virNetSASLSession *virNetSASLSessionNewServer(virNetSAS= LContext *ctxt G_GNUC_UNU goto cleanup; } =20 + sasl->state =3D VIR_NET_SASL_SESSION_STATE_INIT; + return sasl; =20 cleanup: @@ -529,6 +539,13 @@ int virNetSASLSessionServerStart(virNetSASLSession *sa= sl, int ret =3D -1; =20 virObjectLock(sasl); + + if (sasl->state !=3D VIR_NET_SASL_SESSION_STATE_INIT) { + virReportError(VIR_ERR_AUTH_FAILED, "%s", + _("unexpected state of SASL session")); + goto cleanup; + } + err =3D sasl_server_start(sasl->conn, mechname, clientin, @@ -542,12 +559,15 @@ int virNetSASLSessionServerStart(virNetSASLSession *s= asl, case SASL_OK: if (virNetSASLSessionUpdateBufSize(sasl) < 0) goto cleanup; + sasl->state =3D VIR_NET_SASL_SESSION_STATE_START; ret =3D VIR_NET_SASL_COMPLETE; break; case SASL_CONTINUE: + sasl->state =3D VIR_NET_SASL_SESSION_STATE_START; ret =3D VIR_NET_SASL_CONTINUE; break; case SASL_INTERACT: + sasl->state =3D VIR_NET_SASL_SESSION_STATE_START; ret =3D VIR_NET_SASL_INTERACT; break; default: @@ -575,6 +595,14 @@ int virNetSASLSessionServerStep(virNetSASLSession *sas= l, int ret =3D -1; =20 virObjectLock(sasl); + + if (sasl->state !=3D VIR_NET_SASL_SESSION_STATE_START && + sasl->state !=3D VIR_NET_SASL_SESSION_STATE_STEP) { + virReportError(VIR_ERR_AUTH_FAILED, "%s", + _("unexpected state of SASL session")); + goto cleanup; + } + err =3D sasl_server_step(sasl->conn, clientin, inlen, @@ -587,12 +615,15 @@ int virNetSASLSessionServerStep(virNetSASLSession *sa= sl, case SASL_OK: if (virNetSASLSessionUpdateBufSize(sasl) < 0) goto cleanup; + sasl->state =3D VIR_NET_SASL_SESSION_STATE_STEP; ret =3D VIR_NET_SASL_COMPLETE; break; case SASL_CONTINUE: + sasl->state =3D VIR_NET_SASL_SESSION_STATE_STEP; ret =3D VIR_NET_SASL_CONTINUE; break; case SASL_INTERACT: + sasl->state =3D VIR_NET_SASL_SESSION_STATE_STEP; ret =3D VIR_NET_SASL_INTERACT; break; default: --=20 2.56.0