From: Philippe Antoine Date: Tue, 26 Nov 2024 20:44:45 +0000 (+0100) Subject: detect: log app-layer metadata in alert with single tx X-Git-Tag: suricata-7.0.8~15 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=19a638611b4fc88913fee463c1d5738ee2c42f01;p=thirdparty%2Fsuricata.git detect: log app-layer metadata in alert with single tx Ticket: 7199 Uses a config parameter detect.guess-applayer-tx to enable this behavior (off by default) This feature is requested for use cases with signatures not using app-layer keywords but still targetting application layer transactions, such as pass/drop rule combination, or lua usage. This overrides the previous behavior of checking if the signature has a content match, by checking if there is only one live transaction, in addition to the config parameter being set. (cherry picked from commit f2c37763149f16da17326cb313750052e5a2117d) --- diff --git a/doc/userguide/output/eve/eve-json-output.rst b/doc/userguide/output/eve/eve-json-output.rst index 364a80418d..f6ff28c8ae 100644 --- a/doc/userguide/output/eve/eve-json-output.rst +++ b/doc/userguide/output/eve/eve-json-output.rst @@ -62,6 +62,21 @@ Alerts are event records for rule matches. They can be amended with metadata, such as the application layer record (HTTP, DNS, etc) an alert was generated for, and elements of the rule. +The alert is amended with application layer metadata for signatures +using application layer keywords. It is also the case for protocols +over UDP as each single packet is expected to contain a PDU. + +For other signatures, the option ``guess-applayer-tx`` +can be used to force the detect engine to tie a transaction +to an alert. +This transaction is not guaranteed to be the relevant one, +depending on your use case and how you define relevant here. +If there are multiple live transactions, none will get +picked up. +The alert event will have ``"tx_guessed": true`` to recognize +these alerts. + + Metadata:: - alert: diff --git a/doc/userguide/upgrade.rst b/doc/userguide/upgrade.rst index 09c18d96b0..816d7e22db 100644 --- a/doc/userguide/upgrade.rst +++ b/doc/userguide/upgrade.rst @@ -59,6 +59,10 @@ Upgrading to 7.0.8 7.0 releases. It will not be provided in Suricata 8. Please fix any rules that depend on this behavior. +- Application layer metadata is logged with alerts by default **only for rules that + use application layer keywords**. For other rules, the configuration parameter + ``detect.guess-applayer-tx`` can be used to force the detect engine to find a + transaction, which is not guaranteed to be the one you expect. Upgrading 6.0 to 7.0 -------------------- diff --git a/etc/schema.json b/etc/schema.json index 8683bb4816..488cf3d511 100644 --- a/etc/schema.json +++ b/etc/schema.json @@ -112,6 +112,10 @@ "tx_id": { "type": "integer" }, + "tx_guessed": { + "description": "the signature that triggered this alert didn't tie to a transaction, so the transaction (and metadata) logged is a forced estimation and may not be the one you expect", + "type": "boolean" + }, "files": { "type": "array", "minItems": 1, diff --git a/src/decode.h b/src/decode.h index da41726e80..103e42c6fc 100644 --- a/src/decode.h +++ b/src/decode.h @@ -281,6 +281,8 @@ typedef struct PacketAlert_ { #define PACKET_ALERT_RATE_FILTER_MODIFIED 0x10 /** alert is in a frame, frame_id set */ #define PACKET_ALERT_FLAG_FRAME 0x20 +/** alert in a tx was forced */ +#define PACKET_ALERT_FLAG_TX_GUESSED 0x040 extern uint16_t packet_alert_max; #define PACKET_ALERT_MAX 15 diff --git a/src/detect-engine.c b/src/detect-engine.c index f1c47b0fa3..a7b6ee1f26 100644 --- a/src/detect-engine.c +++ b/src/detect-engine.c @@ -2922,7 +2922,14 @@ static int DetectEngineCtxLoadConf(DetectEngineCtx *de_ctx) SCLogDebug("de_ctx->inspection_recursion_limit: %d", de_ctx->inspection_recursion_limit); - /* parse port grouping whitelisting settings */ + int guess_applayer = 0; + if ((ConfGetBool("detect.guess-applayer-tx", &guess_applayer)) == 1) { + if (guess_applayer == 1) { + de_ctx->guess_applayer = true; + } + } + + /* parse port grouping priority settings */ const char *ports = NULL; (void)ConfGet("detect.grouping.tcp-whitelist", &ports); diff --git a/src/detect.c b/src/detect.c index e02977bd01..f3cf0e0ba3 100644 --- a/src/detect.c +++ b/src/detect.c @@ -818,16 +818,19 @@ static inline void DetectRulePacketRules( DetectRunPostMatch(tv, det_ctx, p, s); uint64_t txid = PACKET_ALERT_NOTX; - if ((alert_flags & PACKET_ALERT_FLAG_STREAM_MATCH) || - (s->alproto != ALPROTO_UNKNOWN && pflow->proto == IPPROTO_UDP)) { - // if there is a stream match (TCP), or - // a UDP specific app-layer signature, - // try to use the good tx for the packet direction - if (pflow->alstate) { - uint8_t dir = - (p->flowflags & FLOW_PKT_TOCLIENT) ? STREAM_TOCLIENT : STREAM_TOSERVER; - txid = AppLayerParserGetTransactionInspectId(pflow->alparser, dir); + if (pflow && pflow->alstate) { + uint8_t dir = (p->flowflags & FLOW_PKT_TOCLIENT) ? STREAM_TOCLIENT : STREAM_TOSERVER; + txid = AppLayerParserGetTransactionInspectId(pflow->alparser, dir); + if ((s->alproto != ALPROTO_UNKNOWN && pflow->proto == IPPROTO_UDP) || + (de_ctx->guess_applayer && + AppLayerParserGetTxCnt(pflow, pflow->alstate) == txid + 1)) { + // if there is a UDP specific app-layer signature, + // or only one live transaction + // try to use the good tx for the packet direction alert_flags |= PACKET_ALERT_FLAG_TX; + if (pflow->proto != IPPROTO_UDP) { + alert_flags |= PACKET_ALERT_FLAG_TX_GUESSED; + } } } AlertQueueAppend(det_ctx, s, p, txid, alert_flags); diff --git a/src/detect.h b/src/detect.h index f147d0fda8..2379d32538 100644 --- a/src/detect.h +++ b/src/detect.h @@ -885,6 +885,9 @@ typedef struct DetectEngineCtx_ { /* maximum recursion depth for content inspection */ int inspection_recursion_limit; + /* force app-layer tx finding for alerts with signatures not having app-layer keywords */ + bool guess_applayer; + /* registration id for per thread ctx for the filemagic/file.magic keywords */ int filemagic_thread_ctx_id; diff --git a/src/output-json-alert.c b/src/output-json-alert.c index 4005c48800..72127e5d0f 100644 --- a/src/output-json-alert.c +++ b/src/output-json-alert.c @@ -378,6 +378,9 @@ void AlertJsonHeader(void *ctx, const Packet *p, const PacketAlert *pa, JsonBuil if (pa->flags & PACKET_ALERT_FLAG_TX) { jb_set_uint(js, "tx_id", pa->tx_id); } + if (pa->flags & PACKET_ALERT_FLAG_TX_GUESSED) { + jb_set_bool(js, "tx_guessed", true); + } jb_open_object(js, "alert"); diff --git a/suricata.yaml.in b/suricata.yaml.in index ba9005dc3e..504bfd0b66 100644 --- a/suricata.yaml.in +++ b/suricata.yaml.in @@ -1677,6 +1677,11 @@ detect: toserver-groups: 25 sgh-mpm-context: auto inspection-recursion-limit: 3000 + # try to tie an app-layer transaction for rules without app-layer keywords + # if there is only one live transaction for the flow + # allows to log app-layer metadata in alert + # but the transaction may not be the relevant one. + # guess-applayer-tx: no # If set to yes, the loading of signatures will be made after the capture # is started. This will limit the downtime in IPS mode. #delayed-detect: yes