diff --git a/doc/userguide/output/eve/eve-json-output.rst b/doc/userguide/output/eve/eve-json-output.rst index 269024e5eb..da80a3fd19 100644 --- a/doc/userguide/output/eve/eve-json-output.rst +++ b/doc/userguide/output/eve/eve-json-output.rst @@ -70,6 +70,21 @@ 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 7172c6b1c8..2b16dd31a3 100644 --- a/doc/userguide/upgrade.rst +++ b/doc/userguide/upgrade.rst @@ -99,6 +99,10 @@ Logging changes ~~~~~~~~~~~~~~~ - RFB security result is now consistently logged as ``security_result`` when it was sometimes logged with a dash instead of an underscore. +- 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 e27ffb559b..b335dc5c21 100644 --- a/etc/schema.json +++ b/etc/schema.json @@ -115,6 +115,10 @@ "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 f36c41a842..f7ef222336 100644 --- a/src/decode.h +++ b/src/decode.h @@ -257,6 +257,8 @@ 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 f4195739e2..f923ab81f6 100644 --- a/src/detect-engine.c +++ b/src/detect-engine.c @@ -2940,6 +2940,12 @@ static int DetectEngineCtxLoadConf(DetectEngineCtx *de_ctx) "and 255, will default to 4"); } } + 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 */ diff --git a/src/detect.c b/src/detect.c index 802cf690ce..66770500e2 100644 --- a/src/detect.c +++ b/src/detect.c @@ -813,15 +813,15 @@ 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 void *tx_ptr = AppLayerParserGetTx(pflow->proto, pflow->alproto, pflow->alstate, txid); AppLayerTxData *txd = @@ -829,6 +829,9 @@ static inline void DetectRulePacketRules( : NULL; if (txd && txd->stream_logged < de_ctx->stream_tx_log_limit) { alert_flags |= PACKET_ALERT_FLAG_TX; + if (pflow->proto != IPPROTO_UDP) { + alert_flags |= PACKET_ALERT_FLAG_TX_GUESSED; + } txd->stream_logged++; } } diff --git a/src/detect.h b/src/detect.h index e88b5540ac..c8bdafdcaa 100644 --- a/src/detect.h +++ b/src/detect.h @@ -889,6 +889,9 @@ typedef struct DetectEngineCtx_ { /* maximum number of times a tx will get logged for a stream-only rule match */ uint8_t stream_tx_log_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 48672b9851..c5c15d32b5 100644 --- a/src/output-json-alert.c +++ b/src/output-json-alert.c @@ -221,6 +221,9 @@ void AlertJsonHeader(const Packet *p, const PacketAlert *pa, JsonBuilder *js, ui 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 82a72bad0f..0a1ae54cc4 100644 --- a/suricata.yaml.in +++ b/suricata.yaml.in @@ -1702,6 +1702,11 @@ detect: inspection-recursion-limit: 3000 # maximum number of times a tx will get logged for a stream-only rule match # stream-tx-log-limit: 4 + # 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