detect/firewall: support alert in default app policy

Support `alert` as a secondary action in app-layer firewall policies.

To implement this a Signature object is created per policy that uses
alert, and this is stored in a hash table. When the policy is applied
the signature is looked up and used in the PacketAlert.

Ticket: #8566.

etc/schema.json

@@ -2014,6 +2014,16 @@
                 }
             }
         },
+        "firewall": {
+            "type": "object",
+            "additionalProperties": false,
+            "properties": {
+                "hook": {
+                    "type": "string",
+                    "description": "Firewall hook for the match"
+                }
+            }
+        },
         "flow": {
             "type": "object",
             "additionalProperties": false,

rules/README.md

@@ -10,6 +10,7 @@ signature IDs.
 | Component         | Start   | End     |
 | ----------------- | ------- | ------- |
 | Decoder           | 2200000 | 2200999 |
+| Firewall          | 2201000 | 2201999 |
 | Stream            | 2210000 | 2210999 |
 | Generic App-Layer | 2260000 | 2260999 |
 

src/detect-engine-analyzer.c

@@ -2103,25 +2103,6 @@ void EngineAnalysisRules(const DetectEngineCtx *de_ctx,
 
 #include "app-layer-parser.h"
 
-static const char *ActionScopeToString(enum ActionScope s)
-{
-    switch (s) {
-        case ACTION_SCOPE_PACKET:
-            return "packet";
-        case ACTION_SCOPE_FLOW:
-            return "flow";
-            break;
-        case ACTION_SCOPE_HOOK:
-            return "hook";
-        case ACTION_SCOPE_TX:
-            return "tx";
-        case ACTION_SCOPE_AUTO:
-            return "auto";
-    }
-    DEBUG_VALIDATE_BUG_ON(1);
-    return "unknown";
-}
-
 static void AddPolicy(const DetectEngineCtx *de_ctx, RuleAnalyzer *ctx, const AppProto a,
         const uint8_t state, const uint8_t direction)
 {

src/detect-engine.c

@@ -2801,6 +2801,9 @@ void DetectEngineCtxFree(DetectEngineCtx *de_ctx)
     if (de_ctx->non_pf_engine_names) {
         HashTableFree(de_ctx->non_pf_engine_names);
     }
+    if (de_ctx->fw_policies) {
+        HashTableFree(de_ctx->fw_policies->policy_signatures);
+    }
     SCFree(de_ctx->fw_policies);
     SCFree(de_ctx);
     //DetectAddressGroupPrintMemory();

src/detect-parse.c

@@ -3748,6 +3748,122 @@ void DetectSetupParseRegexes(const char *parse_str, DetectParseRegex *detect_par
     }
 }
 
+static uint32_t PolicySignatureHashFunc(HashTable *ht, void *data, uint16_t datalen)
+{
+    const Signature *s = data;
+    const int dir = 1 + (s->flags & SIG_FLAG_TOSERVER) != 0; // 2 for ts, 1 for tc
+    uint32_t hash = s->alproto * s->app_progress_hook * dir;
+    hash = hash % ht->array_size;
+    return hash;
+}
+
+static char PolicySignatureCompareFunc(
+        void *data1, uint16_t datalen1, void *data2, uint16_t datalen2)
+{
+    const Signature *s1 = data1;
+    const Signature *s2 = data2;
+
+    if (s1 == NULL || s2 == NULL)
+        return 0;
+
+    return s1->flags == s2->flags && s1->alproto == s2->alproto &&
+           s1->app_progress_hook == s2->app_progress_hook;
+}
+
+static void PolicySignatureHashFree(void *data)
+{
+    Signature *s = data;
+    SCFree(s->msg);
+    SCFree(s);
+}
+
+const char *ActionScopeToString(enum ActionScope s)
+{
+    switch (s) {
+        case ACTION_SCOPE_PACKET:
+            return "packet";
+        case ACTION_SCOPE_FLOW:
+            return "flow";
+        case ACTION_SCOPE_HOOK:
+            return "hook";
+        case ACTION_SCOPE_TX:
+            return "tx";
+        case ACTION_SCOPE_AUTO:
+            return "auto";
+    }
+    DEBUG_VALIDATE_BUG_ON(1);
+    return "unknown";
+}
+
+void DetectFirewallPolicyToString(const struct DetectFirewallPolicy *p, char *out, size_t out_size)
+{
+    const char *as = ActionScopeToString(p->action_scope);
+    DEBUG_VALIDATE_BUG_ON(as == NULL);
+    if (as == NULL)
+        return;
+    if (p->action & ACTION_REJECT_ANY) {
+        if (p->action & ACTION_REJECT_DST) {
+            snprintf(out, out_size, "rejectdst:%s", as);
+        } else if (p->action & ACTION_REJECT_BOTH) {
+            snprintf(out, out_size, "rejectboth:%s", as);
+        } else {
+            snprintf(out, out_size, "rejectsrc:%s", as);
+        }
+    } else if (p->action & ACTION_DROP) {
+        snprintf(out, out_size, "drop:%s", as);
+    } else if (p->action & ACTION_ACCEPT) {
+        snprintf(out, out_size, "accept:%s", as);
+    } else {
+        DEBUG_VALIDATE_BUG_ON(1);
+    }
+    if (p->action & ACTION_PASS) {
+        if (p->action_scope == ACTION_SCOPE_FLOW) {
+            strlcat(out, ",pass:flow", out_size);
+        } else {
+            DEBUG_VALIDATE_BUG_ON(1);
+        }
+    }
+    if (p->action & ACTION_ALERT) {
+        strlcat(out, ",alert", out_size);
+    }
+}
+
+static int AddAppPolicySignature(HashTable *ht, const int direction, const AppProto alproto,
+        const char *app_name, const uint8_t hook, const char *hookname,
+        struct DetectFirewallPolicy *pol)
+{
+    Signature *s = SCCalloc(1, sizeof(*s)); // SigAlloc does way more than we need
+    if (s == NULL)
+        return -1;
+    char msg[256];
+    snprintf(msg, sizeof(msg), "SURICATA FW default app policy");
+    s->msg = SCStrdup(msg);
+    if (s->msg == NULL) {
+        SCFree(s);
+        return -1;
+    }
+    s->app_progress_hook = hook;
+    s->action = pol->action;
+    s->action_scope = pol->action_scope;
+    s->alproto = alproto;
+    s->flags = (direction == STREAM_TOSERVER) ? SIG_FLAG_TOSERVER : SIG_FLAG_TOCLIENT;
+    s->flags |= SIG_FLAG_FIREWALL;
+    s->type = SIG_TYPE_APP_TX;
+    s->detect_table = DETECT_TABLE_APP_FILTER;
+    s->id = 2201001;
+    s->rev = 1;
+    s->gid = 1;
+    s->prio = 3;
+
+    if (HashTableAdd(ht, s, 0) != 0) {
+        SCFree(s->msg);
+        SCFree(s);
+        return -1;
+    }
+    SCLogDebug("added to hash");
+    return 0;
+}
+
 static int DoParsePolicy(const char *policy_name, struct DetectFirewallPolicy *pol)
 {
     SCConfNode *policy_actions = SCConfGetNode(policy_name);
@@ -3773,7 +3889,7 @@ static int DoParsePolicy(const char *policy_name, struct DetectFirewallPolicy *p
 
 static int DoParseAppPolicy(const char *prefix, const AppProto app_proto, const char *hookname,
         const uint8_t state, const uint8_t complete_state, const int direction,
-        struct DetectFirewallAppPolicy *app_fw_policies)
+        struct DetectFirewallPolicies *fw_policies, struct DetectFirewallAppPolicy *app_fw_policies)
 {
     char policy_name[256];
     const char *in_name = hookname;
@@ -3807,10 +3923,12 @@ static int DoParseAppPolicy(const char *prefix, const AppProto app_proto, const
         FatalError("internal error: failed to assemble firewall policy config string");
     }
 
+    struct DetectFirewallPolicy *pol;
     if (direction == STREAM_TOSERVER)
-        r = DoParsePolicy(policy_name, &app_fw_policies[app_proto].ts[state]);
+        pol = &app_fw_policies[app_proto].ts[state];
     else
-        r = DoParsePolicy(policy_name, &app_fw_policies[app_proto].tc[state]);
+        pol = &app_fw_policies[app_proto].tc[state];
+    r = DoParsePolicy(policy_name, pol);
     if (r == 0 && in_name != NULL) {
         if (state == 0) {
             if (direction == STREAM_TOSERVER)
@@ -3830,10 +3948,14 @@ static int DoParseAppPolicy(const char *prefix, const AppProto app_proto, const
             FatalError("internal error: failed to assemble firewall policy config string");
         }
 
-        if (direction == STREAM_TOSERVER)
-            return DoParsePolicy(policy_name, &app_fw_policies[app_proto].ts[state]);
-        else
-            return DoParsePolicy(policy_name, &app_fw_policies[app_proto].tc[state]);
+        r = DoParsePolicy(policy_name, pol);
+    }
+
+    /* for policies with an alert action, create a policy sig */
+    if (r == 1 && pol->action & ACTION_ALERT) {
+        SCLogDebug("adding policy signature");
+        return AddAppPolicySignature(fw_policies->policy_signatures, direction, app_proto, app_name,
+                state, hookname, pol);
     }
     return r;
 }
@@ -3848,6 +3970,10 @@ int DetectFirewallInitDefaultPolicies(DetectEngineCtx *de_ctx)
     struct DetectFirewallAppPolicy *app_fw_policies = fw_policies->app;
     if (app_fw_policies == NULL)
         goto error;
+    fw_policies->policy_signatures = HashTableInit(
+            512, PolicySignatureHashFunc, PolicySignatureCompareFunc, PolicySignatureHashFree);
+    if (fw_policies->policy_signatures == NULL)
+        goto error;
 
     fw_policies->pkt[DETECT_FIREWALL_POLICY_PACKET_FILTER].action = ACTION_DROP;
     fw_policies->pkt[DETECT_FIREWALL_POLICY_PACKET_FILTER].action_scope = ACTION_SCOPE_PACKET;
@@ -3924,7 +4050,7 @@ int DetectFirewallLoadDefaultPolicies(DetectEngineCtx *de_ctx)
             const char *name =
                     AppLayerParserGetStateNameById(IPPROTO_TCP, a, state, STREAM_TOSERVER);
             if (DoParseAppPolicy(prefix, a, name, state, complete_state_ts, STREAM_TOSERVER,
-                        app_fw_policies) < 0)
+                        fw_policies, app_fw_policies) < 0)
                 return -1;
         }
 
@@ -3934,7 +4060,7 @@ int DetectFirewallLoadDefaultPolicies(DetectEngineCtx *de_ctx)
             const char *name =
                     AppLayerParserGetStateNameById(IPPROTO_TCP, a, state, STREAM_TOCLIENT);
             if (DoParseAppPolicy(prefix, a, name, state, complete_state_tc, STREAM_TOCLIENT,
-                        app_fw_policies) < 0)
+                        fw_policies, app_fw_policies) < 0)
                 return -1;
         }
     }
@@ -3942,6 +4068,22 @@ int DetectFirewallLoadDefaultPolicies(DetectEngineCtx *de_ctx)
     return 0;
 }
 
+Signature *DetectFirewallGetPolicySignature(struct DetectFirewallPolicies *fw_policies,
+        const AppProto alproto, const int direction, const uint8_t hook)
+{
+    if (fw_policies != NULL && fw_policies->policy_signatures != NULL) {
+        Signature lookup;
+        lookup.alproto = alproto;
+        lookup.flags = SIG_FLAG_FIREWALL |
+                       (direction == STREAM_TOSERVER ? SIG_FLAG_TOSERVER : SIG_FLAG_TOCLIENT);
+        lookup.app_progress_hook = hook;
+
+        Signature *s = HashTableLookup(fw_policies->policy_signatures, &lookup, 0);
+        return s;
+    }
+    return NULL;
+}
+
 /*
  * TESTS
  */

src/detect-parse.h

@@ -24,6 +24,7 @@
 #ifndef SURICATA_DETECT_PARSE_H
 #define SURICATA_DETECT_PARSE_H
 
+#include "action-globals.h"
 #include "app-layer-protos.h"
 #include "detect-engine-register.h"
 // types from detect.h with only forward declarations for bindgen
@@ -32,6 +33,7 @@ typedef struct Signature_ Signature;
 typedef struct SigMatchCtx_ SigMatchCtx;
 typedef struct SigMatch_ SigMatch;
 typedef struct SigMatchData_ SigMatchData;
+struct DetectFirewallPolicies;
 
 /** Flags to indicate if the Signature parsing must be done
 *   switching the source and dest (for ip addresses and ports)
@@ -114,7 +116,13 @@ int SC_Pcre2SubstringGet(pcre2_match_data *match_data, uint32_t number, PCRE2_UC
 void DetectRegisterAppLayerHookLists(void);
 void DetectListSupportedProtocols(void);
 
+const char *ActionScopeToString(enum ActionScope s);
+
+struct DetectFirewallPolicy;
+void DetectFirewallPolicyToString(const struct DetectFirewallPolicy *p, char *out, size_t out_size);
 int DetectFirewallInitDefaultPolicies(DetectEngineCtx *);
 int DetectFirewallLoadDefaultPolicies(DetectEngineCtx *);
+Signature *DetectFirewallGetPolicySignature(struct DetectFirewallPolicies *fw_policies,
+        const AppProto alproto, const int direction, const uint8_t hook);
 
 #endif /* SURICATA_DETECT_PARSE_H */

src/detect.c

@@ -36,6 +36,7 @@
 #include "app-layer-frames.h"
 
 #include "detect.h"
+#include "detect-parse.h"
 #include "detect-dsize.h"
 #include "detect-engine.h"
 #include "detect-engine-build.h"
@@ -1640,6 +1641,20 @@ struct DetectFirewallAppTxState {
     bool last_fw_rule; /**< processing the last fw rule, so we need to eval all hooks after it. */
 };
 
+static inline void DetectRunAppendDefaultAppPolicyAlert(DetectEngineThreadCtx *det_ctx, Packet *p,
+        const bool apply_to_packet, const int direction, const uint64_t tx_id,
+        const AppProto alproto, const uint8_t hook)
+{
+    if (EngineModeIsFirewall()) {
+        Signature *s = DetectFirewallGetPolicySignature(
+                det_ctx->de_ctx->fw_policies, alproto, direction, hook);
+        BUG_ON(s == NULL);
+        uint8_t alert_flags = apply_to_packet ? PACKET_ALERT_FLAG_APPLY_ACTION_TO_PACKET : 0;
+        alert_flags |= PACKET_ALERT_FLAG_TX;
+        AlertQueueAppend(det_ctx, s, p, tx_id, alert_flags);
+    }
+}
+
 /** \internal
  *  \brief apply default policy
  *  \param p packet to apply policy to
@@ -1650,8 +1665,8 @@ struct DetectFirewallAppTxState {
  *        to look up configurable default policies later
  */
 static const struct DetectFirewallPolicy *DetectFirewallApplyDefaultAppPolicy(
-        const struct DetectFirewallAppPolicy *policies, Packet *p, const AppProto alproto,
-        const uint8_t direction, const uint8_t progress)
+        DetectEngineThreadCtx *det_ctx, const struct DetectFirewallAppPolicy *policies, Packet *p,
+        const AppProto alproto, const uint8_t direction, const uint8_t progress)
 {
     const struct DetectFirewallPolicy *policy;
     if (direction & STREAM_TOSERVER) {
@@ -1708,30 +1723,56 @@ static enum DetectTxFirewallFlowControl DetectFirewallApplyDefaultPolicies(
                 direction & STREAM_TOSERVER ? "toserver" : "toclient", hook);
 
         const struct DetectFirewallPolicy *policy = DetectFirewallApplyDefaultAppPolicy(
-                det_ctx->de_ctx->fw_policies->app, p, alproto, direction, hook);
-        SCLogDebug("fw: hook:%u policy:%02x", hook, policy->action);
+                det_ctx, det_ctx->de_ctx->fw_policies->app, p, alproto, direction, hook);
+        SCLogDebug("fw: hook:%u policy:%02x apply_to_packet:%s", hook, policy->action,
+                BOOL2STR(apply_to_packet));
         actions |= policy->action;
         if (policy->action & ACTION_DROP) {
             SCLogDebug("fw: action %02x", policy->action);
             return DETECT_TX_FW_FC_BREAK;
-        } else if (policy->action == ACTION_ACCEPT) {
-            SCLogDebug("fw: accept hook %u", hook);
+
+        } else if (policy->action & ACTION_ACCEPT) {
+            SCLogDebug("fw: accept hook %u action %02x", hook, policy->action);
 
             /* accepting flow, so skip rest of the fw rules */
             if (policy->action_scope == ACTION_SCOPE_FLOW) {
+                if (policy->action & ACTION_ALERT) {
+                    DetectRunAppendDefaultAppPolicyAlert(
+                            det_ctx, p, is_last, direction, tx->tx_id, alproto, hook);
+                } else {
                     DetectRunAppendDefaultAccept(det_ctx, p);
+                }
                 return DETECT_TX_FW_FC_SKIP;
+
             } else if (policy->action_scope == ACTION_SCOPE_TX) {
                 tx->tx_data_ptr->flags |= APP_LAYER_TX_ACCEPT;
                 SCLogDebug("ACTION_SCOPE_TX, setting APP_LAYER_TX_ACCEPT");
-                if (is_last) {
+                if (policy->action & ACTION_ALERT) {
+                    DetectRunAppendDefaultAppPolicyAlert(
+                            det_ctx, p, is_last, direction, tx->tx_id, alproto, hook);
+                } else if (is_last) {
                     DetectRunAppendDefaultAccept(det_ctx, p);
                     SCLogDebug("DetectRunAppendDefaultAccept for last tx");
                 }
                 return DETECT_TX_FW_FC_SKIP;
+
+            } else if (policy->action_scope == ACTION_SCOPE_HOOK) {
+                if (policy->action & ACTION_ALERT) {
+                    DetectRunAppendDefaultAppPolicyAlert(
+                            det_ctx, p, is_last, direction, tx->tx_id, alproto, hook);
+                } else if (is_last) {
+                    DetectRunAppendDefaultAccept(det_ctx, p);
+                    SCLogDebug("DetectRunAppendDefaultAccept for last tx");
+                }
+            }
+        } else {
+            if (policy->action & ACTION_ALERT) {
+                DetectRunAppendDefaultAppPolicyAlert(
+                        det_ctx, p, is_last, direction, tx->tx_id, alproto, hook);
             }
         }
     }
+
     if ((is_last && (actions & (ACTION_ACCEPT | ACTION_DROP)) == ACTION_ACCEPT)) {
         DetectRunAppendDefaultAccept(det_ctx, p);
     }
@@ -2384,9 +2425,9 @@ static void DetectRunTx(ThreadVars *tv,
                         s->app_progress_hook);
                 /* if this rule was the last for our progress state, and it didn't match,
                  * we have to invoke the default policy. We only check the current rule hook. */
-                const struct DetectFirewallPolicy *policy =
-                        DetectFirewallApplyDefaultAppPolicy(det_ctx->de_ctx->fw_policies->app, p,
-                                s->alproto, flow_flags, s->app_progress_hook);
+                const struct DetectFirewallPolicy *policy = DetectFirewallApplyDefaultAppPolicy(
+                        det_ctx, det_ctx->de_ctx->fw_policies->app, p, s->alproto, flow_flags,
+                        s->app_progress_hook);
                 SCLogDebug("fw_last_for_progress policy %02x", policy->action);
                 if (policy->action & ACTION_DROP) {
                     fw_state.fw_skip_app_filter = true;

src/detect.h

@@ -935,6 +935,9 @@ struct DetectFirewallPolicies {
     /** policy for packet_filter, pre_flow, pre_stream hooks */
     struct DetectFirewallPolicy pkt[DETECT_FIREWALL_POLICY_SIZE];
 
+    /* hash table with a Signature object per default policy that has `alert` enabled. */
+    HashTable *policy_signatures;
+
     /** app layer policies, one per alproto */
     struct DetectFirewallAppPolicy app[];
 };