decode: limits the number of decoded layers

so as to avoid overrecursion leading to stack exhaustion

(cherry picked from commit 7500c29)

rules/decoder-events.rules

@@ -146,5 +146,7 @@ alert pkthdr any any -> any any (msg:"SURICATA DCE packet too small"; decode-eve
 # Cisco HDLC
 alert pkthdr any any -> any any (msg:"SURICATA CHDLC packet too small"; decode-event:chdlc.pkt_too_small; classtype:protocol-command-decode; sid:2200115; rev:1;)
 
-# next sid is 2200116
+alert pkthdr any any -> any any (msg:"SURICATA packet with too many layers"; decode-event:too_many_layers; classtype:protocol-command-decode; sid:2200116; rev:1;)
+
+# next sid is 2200117
 

src/decode-chdlc.c

@@ -51,6 +51,9 @@ int DecodeCHDLC(ThreadVars *tv, DecodeThreadVars *dtv, Packet *p,
     if (unlikely(len > CHDLC_HEADER_LEN + USHRT_MAX)) {
         return TM_ECODE_FAILED;
     }
+    if (!PacketIncreaseCheckLayers(p)) {
+        return TM_ECODE_FAILED;
+    }
 
     CHDLCHdr *hdr = (CHDLCHdr *)pkt;
     if (unlikely(hdr == NULL))

src/decode-erspan.c

@@ -80,6 +80,9 @@ int DecodeERSPAN(ThreadVars *tv, DecodeThreadVars *dtv, Packet *p, const uint8_t
         ENGINE_SET_EVENT(p,ERSPAN_HEADER_TOO_SMALL);
         return TM_ECODE_FAILED;
     }
+    if (!PacketIncreaseCheckLayers(p)) {
+        return TM_ECODE_FAILED;
+    }
 
     const ErspanHdr *ehdr = (const ErspanHdr *)pkt;
     uint16_t version = SCNtohs(ehdr->ver_vlan) >> 12;

src/decode-ethernet.c

@@ -48,6 +48,9 @@ int DecodeEthernet(ThreadVars *tv, DecodeThreadVars *dtv, Packet *p,
         return TM_ECODE_FAILED;
     }
 
+    if (!PacketIncreaseCheckLayers(p)) {
+        return TM_ECODE_FAILED;
+    }
     p->ethh = (EthernetHdr *)pkt;
     if (unlikely(p->ethh == NULL))
         return TM_ECODE_FAILED;

src/decode-events.c

@@ -535,6 +535,11 @@ const struct DecodeEvents_ DEvents[] = {
             CHDLC_PKT_TOO_SMALL,
     },
 
+    {
+            "decoder.too_many_layers",
+            GENERIC_TOO_MANY_LAYERS,
+    },
+
     /* STREAM EVENTS */
     {
             "stream.3whs_ack_in_wrong_dir",

src/decode-events.h

@@ -200,8 +200,11 @@ enum {
     /* Cisco HDLC events. */
     CHDLC_PKT_TOO_SMALL,
 
+    /* generic events */
+    GENERIC_TOO_MANY_LAYERS,
+
     /* END OF DECODE EVENTS ON SINGLE PACKET */
-    DECODE_EVENT_PACKET_MAX = CHDLC_PKT_TOO_SMALL,
+    DECODE_EVENT_PACKET_MAX = GENERIC_TOO_MANY_LAYERS,
 
     /* STREAM EVENTS */
     STREAM_3WHS_ACK_IN_WRONG_DIR,

src/decode-geneve.c

@@ -194,6 +194,9 @@ int DecodeGeneve(ThreadVars *tv, DecodeThreadVars *dtv, Packet *p, const uint8_t
 
     if (unlikely(len < GENEVE_MIN_HEADER_LEN))
         return TM_ECODE_FAILED;
+    if (!PacketIncreaseCheckLayers(p)) {
+        return TM_ECODE_FAILED;
+    }
 
     /* Specific Geneve header field validation */
     geneve_hdr_len = GENEVE_TOTAL_HEADER_LEN(geneve_hdr);

src/decode-gre.c

@@ -54,6 +54,9 @@ int DecodeGRE(ThreadVars *tv, DecodeThreadVars *dtv, Packet *p, const uint8_t *p
         ENGINE_SET_INVALID_EVENT(p, GRE_PKT_TOO_SMALL);
         return TM_ECODE_FAILED;
     }
+    if (!PacketIncreaseCheckLayers(p)) {
+        return TM_ECODE_FAILED;
+    }
 
     p->greh = (GREHdr *)pkt;
     if(p->greh == NULL)

src/decode-ipv4.c

@@ -521,6 +521,9 @@ int DecodeIPV4(ThreadVars *tv, DecodeThreadVars *dtv, Packet *p,
 
     SCLogDebug("pkt %p len %"PRIu16"", pkt, len);
 
+    if (!PacketIncreaseCheckLayers(p)) {
+        return TM_ECODE_FAILED;
+    }
     /* do the actual decoding */
     if (unlikely(DecodeIPV4Packet (p, pkt, len) < 0)) {
         SCLogDebug("decoding IPv4 packet failed");

src/decode-ipv6.c

@@ -581,6 +581,9 @@ int DecodeIPV6(ThreadVars *tv, DecodeThreadVars *dtv, Packet *p, const uint8_t *
 {
     StatsIncr(tv, dtv->counter_ipv6);
 
+    if (!PacketIncreaseCheckLayers(p)) {
+        return TM_ECODE_FAILED;
+    }
     /* do the actual decoding */
     int ret = DecodeIPV6Packet (tv, dtv, p, pkt, len);
     if (unlikely(ret < 0)) {

src/decode-mpls.c

@@ -53,6 +53,9 @@ int DecodeMPLS(ThreadVars *tv, DecodeThreadVars *dtv, Packet *p,
 
     StatsIncr(tv, dtv->counter_mpls);
 
+    if (!PacketIncreaseCheckLayers(p)) {
+        return TM_ECODE_FAILED;
+    }
     do {
         if (len < MPLS_HEADER_LEN) {
             ENGINE_SET_INVALID_EVENT(p, MPLS_HEADER_TOO_SMALL);

src/decode-ppp.c

@@ -49,6 +49,9 @@ int DecodePPP(ThreadVars *tv, DecodeThreadVars *dtv, Packet *p,
         ENGINE_SET_INVALID_EVENT(p, PPP_PKT_TOO_SMALL);
         return TM_ECODE_FAILED;
     }
+    if (!PacketIncreaseCheckLayers(p)) {
+        return TM_ECODE_FAILED;
+    }
 
     p->ppph = (PPPHdr *)pkt;
     if (unlikely(p->ppph == NULL))

src/decode-sll.c

@@ -45,6 +45,9 @@ int DecodeSll(ThreadVars *tv, DecodeThreadVars *dtv, Packet *p,
         ENGINE_SET_INVALID_EVENT(p, SLL_PKT_TOO_SMALL);
         return TM_ECODE_FAILED;
     }
+    if (!PacketIncreaseCheckLayers(p)) {
+        return TM_ECODE_FAILED;
+    }
 
     SllHdr *sllh = (SllHdr *)pkt;
     if (unlikely(sllh == NULL))

src/decode-template.c

@@ -62,6 +62,15 @@ int DecodeTEMPLATE(ThreadVars *tv, DecodeThreadVars *dtv, Packet *p,
         //ENGINE_SET_EVENT(p,TEMPLATE_HEADER_TOO_SMALL);
         return TM_ECODE_FAILED;
     }
+    /* Each packet keeps a count of decoded layers
+     * This function increases it and returns false
+     * if we have too many decoded layers, such as
+     * ethernet/MPLS/ethernet/MPLS... which may
+     * lead to stack overflow by a too deep recursion
+     */
+    if (!PacketIncreaseCheckLayers(p)) {
+        return TM_ECODE_FAILED;
+    }
 
     /* Now we can access the header */
     const TemplateHdr *hdr = (const TemplateHdr *)pkt;

src/decode-vlan.c

@@ -70,6 +70,9 @@ int DecodeVLAN(ThreadVars *tv, DecodeThreadVars *dtv, Packet *p,
         ENGINE_SET_INVALID_EVENT(p, VLAN_HEADER_TOO_SMALL);
         return TM_ECODE_FAILED;
     }
+    if (!PacketIncreaseCheckLayers(p)) {
+        return TM_ECODE_FAILED;
+    }
     if (p->vlan_idx >= 2) {
         ENGINE_SET_EVENT(p,VLAN_HEADER_TOO_MANY_LAYERS);
         return TM_ECODE_FAILED;

src/decode-vxlan.c

@@ -136,6 +136,9 @@ int DecodeVXLAN(ThreadVars *tv, DecodeThreadVars *dtv, Packet *p,
 
     if (len < (VXLAN_HEADER_LEN + sizeof(EthernetHdr)))
         return TM_ECODE_FAILED;
+    if (!PacketIncreaseCheckLayers(p)) {
+        return TM_ECODE_FAILED;
+    }
 
     const VXLANHeader *vxlanh = (const VXLANHeader *)pkt;
     if ((vxlanh->flags[0] & 0x08) == 0 || vxlanh->res != 0)

src/decode.c

@@ -72,9 +72,13 @@ uint32_t default_packet_size = 0;
 extern bool stats_decoder_events;
 extern const char *stats_decoder_events_prefix;
 extern bool stats_stream_events;
+uint8_t decoder_max_layers = PKT_DEFAULT_MAX_DECODED_LAYERS;
 
-int DecodeTunnel(ThreadVars *tv, DecodeThreadVars *dtv, Packet *p,
-        const uint8_t *pkt, uint32_t len, enum DecodeTunnelProto proto)
+static int DecodeTunnel(ThreadVars *, DecodeThreadVars *, Packet *, const uint8_t *, uint32_t,
+        enum DecodeTunnelProto) WARN_UNUSED;
+
+static int DecodeTunnel(ThreadVars *tv, DecodeThreadVars *dtv, Packet *p, const uint8_t *pkt,
+        uint32_t len, enum DecodeTunnelProto proto)
 {
     switch (proto) {
         case DECODE_TUNNEL_PPP:
@@ -760,6 +764,14 @@ void DecodeGlobalConfig(void)
     DecodeGeneveConfig();
     DecodeVXLANConfig();
     DecodeERSPANConfig();
+    intmax_t value = 0;
+    if (ConfGetInt("decoder.max-layers", &value) == 1) {
+        if (value < 0 || value > UINT8_MAX) {
+            SCLogWarning(SC_ERR_INVALID_VALUE, "Invalid value for decoder.max-layers");
+        } else {
+            decoder_max_layers = value;
+        }
+    }
 }
 
 /**

src/decode.h

@@ -607,6 +607,11 @@ typedef struct Packet_
      */
     struct PktPool_ *pool;
 
+    /* count decoded layers of packet : too many layers
+     * cause issues with performance and stability (stack exhaustion)
+     */
+    uint8_t nb_decoded_layers;
+
 #ifdef PROFILING
     PktProfiling *profile;
 #endif
@@ -822,6 +827,7 @@ void CaptureStatsSetup(ThreadVars *tv, CaptureStats *s);
         PACKET_RESET_CHECKSUMS((p));            \
         PACKET_PROFILING_RESET((p));            \
         p->tenant_id = 0;                       \
+        p->nb_decoded_layers = 0;                                                                  \
     } while (0)
 
 #define PACKET_RECYCLE(p) do { \
@@ -942,7 +948,6 @@ int DecodeSll(ThreadVars *, DecodeThreadVars *, Packet *, const uint8_t *, uint3
 int DecodePPP(ThreadVars *, DecodeThreadVars *, Packet *, const uint8_t *, uint32_t);
 int DecodePPPOESession(ThreadVars *, DecodeThreadVars *, Packet *, const uint8_t *, uint32_t);
 int DecodePPPOEDiscovery(ThreadVars *, DecodeThreadVars *, Packet *, const uint8_t *, uint32_t);
-int DecodeTunnel(ThreadVars *, DecodeThreadVars *, Packet *, const uint8_t *, uint32_t, enum DecodeTunnelProto) WARN_UNUSED;
 int DecodeNull(ThreadVars *, DecodeThreadVars *, Packet *, const uint8_t *, uint32_t);
 int DecodeRaw(ThreadVars *, DecodeThreadVars *, Packet *, const uint8_t *, uint32_t);
 int DecodeIPV4(ThreadVars *, DecodeThreadVars *, Packet *, const uint8_t *, uint16_t);
@@ -1149,6 +1154,19 @@ void DecodeUnregisterCounters(void);
 
 #define PKT_SET_SRC(p, src_val) ((p)->pkt_src = src_val)
 
+#define PKT_DEFAULT_MAX_DECODED_LAYERS 16
+extern uint8_t decoder_max_layers;
+
+static inline bool PacketIncreaseCheckLayers(Packet *p)
+{
+    p->nb_decoded_layers++;
+    if (p->nb_decoded_layers >= decoder_max_layers) {
+        ENGINE_SET_INVALID_EVENT(p, GENERIC_TOO_MANY_LAYERS);
+        return false;
+    }
+    return true;
+}
+
 /** \brief return true if *this* packet needs to trigger a verdict.
  *
  *  If we have the root packet, and we have none outstanding,

suricata.yaml.in

@@ -1361,6 +1361,9 @@ decoder:
     enabled: true
     ports: $GENEVE_PORTS # syntax: '[6081, 1234]' or '6081'.
 
+  # maximum number of decoder layers for a packet
+  # max-layers: 16
+
 ##
 ## Performance tuning and profiling
 ##