// https://llvm.org/docs/LibFuzzer.html

#define MG_ENABLE_SOCKET 0

#define MG_ENABLE_LOG 0

#define MG_ENABLE_LINES 1

#define MG_ENABLE_TCPIP 1

#define MG_IO_SIZE (32 * 1024 * 1024)  // Big IO size for fast resizes

#include "mongoose.c"

#include "driver_mock.c"

#ifdef __cplusplus

extern "C" int LLVMFuzzerTestOneInput(const uint8_t *, size_t);

#else

int LLVMFuzzerTestOneInput(const uint8_t *, size_t);

#endif

static void fn(struct mg_connection *c, int ev, void *ev_data) {

  struct mg_http_serve_opts opts = {.root_dir = "."};

  if (ev == MG_EV_HTTP_MSG) {

    mg_http_serve_dir(c, (struct mg_http_message *) ev_data, &opts);

  }

}

// deduplicate layer-3 mocking among layer-2s

struct fuzz_l3_state {

  size_t ip_proto, udp_port;

  size_t ip6_next, icmp6_type;

};

static void fuzz_ip4(void *buf, size_t len, struct fuzz_l3_state *st) {

  if (len >= sizeof(struct ip)) {

    uint8_t ip_protos[] = {1, 6, 17}; // ICMP, TCP, UDP

    struct ip *ip4 = (struct ip *) buf;

    ip4->ver = (uint8_t) ((ip4->ver & ~0xf0) | (4 << 4));

    // send all handled IP protos, then 2 random ones

    if (st->ip_proto >= (sizeof(ip_protos) / sizeof(ip_protos[0]) + 2)) st->ip_proto = 0;

    if (st->ip_proto < (sizeof(ip_protos) / sizeof(ip_protos[0]))) ip4->proto = ip_protos[st->ip_proto++];

    if (ip4->proto == 1) { // ICMP

    } else if (ip4->proto == 6) { // TCP

    } else if (ip4->proto == 17 && len >= sizeof(struct ip) + sizeof(struct udp)) { // UDP

      uint16_t udp_ports[] = {67, 68}; // DHCP server and client

      struct udp *udp = (struct udp *) (ip4 + 1);

      // send all handled UDP ports, then 2 random ones

      if (st->udp_port >= (sizeof(udp_ports) / sizeof(udp_ports[0]) + 2)) st->udp_port = 0;

      if (st->udp_port < (sizeof(udp_ports) / sizeof(udp_ports[0]))) udp->dport = mg_htons(udp_ports[st->udp_port++]);

    }

  }

}

static void fuzz_ip6(void *buf, size_t len, struct fuzz_l3_state *st) {

  if (len >= sizeof(struct ip6)) {

    uint8_t ip6_protos[] = {6, 17, 58}; // TCP, UDP, ICMPv6

    struct ip6 *ip6 = (struct ip6 *) buf;

    ip6->ver = (uint8_t) ((ip6->ver & ~0xf0) | (6 << 4));

    // send all handled IPv6 "next headers", then 2 random ones

    if (st->ip6_next >= (sizeof(ip6_protos) / sizeof(ip6_protos[0]) + 2)) st->ip6_next = 0;

    if (st->ip6_next < (sizeof(ip6_protos) / sizeof(ip6_protos[0]))) ip6->next = ip6_protos[st->ip6_next++];

    if (ip6->next == 6) { // TCP

    } else if (ip6->next == 17) { // UDP

    } else if (ip6->next == 58 && len >= sizeof(struct ip6) + sizeof(struct icmp6)) { // ICMPv6

      uint8_t icmp6_types[] = {128, 134, 135, 136}; // Echo Request, RA, NS, NA

      struct icmp6 *icmp6 = (struct icmp6 *) (ip6 + 1);

      // send all handled ICMPv6 types, then 2 random ones

      if (st->icmp6_type >= (sizeof(icmp6_types) / sizeof(icmp6_types[0]) + 2)) st->icmp6_type = 0;

      if (st->icmp6_type < (sizeof(icmp6_types) / sizeof(icmp6_types[0]))) icmp6->type = icmp6_types[st->icmp6_type++];

    }

  }

}

int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {

  mg_log_set(MG_LL_INFO);

  struct mg_dns_message dm;

  mg_dns_parse(data, size, &dm);

  mg_dns_parse(NULL, 0, &dm);

  struct mg_http_message hm;

  if (mg_http_parse((const char *) data, size, &hm) > 0) {

    mg_crc32(0, hm.method.buf, hm.method.len);

    mg_crc32(0, hm.uri.buf, hm.uri.len);

    mg_crc32(0, hm.uri.buf, hm.uri.len);

    for (size_t i = 0; i < sizeof(hm.headers) / sizeof(hm.headers[0]); i++) {

      struct mg_str *k = &hm.headers[i].name, *v = &hm.headers[i].value;

      mg_crc32(0, k->buf, k->len);

      mg_crc32(0, v->buf, v->len);

    }

  }

  mg_http_parse(NULL, 0, &hm);

  struct mg_str body = mg_str_n((const char *) data, size);

  char tmp[256];

  mg_http_get_var(&body, "key", tmp, sizeof(tmp));

  mg_http_get_var(&body, "key", NULL, 0);

  mg_url_decode((char *) data, size, tmp, sizeof(tmp), 1);

  mg_url_decode((char *) data, size, tmp, 1, 1);

  mg_url_decode(NULL, 0, tmp, 1, 1);

  struct mg_mqtt_message mm;

  if (mg_mqtt_parse(data, size, 0, &mm) == MQTT_OK) {

    mg_crc32(0, mm.topic.buf, mm.topic.len);

    mg_crc32(0, mm.data.buf, mm.data.len);

    mg_crc32(0, mm.dgram.buf, mm.dgram.len);

  }

  mg_mqtt_parse(NULL, 0, 0, &mm);

  if (mg_mqtt_parse(data, size, 5, &mm) == MQTT_OK) {

    mg_crc32(0, mm.topic.buf, mm.topic.len);

    mg_crc32(0, mm.data.buf, mm.data.len);

    mg_crc32(0, mm.dgram.buf, mm.dgram.len);

    {

      struct mg_mqtt_prop prop;

      size_t ofs = 0;

      while ((ofs = mg_mqtt_next_prop(&mm, &prop, ofs)) > 0) {

          mg_crc32(0, prop.key.buf, prop.key.len);

          mg_crc32(0, prop.val.buf, prop.val.len);

      }

    }

  }

  mg_mqtt_parse(NULL, 0, 5, &mm);

  mg_sntp_parse(data, size);

  mg_sntp_parse(NULL, 0);

  char buf[size * 4 / 3 + 5];  // At least 4 chars and nul termination

  mg_base64_decode((char *) data, size, buf, sizeof(buf));

  mg_base64_decode(NULL, 0, buf, sizeof(buf));

  mg_base64_encode(data, size, buf, sizeof(buf));

  mg_base64_encode(NULL, 0, buf, sizeof(buf));

  mg_match(mg_str_n((char *) data, size), mg_str_n((char *) data, size), NULL);

  struct mg_str entry, s = mg_str_n((char *) data, size);

  while (mg_span(s, &entry, &s, ',')) entry.len = 0;

  int n;

  mg_json_get(mg_str_n((char *) data, size), "$", &n);

  mg_json_get(mg_str_n((char *) data, size), "$.a.b", &n);

  mg_json_get(mg_str_n((char *) data, size), "$[0]", &n);

  // Test built-in TCP/IP stack

  if (size > 0) {

    static size_t t;

    struct mg_tcpip_if mif = {.ip = 1,

                              .mask = 255,

                              .gw = 1,

                              .gw_ready = true,

                              .state = MG_TCPIP_STATE_READY,

#if MG_ENABLE_IPV6

                              .ip6[0] = 1,

                              .prefix[0] = 1,

                              .prefix_len = 64,

                              .gw6[0] = 1,

                              .gw6_ready = true,

                              .state6 = MG_TCPIP_STATE_READY,  // so mg_send() works and RS stops

#endif

                              .driver = &mg_tcpip_driver_mock};

    struct mg_mgr mgr;

    if (t >= MG_TCPIP_L2_USER) t = 0; // defined in l2.h

    mif.l2type = (enum mg_l2type) t++; // configure to a L2 type

    mg_mgr_init(&mgr);

    mg_tcpip_init(&mgr, &mif);

    // Make a copy of the random data, in order to modify it

    void *pkt = malloc(size);

    struct eth *eth = (struct eth *) pkt;

    memcpy(pkt, data, size);

    if ((mif.l2type == MG_TCPIP_L2_ETH || mif.l2type == MG_TCPIP_L2_PPPoE) && size > sizeof(*eth)) {

      static size_t i, v;

      static struct fuzz_l3_state l3;

      uint8_t *ethpay = (uint8_t *) (eth + 1);

      size_t ethhdrsz = sizeof(*eth);

      uint16_t etype;

      // eth_types[] exists in l2_eth.c

      memcpy(eth->dst, mif.mac, 6);  // Set valid destination MAC

      // send all handled eth types, then 2 random ones

      if (i >= (sizeof(eth_types) / sizeof(eth_types[0]) + 2)) i = 0;

      if (i < (sizeof(eth_types) / sizeof(eth_types[0]))) eth->type = mg_htons(eth_types[i++]);

      etype = mg_ntohs(eth->type);

      if (v >= 10) v = 0; // 802.1Q tag 3 out of 10 frames

      if (v < 3) mif.l2data.eth.vlan_id = 123;

      if (size > sizeof(*eth) + sizeof(struct qtag)) {

        struct qtag *qtag = (struct qtag *) &eth->type;

        if (v == 0) {

          // v=0: configured for VLAN 123, untagged frame, discard path

        } else if (v == 1) {

          // v=1: configured for VLAN 123, tagged VLAN 123, accept path

          qtag->tpid = mg_htons(0x8100);

          qtag->tci = mg_htons(123);

          MG_STORE_BE16(qtag + 1, etype);

          ethhdrsz += sizeof(*qtag);

          ethpay += sizeof(*qtag);

        } else if (v == 2) {

          // v=2: configured for VLAN 123, tagged random VLAN, mismatch path

          qtag->tpid = mg_htons(0x8100);

          MG_STORE_BE16(qtag + 1, etype);

          ethhdrsz += sizeof(*qtag);

          ethpay += sizeof(*qtag);

        } else if (v == 3) {

          // v=3: unconfigured VLAN, tagged frame, discard path

          qtag->tpid = mg_htons(0x8100);

          MG_STORE_BE16(qtag + 1, etype);

          ethhdrsz += sizeof(*qtag);

          ethpay += sizeof(*qtag);

        } // else unconfigured VLAN, untagged frame, normal path

      }

      ++v;

      if (etype == 0x8863 && size > (ethhdrsz + sizeof(struct pppoe))) { // PPPoE disc

        static size_t j;

        uint8_t pppoe_codes[] = {MG_PPPoE_PADO, MG_PPPoE_PADS, MG_PPPoE_PADT}; // defined in l2_ppp.c

        struct pppoe *pppoe = (struct pppoe *) ethpay;

        pppoe->vertype = 0x11;

        // send all handled PPPoE codes, then 2 random ones

        if (j >= (sizeof(pppoe_codes) / sizeof(pppoe_codes[0]) + 2)) j = 0;

        if (j < (sizeof(pppoe_codes) / sizeof(pppoe_codes[0]))) pppoe->code = (pppoe_codes[j++]);

        if (pppoe->code == MG_PPPoE_PADO) {

          static size_t k;

          // send id=0, then 2 random ids

          if (k >= 3) k = 0;

          if (k == 0) pppoe->id = 0;

          ++k;

        } else if (pppoe->code == MG_PPPoE_PADS) {

          static size_t k;

          // send id=x, then 2 random ids

          if (k >= 3) k = 0;

          if (k == 0) pppoe->id = 0x1234;

          ++k;

        } else if (pppoe->code == MG_PPPoE_PADT) { // keep separate so they do not correlate too much

          static size_t k;

          // send id=x, then 2 random ids

          if (k >= 3) k = 0;

          if (k == 0) pppoe->id = 0x1234;

          ++k;

        }

      } else if (etype == 0x8864 && size > (ethhdrsz + sizeof(struct pppoe))) { // PPPoE sess

        // PPP rx is covered via HDLC too; PPPoE tx wrapping may remain unexercised.

        struct pppoe *pppoe = (struct pppoe *) ethpay;

        static size_t k, l;

        // send code=0, then 2 random codes

        if (k >= 3) k = 0;

        if (k == 0)  {

          static size_t m;

          pppoe->code = 0;

          // send id=x, then 2 random ids

          if (m >= 3) m = 0;

          if (m == 0) pppoe->id = 0x1234;

          ++m;

        }

        ++k;

        // set s_state to valid and invalid

        if (l >= 2) l = 0;

        if (l == 0) s_state = MG_PPPoE_ST_SESS; // defined in l2_ppp.c

        if (l == 1) s_state = MG_PPPoE_ST_REQ;

        ++l;

        // PPP exercised in other block

      }

      // build proper layer-3 datagrams, to be able to exercise layers above

      else if (etype == 0x800 && size > (ethhdrsz + sizeof(struct ip))) {         // IPv4

        fuzz_ip4(ethpay, size - ethhdrsz, &l3);

      } else if (etype == 0x806) {      // ARP

      } else if (etype == 0x86dd && size > (ethhdrsz + sizeof(struct ip6))) {     // IPv6

        fuzz_ip6(ethpay, size - ethhdrsz, &l3);

      }

    } else if (mif.l2type == MG_TCPIP_L2_PPP && size > (sizeof(struct hdlc_) + sizeof(struct ppp) + 2)) {

      static size_t i;

      static struct fuzz_l3_state l3;

      uint16_t ppp_protos[] = {

          MG_PPP_PROTO_LCP, MG_PPP_PROTO_IPCP, MG_PPP_PROTO_IP, MG_PPP_PROTO_IPV6CP, MG_PPP_PROTO_IPV6

      };

      struct hdlc_ *hdlc = (struct hdlc_ *) pkt;

      struct ppp *ppp = (struct ppp *) (hdlc + 1);

      size_t len = size - sizeof(*hdlc) - sizeof(*ppp) - 2;

      hdlc->addr = MG_PPP_ADDR;

      hdlc->ctrl = MG_PPP_CTRL;

      s_lcpup = true;

      // send all handled PPP protocols, then 2 random ones

      if (i >= (sizeof(ppp_protos) / sizeof(ppp_protos[0]) + 2)) i = 0;

      if (i < (sizeof(ppp_protos) / sizeof(ppp_protos[0]))) ppp->proto = mg_htons(ppp_protos[i++]);

      if (ppp->proto == mg_htons(MG_PPP_PROTO_LCP) && len >= sizeof(struct lcp)) {

        static size_t j, k;

        uint8_t lcp_codes[] = {MG_PPP_LCP_CFG_REQ, MG_PPP_LCP_CFG_ACK, MG_PPP_LCP_CFG_TERM_REQ, MG_PPP_LCP_ECHO_REQ};

        struct lcp *lcp = (struct lcp *) (ppp + 1);

        // send all handled LCP codes, then 2 random ones

        if (j >= (sizeof(lcp_codes) / sizeof(lcp_codes[0]) + 2)) j = 0;

        if (j < (sizeof(lcp_codes) / sizeof(lcp_codes[0]))) lcp->code = lcp_codes[j++];

        // send valid length, then 2 random lengths

        if (k >= 3) k = 0;

        if (k == 0) lcp->len = mg_htons((uint16_t) sizeof(*lcp));

        ++k;

      } else if (ppp->proto == mg_htons(MG_PPP_PROTO_IPCP) && len >= 10) {

        static size_t j, k, m;

        uint8_t ipcp_codes[] = {MG_PPP_IPCP_CFG_REQ, MG_PPP_IPCP_CFG_ACK, MG_PPP_IPCP_CFG_NACK, MG_PPP_IPCP_CFG_REJECT};

        struct ipcp *ipcp = (struct ipcp *) (ppp + 1);

        uint8_t *opts = (uint8_t *) (ipcp + 1);

        // send all handled IPCP codes, then 2 random ones

        if (j >= (sizeof(ipcp_codes) / sizeof(ipcp_codes[0]) + 2)) j = 0;

        if (j < (sizeof(ipcp_codes) / sizeof(ipcp_codes[0]))) ipcp->code = ipcp_codes[j++];

        // send valid length, then 2 random lengths

        if (m >= 3) m = 0;

        if (m == 0) ipcp->len = mg_htons(10);

        ++m;

        // send valid IPADDR option, then 2 random option types

        if (k >= 3) k = 0;

        if (k == 0) {

          static size_t l;

          opts[0] = MG_PPP_IPCP_OPT_IPADDR;

          // for valid option type, send valid length, then random length

          if (l >= 2) l = 0;

          if (l == 0) opts[1] = 6;

          ++l;

        }

        ++k;

      } else if (ppp->proto == mg_htons(MG_PPP_PROTO_IP) && len >= sizeof(struct ip)) {

        fuzz_ip4(ppp + 1, len, &l3);

      } else if (ppp->proto == mg_htons(MG_PPP_PROTO_IPV6CP) && len >= 14) {

        static size_t j, k, m;

        uint8_t ipv6cp_codes[] = {MG_PPP_IPV6CP_CFG_REQ, MG_PPP_IPV6CP_CFG_ACK, MG_PPP_IPV6CP_CFG_NACK, MG_PPP_IPV6CP_CFG_REJECT};

        struct ipv6cp *ipv6cp = (struct ipv6cp *) (ppp + 1);

        uint8_t *opts = (uint8_t *) (ipv6cp + 1);

        // send all handled IPV6CP codes, then 2 random ones

        if (j >= (sizeof(ipv6cp_codes) / sizeof(ipv6cp_codes[0]) + 2)) j = 0;

        if (j < (sizeof(ipv6cp_codes) / sizeof(ipv6cp_codes[0]))) ipv6cp->code = ipv6cp_codes[j++];

        // send valid length, then 2 random lengths

        if (m >= 3) m = 0;

        if (m == 0) ipv6cp->len = mg_htons(14);

        ++m;

        // send valid IFCID option, then 2 random option types

        if (k >= 3) k = 0;

        if (k == 0) {

          static size_t l;

          opts[0] = MG_PPP_IPV6CP_OPT_IFCID;

          // for valid option type, send valid length, then random length

          if (l >= 2) l = 0;

          if (l == 0) {

            static size_t o;

            opts[1] = 10;

            // for valid option length, send non-zero IFCID, then 2 random IFCIDs

            if (o >= 3) o = 0;

            if (o == 0) opts[9] = 1;

            ++o;

          }

          ++l;

        }

        ++k;

      } else if (ppp->proto == mg_htons(MG_PPP_PROTO_IPV6) && len >= sizeof(struct ip6)) {

        fuzz_ip6(ppp + 1, len, &l3);

      }

    }

#if defined(MAIN)

    printf("Sending to net_builtin:\n");

    mg_hexdump(pkt, size);

#endif

    mg_tcpip_rx(&mif, pkt, size);

    // prior actions may have had consequences on link state

    mif.state = MG_TCPIP_STATE_READY;

    // Test HTTP serving (via our built-in TCP/IP stack)

    const char *url = "http://localhost:12345"; // internally resolves

    // creates a connection and sends SYN via the router, unless OOM

    struct mg_connection *c = mg_http_connect(&mgr, url, fn, NULL);

    mg_iobuf_add(&c->recv, 0, data, size);

    c->pfn(c, MG_EV_READ, NULL); // manually invoke protocol event handler

    free(pkt);

    mg_mgr_free(&mgr);

  }

  return 0;

}

#if defined(MAIN)

int main(int argc, char *argv[]) {

  int res = EXIT_FAILURE;

  if (argc > 1) {

    struct mg_str data = mg_file_read(&mg_fs_posix, argv[1]);

    if (data.buf != NULL) {

      LLVMFuzzerTestOneInput((uint8_t *) data.buf, data.len);

      res = EXIT_SUCCESS;

    }

    free(data.buf);

  }

  return res;

}

#endif