Add tcp syn packet fingerprinting to redbean

This change also fixes bugs in enoprotoopt reporting with setsockopt and getsockopt error returns.
2025-06-28 07:18:30 +00:00 · 2022-07-17 02:40:39 -07:00 · 2022-07-17 02:40:39 -07:00 · 4d25f8c3c9
commit 4d25f8c3c9
parent 866b21a151
75 changed files with 1551 additions and 115 deletions
--- a/net/finger/fingersyn.c
+++ b/net/finger/fingersyn.c
@ -0,0 +1,64 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2022 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/macros.internal.h"
+#include "libc/nexgen32e/bsr.h"
+
+/**
+ * Fingers IP+TCP SYN packet.
+ *
+ * This returns a hash-like magic number that reflects the SYN packet
+ * structure, e.g. ordering of options, maximum segment size, etc.
+ */
+uint32_t FingerSyn(const char *p, size_t n) {
+  uint32_t h = 0;
+  int i, j, k, q, r, iplen, tcplen, ttl;
+  if (n >= 20 + 20 && n >= (iplen = (p[0] & 0x0F) * 4) + 20 &&
+      n >= iplen + (tcplen = ((p[iplen + 12] & 0xF0) >> 4) * 4)) {
+    n = iplen + tcplen;
+    // Time to Live
+    // ttl<=256 Crisco, Solaris 6
+    // ttl<=128 Windows, OpenVMS 8+
+    // ttl<=64  Mac, Linux, BSD, Solaris 8+, Tru64, HP-UX
+    ttl = p[8] & 255;
+    h += bsr(MAX(1, ttl - 1));
+    h *= 0x9e3779b1;
+    // TCP Options
+    // We care about the order and presence of leading common options.
+    for (j = 0, i = iplen + 20; i < n; ++j) {
+      k = p[i] & 255;
+      if (k == 0 || k == 1 || k == 2 || k == 3 || k == 4 || k == 8) {
+        if (k <= 1) {
+          ++i;
+        } else if (i + 1 < n) {
+          i += p[i + 1] & 255;
+        } else {
+          break;
+        }
+      } else {
+        break;
+      }
+      h += j << 8 | k;
+      h *= 0x9e3779b1;
+    }
+    if (!h) {
+      ++h;
+    }
+  }
+  return h;
+}