+/*
+ * RFC1122 says the following on data in RST segments:
+ *
+ * 4.2.2.12 RST Segment: RFC-793 Section 3.4
+ *
+ * A TCP SHOULD allow a received RST segment to include data.
+ *
+ * DISCUSSION
+ * It has been suggested that a RST segment could contain
+ * ASCII text that encoded and explained the cause of the
+ * RST. No standard has yet been established for such
+ * data.
+ *
+ */
+
+static void
+print_tcp_rst_data(register const u_char *sp, u_int length)
+{
+ int c;
+
+ if (TTEST2(*sp, length))
+ printf(" [RST");
+ else
+ printf(" [!RST");
+ if (length > MAX_RST_DATA_LEN) {
+ length = MAX_RST_DATA_LEN; /* can use -X for longer */
+ putchar('+'); /* indicate we truncate */
+ }
+ putchar(' ');
+ while (length-- && sp <= snapend) {
+ c = *sp++;
+ safeputchar(c);
+ }
+ putchar(']');
+}
+
+#ifdef HAVE_LIBCRYPTO
+static int
+tcp_verify_signature(const struct ip *ip, const struct tcphdr *tp,
+ const u_char *data, int length, const u_char *rcvsig)
+{
+ struct tcphdr tp1;
+ char sig[TCP_SIGLEN];
+ char zero_proto = 0;
+ MD5_CTX ctx;
+ u_short savecsum, tlen;
+
+ tp1 = *tp;
+
+ if (tcpmd5secret == NULL)
+ return (-1);
+
+ MD5_Init(&ctx);
+ /*
+ * Step 1: Update MD5 hash with IP pseudo-header.
+ */
+ MD5_Update(&ctx, (char *)&ip->ip_src, sizeof(ip->ip_src));
+ MD5_Update(&ctx, (char *)&ip->ip_dst, sizeof(ip->ip_dst));
+ MD5_Update(&ctx, (char *)&zero_proto, sizeof(zero_proto));
+ MD5_Update(&ctx, (char *)&ip->ip_p, sizeof(ip->ip_p));
+ tlen = EXTRACT_16BITS(&ip->ip_len) - IP_HL(ip) * 4;
+ tlen = htons(tlen);
+ MD5_Update(&ctx, (char *)&tlen, sizeof(tlen));
+
+ /*
+ * Step 2: Update MD5 hash with TCP header, excluding options.
+ * The TCP checksum must be set to zero.
+ */
+ savecsum = tp1.th_sum;
+ tp1.th_sum = 0;
+ MD5_Update(&ctx, (char *)&tp1, sizeof(struct tcphdr));
+ tp1.th_sum = savecsum;
+ /*
+ * Step 3: Update MD5 hash with TCP segment data, if present.
+ */
+ if (length > 0)
+ MD5_Update(&ctx, data, length);
+ /*
+ * Step 4: Update MD5 hash with shared secret.
+ */
+ MD5_Update(&ctx, tcpmd5secret, strlen(tcpmd5secret));
+ MD5_Final(sig, &ctx);
+
+ return (memcmp(rcvsig, sig, 16));
+}
+#endif /* HAVE_LIBCRYPTO */
projects / tcpdump / blobdiff