From f0f075abae47994279864fcdfe76c9e31b65bc25 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Anton=20Luka=20=C5=A0ijanec?= <anton@sijanec.eu>
Date: Tue, 4 Jan 2022 00:33:23 +0100
Subject: prvi commit

---
 .gitignore             |   1 +
 domain2name.c          |  40 +++++++++++
 domain2name_test.c     |  16 +++++
 domain2name_testcase.c |  14 ++++
 main.c                 | 190 +++++++++++++++++++++++++++++++++++++++++++++++++
 test.c                 |   8 +++
 6 files changed, 269 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 domain2name.c
 create mode 100644 domain2name_test.c
 create mode 100644 domain2name_testcase.c
 create mode 100644 main.c
 create mode 100644 test.c

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..cba7efc
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+a.out
diff --git a/domain2name.c b/domain2name.c
new file mode 100644
index 0000000..46fd2a3
--- /dev/null
+++ b/domain2name.c
@@ -0,0 +1,40 @@
+int domain2name_len (const char * s, int l) {
+	int r = 1; /* ending terminator */
+	int o = 0; /* label offset */
+	for (int i = 0; i < l; i++) {
+		if (s[i] == '.') {
+			if (!o) /* double period or starting period, label is empty */
+				break;
+			o = 0;
+			continue;
+		}
+		if (!o) /* label has started */
+			r++;
+		r++;
+		o++;
+	}
+	return r;
+}
+int domain2name (char * d, const char * s, int l) { /* l is length of s */
+	char * c = d; /* where to write the label size when done with label */
+	char * w = d;
+	int o = 0; /* label offset */
+	for (int i = 0; i <= l /* yes, we go one more ... */; i++) {
+		if (i == l /* ... here */ || s[i] == '.') { /* end of label or end of last label */
+			if (!o) /* double period or starting period, label is empty */
+				break;
+			if (o <= 63) /* max length of label (six bits) */
+				*c = o;
+			o = 0;
+			continue;
+		}
+		if (!o++) /* label has started */
+			c = w++; /* to be filled with length */
+		if (o <= 63)
+			*w++ = s[i];
+		if (o == 64) /* if this label is too long, instead of writing it, we silently cap */
+			*c = 63; /* it at 63 bytes */
+	}
+	*w++ = '\0'; /* luckily this makes domain2name kind of safe for handling as a string (: */
+	return w-d; /* we return number of bytes written */
+} /* d must be allocated for at least _len. */
diff --git a/domain2name_test.c b/domain2name_test.c
new file mode 100644
index 0000000..f0a6898
--- /dev/null
+++ b/domain2name_test.c
@@ -0,0 +1,16 @@
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include "domain2name.c"
+int main (int argc, char * const argv[]) {
+	if (argc != 2) {
+		fprintf(stderr, "%s domain\n", argv[0]);
+		return 1;
+	}
+	int r, s = domain2name_len(argv[1], strlen(argv[1]));
+	char * b = alloca(s);
+	r = domain2name(b, argv[1], strlen(argv[1]));
+	printf("%4dB %4dB (-:\n", s, r); /* xxd has 16 bytes per row */
+	printf("%s", b);
+	fflush(stdout);
+}
diff --git a/domain2name_testcase.c b/domain2name_testcase.c
new file mode 100644
index 0000000..dfb7334
--- /dev/null
+++ b/domain2name_testcase.c
@@ -0,0 +1,14 @@
+#define D2NL(x,y) assert(domain2name_len(x, strlen(x)) == y); assert(domain2name_len(x ".", strlen(x ".")) == y); assert(domain2name_len("." x, strlen("." x)) == 1)
+D2NL("", 1);
+D2NL("localhost", 11);
+D2NL("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa", 2002);
+D2NL("a", 3);
+D2NL("sijanec.eu", 12);
+D2NL("splet.sijanec.eu", 18);
+D2NL("splet.sijanec..eu", 15);
+D2NL(".", 1);
+D2NL("a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a", 2001);
+D2NL("a...........................", 3);
+D2NL("splet..sijanec..eu", 7);
+D2NL("splet..sijanec.eu", 7);
+D2NL("193.2.1.66.sijanec.eu", 23);
diff --git a/main.c b/main.c
new file mode 100644
index 0000000..ec94e3f
--- /dev/null
+++ b/main.c
@@ -0,0 +1,190 @@
+#include <sys/socket.h> /* udp(7) */	/* TODO: random XID */
+#include <netinet/in.h>
+#include <netinet/udp.h>
+#include <poll.h> /* poll(2) */
+#include <sys/types.h> /* socket(2) */
+#include <sys/socket.h>
+#include <unistd.h> /* close(2) */
+#include <stdio.h> /* perror(3) */
+#include <sys/stat.h> /* open(2) */
+#include <fcntl.h>
+#include <errno.h> /* errno(3) */
+#include <arpa/inet.h> /* byteorder(3) */
+#include <string.h> /* strlen(3) */
+#include "domain2name.c"
+#define MIN(a,b) ((a) < (b) ? (a) : (b))
+#define MAX(a,b) ((a) > (b) ? (a) : (b))
+#define MAXDOMAIN 255
+#define QUERYDOMAIN "http://sijanec.eu/link?r=.sijanec.eu."
+#define	EXPECTEDA 93.103.235.126
+#define HELP "find recursive DNS resolvers on IPv4 networks\n" \
+	"%s [-h] [-d domain] [-a ipv4] network1 [network2 [network3 ...]]\n" \
+	"	-a Specify the IPv4 of the -d domain to be used instead of getaddrinfo(3).\n" \
+	"	-d Specify the domain name to be used in queries that has a single A record.\n" \
+	"	-h Show this help and exit.\n" \
+	"Networks are specified as domain names or IPv4 addresses followed by a forward slash\n" \
+	"and the netmask in decimal (0-32) or dot notation. For example: example.com/32. \n" \
+	"When scanning the Internet please make sure that you specify your own domain instead\n" \
+	"of the default one (f@sijanec.eu-http://sijanec.eu/link?r=.sijanec.eu). Make sure it\n" \
+	"somehow contains your contact information so the network/server administrator when\n" \
+	"looking at the logs will be able to contact you.\n"
+/* DNS PACKET: HEADER (12 bytes) QUESTION ANSWER AUTHORITY ADDITIONAL
+
+DEFINITIONS: (those appear somewhere in the packet, packet does not start with definitions!)
+	LABLEN	 8 bits: first two bits zero, then 6 bits length of label
+	POINTER	 8 bits: first two bits one, then 6 bits as offset from first byte of packet
+	STRING	a single byte for defining length (0-256 - all eight bits) and then string of chars
+	DOMAIN	 i.) one or more LABLEN followed by ASCII label (no dots) end with either LABLEN 0
+		or a POINTER that points to some LABLEN somewhere else in the packet		-OR-:
+		ii.) a POINTER that points to some LABLEN somewhere else in the packet
+
+HEADER:
+	XID	16 bits: random string to be matched in response to prevent cache poisoning
+     /	QR	 1 bit : what type is this packet?	0 query	1 response
+    |	OPCODE   4 bits: type of query			0 std	1 invrs	2 srvst	3-15 reserved
+1 byte	AA	 1 bit : is response authoritative?	0 no	1 yes
+    |	TC	 1 bit : was response truncated?	0 no	1 yes
+     \	RD       1 bit : does query desire recursion?	0 no	1 yes
+     /	RA	 1 bit : does response server recurse?	0 no	1 yes
+1 byte	Z	 3 bits: reserved for future		0 only option
+     \	RCODE	 4 bits: error condition	0 ok	1 fmter	2 srvfa	3 nxdom	4 N/I	5 forbidden
+    	QDCOUNT	16 bits: number of questions
+	ANCOUNT 16 bits: number of answers
+	NSCOUNT 16 bits: authority section (where to ask for actual response - NS RECORDS)
+	ARCOUNT 16 bits: additional section (glue records)
+QUESTION:
+	QNAME	DOMAIN
+	QTYPE	16 bits: 1 A 	2 NS	5 CNAME	6 SOA	10 NULL	12 PTR 13 HINFO	15 MX	16 TXT ...
+	QCLASS	16 bits: 1 INTERNET	2 CSNET	(obsolete)	3 CHAOS	4 HESIOD	255 ANY ...
+ANSWER:
+	NAME	DOMAIN
+	TYPE	same as QTYPE
+	CLASS	same description as QCLASS, except class 255 ANY is not allowed here
+	RDLEN	16 bits: length of RDATA field - this is a number 0-65536, no two zero bits
+	RDATA	A: 4 bytes IP address		NS: DOMAIN	CNAME: DOMAIN
+		SOA: NAME-ns1 NAME-email 32b-serial 32b-refresh 32b-retry 32b-expire 32b-nxdomainttl
+		NULL: any data up to RDLEN 	PTR: DOMAIN	HINFO: STRING-CPU, STRING-OS
+		MX: 16 bit preference, NAME-like domain		TXT: one or more STRING
+
+
+*/
+enum qr {
+	Query,
+	Response
+};
+enum opcode {
+	Query,
+	Iquery,
+	Stauts
+};
+enum rcode {
+	Success,
+	Format_error,
+	Servfail,
+	Nxdomain,
+	Ni,
+	Forbidden
+};
+enum type {
+	A = 1,
+	Ns,
+	Md,
+	Mf,
+	Cname,
+	Soa,
+	Mb,
+	Mg,
+	Mr,
+	Null,
+	Wks,
+	Ptr,
+	Hinfo,
+	Minfo,
+	Mx,
+	Txt
+}
+enum class {
+	In = 1,
+	Cs,
+	Ch,
+	He,
+	Any = 255
+}
+struct header {
+	uint16_t xid;
+	enum qr qr : 1;
+	enum opcode opcode : 4;
+	unsigned int aa : 1;
+	unsigned int tc : 1;
+	unsigned int rd : 1;
+	unsigned int ra : 1;
+	unsigned int z : 3;
+	enum rcode rcode : 4;
+	uint16_t qdcount;
+	uint16_t ancount;
+	uint16_t nscount;
+	uint16_t arcount;
+};
+struct question {
+	char * qname;
+	enum qtype qtype : 16;
+	enum qclass qclass : 16;
+};
+struct answer {
+	char * name;
+	enum class class : 16;
+	uint16_t rdlen;
+	char * rdata;
+}
+int main (int argc, char ** argv) {
+	int r = 0;
+	while (t) {
+		switch (getopt(argc, argv, ":a:d:h")) {
+			/* TODO */
+			case 'h':
+				printf(HELP, argv[0]);
+				r = 0;
+				goto r;
+			case -1:
+				d = optarg;
+				if (!d || !*d) {
+					fprintf(stderr, "specify the domain :: " HELP, argv[0]);
+					r = 4;
+					goto r;
+				}
+				if (strlen(d) > MAXDOMAIN) {
+					fprintf(stderr, "domain is too long - max "#MAXDOMAIN".\n");
+					r = 5;
+					goto r;
+				}
+				t = 0;
+				break;
+			case '?':
+				fprintf(stderr, "unknown option :: " HELP, argv[0]);
+				if (db != -1)
+					close(db);
+				r = 6;
+				goto r;
+			case ':':
+				fprintf(stderr, "missing option argument :: " HELP, argv[0]);
+				r = 7;
+				goto r;
+		}
+	}
+r:
+	if (s != -1)
+		if (close(s))
+			perror("close(s)");
+	}
+	return r;
+}
+int handle () {
+	char buf[512]; /* we don't support EDNS0 here, so max DNS packet is 512 bytes */
+	recvfrom();
+}
+int query () {
+	sendto();
+}
+int erase (char * dbfn, int dbfd, char * db) {
+	
+}
diff --git a/test.c b/test.c
new file mode 100644
index 0000000..eaa490e
--- /dev/null
+++ b/test.c
@@ -0,0 +1,8 @@
+#include <string.h>
+#include <stdio.h>
+#include <assert.h>
+#include "domain2name.c"
+int main (void) {
+#include "domain2name_testcase.c"
+	return 0;
+}
-- 
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