/*
DISKUSIJA
Bolje bi bilo uporabiti frida gadget: https://frida.re/docs/gadget/
Kako deluje: https://tbrindus.ca/correct-ld-preload-hooking-libc/
Prevedi z: gcc -shared -fPIC -ldl ldmitm.c -o ldmitm.so
Poženi z: LD_PRELOAD=$PWD/ldmitm.so php -S 0:1234
A je treba beležit execve in fopen? Po mojem ne. Odtekanje flagov itak vidimo v TCP sessionu.
TODO: add mutex locks!!!
*/
#include <stdio.h>
#include <dlfcn.h>
#include <sys/socket.h>
#include <stdbool.h>
#include <stdlib.h>
#include <errno.h>
#include <fcntl.h>
#include <sqlite3.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#if SQLITE_VERSION_NUMBER < 3037000
#error "we require sqlite newer than 3037000, yours is " #SQLITE_VERSION_NUMBER " --- because of STRICT!"
#endif
#define LOG(x, ...) if (getenv("LDMITM_LOG")) printf("[ldmitm %s] " x "\n", __func__ __VA_OPT__(,) __VA_ARGS__)
struct stream {
	bool active;
	bool silenced;
	int id; // id in sqlite3 database
};
typedef int (*accept_t)(int socket, struct sockaddr *restrict address, socklen_t *restrict address_len);
typedef int (*close_t)(int fd);
static accept_t real_accept;
static close_t real_close;
static __thread sqlite3 * db = NULL;
struct stream * streams = NULL;
int streams_sizeof = 0;
static void setup_db () { // should be able to ignore being called in case db is already set up on this thread
	if (db)
		return;
	int ret = sqlite3_open_v2(getenv("LDMITM_DB") ? getenv("LDMITM_DB") : ":memory:", &db, SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_URI | SQLITE_OPEN_FULLMUTEX | SQLITE_OPEN_EXRESCODE, NULL);
	if (ret != SQLITE_OK) {
		LOG("failed to open db: %s", sqlite3_errstr(ret));
		goto fail;
	}
	sqlite3_stmt * stmt = NULL;
	ret = sqlite3_prepare_v3(db, "PRAGMA foreign_keys = ON;", -1, 0, &stmt, NULL);
	if (ret != SQLITE_OK) {
		LOG("failed to prepare pragma foreign_keys: %s", sqlite3_errstr(ret));
		if (stmt)
			sqlite3_finalize(stmt);
		stmt = NULL;
		goto fail;
	}
	ret = sqlite3_step(stmt);
	sqlite3_finalize(stmt);
	stmt = NULL;
	if (ret != SQLITE_DONE) {
		LOG("failed to step pragma foreign_keys: %s", sqlite3_errstr(ret));
		goto fail;
	}
#define CREATE_TABLE(name, columns) \
	ret = sqlite3_prepare_v3(db, "create table if not exists " name " (" columns ") STRICT;", -1, 0, &stmt, NULL); \
	if (ret != SQLITE_OK) { \
		LOG("failed to prepare create " name ": %s, statement: %s", sqlite3_errstr(ret), "create table if not exists " name " (" columns ") STRICT;"); \
		if (stmt) \
			sqlite3_finalize(stmt); \
		stmt = NULL; \
		goto fail; \
	} \
	ret = sqlite3_step(stmt); \
	sqlite3_finalize(stmt); \
	stmt = NULL; \
	if (ret != SQLITE_DONE) { \
		LOG("failed to step create " name ": %s", sqlite3_errstr(ret)); \
		goto fail; \
	}
	CREATE_TABLE("connections", "id INTEGER PRIMARY KEY, peer TEXT NOT NULL, accepted TEXT DEFAULT (strftime('%FT%R:%f', 'now')) NOT NULL, closed TEXT, silenced TEXT"); // accepted, closed and silenced are iso datestrings
	CREATE_TABLE("messages", "connection INTEGER NOT NULL, direction INTEGER NOT NULL CHECK (direction IN (0, 1)), time TEXT DEFAULT (strftime('%FT%R:%f', 'now')) NOT NULL, FOREIGN KEY(connection) REFERENCES connections(id)");
	return;
fail:
	if (db)
		sqlite3_close_v2(db);
	db = NULL;
	return;
}
static void end_stream (int fd) { // cleanup function, should be able to handle being called on already ended stream
	if (fd >= streams_sizeof || !streams[fd].active)
		return;
	setup_db();
	if (db) {
		sqlite3_stmt * stmt = NULL;
		int ret = sqlite3_prepare_v3(db, "update connections set closed=strftime('%FT%R:%f', 'now') WHERE id=:i;", -1, 0, &stmt, NULL);
		if (ret != SQLITE_OK) {
			LOG("failed to prepare update connections set closed: %s", sqlite3_errstr(ret));
			sqlite3_finalize(stmt);
			stmt = NULL;
			goto fail;
		}
		ret = sqlite3_bind_int64(stmt, sqlite3_bind_parameter_index(stmt, ":i"), streams[fd].id);
		if (ret != SQLITE_OK) {
			LOG("failed to bind update connections set closed: %s", sqlite3_errstr(ret));
			sqlite3_finalize(stmt);
			stmt = NULL;
			goto fail;
		}
		ret = sqlite3_step(stmt);
		sqlite3_finalize(stmt);
		stmt = NULL;
		if (ret != SQLITE_DONE) {
			LOG("failed to step update connections set closed: %s", sqlite3_errstr(ret));
			goto fail;
		}
	}
fail:
	memset(&(streams[fd]), 0, sizeof streams[fd]);
}
int close (int fd) {
	if (!real_close)
		real_close = dlsym(RTLD_NEXT, "close");
	LOG("called close()");
	int ret = real_close(fd);
	int old_errno = errno;
	end_stream(fd);
	errno = old_errno;
	return ret;
}
int accept (int socket, struct sockaddr *restrict address, socklen_t *restrict address_len) {
	if (!real_accept)
		real_accept = dlsym(RTLD_NEXT, "accept");
	LOG("called accept()");
	int ret = real_accept(socket, address, address_len);
	int saved_errno = errno;
	if (ret >= streams_sizeof) {
		int streams_sizeof_new;
		if (streams_sizeof == 0)
			streams_sizeof_new = 128;
		else
			streams_sizeof_new = streams_sizeof * 2;
		struct stream * streams_new = realloc(streams, streams_sizeof_new*sizeof *streams);
		if (!streams_new) {
			LOG("ENOMEM realloc streams!");
			goto fail;
		}
		memset(streams_new+streams_sizeof, 0, (streams_sizeof_new-streams_sizeof)*sizeof *streams);
		streams = streams_new;
		streams_sizeof = streams_sizeof_new;
	}
	end_stream(ret);
	streams[ret].active = true;
	setup_db();
	if (db) {
		sqlite3_stmt * stmt = NULL;
		int sqlret = sqlite3_prepare_v3(db, "insert into connections (peer) values (:p);", -1, 0, &stmt, NULL);
		if (sqlret != SQLITE_OK) {
			LOG("failed to prepare insert connections: %s", sqlite3_errstr(sqlret));
			goto sqlfail;
		}
		char peeraddress[INET_ADDRSTRLEN+128];
		switch (address->sa_family) {
			case AF_INET:
				if (!inet_ntop(AF_INET, &(((struct sockaddr_in *) address)->sin_addr), peeraddress, *address_len)) {
					int myerrno = errno;
					strcpy(peeraddress, "!");
					strcat(peeraddress, strerror(myerrno));
				}
				sprintf(peeraddress+strlen(peeraddress), "/%d", ntohs(((struct sockaddr_in *) address)->sin_port));
				break;
			case AF_INET6:
				if (!inet_ntop(AF_INET6, &(((struct sockaddr_in6 *) address)->sin6_addr), peeraddress, *address_len)) {
					int myerrno = errno;
					strcpy(peeraddress, "!");
					strcat(peeraddress, strerror(myerrno));
				}
				sprintf(peeraddress+strlen(peeraddress), "/%d", ntohs(((struct sockaddr_in6 *) address)->sin6_port));
				break;
			default:
				strcpy(peeraddress, "unknown family");
				break;
		}
		sqlret = sqlite3_bind_text(stmt, sqlite3_bind_parameter_index(stmt, ":p"), peeraddress, -1, SQLITE_STATIC);
		if (sqlret != SQLITE_OK) {
			LOG("failed to bind insert connection: %s", sqlite3_errstr(sqlret));
			goto sqlfail;
		}
		sqlret = sqlite3_step(stmt);
		sqlite3_finalize(stmt);
		stmt = NULL;
		if (sqlret != SQLITE_DONE) {
			LOG("failed to step insert connection: %s", sqlite3_errstr(ret));
			goto sqlfail;
		}
sqlfail:
		sqlite3_finalize(stmt);
		stmt = NULL;
		goto fail;
	}
fail:
	errno = saved_errno;
	return ret;
}
__attribute__((constructor)) static void setup (void) {
	LOG("called setup()");
}