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// Copyright (C) 2016-2019 Internet Systems Consortium, Inc. ("ISC")
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
#include <config.h>
#ifdef ENABLE_AFL
#ifndef __AFL_LOOP
#error To use American Fuzzy Lop you have to set CXX to afl-clang-fast++
#endif
#include <dhcp/dhcp6.h>
#include <dhcpsrv/fuzz.h>
#include <dhcpsrv/fuzz_log.h>
#include <boost/lexical_cast.hpp>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <iostream>
#include <sstream>
#include <fstream>
#include <ctime>
using namespace isc;
using namespace isc::dhcp;
using namespace std;
// Constants defined in the Fuzz class definition.
constexpr size_t Fuzz::BUFFER_SIZE;
constexpr size_t Fuzz::MAX_SEND_SIZE;
constexpr long Fuzz::MAX_LOOP_COUNT;
// Constructor
Fuzz::Fuzz(int ipversion, uint16_t port) :
loop_max_(MAX_LOOP_COUNT), sockaddr_len_(0), sockaddr_ptr_(nullptr),
sockfd_(-1) {
try {
stringstream reason; // Used to construct exception messages
// Get the values of the environment variables used to control the
// fuzzing.
// Specfies the interface to be used to pass packets from AFL to Kea.
const char* interface = getenv("KEA_AFL_INTERFACE");
if (! interface) {
isc_throw(FuzzInitFail, "no fuzzing interface has been set");
}
// The address on the interface to be used.
const char* address = getenv("KEA_AFL_ADDRESS");
if (address == 0) {
isc_throw(FuzzInitFail, "no fuzzing address has been set");
}
// Number of Kea packet-read loops before Kea exits and AFL starts a
// new instance. This is optional: the default is set by the constant
// MAX_LOOP_COUNT.
const char *loop_max_ptr = getenv("KEA_AFL_LOOP_MAX");
if (loop_max_ptr != 0) {
try {
loop_max_ = boost::lexical_cast<long>(loop_max_ptr);
} catch (const boost::bad_lexical_cast&) {
reason << "cannot convert loop count " << loop_max_ptr
<< " to an integer";
isc_throw(FuzzInitFail, reason.str());
}
if (loop_max_ <= 0) {
reason << "KEA_AFL_LOOP_MAX is " << loop_max_ << ". "
<< "It must be an integer greater than zero.";
isc_throw(FuzzInitFail, reason.str());
}
}
// Set up address structures used to route the packets from AFL to Kea.
createAddressStructures(ipversion, interface, address, port);
// Create the socket through which packets read from stdin will be sent
// to the port on which Kea is listening. This is closed in the
// destructor.
sockfd_ = socket((ipversion == 4) ? AF_INET : AF_INET6, SOCK_DGRAM, 0);
if (sockfd_ < 0) {
LOG_FATAL(fuzz_logger, FUZZ_SOCKET_CREATE_FAIL)
.arg(strerror(errno));
return;
}
LOG_INFO(fuzz_logger, FUZZ_INIT_COMPLETE).arg(interface).arg(address)
.arg(port).arg(loop_max_);
} catch (const FuzzInitFail& e) {
// AFL tends to make it difficult to find out what exactly has failed:
// make sure that the error is logged.
LOG_FATAL(fuzz_logger, FUZZ_INIT_FAIL).arg(e.what());
throw;
}
}
// Destructor
Fuzz::~Fuzz() {
static_cast<void>(close(sockfd_));
}
// Set up address structures.
void
Fuzz::createAddressStructures(int ipversion, const char* interface,
const char* address, uint16_t port) {
stringstream reason; // Used in error messages
// Set up the appropriate data structure depending on the address given.
if ((ipversion == 6) && (strstr(address, ":") != NULL)) {
// Expecting IPv6 and the address contains a colon, so assume it is an
// an IPv6 address.
memset(&servaddr6_, 0, sizeof (servaddr6_));
servaddr6_.sin6_family = AF_INET6;
if (inet_pton(AF_INET6, address, &servaddr6_.sin6_addr) != 1) {
reason << "inet_pton() failed: can't convert "
<< address << " to an IPv6 address" << endl;
isc_throw(FuzzInitFail, reason.str());
}
servaddr6_.sin6_port = htons(port);
// Interface ID is needed for IPv6 address structures.
servaddr6_.sin6_scope_id = if_nametoindex(interface);
if (servaddr6_.sin6_scope_id == 0) {
reason << "error retrieving interface ID for "
<< interface << ": " << strerror(errno);
isc_throw(FuzzInitFail, reason.str());
}
sockaddr_ptr_ = reinterpret_cast<sockaddr*>(&servaddr6_);
sockaddr_len_ = sizeof(servaddr6_);
} else if ((ipversion == 4) && (strstr(address, ".") != NULL)) {
// Expecting an IPv4 address and it contains a dot, so assume it is.
// This check is done after the IPv6 check, as it is possible for an
// IPv4 address to be embedded in an IPv6 one.
memset(&servaddr4_, 0, sizeof(servaddr4_));
servaddr4_.sin_family = AF_INET;
if (inet_pton(AF_INET, address, &servaddr4_.sin_addr) != 1) {
reason << "inet_pton() failed: can't convert "
<< address << " to an IPv6 address" << endl;
isc_throw(FuzzInitFail, reason.str());
}
servaddr4_.sin_port = htons(port);
sockaddr_ptr_ = reinterpret_cast<sockaddr*>(&servaddr4_);
sockaddr_len_ = sizeof(servaddr4_);
} else {
reason << "Expected IP version (" << ipversion << ") is not "
<< "4 or 6, or the given address " << address << " does not "
<< "match the IP version expected";
isc_throw(FuzzInitFail, reason.str());
}
}
// This is the main fuzzing function. It receives data from fuzzing engine over
// stdin and then sends it to the configured UDP socket.
void
Fuzz::transfer(void) const {
// Read from stdin. Just return if nothing is read (or there is an error)
// and hope that this does not cause a hang.
char buf[BUFFER_SIZE];
ssize_t length = read(0, buf, sizeof(buf));
// Save the errno in case there was an error because if debugging is
// enabled, the following LOG_DEBUG call may destroy its value.
int errnum = errno;
LOG_DEBUG(fuzz_logger, FUZZ_DBG_TRACE_DETAIL, FUZZ_DATA_READ).arg(length);
if (length > 0) {
// Now send the data to the UDP port on which Kea is listening.
// Send the data to the main Kea thread. Limit the size of the
// packets that can be sent.
size_t send_len = (length < MAX_SEND_SIZE) ? length : MAX_SEND_SIZE;
ssize_t sent = sendto(sockfd_, buf, send_len, 0, sockaddr_ptr_,
sockaddr_len_);
if (sent > 0) {
LOG_DEBUG(fuzz_logger, FUZZ_DBG_TRACE_DETAIL, FUZZ_SEND).arg(sent);
} else if (sent != length) {
LOG_WARN(fuzz_logger, FUZZ_SHORT_SEND).arg(length).arg(sent);
} else {
LOG_ERROR(fuzz_logger, FUZZ_SEND_ERROR).arg(strerror(errno));
}
} else {
// Read did not get any bytes. A zero-length read (EOF) may have been
// generated by AFL, so don't log that. But otherwise log an error.
if (length != 0) {
LOG_ERROR(fuzz_logger, FUZZ_READ_FAIL).arg(strerror(errnum));
}
}
}
#endif // ENABLE_AFL
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