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NetGuard/app/src/main/jni/netguard/netguard.c

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#include <jni.h>
#include <android/log.h>
#include <stdio.h>
#include <time.h>
#include <unistd.h>
#include <pthread.h>
#include <arpa/inet.h>
#include <netinet/ip.h>
#include <netinet/ip6.h>
#include <netinet/udp.h>
#include <netinet/tcp.h>
// 3 way handshake
// -> SYN seq=x
// <- SYN-ACK ack=x+1 seq=y
// -> ACK=y+1 seq=x+1
// https://www.gasmi.net/hpd/
// Ethernet frame: 0800 2086 354b 00e0 f726 3fe9 0800
// TODO TCP fragmentation
// TODO TCP push
// TODO header file
#define TAG "NetGuard.JNI"
#define MAXPKT 32678
#define TIMEOUTPKT 30
#define TTL 64
struct arguments {
jobject instance;
int tun;
};
struct data {
uint32_t len;
uint8_t *data;
struct data *next;
};
struct connection {
time_t time;
uint32_t remote_seq; // confirmed bytes received, host notation
uint32_t local_seq; // confirmed bytes sent, host notation
int32_t saddr; // network notation
__be16 source; // network notation
int32_t daddr; // network notation
__be16 dest; // network notation
uint8_t state;
jint socket;
uint32_t lport; // host notation
struct data *sent;
struct connection *next;
};
void *handle_events(void *);
void handle_tcp(JNIEnv *, jobject, const struct arguments *args, const uint8_t *, const uint16_t);
int openSocket(JNIEnv *, jobject, const struct sockaddr_in *);
int getLocalPort(const int);
int canWrite(const int);
int writeSYN(const struct connection *, const int);
void decode(JNIEnv *, jobject, const struct arguments *args, const uint8_t *, const uint16_t);
jint getUid(const int, const int, const void *, const uint16_t);
unsigned short checksum(unsigned short *, int);
void nsleep(const long);
char *hex(const u_int8_t *, const u_int16_t);
// Global variables
static JavaVM *jvm;
pthread_t thread_id;
int signaled = 0;
struct connection *connection = NULL;
// JNI
JNIEXPORT void JNICALL
Java_eu_faircode_netguard_SinkholeService_jni_1init(JNIEnv *env, jobject instance) {
__android_log_print(ANDROID_LOG_DEBUG, TAG, "Init");
connection = NULL;
}
JNIEXPORT void JNICALL
Java_eu_faircode_netguard_SinkholeService_jni_1start(JNIEnv *env, jobject instance, jint tun) {
__android_log_print(ANDROID_LOG_DEBUG, TAG, "Starting tun=%d", tun);
if (pthread_kill(thread_id, 0) == 0)
__android_log_print(ANDROID_LOG_WARN, TAG, "Already running thread %u", thread_id);
else {
jint rs = (*env)->GetJavaVM(env, &jvm);
if (rs != JNI_OK)
__android_log_print(ANDROID_LOG_ERROR, TAG, "GetJavaVM failed");
struct arguments *args = malloc(sizeof(struct arguments));
args->instance = (*env)->NewGlobalRef(env, instance);
args->tun = tun;
int err = pthread_create(&thread_id, NULL, handle_events, args);
if (err != 0)
__android_log_print(ANDROID_LOG_ERROR, TAG, "pthread_create error %d: %s",
err, strerror(err));
}
}
JNIEXPORT void JNICALL
Java_eu_faircode_netguard_SinkholeService_jni_1stop(JNIEnv *env, jobject instance, jint tun) {
__android_log_print(ANDROID_LOG_DEBUG, TAG, "Stop thread %u", thread_id);
if (pthread_kill(thread_id, 0) == 0) {
__android_log_print(ANDROID_LOG_DEBUG, TAG, "Kill thread %u", thread_id);
int err = pthread_kill(thread_id, SIGUSR1);
if (err != 0)
__android_log_print(ANDROID_LOG_WARN, TAG, "pthread_kill error %d: %s",
err, strerror(err));
else {
__android_log_print(ANDROID_LOG_DEBUG, TAG, "Join thread %u", thread_id);
pthread_join(thread_id, NULL);
if (err != 0)
__android_log_print(ANDROID_LOG_WARN, TAG, "pthread_join error %d: %s",
err, strerror(err));
}
__android_log_print(ANDROID_LOG_DEBUG, TAG, "Stopped");
} else
__android_log_print(ANDROID_LOG_WARN, TAG, "Not running");
}
JNIEXPORT void JNICALL
Java_eu_faircode_netguard_SinkholeService_jni_1reload(JNIEnv *env, jobject instance, jint tun) {
// TODO seamless handover
__android_log_print(ANDROID_LOG_DEBUG, TAG, "Reload tun=%d", tun);
Java_eu_faircode_netguard_SinkholeService_jni_1stop(env, instance, tun);
Java_eu_faircode_netguard_SinkholeService_jni_1start(env, instance, tun);
}
// Private functions
void sig_handler(int sig, siginfo_t *info, void *context) {
__android_log_print(ANDROID_LOG_DEBUG, TAG, "Signal %d", sig);
signaled = 1;
}
void *handle_events(void *a) {
struct arguments *args = (struct arguments *) a;
__android_log_print(ANDROID_LOG_DEBUG, TAG, "Start events tun=%d thread %u", args->tun,
thread_id);
JNIEnv *env;
jint rs = (*jvm)->AttachCurrentThread(jvm, &env, NULL);
if (rs != JNI_OK)
__android_log_print(ANDROID_LOG_ERROR, TAG, "AttachCurrentThread failed");
int max;
fd_set rfds;
fd_set wfds;
fd_set efds;
struct timespec ts;
char dest[20];
sigset_t blockset;
sigset_t emptyset;
struct sigaction sa;
// Block SIGUSR1
sigemptyset(&blockset);
sigaddset(&blockset, SIGUSR1);
sigprocmask(SIG_BLOCK, &blockset, NULL);
/// Handle SIGUSR1
sa.sa_sigaction = sig_handler;
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_RESTART;
sigaction(SIGUSR1, &sa, NULL);
signaled = 0;
// Loop
while (1) {
time_t now = time(NULL);
__android_log_print(ANDROID_LOG_DEBUG, TAG, "Select thread %u", thread_id);
// Select
FD_ZERO(&rfds);
FD_ZERO(&wfds);
FD_ZERO(&efds);
FD_SET(args->tun, &rfds);
FD_SET(args->tun, &efds);
max = args->tun;
struct connection *last = NULL;
struct connection *cur = connection;
while (cur != NULL) {
if (cur->time + TIMEOUTPKT < now) {
// Log
inet_ntop(AF_INET, &(cur->daddr), dest, sizeof(dest));
__android_log_print(ANDROID_LOG_DEBUG, TAG, "Idle %s/%u lport %u",
dest, ntohs(cur->dest), cur->lport);
// TODO check if open
shutdown(cur->socket, SHUT_RDWR);
// TODO check for errors
struct data *prev;
struct data *sent = cur->sent;
while (sent != NULL) {
prev = sent;
sent = sent->next;
if (prev->data != NULL)
free(prev->data);
free(prev);
}
if (last == NULL)
connection = cur->next;
else
last->next = cur->next;
struct connection *c = cur;
cur = cur->next;
free(c);
continue;
} else {
if (cur->state == TCP_SYN_RECV) {
FD_SET(cur->socket, &wfds);
if (cur->socket > max)
max = cur->socket;
}
else if (cur->state == TCP_ESTABLISHED) {
FD_SET(cur->socket, &rfds);
if (cur->socket > max)
max = cur->socket;
}
}
last = cur;
cur = cur->next;
}
ts.tv_sec = 10;
ts.tv_nsec = 0;
sigemptyset(&emptyset);
int ready = pselect(max + 1, &rfds, &wfds, &efds, &ts, &emptyset);
if (ready < 0) {
if (errno == EINTR) {
if (signaled) { ;
__android_log_print(ANDROID_LOG_DEBUG, TAG, "pselect signaled");
break;
} else {
__android_log_print(ANDROID_LOG_WARN, TAG, "pselect interrupted");
continue;
}
} else {
__android_log_print(ANDROID_LOG_ERROR, TAG, "select error %d: %s",
errno, strerror(errno));
break;
}
}
if (ready == 0)
__android_log_print(ANDROID_LOG_DEBUG, TAG, "Yield");
else {
// Check tun exception
if (FD_ISSET(args->tun, &efds)) {
__android_log_print(ANDROID_LOG_ERROR, TAG, "tun exception");
break;
}
// Check tun read
if (FD_ISSET(args->tun, &rfds)) {
uint8_t buffer[MAXPKT];
ssize_t length = read(args->tun, buffer, MAXPKT);
if (length < 0) {
__android_log_print(ANDROID_LOG_ERROR, TAG, "tun read error %d: %s",
errno, strerror(errno));
break;
}
if (length > 0)
decode(env, args->instance, args, buffer, length);
else {
__android_log_print(ANDROID_LOG_ERROR, TAG, "tun empty read");
break;
}
}
// Check sockets
struct connection *cur = connection;
while (cur != NULL) {
// Check socket exception
if (FD_ISSET(cur->socket, &efds)) {
int serr;
socklen_t optlen = sizeof(serr);
if (getsockopt(cur->socket, SOL_SOCKET, SO_ERROR, &serr, &optlen) < 0) {
__android_log_print(ANDROID_LOG_ERROR, TAG, "getsockopt error %d: %s",
errno, strerror(errno));
cur->state = TCP_CLOSE;
continue;
}
if (serr) {
__android_log_print(ANDROID_LOG_ERROR, TAG, "SO_ERROR %d: %s",
serr, strerror(serr));
cur->state = TCP_CLOSE;
continue;
}
}
if (cur->state == TCP_SYN_RECV) {
// Check socket connect
if (FD_ISSET(cur->socket, &wfds) && canWrite(args->tun)) {
// Log
char dest[20];
inet_ntop(AF_INET, &(cur->daddr), dest, sizeof(dest));
__android_log_print(ANDROID_LOG_DEBUG, TAG, "Established %s/%u lport %u",
dest, ntohs(cur->dest), cur->lport);
if (writeSYN(cur, args->tun) < 0)
cur->state = TCP_CLOSE;
else
cur->state = TCP_SYN_SENT;
}
}
else if (cur->state == TCP_ESTABLISHED) {
// Check socket read
if (FD_ISSET(cur->socket, &rfds)) {
uint8_t buffer[MAXPKT];
ssize_t bytes = recv(cur->socket, buffer, MAXPKT, 0);
if (bytes < 0) {
__android_log_print(ANDROID_LOG_ERROR, TAG, "recv socket error %d: %s",
errno, strerror(errno));
if (errno != EINTR)
cur->state = TCP_CLOSE;
}
else if (bytes == 0) {
__android_log_print(ANDROID_LOG_ERROR, TAG, "recv socket empty");
cur->state = TCP_CLOSE;
} else {
__android_log_print(ANDROID_LOG_DEBUG, TAG,
"recv socket lport %u bytes %d",
cur->lport, bytes);
}
}
}
cur = cur->next;
}
}
}
(*env)->DeleteGlobalRef(env, args->instance);
rs = (*jvm)->DetachCurrentThread(jvm);
if (rs != JNI_OK)
__android_log_print(ANDROID_LOG_ERROR, TAG, "DetachCurrentThread failed");
free(args);
__android_log_print(ANDROID_LOG_DEBUG, TAG, "Stopped events tun=%d thread %u",
args->tun, thread_id);
}
void handle_tcp(JNIEnv *env, jobject instance, const struct arguments *args,
const uint8_t *buffer, uint16_t length) {
// Check version
uint8_t version = (*buffer) >> 4;
if (version != 4)
return;
// Get headers
struct iphdr *iphdr = buffer;
uint8_t optlen = (iphdr->ihl - 5) * 4;
struct tcphdr *tcphdr = buffer + sizeof(struct iphdr) + optlen;
__android_log_print(ANDROID_LOG_DEBUG, TAG, "optlen %d", optlen);
if (ntohs(iphdr->tot_len) != length)
__android_log_print(ANDROID_LOG_WARN, TAG, "Invalid length %u/%d", iphdr->tot_len, length);
// Get data
uint16_t dataoff = sizeof(struct iphdr) + optlen + sizeof(struct tcphdr);
uint16_t datalen = length - dataoff;
struct data *data = NULL;
if (datalen > 0) {
data = malloc(sizeof(struct data));
data->len = datalen;
data->data = malloc(datalen); // TODO free
memcpy(data->data, buffer + dataoff, datalen);
data->next = NULL;
}
// Search connection
struct connection *last = NULL;
struct connection *cur = connection;
while (cur != NULL && !(cur->saddr == iphdr->saddr && cur->source == tcphdr->source)) {
last = cur;
cur = cur->next;
}
// Log
char dest[20];
inet_ntop(AF_INET, &(iphdr->daddr), dest, sizeof(dest));
__android_log_print(ANDROID_LOG_DEBUG, TAG, "%s/%u seq %u ack %u data %d",
dest, ntohs(tcphdr->dest),
ntohl(tcphdr->seq), ntohl(tcphdr->ack_seq), datalen);
if (cur == NULL) {
if (tcphdr->syn) {
__android_log_print(ANDROID_LOG_DEBUG, TAG, "New SYN");
// Register connection
struct connection *syn = malloc(sizeof(struct connection)); // TODO check/free
syn->time = time(NULL);
syn->remote_seq = ntohl(tcphdr->seq); // ISN remote
syn->local_seq = 123; // ISN local TODO randomize
syn->saddr = iphdr->saddr;
syn->source = tcphdr->source;
syn->daddr = iphdr->daddr;
syn->dest = tcphdr->dest;
syn->state = TCP_SYN_RECV;
syn->sent = NULL;
syn->next = NULL;
// Ignore data
if (data != NULL) {
free(data->data);
free(data);
}
// Build target address
struct sockaddr_in daddr;
memset(&daddr, 0, sizeof(struct sockaddr_in));
daddr.sin_family = AF_INET;
daddr.sin_port = tcphdr->dest;
daddr.sin_addr.s_addr = iphdr->daddr;
// Open socket
syn->socket = openSocket(env, instance, &daddr);
if (syn->socket < 0)
syn->state = TCP_CLOSE;
else {
syn->lport = getLocalPort(syn->socket);
__android_log_print(ANDROID_LOG_DEBUG, TAG, "Connecting to %s/%u lport %u",
dest, ntohs(tcphdr->dest), syn->lport);
}
if (last == NULL)
connection = syn;
else
last->next = syn;
}
else
__android_log_print(ANDROID_LOG_WARN, TAG, "Unknown connection");
}
else {
__android_log_print(ANDROID_LOG_DEBUG, TAG, "Existing connection lport %u", cur->lport);
if (tcphdr->syn)
__android_log_print(ANDROID_LOG_DEBUG, TAG, "Ignoring repeated SYN");
else if (tcphdr->ack) {
cur->time = time(NULL);
if (cur->state == TCP_SYN_SENT) {
// TODO proper warp around
if (ntohl(tcphdr->ack_seq) == cur->local_seq + 1 &&
ntohl(tcphdr->seq) >= cur->remote_seq + 1) {
cur->local_seq += 1;
cur->remote_seq += 1;
// TODO process data
__android_log_print(ANDROID_LOG_DEBUG, TAG, "Established");
cur->state = TCP_ESTABLISHED;
}
else
__android_log_print(ANDROID_LOG_WARN, TAG, "Invalid seq/ack");
}
else if (cur->state == TCP_ESTABLISHED) {
// TODO proper wrap around
if (ntohl(tcphdr->seq) + 1 == cur->remote_seq)
// TODO respond to keepalive?
__android_log_print(ANDROID_LOG_DEBUG, TAG, "Keep alive");
else if (ntohl(tcphdr->seq) < cur->remote_seq)
__android_log_print(ANDROID_LOG_WARN, TAG, "Processed ack");
else {
__android_log_print(ANDROID_LOG_DEBUG, TAG, "New ack");
if (data != NULL && data->len) {
// TODO non blocking
__android_log_print(ANDROID_LOG_DEBUG, TAG, "send socket data %u",
data->len);
if (send(cur->socket, data->data, data->len, 0) < 0)
__android_log_print(ANDROID_LOG_ERROR, TAG, "send error %d: %s",
errno, strerror(errno));
else {
if (writeACK(cur, data->len, args->tun))
cur->remote_seq += data->len;
}
}
}
}
else {
__android_log_print(ANDROID_LOG_WARN, TAG, "Ignored state %d", cur->state);
}
}
}
}
int openSocket(JNIEnv *env, jobject instance, const struct sockaddr_in *daddr) {
int sock = -1;
// Get TCP socket
// TODO socket options (SO_REUSEADDR, etc)
if ((sock = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
__android_log_print(ANDROID_LOG_ERROR, TAG, "socket error %d: %s",
errno, strerror(errno));
return -1;
}
// Protect
jclass cls = (*env)->GetObjectClass(env, instance);
jmethodID mid = (*env)->GetMethodID(env, cls, "protect", "(I)Z");
if (mid == 0) {
__android_log_print(ANDROID_LOG_ERROR, TAG, "protect not found");
return -1;
}
else {
jboolean isProtected = (*env)->CallBooleanMethod(env, instance, mid, sock);
if (!isProtected)
__android_log_print(ANDROID_LOG_ERROR, TAG, "protect failed");
jthrowable ex = (*env)->ExceptionOccurred(env);
if (ex) {
(*env)->ExceptionDescribe(env);
(*env)->ExceptionClear(env);
(*env)->DeleteLocalRef(env, ex);
}
}
// Set non blocking
uint8_t flags = fcntl(sock, F_GETFL, 0);
if (flags < 0 || fcntl(sock, F_SETFL, flags | O_NONBLOCK) < 0) {
__android_log_print(ANDROID_LOG_ERROR, TAG, "fcntl O_NONBLOCK error %d: %s",
errno, strerror(errno));
return -1;
}
// Initiate connect
int err = connect(sock, daddr, sizeof(struct sockaddr_in));
if (err < 0 && errno != EINPROGRESS) {
__android_log_print(ANDROID_LOG_ERROR, TAG, "connect error %d: %s",
errno, strerror(errno));
return -1;
}
// Set blocking
if (fcntl(sock, F_SETFL, flags & ~O_NONBLOCK) < 0) {
__android_log_print(ANDROID_LOG_ERROR, TAG, "fcntl error %d: %s",
errno, strerror(errno));
return -1;
}
return sock;
}
int getLocalPort(const int sock) {
struct sockaddr_in sin;
int len = sizeof(sin);
if (getsockname(sock, &sin, &len) < 0) {
__android_log_print(ANDROID_LOG_ERROR, TAG, "getsockname error %d: %s",
errno, strerror(errno));
return -1;
} else
return ntohs(sin.sin_port);
}
int canWrite(const int fd) {
struct timeval tv;
tv.tv_sec = 0;
tv.tv_usec = 0;
fd_set wfds;
FD_ZERO(&wfds);
FD_SET(fd, &wfds);
return (select(fd + 1, NULL, &wfds, NULL, &tv) > 0);
}
int writeSYN(const struct connection *cur, int tun) {
// Build packet
uint16_t len = sizeof(struct iphdr) + sizeof(struct tcphdr); // no data
u_int8_t *buffer = calloc(len, 1);
struct iphdr *ip = buffer;
struct tcphdr *tcp = buffer + sizeof(struct iphdr);
// Build IP header
ip->version = 4;
ip->ihl = sizeof(struct iphdr) >> 2;
ip->tot_len = htons(len);
ip->ttl = TTL;
ip->protocol = IPPROTO_TCP;
ip->saddr = cur->daddr;
ip->daddr = cur->saddr;
// Calculate IP checksum
ip->check = checksum(ip, sizeof(struct iphdr));
// Build TCP header
tcp->source = cur->dest;
tcp->dest = cur->source;
tcp->seq = htonl(cur->local_seq);
tcp->ack_seq = htonl(cur->remote_seq + 1); // TODO proper wrap around
tcp->doff = sizeof(struct tcphdr) >> 2;
tcp->syn = 1;
tcp->ack = 1;
tcp->window = htons(2048);
// Calculate TCP checksum
uint16_t clen = sizeof(struct ippseudo) + sizeof(struct tcphdr);
uint8_t csum[clen];
// Build pseudo header
struct ippseudo *pseudo = csum;
pseudo->ippseudo_src.s_addr = ip->saddr;
pseudo->ippseudo_dst.s_addr = ip->daddr;
pseudo->ippseudo_pad = 0;
pseudo->ippseudo_p = ip->protocol;
pseudo->ippseudo_len = htons(sizeof(struct tcphdr)); // no data
// Copy TCP header
memcpy(csum + sizeof(struct ippseudo), tcp, sizeof(struct tcphdr));
tcp->check = checksum(csum, clen);
char to[20];
inet_ntop(AF_INET, &(ip->daddr), to, sizeof(to));
// Send packet
__android_log_print(ANDROID_LOG_DEBUG, TAG,
"Sending SYN+ACK to tun %s/%u seq %u ack %u",
to, ntohs(tcp->dest),
ntohl(tcp->seq), ntohl(tcp->ack_seq));
int res = write(tun, buffer, len);
if (res < 0) {
// TODO handle EINTR
__android_log_print(ANDROID_LOG_ERROR, TAG, "write error %d: %s",
errno, strerror(errno));
}
free(buffer);
return res;
}
int writeACK(const struct connection *cur, uint32_t datalen, int tun) {
// Build packet
uint16_t len = sizeof(struct iphdr) + sizeof(struct tcphdr); // no data
u_int8_t *buffer = calloc(len, 1);
struct iphdr *ip = buffer;
struct tcphdr *tcp = buffer + sizeof(struct iphdr);
// Build IP header
ip->version = 4;
ip->ihl = sizeof(struct iphdr) >> 2;
ip->tot_len = htons(len);
ip->ttl = TTL;
ip->protocol = IPPROTO_TCP;
ip->saddr = cur->daddr;
ip->daddr = cur->saddr;
// Calculate IP checksum
ip->check = checksum(ip, sizeof(struct iphdr));
// Build TCP header
tcp->source = cur->dest;
tcp->dest = cur->source;
tcp->seq = htonl(cur->local_seq);
tcp->ack_seq = htonl(cur->remote_seq + datalen); // TODO proper wrap around
tcp->doff = sizeof(struct tcphdr) >> 2;
tcp->ack = 1;
tcp->window = htons(2048);
// Calculate TCP checksum
uint16_t clen = sizeof(struct ippseudo) + sizeof(struct tcphdr);
uint8_t csum[clen];
// Build pseudo header
struct ippseudo *pseudo = csum;
pseudo->ippseudo_src.s_addr = ip->saddr;
pseudo->ippseudo_dst.s_addr = ip->daddr;
pseudo->ippseudo_pad = 0;
pseudo->ippseudo_p = ip->protocol;
pseudo->ippseudo_len = htons(sizeof(struct tcphdr)); // no data
// Copy TCP header
memcpy(csum + sizeof(struct ippseudo), tcp, sizeof(struct tcphdr));
tcp->check = checksum(csum, clen);
char to[20];
inet_ntop(AF_INET, &(ip->daddr), to, sizeof(to));
// Send packet
__android_log_print(ANDROID_LOG_DEBUG, TAG,
"Sending ACK to tun %s/%u seq %u ack %u",
to, ntohs(tcp->dest),
ntohl(tcp->seq), ntohl(tcp->ack_seq));
int res = write(tun, buffer, len);
if (res < 0) {
// TODO handle EINTR
__android_log_print(ANDROID_LOG_ERROR, TAG, "write error %d: %s",
errno, strerror(errno));
}
free(buffer);
return res;
}
void decode(JNIEnv *env, jobject instance, const struct arguments *args,
const uint8_t *buffer, const uint16_t length) {
uint8_t protocol;
void *saddr;
void *daddr;
char source[40];
char dest[40];
char flags[10];
int flen = 0;
uint8_t *payload;
// Get protocol, addresses & payload
uint8_t version = (*buffer) >> 4;
if (version == 4) {
struct iphdr *ip4hdr = buffer;
protocol = ip4hdr->protocol;
saddr = &ip4hdr->saddr;
daddr = &ip4hdr->daddr;
if (ip4hdr->frag_off & IP_MF)
flags[flen++] = '+';
uint8_t optlen = (ip4hdr->ihl - 5) * 4;
payload = buffer + 20 + optlen;
if (ntohs(ip4hdr->tot_len) != length) {
__android_log_print(ANDROID_LOG_ERROR, TAG, "Invalid length %u header length %u",
length, ntohs(ip4hdr->tot_len));
return;
}
uint16_t csum = checksum(ip4hdr, sizeof(struct iphdr));
if (csum != 0) {
__android_log_print(ANDROID_LOG_ERROR, TAG, "Invalid IP checksum");
return;
}
}
else if (version == 6) {
struct ip6_hdr *ip6hdr = buffer;
protocol = ip6hdr->ip6_nxt;
saddr = &ip6hdr->ip6_src;
daddr = &ip6hdr->ip6_dst;
payload = buffer + 40;
// TODO check length
// TODO checksum
}
else {
__android_log_print(ANDROID_LOG_WARN, TAG, "Unknown version %d", version);
return;
}
inet_ntop(version == 4 ? AF_INET : AF_INET6, saddr, source, sizeof(source));
inet_ntop(version == 4 ? AF_INET : AF_INET6, daddr, dest, sizeof(dest));
// Get ports & flags
uint16_t sport = -1;
uint16_t dport = -1;
if (protocol == IPPROTO_TCP) {
struct tcphdr *tcp = payload;
sport = ntohs(tcp->source);
dport = ntohs(tcp->dest);
if (tcp->syn)
flags[flen++] = 'S';
if (tcp->ack)
flags[flen++] = 'A';
if (tcp->psh)
flags[flen++] = 'P';
if (tcp->fin)
flags[flen++] = 'F';
if (tcp->fin)
flags[flen++] = 'R';
// TODO checksum
} else if (protocol == IPPROTO_UDP) {
struct udphdr *udp = payload;
sport = ntohs(udp->source);
dport = ntohs(udp->dest);
// TODO checksum
}
flags[flen] = 0;
// Get uid
jint uid = -1;
if (protocol == IPPROTO_TCP || protocol == IPPROTO_UDP) {
// Sleep 10 ms
struct timespec tim, tim2;
tim.tv_sec = 0;
tim.tv_nsec = 10000000L;
nanosleep(&tim, &tim2);
// Lookup uid
uid = getUid(protocol, version, saddr, sport);
if (uid < 0 && version == 4) {
int8_t saddr128[16];
memset(saddr128, 0, 10);
saddr128[10] = 0xFF;
saddr128[11] = 0xFF;
memcpy(saddr128 + 12, saddr, 4);
uid = getUid(protocol, 6, saddr128, sport);
}
}
__android_log_print(ANDROID_LOG_DEBUG, TAG,
"Packet v%d %s/%u -> %s/%u proto %d flags %s uid %d",
version, source, sport, dest, dport, protocol, flags, uid);
if (protocol == IPPROTO_TCP)
handle_tcp(env, instance, args, buffer, length);
// Call back
jclass cls = (*env)->GetObjectClass(env, instance);
jmethodID mid = (*env)->GetMethodID(env, cls, "logPacket",
"(ILjava/lang/String;ILjava/lang/String;IILjava/lang/String;IZ)V");
if (mid == 0)
__android_log_print(ANDROID_LOG_ERROR, TAG, "logPacket not found");
else {
jboolean allowed = 0;
jstring jsource = (*env)->NewStringUTF(env, source);
jstring jdest = (*env)->NewStringUTF(env, dest);
jstring jflags = (*env)->NewStringUTF(env, flags);
(*env)->CallVoidMethod(env, instance, mid,
version,
jsource, sport,
jdest, dport,
protocol, jflags,
uid, allowed);
(*env)->DeleteLocalRef(env, jsource);
(*env)->DeleteLocalRef(env, jdest);
(*env)->DeleteLocalRef(env, jflags);
jthrowable ex = (*env)->ExceptionOccurred(env);
if (ex) {
(*env)->ExceptionDescribe(env);
(*env)->ExceptionClear(env);
(*env)->DeleteLocalRef(env, ex);
}
}
}
jint getUid(const int protocol, const int version, const void *saddr, const uint16_t sport) {
char line[250];
int fields;
int32_t addr32;
int8_t addr128[16];
uint16_t port;
jint uid = -1;
// Get proc file name
char *fn = NULL;
if (protocol == IPPROTO_TCP)
fn = (version == 4 ? "/proc/net/tcp" : "/proc/net/tcp6");
else if (protocol == IPPROTO_UDP)
fn = (version == 4 ? "/proc/net/udp" : "/proc/net/udp6");
else
return -1;
// Open proc file
FILE *fd = fopen(fn, "r");
if (fd == NULL) {
__android_log_print(ANDROID_LOG_ERROR, TAG, "Error opening %s", fn);
return -1;
}
// Scan proc file
int i = 0;
while (fgets(line, sizeof(line), fd) != NULL) {
if (i++) {
if (version == 4)
fields = sscanf(line,
"%*d: %X:%X %*X:%*X %*X %*lX:%*lX %*X:%*X %*X %d %*d %*ld ",
&addr32, &port, &uid);
else
fields = sscanf(line,
"%*d: %8X%8X%8X%8X:%X %*X:%*X %*X %*lX:%*lX %*X:%*X %*X %d %*d %*ld ",
addr128, addr128 + 4, addr128 + 8, addr128 + 12, &port, &uid);
if (fields < 3) {
__android_log_print(ANDROID_LOG_ERROR, TAG, "Invalid field #%d: %s", fields, line);
break;
}
if (port == sport) {
if (version == 4) {
if (addr32 == *((int32_t *) saddr))
return uid;
}
else {
if (memcmp(addr128, saddr, (size_t) 16) == 0)
return uid;
}
}
}
}
fclose(fd);
return -1;
}
// TODO data types
// TODO endianess?
unsigned short checksum(unsigned short *addr, int len) {
register int sum = 0;
u_short answer = 0;
register u_short *w = addr;
register int nleft = len;
/*
* Our algorithm is simple, using a 32-bit accumulator (sum),
* we add sequential 16-bit words to it, and at the end, fold back
* all the carry bits from the top 16 bits into the lower 16 bits.
*/
while (nleft > 1) {
sum += *w++;
nleft -= 2;
}
/* mop up an odd byte, if necessary */
if (nleft == 1) {
*(u_char *) (&answer) = *(u_char *) w;
sum += answer;
}
/* add back carry outs from top 16 bits to low 16 bits */
sum = (sum >> 16) + (sum & 0xffff); /* add hi 16 to low 16 */
sum += (sum >> 16); /* add carry */
answer = ~sum; /* truncate to 16 bits */
return (answer);
}
void nsleep(const long ns) {
struct timespec tim, tim2;
tim.tv_sec = ns / 1000000000L;
tim.tv_nsec = ns % 1000000000L;
nanosleep(&tim, &tim2);
}
char hexout[250];
char *hex(const u_int8_t *data, const u_int16_t len) {
char hex_str[] = "0123456789ABCDEF";
//char *out;
//out = (char *) malloc(len * 3 + 1); // TODO free
hexout[len * 3] = 0;
for (size_t i = 0; i < len; i++) {
hexout[i * 3 + 0] = hex_str[(data[i] >> 4) & 0x0F];
hexout[i * 3 + 1] = hex_str[(data[i]) & 0x0F];
hexout[i * 3 + 2] = ' ';
}
return hexout;
}
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