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#include "fuzz.h"
#include "dbutil.h"
size_t LLVMFuzzerMutate(uint8_t *Data, size_t Size, size_t MaxSize);
/* out_packets an array of num_out_packets*buffer, each of size RECV_MAX_PACKET_LEN */
static void fuzz_get_packets(buffer *inp, buffer **out_packets, unsigned int *num_out_packets) {
/* Skip any existing banner. Format is
SSH-protoversion-softwareversion SP comments CR LF
so we look for SSH-2. then a subsequent LF */
unsigned char* version = memmem(inp->data, inp->len, "SSH-2.", strlen("SSH-2."));
if (version) {
buf_incrpos(inp, version - inp->data);
unsigned char* newline = memchr(&inp->data[inp->pos], '\n', inp->len - inp->pos);
if (newline) {
buf_incrpos(inp, newline - &inp->data[inp->pos]+1);
} else {
/* Give up on any version string */
buf_setpos(inp, 0);
}
}
const unsigned int max_out_packets = *num_out_packets;
*num_out_packets = 0;
while (1) {
if (inp->pos + 4 > inp->len) {
/* End of input */
break;
}
if (*num_out_packets >= max_out_packets) {
/* End of output */
break;
}
/* Read packet */
unsigned int packet_len = buf_getint(inp);
if (packet_len > RECV_MAX_PACKET_LEN-4) {
/* Bad length, try skipping a single byte */
buf_decrpos(inp, 3);
continue;
}
packet_len = MIN(packet_len, inp->len - inp->pos);
/* Copy to output buffer. We're reusing buffers */
buffer* new_packet = out_packets[*num_out_packets];
(*num_out_packets)++;
buf_setlen(new_packet, 0);
buf_putint(new_packet, packet_len);
buf_putbytes(new_packet, buf_getptr(inp, packet_len), packet_len);
buf_incrpos(inp, packet_len);
}
}
/* Mutate in-place */
void buf_llvm_mutate(buffer *buf) {
/* Position it after packet_length and padding_length */
const unsigned int offset = 5;
if (buf->len < offset) {
return;
}
buf_setpos(buf, offset);
size_t max_size = buf->size - buf->pos;
size_t new_size = LLVMFuzzerMutate(buf_getwriteptr(buf, max_size),
buf->len - buf->pos, max_size);
buf_setpos(buf, 0);
buf_putint(buf, new_size);
buf_setlen(buf, offset + new_size);
}
static const char* FIXED_VERSION = "SSH-2.0-dbfuzz\r\n";
static const size_t MAX_FUZZ_PACKETS = 500;
/* XXX This might need tuning */
static const size_t MAX_OUT_SIZE = 50000;
/* Persistent buffers to avoid constant allocations */
static buffer *oup;
static buffer *alloc_packetA;
static buffer *alloc_packetB;
buffer* packets1[MAX_FUZZ_PACKETS];
buffer* packets2[MAX_FUZZ_PACKETS];
/* Allocate buffers once at startup.
'constructor' here so it runs before dbmalloc's interceptor */
static void alloc_static_buffers() __attribute__((constructor));
static void alloc_static_buffers() {
int i;
oup = buf_new(MAX_OUT_SIZE);
alloc_packetA = buf_new(RECV_MAX_PACKET_LEN);
alloc_packetB = buf_new(RECV_MAX_PACKET_LEN);
for (i = 0; i < MAX_FUZZ_PACKETS; i++) {
packets1[i] = buf_new(RECV_MAX_PACKET_LEN);
}
for (i = 0; i < MAX_FUZZ_PACKETS; i++) {
packets2[i] = buf_new(RECV_MAX_PACKET_LEN);
}
}
size_t LLVMFuzzerCustomMutator(uint8_t *Data, size_t Size,
size_t MaxSize, unsigned int Seed) {
buf_setlen(alloc_packetA, 0);
buf_setlen(alloc_packetB, 0);
buf_setlen(oup, 0);
unsigned int i;
unsigned short randstate[3] = {0,0,0};
memcpy(randstate, &Seed, sizeof(Seed));
// printhex("mutator input", Data, Size);
#if 0
/* 1% chance straight llvm mutate */
if (nrand48(randstate) % 100 == 0) {
return LLVMFuzzerMutate(Data, Size, MaxSize);
}
#endif
buffer inp_buf = {.data = Data, .size = Size, .len = Size, .pos = 0};
buffer *inp = &inp_buf;
/* Parse packets */
unsigned int num_packets = MAX_FUZZ_PACKETS;
buffer **packets = packets1;
fuzz_get_packets(inp, packets, &num_packets);
if (num_packets == 0) {
// gotta do something
memcpy(Data, FIXED_VERSION, MIN(strlen(FIXED_VERSION), MaxSize));
return LLVMFuzzerMutate(Data, Size, MaxSize);
}
/* Start output */
/* Put a new banner to output */
buf_putbytes(oup, FIXED_VERSION, strlen(FIXED_VERSION));
/* Iterate output */
for (i = 0; i < num_packets+1; i++) {
// These are pointers to output
buffer *out_packetA = NULL, *out_packetB = NULL;
buf_setlen(alloc_packetA, 0);
buf_setlen(alloc_packetB, 0);
/* 5% chance each */
const int optA = nrand48(randstate) % 20;
if (optA == 0) {
/* Copy another */
unsigned int other = nrand48(randstate) % num_packets;
out_packetA = packets[other];
}
if (optA == 1) {
/* Mutate another */
unsigned int other = nrand48(randstate) % num_packets;
buffer *from = packets[other];
buf_putbytes(alloc_packetA, from->data, from->len);
out_packetA = alloc_packetA;
buf_llvm_mutate(out_packetA);
}
if (i < num_packets) {
int optB = nrand48(randstate) % 10;
if (optB == 1) {
/* 10% chance of drop */
/* Drop it */
// printf("%d drop\n", i);
} else if (optB <= 6) {
/* Mutate it, 50% chance */
// printf("%d mutate\n", i);
buffer *from = packets[nrand48(randstate) % num_packets];
buf_putbytes(alloc_packetB, from->data, from->len);
out_packetB = alloc_packetB;
buf_llvm_mutate(out_packetB);
} else {
/* Copy as-is */
out_packetB = packets[i];
// printf("%d as-is\n", i);
}
}
if (out_packetA && oup->len + out_packetA->len <= oup->size) {
buf_putbytes(oup, out_packetA->data, out_packetA->len);
}
if (out_packetB && oup->len + out_packetB->len <= oup->size) {
buf_putbytes(oup, out_packetB->data, out_packetB->len);
}
}
size_t ret_len = MIN(MaxSize, oup->len);
memcpy(Data, oup->data, ret_len);
// printhex("mutator done", Data, ret_len);
return ret_len;
}
size_t LLVMFuzzerCustomCrossOver(const uint8_t *Data1, size_t Size1,
const uint8_t *Data2, size_t Size2,
uint8_t *Out, size_t MaxOutSize,
unsigned int Seed) {
unsigned short randstate[3] = {0,0,0};
memcpy(randstate, &Seed, sizeof(Seed));
unsigned int i;
buffer inp_buf1 = {.data = (void*)Data1, .size = Size1, .len = Size1, .pos = 0};
buffer *inp1 = &inp_buf1;
buffer inp_buf2 = {.data = (void*)Data2, .size = Size2, .len = Size2, .pos = 0};
buffer *inp2 = &inp_buf2;
unsigned int num_packets1 = MAX_FUZZ_PACKETS;
fuzz_get_packets(inp1, packets1, &num_packets1);
unsigned int num_packets2 = MAX_FUZZ_PACKETS;
fuzz_get_packets(inp2, packets2, &num_packets2);
buf_setlen(oup, 0);
/* Put a new banner to output */
buf_putbytes(oup, FIXED_VERSION, strlen(FIXED_VERSION));
for (i = 0; i < num_packets1+1; i++) {
if (num_packets2 > 0 && nrand48(randstate) % 10 == 0) {
/* 10% chance of taking another packet at each position */
int other = nrand48(randstate) % num_packets2;
// printf("inserted other packet %d at %d\n", other, i);
buffer *otherp = packets2[other];
if (oup->len + otherp->len <= oup->size) {
buf_putbytes(oup, otherp->data, otherp->len);
}
}
if (i < num_packets1) {
buffer *thisp = packets1[i];
if (oup->len + thisp->len <= oup->size) {
buf_putbytes(oup, thisp->data, thisp->len);
}
}
}
size_t ret_len = MIN(MaxOutSize, oup->len);
memcpy(Out, oup->data, ret_len);
return ret_len;
}
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