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#include "fuzz.h"
#include "dbutil.h"
size_t LLVMFuzzerMutate(uint8_t *Data, size_t Size, size_t MaxSize);
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 */
//printf("at %d\n", inp->pos);
//printhex("lenget", buf_getptr(inp, 48), 48);
unsigned int packet_len = buf_getint(inp);
// printf("len %u\n", packet_len);
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 */
buffer* new_packet = buf_new(RECV_MAX_PACKET_LEN);
buf_putint(new_packet, packet_len);
buf_putbytes(new_packet, buf_getptr(inp, packet_len), packet_len);
buf_incrpos(inp, packet_len);
// printf("incr pos %d to %d\n", packet_len, inp->pos);
out_packets[*num_out_packets] = new_packet;
(*num_out_packets)++;
}
}
/* 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;
size_t LLVMFuzzerCustomMutator(uint8_t *Data, size_t Size,
size_t MaxSize, unsigned int Seed) {
/* Avoid some allocations */
/* XXX perhaps this complication isn't worthwhile */
static buffer buf_oup, buf_alloc_packetA, buf_alloc_packetB;
static buffer *oup = &buf_oup;
static buffer *alloc_packetA = &buf_alloc_packetA;
static buffer *alloc_packetB = &buf_alloc_packetB;
static int once = 1;
if (once) {
once = 0;
// malloc doesn't get intercepted by epoch deallocator
oup->size = MAX_OUT_SIZE;
alloc_packetA->size = RECV_MAX_PACKET_LEN;
alloc_packetB->size = RECV_MAX_PACKET_LEN;
oup->data = malloc(oup->size);
alloc_packetA->data = malloc(alloc_packetA->size);
alloc_packetB->data = malloc(alloc_packetB->size);
}
alloc_packetA->pos = 0;
alloc_packetA->len = 0;
alloc_packetB->pos = 0;
alloc_packetB->len = 0;
oup->pos = 0;
oup->len = 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 */
buffer* packets[MAX_FUZZ_PACKETS];
unsigned int num_packets = MAX_FUZZ_PACKETS;
fuzz_get_packets(inp, packets, &num_packets);
// printf("%d packets\n", 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;
alloc_packetA->pos = 0;
alloc_packetA->len = 0;
alloc_packetB->pos = 0;
alloc_packetB->len = 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];
// printf("%d copy another %d\n", i, 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);
// printf("%d mutate another %d\n", i, other);
}
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);
}
}
for (i = 0; i < num_packets; i++) {
buf_free(packets[i]);
}
size_t ret_len = MIN(MaxSize, oup->len);
memcpy(Data, oup->data, ret_len);
// printhex("mutator done", Data, ret_len);
return ret_len;
}
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