Mercurial > dropbear
changeset 1767:3e1e1f82eba6
Preallocate memory for sshpacketmutator. Add fuzzer-client_mutator_nomaths
| author | Matt Johnston <matt@ucc.asn.au> |
|---|---|
| date | Mon, 26 Oct 2020 23:31:24 +0800 |
| parents | b14e0a19bcbe |
| children | 096a66e45212 |
| files | Makefile.in fuzz/fuzz-common.c fuzz/fuzz-sshpacketmutator.c fuzz/fuzzer-client_mutator_nomaths.c |
| diffstat | 4 files changed, 54 insertions(+), 60 deletions(-) [+] |
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--- a/Makefile.in Mon Oct 26 23:06:41 2020 +0800 +++ b/Makefile.in Mon Oct 26 23:31:24 2020 +0800 @@ -270,7 +270,7 @@ # list of fuzz targets FUZZ_TARGETS=fuzzer-preauth fuzzer-pubkey fuzzer-verify fuzzer-preauth_nomaths \ fuzzer-kexdh fuzzer-kexecdh fuzzer-kexcurve25519 fuzzer-client fuzzer-client_nomaths \ - fuzzer-client_mutator + fuzzer-client_mutator fuzzer-client_mutator_nomaths FUZZER_OPTIONS = $(addsuffix .options, $(FUZZ_TARGETS)) FUZZ_OBJS = $(addprefix fuzz/,$(addsuffix .o,$(FUZZ_TARGETS))) \ @@ -293,7 +293,8 @@ $(FUZZ_TARGETS): $(FUZZ_OBJS) $(allobjs) $(LIBTOM_DEPS) $(CXX) $(CXXFLAGS) fuzz/[email protected] $(LDFLAGS) $(allobjs) -o $@$(EXEEXT) $(LIBTOM_LIBS) $(LIBS) $(FUZZLIB) -lcrypt -fuzzer-client_mutator: allobjs += fuzz/fuzz-sshpacketmutator.o +# fuzzers that use the custom mutator +fuzzer-client_mutator fuzzer-client_mutator_nomaths: allobjs += fuzz/fuzz-sshpacketmutator.o fuzzer-%.options: Makefile echo "[libfuzzer]" > $@
--- a/fuzz/fuzz-common.c Mon Oct 26 23:06:41 2020 +0800 +++ b/fuzz/fuzz-common.c Mon Oct 26 23:31:24 2020 +0800 @@ -44,10 +44,14 @@ } else #endif + if (getenv("DROPBEAR_KEEP_STDERR")) { + fprintf(stderr, "Dropbear fuzzer: DROPBEAR_KEEP_STDERR, not disabling stderr output\n"); + } + else { - // fprintf(stderr, "Dropbear fuzzer: Disabling stderr output\n"); - // fuzz.stderr = fopen("/dev/null", "w"); - // assert(fuzz.stderr); + fprintf(stderr, "Dropbear fuzzer: Disabling stderr output\n"); + fuzz.stderr = fopen("/dev/null", "w"); + assert(fuzz.stderr); } }
--- a/fuzz/fuzz-sshpacketmutator.c Mon Oct 26 23:06:41 2020 +0800 +++ b/fuzz/fuzz-sshpacketmutator.c Mon Oct 26 23:31:24 2020 +0800 @@ -3,6 +3,7 @@ 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 @@ -33,10 +34,7 @@ } /* 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); @@ -44,15 +42,13 @@ } packet_len = MIN(packet_len, inp->len - inp->pos); - /* Copy to output buffer */ - buffer* new_packet = buf_new(RECV_MAX_PACKET_LEN); + /* 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); - // printf("incr pos %d to %d\n", packet_len, inp->pos); - - out_packets[*num_out_packets] = new_packet; - (*num_out_packets)++; } } @@ -78,32 +74,37 @@ /* 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) { - /* 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; + buf_setlen(alloc_packetA, 0); + buf_setlen(alloc_packetB, 0); + buf_setlen(oup, 0); unsigned int i; unsigned short randstate[3] = {0,0,0}; @@ -121,10 +122,9 @@ buffer *inp = &inp_buf; /* Parse packets */ - buffer* packets[MAX_FUZZ_PACKETS]; unsigned int num_packets = MAX_FUZZ_PACKETS; + buffer **packets = packets1; fuzz_get_packets(inp, packets, &num_packets); - // printf("%d packets\n", num_packets); if (num_packets == 0) { // gotta do something @@ -140,10 +140,8 @@ 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; + buf_setlen(alloc_packetA, 0); + buf_setlen(alloc_packetB, 0); /* 5% chance each */ const int optA = nrand48(randstate) % 20; @@ -151,7 +149,6 @@ /* 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 */ @@ -160,7 +157,6 @@ 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) { @@ -191,10 +187,6 @@ } } - 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); @@ -214,14 +206,12 @@ buffer inp_buf2 = {.data = (void*)Data2, .size = Size2, .len = Size2, .pos = 0}; buffer *inp2 = &inp_buf2; - buffer* packets1[MAX_FUZZ_PACKETS]; unsigned int num_packets1 = MAX_FUZZ_PACKETS; fuzz_get_packets(inp1, packets1, &num_packets1); - buffer* packets2[MAX_FUZZ_PACKETS]; unsigned int num_packets2 = MAX_FUZZ_PACKETS; fuzz_get_packets(inp2, packets2, &num_packets2); - buffer *oup = buf_new(MAX_OUT_SIZE); + buf_setlen(oup, 0); /* Put a new banner to output */ buf_putbytes(oup, FIXED_VERSION, strlen(FIXED_VERSION)); @@ -229,6 +219,7 @@ 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); @@ -242,16 +233,8 @@ } } - for (i = 0; i < num_packets1; i++) { - buf_free(packets1[i]); - } - for (i = 0; i < num_packets2; i++) { - buf_free(packets2[i]); - } - size_t ret_len = MIN(MaxOutSize, oup->len); memcpy(Out, oup->data, ret_len); - buf_free(oup); return ret_len; }