Fuzzing module for various string operations, currently focusing on

encoding and decoding.

There are bunches of places where we don't want to invest in a full
fuzzer, but we would like to make sure that some string operation
can handle all its possible inputs.  This fuzzer uses the first byte
of its input to decide what to do with the rest of the input.  Right
now, all the possibilities are decoding a string, and seeing whether
it is decodeable.  If it is, we try to re-encode it and do the whole
thing again, to make sure we get the same result.

This turned up a lot of bugs in the key-value parser, and I think it
will help in other cases too.

Closes ticket 28808.

diff --git a/scripts/codegen/fuzzing_include_am.py b/scripts/codegen/fuzzing_include_am.py
index 3c948d87cfe642dbc7a6f5462f5a3145cf659f07..5b51158843a524d5be5278db672c34ae530460c1 100755 (executable)
--- a/scripts/codegen/fuzzing_include_am.py
+++ b/scripts/codegen/fuzzing_include_am.py
@@ -13,6 +13,7 @@ FUZZERS = """
        iptsv2
        microdesc
        socks
+       strops
        vrs
 """
 

diff --git a/src/test/fuzz/fuzz_strops.c b/src/test/fuzz/fuzz_strops.c
new file mode 100644 (file)
index 0000000..5da590a
--- /dev/null
+++ b/src/test/fuzz/fuzz_strops.c
@@ -0,0 +1,247 @@
+/* Copyright (c) 2018, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file fuzz_strops.c
+ * \brief Fuzzers for various string encoding/decoding operations
+ **/
+
+#include "orconfig.h"
+
+#include "lib/cc/torint.h"
+#include "lib/ctime/di_ops.h"
+#include "lib/encoding/binascii.h"
+#include "lib/encoding/cstring.h"
+#include "lib/encoding/kvline.h"
+#include "lib/encoding/confline.h"
+#include "lib/malloc/malloc.h"
+#include "lib/log/escape.h"
+#include "lib/log/util_bug.h"
+#include "lib/intmath/muldiv.h"
+
+#include "test/fuzz/fuzzing.h"
+
+#include <stdio.h>
+#include <string.h>
+
+int
+fuzz_init(void)
+{
+  return 0;
+}
+
+int
+fuzz_cleanup(void)
+{
+  return 0;
+}
+
+typedef struct chunk_t {
+  uint8_t *buf;
+  size_t len;
+} chunk_t;
+
+#define chunk_free(ch)                          \
+  FREE_AND_NULL(chunk_t, chunk_free_, (ch))
+
+static chunk_t *
+chunk_new(size_t len)
+{
+  chunk_t *ch = tor_malloc(sizeof(chunk_t));
+  ch->buf = tor_malloc(len);
+  ch->len = len;
+  return ch;
+}
+static void
+chunk_free_(chunk_t *ch)
+{
+  if (!ch)
+    return;
+  tor_free(ch->buf);
+  tor_free(ch);
+}
+static bool
+chunk_eq(const chunk_t *a, const chunk_t *b)
+{
+  return a->len == b->len && fast_memeq(a->buf, b->buf, a->len);
+}
+
+static chunk_t *
+b16_dec(const chunk_t *inp)
+{
+  chunk_t *ch = chunk_new(CEIL_DIV(inp->len, 2));
+  int r = base16_decode((char *)ch->buf, ch->len, (char *)inp->buf, inp->len);
+  if (r >= 0) {
+    ch->len = r;
+  } else {
+    chunk_free(ch);
+  }
+  return ch;
+}
+static chunk_t *
+b16_enc(const chunk_t *inp)
+{
+  chunk_t *ch = chunk_new(inp->len * 2 + 1);
+  base16_encode((char *)ch->buf, ch->len, (char*)inp->buf, inp->len);
+  return ch;
+}
+
+#if 0
+static chunk_t *
+b32_dec(const chunk_t *inp)
+{
+  chunk_t *ch = chunk_new(inp->len);//XXXX
+  int r = base32_decode((char *)ch->buf, ch->len, (char *)inp->buf, inp->len);
+  if (r >= 0) {
+    ch->len = r; // XXXX we need some way to get the actual length of
+                 // XXXX the output here.
+  } else {
+    chunk_free(ch);
+  }
+  return ch;
+}
+static chunk_t *
+b32_enc(const chunk_t *inp)
+{
+  chunk_t *ch = chunk_new(base32_encoded_size(inp->len));
+  base32_encode((char *)ch->buf, ch->len, (char*)inp->buf, inp->len);
+  ch->len = strlen((char *) ch->buf);
+  return ch;
+}
+#endif
+
+static chunk_t *
+b64_dec(const chunk_t *inp)
+{
+  chunk_t *ch = chunk_new(inp->len);//XXXX This could be shorter.
+  int r = base64_decode((char *)ch->buf, ch->len, (char *)inp->buf, inp->len);
+  if (r >= 0) {
+    ch->len = r;
+  } else {
+    chunk_free(ch);
+  }
+  return ch;
+}
+static chunk_t *
+b64_enc(const chunk_t *inp)
+{
+  chunk_t *ch = chunk_new(BASE64_BUFSIZE(inp->len));
+  base64_encode((char *)ch->buf, ch->len, (char *)inp->buf, inp->len, 0);
+  ch->len = strlen((char *) ch->buf);
+  return ch;
+}
+
+static chunk_t *
+c_dec(const chunk_t *inp)
+{
+  char *s = tor_memdup_nulterm(inp->buf, inp->len);
+  chunk_t *ch = tor_malloc(sizeof(chunk_t));
+  char *r = NULL;
+  (void) unescape_string(s, &r, &ch->len);
+  tor_free(s);
+  ch->buf = (uint8_t*) r;
+  if (!ch->buf) {
+    tor_free(ch);
+  }
+  return ch;
+}
+static chunk_t *
+c_enc(const chunk_t *inp)
+{
+  char *s = tor_memdup_nulterm(inp->buf, inp->len);
+  chunk_t *ch = tor_malloc(sizeof(chunk_t));
+  ch->buf = (uint8_t*)esc_for_log(s);
+  tor_free(s);
+  ch->len = strlen((char*)ch->buf);
+  return ch;
+}
+
+static int kv_flags = 0;
+static config_line_t *
+kv_dec(const chunk_t *inp)
+{
+  char *s = tor_memdup_nulterm(inp->buf, inp->len);
+  config_line_t *res = kvline_parse(s, kv_flags);
+  tor_free(s);
+  return res;
+}
+static chunk_t *
+kv_enc(const config_line_t *inp)
+{
+  char *s = kvline_encode(inp, kv_flags);
+  if (!s)
+    return NULL;
+  chunk_t *res = tor_malloc(sizeof(chunk_t));
+  res->buf = (uint8_t*)s;
+  res->len = strlen(s);
+  return res;
+}
+
+/* Given an encoder function, a decoder function, and a function to free
+ * the decoded object, check whether any string that successfully decoded
+ * will then survive an encode-decode-encode round-trip unchanged.
+ */
+#define ENCODE_ROUNDTRIP(E,D,FREE)              \
+  STMT_BEGIN {                                  \
+    bool err = false;                           \
+    a = D(&inp);                                \
+    if (!a)                                     \
+      return 0;                                 \
+    b = E(a);                                   \
+    tor_assert(b);                              \
+    c = D(b);                                   \
+    tor_assert(c);                              \
+    d = E(c);                                   \
+    tor_assert(d);                              \
+    if (!chunk_eq(b,d)) {                       \
+      printf("Unequal chunks: %s\n",            \
+             hex_str((char*)b->buf, b->len));   \
+      printf("             vs %s\n",            \
+             hex_str((char*)d->buf, d->len));   \
+      err = true;                               \
+    }                                           \
+    FREE(a);                                    \
+    chunk_free(b);                              \
+    FREE(c);                                    \
+    chunk_free(d);                              \
+    tor_assert(!err);                           \
+  } STMT_END
+
+int
+fuzz_main(const uint8_t *stdin_buf, size_t data_size)
+{
+  if (!data_size)
+    return 0;
+
+  chunk_t inp = { (uint8_t*)stdin_buf, data_size };
+  chunk_t *b=NULL,*d=NULL;
+  void *a=NULL,*c=NULL;
+
+  switch (stdin_buf[0]) {
+    case 0:
+      ENCODE_ROUNDTRIP(b16_enc, b16_dec, chunk_free_);
+      break;
+    case 1:
+      /*
+        XXXX see notes above about our base-32 functions.
+      ENCODE_ROUNDTRIP(b32_enc, b32_dec, chunk_free_);
+      */
+      break;
+    case 2:
+      ENCODE_ROUNDTRIP(b64_enc, b64_dec, chunk_free_);
+      break;
+    case 3:
+      ENCODE_ROUNDTRIP(c_enc, c_dec, chunk_free_);
+      break;
+    case 5:
+      kv_flags = KV_QUOTED|KV_OMIT_KEYS;
+      ENCODE_ROUNDTRIP(kv_enc, kv_dec, config_free_lines_);
+      break;
+    case 6:
+      kv_flags = 0;
+      ENCODE_ROUNDTRIP(kv_enc, kv_dec, config_free_lines_);
+      break;
+    }
+
+  return 0;
+}

diff --git a/src/test/fuzz/include.am b/src/test/fuzz/include.am
index 27eeced8c52854a7dced03188df79826e1ed1722..d0711f05d6306521e6129c69502fa6d02c83d6bf 100644 (file)
--- a/src/test/fuzz/include.am
+++ b/src/test/fuzz/include.am
@@ -152,6 +152,16 @@ src_test_fuzz_fuzz_socks_LDFLAGS = $(FUZZING_LDFLAG)
 src_test_fuzz_fuzz_socks_LDADD = $(FUZZING_LIBS)
 endif
 
+if UNITTESTS_ENABLED
+src_test_fuzz_fuzz_strops_SOURCES = \
+       src/test/fuzz/fuzzing_common.c \
+       src/test/fuzz/fuzz_strops.c
+src_test_fuzz_fuzz_strops_CPPFLAGS = $(FUZZING_CPPFLAGS)
+src_test_fuzz_fuzz_strops_CFLAGS = $(FUZZING_CFLAGS)
+src_test_fuzz_fuzz_strops_LDFLAGS = $(FUZZING_LDFLAG)
+src_test_fuzz_fuzz_strops_LDADD = $(FUZZING_LIBS)
+endif
+
 if UNITTESTS_ENABLED
 src_test_fuzz_fuzz_vrs_SOURCES = \
        src/test/fuzz/fuzzing_common.c \
@@ -176,6 +186,7 @@ FUZZERS = \
        src/test/fuzz/fuzz-iptsv2 \
        src/test/fuzz/fuzz-microdesc \
        src/test/fuzz/fuzz-socks \
+       src/test/fuzz/fuzz-strops \
        src/test/fuzz/fuzz-vrs
 endif
 
@@ -290,6 +301,15 @@ src_test_fuzz_lf_fuzz_socks_LDFLAGS = $(LIBFUZZER_LDFLAG)
 src_test_fuzz_lf_fuzz_socks_LDADD = $(LIBFUZZER_LIBS)
 endif
 
+if UNITTESTS_ENABLED
+src_test_fuzz_lf_fuzz_strops_SOURCES = \
+       $(src_test_fuzz_fuzz_strops_SOURCES)
+src_test_fuzz_lf_fuzz_strops_CPPFLAGS = $(LIBFUZZER_CPPFLAGS)
+src_test_fuzz_lf_fuzz_strops_CFLAGS = $(LIBFUZZER_CFLAGS)
+src_test_fuzz_lf_fuzz_strops_LDFLAGS = $(LIBFUZZER_LDFLAG)
+src_test_fuzz_lf_fuzz_strops_LDADD = $(LIBFUZZER_LIBS)
+endif
+
 if UNITTESTS_ENABLED
 src_test_fuzz_lf_fuzz_vrs_SOURCES = \
        $(src_test_fuzz_fuzz_vrs_SOURCES)
@@ -312,6 +332,7 @@ LIBFUZZER_FUZZERS = \
        src/test/fuzz/lf-fuzz-iptsv2 \
        src/test/fuzz/lf-fuzz-microdesc \
        src/test/fuzz/lf-fuzz-socks \
+       src/test/fuzz/lf-fuzz-strops \
        src/test/fuzz/lf-fuzz-vrs
 
 else
@@ -405,6 +426,13 @@ src_test_fuzz_liboss_fuzz_socks_a_CPPFLAGS = $(LIBOSS_FUZZ_CPPFLAGS)
 src_test_fuzz_liboss_fuzz_socks_a_CFLAGS = $(LIBOSS_FUZZ_CFLAGS)
 endif
 
+if UNITTESTS_ENABLED
+src_test_fuzz_liboss_fuzz_strops_a_SOURCES = \
+       $(src_test_fuzz_fuzz_strops_SOURCES)
+src_test_fuzz_liboss_fuzz_strops_a_CPPFLAGS = $(LIBOSS_FUZZ_CPPFLAGS)
+src_test_fuzz_liboss_fuzz_strops_a_CFLAGS = $(LIBOSS_FUZZ_CFLAGS)
+endif
+
 if UNITTESTS_ENABLED
 src_test_fuzz_liboss_fuzz_vrs_a_SOURCES = \
        $(src_test_fuzz_fuzz_vrs_SOURCES)
@@ -425,6 +453,7 @@ OSS_FUZZ_FUZZERS = \
        src/test/fuzz/liboss-fuzz-iptsv2.a \
        src/test/fuzz/liboss-fuzz-microdesc.a \
        src/test/fuzz/liboss-fuzz-socks.a \
+       src/test/fuzz/liboss-fuzz-strops.a \
        src/test/fuzz/liboss-fuzz-vrs.a
 
 else