Add ALTS fuzzer

216 files changed, 374 insertions, 95 deletions

diff --git a/test/core/end2end/fuzzers/api_fuzzer.cc b/test/core/end2end/fuzzers/api_fuzzer.cc
index 9ace7d04aa..36f257d6da 100644
--- a/test/core/end2end/fuzzers/api_fuzzer.cc
+++ b/test/core/end2end/fuzzers/api_fuzzer.cc
@@ -38,8 +38,14 @@
 #include "src/core/lib/surface/server.h"
 #include "src/core/lib/transport/metadata.h"
 #include "test/core/end2end/data/ssl_test_data.h"
+#include "test/core/util/fuzzer_util.h"
 #include "test/core/util/passthru_endpoint.h"
 
+using grpc_core::testing::grpc_fuzzer_get_next_byte;
+using grpc_core::testing::grpc_fuzzer_get_next_string;
+using grpc_core::testing::grpc_fuzzer_get_next_uint32;
+using grpc_core::testing::input_stream;
+
 ////////////////////////////////////////////////////////////////////////////////
 // logging
 
@@ -65,58 +71,20 @@ static gpr_timespec now_impl(gpr_clock_type clock_type) {
   return ts;
 }
 
-////////////////////////////////////////////////////////////////////////////////
-// input_stream: allows easy access to input bytes, and allows reading a little
-//               past the end (avoiding needing to check everywhere)
-
-typedef struct {
-  const uint8_t* cur;
-  const uint8_t* end;
-} input_stream;
-
-static uint8_t next_byte(input_stream* inp) {
-  if (inp->cur == inp->end) {
-    return 0;
-  }
-  return *inp->cur++;
-}
-
 static void end(input_stream* inp) { inp->cur = inp->end; }
 
-static char* read_string(input_stream* inp, bool* special) {
-  char* str = nullptr;
-  size_t cap = 0;
-  size_t sz = 0;
-  char c;
-  do {
-    if (cap == sz) {
-      cap = GPR_MAX(3 * cap / 2, cap + 8);
-      str = static_cast<char*>(gpr_realloc(str, cap));
-    }
-    c = static_cast<char>(next_byte(inp));
-    str[sz++] = c;
-  } while (c != 0 && c != 1);
-  if (special != nullptr) {
-    *special = (c == 1);
-  }
-  if (c == 1) {
-    str[sz - 1] = 0;
-  }
-  return str;
-}
-
 static void read_buffer(input_stream* inp, char** buffer, size_t* length,
                         bool* special) {
-  *length = next_byte(inp);
+  *length = grpc_fuzzer_get_next_byte(inp);
   if (*length == 255) {
     if (special != nullptr) *special = true;
-    *length = next_byte(inp);
+    *length = grpc_fuzzer_get_next_byte(inp);
   } else {
     if (special != nullptr) *special = false;
   }
   *buffer = static_cast<char*>(gpr_malloc(*length));
   for (size_t i = 0; i < *length; i++) {
-    (*buffer)[i] = static_cast<char>(next_byte(inp));
+    (*buffer)[i] = static_cast<char>(grpc_fuzzer_get_next_byte(inp));
   }
 }
 
@@ -128,7 +96,7 @@ static grpc_slice maybe_intern(grpc_slice s, bool intern) {
 
 static grpc_slice read_string_like_slice(input_stream* inp) {
   bool special;
-  char* s = read_string(inp, &special);
+  char* s = grpc_fuzzer_get_next_string(inp, &special);
   grpc_slice r = maybe_intern(grpc_slice_from_copied_string(s), special);
   gpr_free(s);
   return r;
@@ -146,39 +114,15 @@ static grpc_slice read_buffer_like_slice(input_stream* inp) {
 }
 
 static uint32_t read_uint22(input_stream* inp) {
-  uint8_t b = next_byte(inp);
+  uint8_t b = grpc_fuzzer_get_next_byte(inp);
   uint32_t x = b & 0x7f;
   if (b & 0x80) {
     x <<= 7;
-    b = next_byte(inp);
+    b = grpc_fuzzer_get_next_byte(inp);
     x |= b & 0x7f;
     if (b & 0x80) {
       x <<= 8;
-      x |= next_byte(inp);
-    }
-  }
-  return x;
-}
-
-static uint32_t read_uint32(input_stream* inp) {
-  uint8_t b = next_byte(inp);
-  uint32_t x = b & 0x7f;
-  if (b & 0x80) {
-    x <<= 7;
-    b = next_byte(inp);
-    x |= b & 0x7f;
-    if (b & 0x80) {
-      x <<= 7;
-      b = next_byte(inp);
-      x |= b & 0x7f;
-      if (b & 0x80) {
-        x <<= 7;
-        b = next_byte(inp);
-        x |= b & 0x7f;
-        if (b & 0x80) {
-          x = (x << 4) | (next_byte(inp) & 0x0f);
-        }
-      }
+      x |= grpc_fuzzer_get_next_byte(inp);
     }
   }
   return x;
@@ -193,22 +137,22 @@ static grpc_byte_buffer* read_message(input_stream* inp) {
 }
 
 static int read_int(input_stream* inp) {
-  return static_cast<int>(read_uint32(inp));
+  return static_cast<int>(grpc_fuzzer_get_next_uint32(inp));
 }
 
 static grpc_channel_args* read_args(input_stream* inp) {
-  size_t n = next_byte(inp);
+  size_t n = grpc_fuzzer_get_next_byte(inp);
   grpc_arg* args = static_cast<grpc_arg*>(gpr_malloc(sizeof(*args) * n));
   for (size_t i = 0; i < n; i++) {
-    switch (next_byte(inp)) {
+    switch (grpc_fuzzer_get_next_byte(inp)) {
       case 1:
         args[i].type = GRPC_ARG_STRING;
-        args[i].key = read_string(inp, nullptr);
-        args[i].value.string = read_string(inp, nullptr);
+        args[i].key = grpc_fuzzer_get_next_string(inp, nullptr);
+        args[i].value.string = grpc_fuzzer_get_next_string(inp, nullptr);
         break;
       case 2:
         args[i].type = GRPC_ARG_INTEGER;
-        args[i].key = read_string(inp, nullptr);
+        args[i].key = grpc_fuzzer_get_next_string(inp, nullptr);
         args[i].value.integer = read_int(inp);
         break;
       case 3:
@@ -249,10 +193,11 @@ static void cred_artifact_ctx_finish(cred_artifact_ctx* ctx) {
 static const char* read_cred_artifact(cred_artifact_ctx* ctx, input_stream* inp,
                                       const char** builtins,
                                       size_t num_builtins) {
-  uint8_t b = next_byte(inp);
+  uint8_t b = grpc_fuzzer_get_next_byte(inp);
   if (b == 0) return nullptr;
   if (b == 1)
-    return ctx->release[ctx->num_release++] = read_string(inp, nullptr);
+    return ctx->release[ctx->num_release++] =
+               grpc_fuzzer_get_next_string(inp, nullptr);
   if (b >= num_builtins + 1) {
     end(inp);
     return nullptr;
@@ -288,7 +233,7 @@ static grpc_call_credentials* read_call_creds(input_stream* inp, int depth) {
     end(inp);
     return nullptr;
   }
-  switch (next_byte(inp)) {
+  switch (grpc_fuzzer_get_next_byte(inp)) {
     default:
       end(inp);
       return nullptr;
@@ -339,7 +284,7 @@ static grpc_call_credentials* read_call_creds(input_stream* inp, int depth) {
 }
 
 static grpc_channel_credentials* read_channel_creds(input_stream* inp) {
-  switch (next_byte(inp)) {
+  switch (grpc_fuzzer_get_next_byte(inp)) {
     case 0:
       return read_ssl_channel_creds(inp);
       break;
@@ -673,7 +618,7 @@ static grpc_slice* add_slice_to_unref(call_state* call, grpc_slice s) {
 
 static void read_metadata(input_stream* inp, size_t* count,
                           grpc_metadata** metadata, call_state* cs) {
-  *count = next_byte(inp);
+  *count = grpc_fuzzer_get_next_byte(inp);
   if (*count) {
     *metadata =
         static_cast<grpc_metadata*>(gpr_malloc(*count * sizeof(**metadata)));
@@ -681,7 +626,7 @@ static void read_metadata(input_stream* inp, size_t* count,
     for (size_t i = 0; i < *count; i++) {
       (*metadata)[i].key = read_string_like_slice(inp);
       (*metadata)[i].value = read_buffer_like_slice(inp);
-      (*metadata)[i].flags = read_uint32(inp);
+      (*metadata)[i].flags = grpc_fuzzer_get_next_uint32(inp);
       add_slice_to_unref(cs, (*metadata)[i].key);
       add_slice_to_unref(cs, (*metadata)[i].value);
     }
@@ -811,7 +756,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
 
     grpc_timer_manager_tick();
 
-    switch (next_byte(&inp)) {
+    switch (grpc_fuzzer_get_next_byte(&inp)) {
       // terminate on bad bytes
       default:
         end(&inp);
@@ -838,13 +783,14 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
       // increment global time
       case 1: {
         g_now = gpr_time_add(
-            g_now, gpr_time_from_micros(read_uint32(&inp), GPR_TIMESPAN));
+            g_now, gpr_time_from_micros(grpc_fuzzer_get_next_uint32(&inp),
+                                        GPR_TIMESPAN));
         break;
       }
       // create an insecure channel
       case 2: {
         if (g_channel == nullptr) {
-          char* target = read_string(&inp, nullptr);
+          char* target = grpc_fuzzer_get_next_string(&inp, nullptr);
           char* target_uri;
           gpr_asprintf(&target_uri, "dns:%s", target);
           grpc_channel_args* args = read_args(&inp);
@@ -927,7 +873,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
       // check connectivity
       case 8: {
         if (g_channel != nullptr) {
-          uint8_t try_to_connect = next_byte(&inp);
+          uint8_t try_to_connect = grpc_fuzzer_get_next_byte(&inp);
           if (try_to_connect == 0 || try_to_connect == 1) {
             grpc_channel_check_connectivity_state(g_channel, try_to_connect);
           } else {
@@ -946,7 +892,8 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
           if (st != GRPC_CHANNEL_SHUTDOWN) {
             gpr_timespec deadline = gpr_time_add(
                 gpr_now(GPR_CLOCK_REALTIME),
-                gpr_time_from_micros(read_uint32(&inp), GPR_TIMESPAN));
+                gpr_time_from_micros(grpc_fuzzer_get_next_uint32(&inp),
+                                     GPR_TIMESPAN));
             grpc_channel_watch_connectivity_state(
                 g_channel, st, deadline, cq,
                 create_validator(validate_connectivity_watch,
@@ -971,7 +918,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
           }
           parent_call = g_active_call->call;
         }
-        uint32_t propagation_mask = read_uint32(&inp);
+        uint32_t propagation_mask = grpc_fuzzer_get_next_uint32(&inp);
         grpc_slice method = read_string_like_slice(&inp);
         if (GRPC_SLICE_LENGTH(method) == 0) {
           ok = false;
@@ -979,7 +926,8 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
         grpc_slice host = read_string_like_slice(&inp);
         gpr_timespec deadline =
             gpr_time_add(gpr_now(GPR_CLOCK_REALTIME),
-                         gpr_time_from_micros(read_uint32(&inp), GPR_TIMESPAN));
+                         gpr_time_from_micros(grpc_fuzzer_get_next_uint32(&inp),
+                                              GPR_TIMESPAN));
 
         if (ok) {
           call_state* cs = new_call(g_active_call, CLIENT);
@@ -1005,7 +953,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
           end(&inp);
           break;
         }
-        size_t num_ops = next_byte(&inp);
+        size_t num_ops = grpc_fuzzer_get_next_byte(&inp);
         if (num_ops > 6) {
           end(&inp);
           break;
@@ -1019,7 +967,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
         uint8_t has_ops = 0;
         for (i = 0; i < num_ops; i++) {
           op = &ops[i];
-          switch (next_byte(&inp)) {
+          switch (grpc_fuzzer_get_next_byte(&inp)) {
             default:
               /* invalid value */
               op->op = (grpc_op_type)-1;
@@ -1060,7 +1008,8 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
                   &op->data.send_status_from_server.trailing_metadata,
                   g_active_call);
               op->data.send_status_from_server.status =
-                  static_cast<grpc_status_code>(next_byte(&inp));
+                  static_cast<grpc_status_code>(
+                      grpc_fuzzer_get_next_byte(&inp));
               op->data.send_status_from_server.status_details =
                   add_slice_to_unref(g_active_call,
                                      read_buffer_like_slice(&inp));
@@ -1097,7 +1046,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
               break;
           }
           op->reserved = nullptr;
-          op->flags = read_uint32(&inp);
+          op->flags = grpc_fuzzer_get_next_uint32(&inp);
         }
         if (ok) {
           validator* v = make_finished_batch_validator(g_active_call, has_ops);
@@ -1160,14 +1109,14 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
       }
       // enable a tracer
       case 17: {
-        char* tracer = read_string(&inp, nullptr);
+        char* tracer = grpc_fuzzer_get_next_string(&inp, nullptr);
         grpc_tracer_set_enabled(tracer, 1);
         gpr_free(tracer);
         break;
       }
       // disable a tracer
       case 18: {
-        char* tracer = read_string(&inp, nullptr);
+        char* tracer = grpc_fuzzer_get_next_string(&inp, nullptr);
         grpc_tracer_set_enabled(tracer, 0);
         gpr_free(tracer);
         break;
@@ -1209,7 +1158,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
       // create a secure channel
       case 22: {
         if (g_channel == nullptr) {
-          char* target = read_string(&inp, nullptr);
+          char* target = grpc_fuzzer_get_next_string(&inp, nullptr);
           char* target_uri;
           gpr_asprintf(&target_uri, "dns:%s", target);
           grpc_channel_args* args = read_args(&inp);
diff --git a/test/core/security/BUILD b/test/core/security/BUILD
index 9db73b9123..70bcc8c9c3 100644
--- a/test/core/security/BUILD
+++ b/test/core/security/BUILD
@@ -21,6 +21,18 @@ grpc_package(name = "test/core/security")
 load("//test/core/util:grpc_fuzzer.bzl", "grpc_fuzzer")
 
 grpc_fuzzer(
+    name = "alts_credentials_fuzzer",
+    srcs = ["alts_credentials_fuzzer.cc"],
+    language = "C++",
+    corpus = "corpus/alts_credentials_corpus",
+    deps = [
+        "//:gpr",
+        "//:grpc",
+        "//test/core/util:grpc_test_util",
+    ],
+)
+
+grpc_fuzzer(
     name = "ssl_server_fuzzer",
     srcs = ["ssl_server_fuzzer.cc"],
     language = "C++",
diff --git a/test/core/security/alts_credentials_fuzzer.cc b/test/core/security/alts_credentials_fuzzer.cc
new file mode 100644
index 0000000000..bf18f0a589
--- /dev/null
+++ b/test/core/security/alts_credentials_fuzzer.cc
@@ -0,0 +1,120 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include <string.h>
+
+#include <grpc/grpc.h>
+#include <grpc/grpc_security.h>
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/string_util.h>
+#include "test/core/util/fuzzer_util.h"
+#include "test/core/util/memory_counters.h"
+
+#include "src/core/lib/gpr/env.h"
+#include "src/core/lib/security/credentials/alts/alts_credentials.h"
+#include "src/core/lib/security/credentials/alts/check_gcp_environment.h"
+#include "src/core/lib/security/credentials/alts/grpc_alts_credentials_options.h"
+
+using grpc_core::testing::grpc_fuzzer_get_next_byte;
+using grpc_core::testing::grpc_fuzzer_get_next_string;
+using grpc_core::testing::input_stream;
+
+// Logging
+bool squelch = true;
+bool leak_check = true;
+
+static void dont_log(gpr_log_func_args* args) {}
+
+// Add a random number of target service accounts to client options.
+static void read_target_service_accounts(
+    input_stream* inp, grpc_alts_credentials_options* options) {
+  size_t n = grpc_fuzzer_get_next_byte(inp);
+  for (size_t i = 0; i < n; i++) {
+    char* service_account = grpc_fuzzer_get_next_string(inp, nullptr);
+    if (service_account != nullptr) {
+      grpc_alts_credentials_client_options_add_target_service_account(
+          options, service_account);
+      gpr_free(service_account);
+    }
+  }
+  // Added to improve code coverage.
+  grpc_alts_credentials_client_options_add_target_service_account(options,
+                                                                  nullptr);
+  grpc_alts_credentials_client_options_add_target_service_account(
+      nullptr, "this is service account");
+}
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+  char* grpc_trace_fuzzer = gpr_getenv("GRPC_TRACE_FUZZER");
+  if (squelch && grpc_trace_fuzzer == nullptr) {
+    gpr_set_log_function(dont_log);
+  }
+  gpr_free(grpc_trace_fuzzer);
+  struct grpc_memory_counters counters;
+  if (leak_check) {
+    grpc_memory_counters_init();
+  }
+  input_stream inp = {data, data + size};
+  grpc_init();
+  bool is_on_gcp = grpc_alts_is_running_on_gcp();
+  while (inp.cur != inp.end) {
+    bool enable_untrusted_alts = grpc_fuzzer_get_next_byte(&inp) & 0x01;
+    char* handshaker_service_url =
+        grpc_fuzzer_get_next_byte(&inp) & 0x01
+            ? grpc_fuzzer_get_next_string(&inp, nullptr)
+            : nullptr;
+    if (grpc_fuzzer_get_next_byte(&inp) & 0x01) {
+      // Test ALTS channel credentials.
+      grpc_alts_credentials_options* options =
+          grpc_alts_credentials_client_options_create();
+      read_target_service_accounts(&inp, options);
+      grpc_channel_credentials* cred = grpc_alts_credentials_create_customized(
+          options, handshaker_service_url, enable_untrusted_alts);
+      if (!enable_untrusted_alts && !is_on_gcp) {
+        GPR_ASSERT(cred == nullptr);
+      } else {
+        GPR_ASSERT(cred != nullptr);
+      }
+      grpc_channel_credentials_release(cred);
+      grpc_alts_credentials_options_destroy(options);
+    } else {
+      // Test ALTS server credentials.
+      grpc_alts_credentials_options* options =
+          grpc_alts_credentials_server_options_create();
+      grpc_server_credentials* cred =
+          grpc_alts_server_credentials_create_customized(
+              options, handshaker_service_url, enable_untrusted_alts);
+      if (!enable_untrusted_alts && !is_on_gcp) {
+        GPR_ASSERT(cred == nullptr);
+      } else {
+        GPR_ASSERT(cred != nullptr);
+      }
+      grpc_server_credentials_release(cred);
+      grpc_alts_credentials_options_destroy(options);
+    }
+    gpr_free(handshaker_service_url);
+  }
+  grpc_shutdown();
+  if (leak_check) {
+    counters = grpc_memory_counters_snapshot();
+    grpc_memory_counters_destroy();
+    GPR_ASSERT(counters.total_size_relative == 0);
+  }
+  return 0;
+}
diff --git a/test/core/security/corpus/alts_credentials_corpus/0149b46b88d583e05be0fb1423d10f2a14d36c48 b/test/core/security/corpus/alts_credentials_corpus/0149b46b88d583e05be0fb1423d10f2a14d36c48
new file mode 100644
index 0000000000..c062c7f179
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/0149b46b88d583e05be0fb1423d10f2a14d36c48
diff --git a/test/core/security/corpus/alts_credentials_corpus/047fc351e73f760d329d5a8845944720be9ce773 b/test/core/security/corpus/alts_credentials_corpus/047fc351e73f760d329d5a8845944720be9ce773
new file mode 100644
index 0000000000..d943cfeacd
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/047fc351e73f760d329d5a8845944720be9ce773
diff --git a/test/core/security/corpus/alts_credentials_corpus/04ef96c66d8222d1a2c07e6b2a6548e6a527042b b/test/core/security/corpus/alts_credentials_corpus/04ef96c66d8222d1a2c07e6b2a6548e6a527042b
new file mode 100644
index 0000000000..e7346f33ef
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/04ef96c66d8222d1a2c07e6b2a6548e6a527042b
diff --git a/test/core/security/corpus/alts_credentials_corpus/05a7e16c1d7f92111f43e9c777421879920e79a4 b/test/core/security/corpus/alts_credentials_corpus/05a7e16c1d7f92111f43e9c777421879920e79a4
new file mode 100644
index 0000000000..43b8b47d03
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/05a7e16c1d7f92111f43e9c777421879920e79a4
diff --git a/test/core/security/corpus/alts_credentials_corpus/063eb46f202fdfe7935c30ca38d7eb81c82db419 b/test/core/security/corpus/alts_credentials_corpus/063eb46f202fdfe7935c30ca38d7eb81c82db419
new file mode 100644
index 0000000000..5b30f12418
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/063eb46f202fdfe7935c30ca38d7eb81c82db419
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diff --git a/test/core/security/corpus/alts_credentials_corpus/087449740758b114d16790067707934479946bd6 b/test/core/security/corpus/alts_credentials_corpus/087449740758b114d16790067707934479946bd6
new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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ь





















~








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ѕ





ь














































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;













ь


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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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new file mode 100644
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index 0000000000..8e8b1e2001
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/e5a1ba11af830e9d2db201c5164f75747a85fe9b
diff --git a/test/core/security/corpus/alts_credentials_corpus/e6026ee0badf216b326443a5f708446b2f2e579f b/test/core/security/corpus/alts_credentials_corpus/e6026ee0badf216b326443a5f708446b2f2e579f
new file mode 100644
index 0000000000..a99014fa41
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/e6026ee0badf216b326443a5f708446b2f2e579f
diff --git a/test/core/security/corpus/alts_credentials_corpus/e6c7d2c0038fa1f03fc6590a726abc98f4c641f3 b/test/core/security/corpus/alts_credentials_corpus/e6c7d2c0038fa1f03fc6590a726abc98f4c641f3
new file mode 100644
index 0000000000..8f5a9f5b33
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/e6c7d2c0038fa1f03fc6590a726abc98f4c641f3
@@ -0,0 +1 @@
+ђi
\ No newline at end of file
diff --git a/test/core/security/corpus/alts_credentials_corpus/eafdef6a630bed71bd0e4f3d4a16b5fa0c920651 b/test/core/security/corpus/alts_credentials_corpus/eafdef6a630bed71bd0e4f3d4a16b5fa0c920651
new file mode 100644
index 0000000000..6fbe750e01
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/eafdef6a630bed71bd0e4f3d4a16b5fa0c920651
diff --git a/test/core/security/corpus/alts_credentials_corpus/ece985b9b82e27281514d460709d7edf8203ded7 b/test/core/security/corpus/alts_credentials_corpus/ece985b9b82e27281514d460709d7edf8203ded7
new file mode 100644
index 0000000000..c1243022a0
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/ece985b9b82e27281514d460709d7edf8203ded7
diff --git a/test/core/security/corpus/alts_credentials_corpus/edb8f4259f756c2c4bc731f05beaa36f992cf079 b/test/core/security/corpus/alts_credentials_corpus/edb8f4259f756c2c4bc731f05beaa36f992cf079
new file mode 100644
index 0000000000..1cc08a4d39
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/edb8f4259f756c2c4bc731f05beaa36f992cf079
diff --git a/test/core/security/corpus/alts_credentials_corpus/edce7778c2e1adb81dda3d057a6536759a7cb293 b/test/core/security/corpus/alts_credentials_corpus/edce7778c2e1adb81dda3d057a6536759a7cb293
new file mode 100644
index 0000000000..39b52cf971
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/edce7778c2e1adb81dda3d057a6536759a7cb293
@@ -0,0 +1 @@
++

\ No newline at end of file
diff --git a/test/core/security/corpus/alts_credentials_corpus/ee4040c0dd406dd616c49ed2c37b40478dabfe0f b/test/core/security/corpus/alts_credentials_corpus/ee4040c0dd406dd616c49ed2c37b40478dabfe0f
new file mode 100644
index 0000000000..48325e312e
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/ee4040c0dd406dd616c49ed2c37b40478dabfe0f
diff --git a/test/core/security/corpus/alts_credentials_corpus/ee69f2b380663d051a70f30fcfce9f79f5341e5a b/test/core/security/corpus/alts_credentials_corpus/ee69f2b380663d051a70f30fcfce9f79f5341e5a
new file mode 100644
index 0000000000..7e0ad2a61a
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/ee69f2b380663d051a70f30fcfce9f79f5341e5a
diff --git a/test/core/security/corpus/alts_credentials_corpus/efc6743e47274058771bb6eda1fefa017bde4a95 b/test/core/security/corpus/alts_credentials_corpus/efc6743e47274058771bb6eda1fefa017bde4a95
new file mode 100644
index 0000000000..4418e8ab73
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/efc6743e47274058771bb6eda1fefa017bde4a95
diff --git a/test/core/security/corpus/alts_credentials_corpus/f0038e54162000694d882b1acb80930c807b41d2 b/test/core/security/corpus/alts_credentials_corpus/f0038e54162000694d882b1acb80930c807b41d2
new file mode 100644
index 0000000000..292a5e4bd3
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/f0038e54162000694d882b1acb80930c807b41d2
diff --git a/test/core/security/corpus/alts_credentials_corpus/f1deb9e388c877337dabe92f31b01e2a019a10f4 b/test/core/security/corpus/alts_credentials_corpus/f1deb9e388c877337dabe92f31b01e2a019a10f4
new file mode 100644
index 0000000000..46464ee9c2
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/f1deb9e388c877337dabe92f31b01e2a019a10f4
diff --git a/test/core/security/corpus/alts_credentials_corpus/f3a09373e4d3c7310d372089e6deb15d6b22c198 b/test/core/security/corpus/alts_credentials_corpus/f3a09373e4d3c7310d372089e6deb15d6b22c198
new file mode 100644
index 0000000000..a974996100
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/f3a09373e4d3c7310d372089e6deb15d6b22c198
@@ -0,0 +1 @@
+ќвћў
\ No newline at end of file
diff --git a/test/core/security/corpus/alts_credentials_corpus/f3db7ef6495fa1ac5bb4db293fb38dd59122bb7c b/test/core/security/corpus/alts_credentials_corpus/f3db7ef6495fa1ac5bb4db293fb38dd59122bb7c
new file mode 100644
index 0000000000..8afc32bf9d
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/f3db7ef6495fa1ac5bb4db293fb38dd59122bb7c
@@ -0,0 +1,2 @@
+[џџ[џџџ	
+ЁŠ
\ No newline at end of file
diff --git a/test/core/security/corpus/alts_credentials_corpus/f434bb4ceecc573e085d4c3ef453ef01e93d9c89 b/test/core/security/corpus/alts_credentials_corpus/f434bb4ceecc573e085d4c3ef453ef01e93d9c89
new file mode 100644
index 0000000000..2b66a00cd8
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/f434bb4ceecc573e085d4c3ef453ef01e93d9c89
diff --git a/test/core/security/corpus/alts_credentials_corpus/f55bceaad42ddf9d2b37fdfca68255d29a696109 b/test/core/security/corpus/alts_credentials_corpus/f55bceaad42ddf9d2b37fdfca68255d29a696109
new file mode 100644
index 0000000000..a8eef8f96a
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/f55bceaad42ddf9d2b37fdfca68255d29a696109
@@ -0,0 +1 @@
+ђв


\ No newline at end of file
diff --git a/test/core/security/corpus/alts_credentials_corpus/f62ca5321428a5d23f3c804fb51eb4e65bc58716 b/test/core/security/corpus/alts_credentials_corpus/f62ca5321428a5d23f3c804fb51eb4e65bc58716
new file mode 100644
index 0000000000..0d80f7be69
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/f62ca5321428a5d23f3c804fb51eb4e65bc58716
diff --git a/test/core/security/corpus/alts_credentials_corpus/f7c6a558b8d0af64db2b139371a7af7068b01b92 b/test/core/security/corpus/alts_credentials_corpus/f7c6a558b8d0af64db2b139371a7af7068b01b92
new file mode 100644
index 0000000000..d46ea45bc4
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/f7c6a558b8d0af64db2b139371a7af7068b01b92
diff --git a/test/core/security/corpus/alts_credentials_corpus/faa1781e1444bba5b8c677bc5e2a38d023a1ec65 b/test/core/security/corpus/alts_credentials_corpus/faa1781e1444bba5b8c677bc5e2a38d023a1ec65
new file mode 100644
index 0000000000..013d565bb4
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/faa1781e1444bba5b8c677bc5e2a38d023a1ec65
@@ -0,0 +1 @@
+‚
\ No newline at end of file
diff --git a/test/core/security/corpus/alts_credentials_corpus/fceba33ada1dda05fccedfefd331c9a201f1a2e5 b/test/core/security/corpus/alts_credentials_corpus/fceba33ada1dda05fccedfefd331c9a201f1a2e5
new file mode 100644
index 0000000000..f3db26dc2f
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/fceba33ada1dda05fccedfefd331c9a201f1a2e5
@@ -0,0 +1 @@
+П
\ No newline at end of file
diff --git a/test/core/security/corpus/alts_credentials_corpus/fd668bef6fdaf7f3ffd58d8c60ce550476652e60 b/test/core/security/corpus/alts_credentials_corpus/fd668bef6fdaf7f3ffd58d8c60ce550476652e60
new file mode 100644
index 0000000000..dcefd99985
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/fd668bef6fdaf7f3ffd58d8c60ce550476652e60
diff --git a/test/core/security/corpus/alts_credentials_corpus/fdf06b928e37e7c4ae59a568b5723ad98bbed6e5 b/test/core/security/corpus/alts_credentials_corpus/fdf06b928e37e7c4ae59a568b5723ad98bbed6e5
new file mode 100644
index 0000000000..fe28d69b5f
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/fdf06b928e37e7c4ae59a568b5723ad98bbed6e5
diff --git a/test/core/security/corpus/alts_credentials_corpus/fe2fc5d499aeb2762387ef2e3ce939280813dec0 b/test/core/security/corpus/alts_credentials_corpus/fe2fc5d499aeb2762387ef2e3ce939280813dec0
new file mode 100644
index 0000000000..cb035e7101
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/fe2fc5d499aeb2762387ef2e3ce939280813dec0
diff --git a/test/core/security/corpus/alts_credentials_corpus/ff548d368b090409a138e5cc4afc7f43b4a3fbbd b/test/core/security/corpus/alts_credentials_corpus/ff548d368b090409a138e5cc4afc7f43b4a3fbbd
new file mode 100644
index 0000000000..caadbc0309
--- /dev/null
+++ b/test/core/security/corpus/alts_credentials_corpus/ff548d368b090409a138e5cc4afc7f43b4a3fbbd
diff --git a/test/core/util/BUILD b/test/core/util/BUILD
index 886cfddf86..f52570cde5 100644
--- a/test/core/util/BUILD
+++ b/test/core/util/BUILD
@@ -52,6 +52,7 @@ grpc_cc_library(
     name = "grpc_test_util_base",
     srcs = [
         "cmdline.cc",
+        "fuzzer_util.cc",
         "grpc_profiler.cc",
         "histogram.cc",
         "mock_endpoint.cc",
@@ -70,6 +71,7 @@ grpc_cc_library(
     ],
     hdrs = [
         "cmdline.h",
+        "fuzzer_util.h",
         "grpc_profiler.h",
         "histogram.h",
         "mock_endpoint.h",
diff --git a/test/core/util/fuzzer_util.cc b/test/core/util/fuzzer_util.cc
new file mode 100644
index 0000000000..29c9b8875f
--- /dev/null
+++ b/test/core/util/fuzzer_util.cc
@@ -0,0 +1,82 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "test/core/util/fuzzer_util.h"
+
+#include <grpc/support/alloc.h>
+
+#include "src/core/lib/gpr/useful.h"
+
+namespace grpc_core {
+namespace testing {
+
+uint8_t grpc_fuzzer_get_next_byte(input_stream* inp) {
+  if (inp->cur == inp->end) {
+    return 0;
+  }
+  return *inp->cur++;
+}
+
+char* grpc_fuzzer_get_next_string(input_stream* inp, bool* special) {
+  char* str = nullptr;
+  size_t cap = 0;
+  size_t sz = 0;
+  char c;
+  do {
+    if (cap == sz) {
+      cap = GPR_MAX(3 * cap / 2, cap + 8);
+      str = static_cast<char*>(gpr_realloc(str, cap));
+    }
+    c = static_cast<char>(grpc_fuzzer_get_next_byte(inp));
+    str[sz++] = c;
+  } while (c != 0 && c != 1);
+  if (special != nullptr) {
+    *special = (c == 1);
+  }
+  if (c == 1) {
+    str[sz - 1] = 0;
+  }
+  return str;
+}
+
+uint32_t grpc_fuzzer_get_next_uint32(input_stream* inp) {
+  uint8_t b = grpc_fuzzer_get_next_byte(inp);
+  uint32_t x = b & 0x7f;
+  if (b & 0x80) {
+    x <<= 7;
+    b = grpc_fuzzer_get_next_byte(inp);
+    x |= b & 0x7f;
+    if (b & 0x80) {
+      x <<= 7;
+      b = grpc_fuzzer_get_next_byte(inp);
+      x |= b & 0x7f;
+      if (b & 0x80) {
+        x <<= 7;
+        b = grpc_fuzzer_get_next_byte(inp);
+        x |= b & 0x7f;
+        if (b & 0x80) {
+          x = (x << 4) | (grpc_fuzzer_get_next_byte(inp) & 0x0f);
+        }
+      }
+    }
+  }
+  return x;
+}
+
+}  // namespace testing
+}  // namespace grpc_core
diff --git a/test/core/util/fuzzer_util.h b/test/core/util/fuzzer_util.h
new file mode 100644
index 0000000000..0e938399a1
--- /dev/null
+++ b/test/core/util/fuzzer_util.h
@@ -0,0 +1,49 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_TEST_CORE_UTIL_FUZZER_UTIL_H
+#define GRPC_TEST_CORE_UTIL_FUZZER_UTIL_H
+
+#include <stdint.h>
+
+namespace grpc_core {
+
+namespace testing {
+
+// Main struct for input_stream. It allows easy access to input
+// bytes, and allows reading a little past the end(avoiding
+// needing to check everywhere).
+typedef struct {
+  const uint8_t* cur;
+  const uint8_t* end;
+} input_stream;
+
+// get a byte from an input stream.
+uint8_t grpc_fuzzer_get_next_byte(input_stream* inp);
+
+// get a string and boolean values (if special is not null) from an input
+// stream.
+char* grpc_fuzzer_get_next_string(input_stream* inp, bool* special);
+
+// get a uint32 value from an input stream.
+uint32_t grpc_fuzzer_get_next_uint32(input_stream* inp);
+
+}  // namespace testing
+}  // namespace grpc_core
+
+#endif /* GRPC_TEST_CORE_UTIL_FUZZER_UTIL_H */