Added support for default credentials.

- Tested with new tool (print_default_creds_token) on:
  - workstation for env var and well known place.
  - GCE for compute engine default creds.
- I'd prefer the grpc_default_credentials_create() API to remain
  synchronous even though there may be an async call for gce detection
  on which we block.

6 files changed, 313 insertions, 4 deletions

diff --git a/src/core/httpcli/httpcli.c b/src/core/httpcli/httpcli.c
index d372e694e9..d2cf09a8df 100644
--- a/src/core/httpcli/httpcli.c
+++ b/src/core/httpcli/httpcli.c
@@ -216,6 +216,7 @@ static void on_resolved(void *arg, grpc_resolved_addresses *addresses) {
   gpr_log(GPR_DEBUG, "%s", __FUNCTION__);
   if (!addresses) {
     finish(req, 0);
+    return;
   }
   req->addresses = addresses;
   req->next_address = 0;
diff --git a/src/core/security/credentials.c b/src/core/security/credentials.c
index 42d1a900fc..7e72b238c8 100644
--- a/src/core/security/credentials.c
+++ b/src/core/security/credentials.c
@@ -1076,7 +1076,3 @@ grpc_credentials *grpc_iam_credentials_create(const char *token,
       c->md_ctx, GRPC_IAM_AUTHORITY_SELECTOR_METADATA_KEY, authority_selector);
   return &c->base;
 }
-
-/* -- Default credentials TODO(jboeuf). -- */
-
-grpc_credentials *grpc_default_credentials_create(void) { return NULL; }
diff --git a/src/core/security/credentials.h b/src/core/security/credentials.h
index 7b8929492b..9886afc9c0 100644
--- a/src/core/security/credentials.h
+++ b/src/core/security/credentials.h
@@ -60,8 +60,15 @@ typedef enum {
   "x-goog-iam-authorization-token"
 #define GRPC_IAM_AUTHORITY_SELECTOR_METADATA_KEY "x-goog-iam-authority-selector"
 
+#define GRPC_GOOGLE_CLOUD_SDK_CONFIG_DIRECTORY "gcloud"
+#define GRPC_GOOGLE_WELL_KNOWN_CREDENTIALS_FILE \
+  "application_default_credentials.json"
+
 /* --- grpc_credentials. --- */
 
+/* It is the caller's responsibility to gpr_free the result if not NULL. */
+char *grpc_get_well_known_credentials_file_path(void);
+
 typedef void (*grpc_credentials_metadata_cb)(void *user_data,
                                              grpc_mdelem **md_elems,
                                              size_t num_md,
diff --git a/src/core/security/credentials_posix.c b/src/core/security/credentials_posix.c
new file mode 100644
index 0000000000..9cffd64d31
--- /dev/null
+++ b/src/core/security/credentials_posix.c
@@ -0,0 +1,60 @@
+/*
+ *
+ * Copyright 2015, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_POSIX_FILE
+
+#include "src/core/security/credentials.h"
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/support/env.h"
+#include "src/core/support/string.h"
+
+char *grpc_get_well_known_credentials_file_path(void) {
+  char *result = NULL;
+  char *home = gpr_getenv("HOME");
+  if (home == NULL) {
+    gpr_log(GPR_ERROR, "Could not get HOME environment variable.");
+    return NULL;
+  }
+  gpr_asprintf(&result, "%s/.config/%s/%s", home,
+               GRPC_GOOGLE_CLOUD_SDK_CONFIG_DIRECTORY,
+               GRPC_GOOGLE_WELL_KNOWN_CREDENTIALS_FILE);
+  gpr_free(home);
+  return result;
+}
+
+#endif /* GPR_POSIX_FILE */
diff --git a/src/core/security/credentials_win32.c b/src/core/security/credentials_win32.c
new file mode 100644
index 0000000000..a8b711517b
--- /dev/null
+++ b/src/core/security/credentials_win32.c
@@ -0,0 +1,60 @@
+/*
+ *
+ * Copyright 2015, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#ifdef GPR_WIN32
+
+#include "src/core/security/credentials.h"
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/support/env.h"
+#include "src/core/support/string.h"
+
+char *grpc_get_well_known_credentials_file_path(void) {
+  char *result = NULL;
+  char *appdata_path = gpr_getenv("APPDATA");
+  if (appdata_path == NULL) {
+    gpr_log(GPR_ERROR, "Could not get APPDATA environment variable.");
+    return NULL;
+  }
+  gpr_asprintf(&result, "%s/%s/%s", appdata_path,
+               GRPC_GOOGLE_CLOUD_SDK_CONFIG_DIRECTORY,
+               GRPC_GOOGLE_WELL_KNOWN_CREDENTIALS_FILE);
+  gpr_free(appdata_path);
+  return result;
+}
+
+#endif /* GPR_WIN32 */
diff --git a/src/core/security/default_credentials.c b/src/core/security/default_credentials.c
new file mode 100644
index 0000000000..d7a974d8a1
--- /dev/null
+++ b/src/core/security/default_credentials.c
@@ -0,0 +1,185 @@
+/*
+ *
+ * Copyright 2015, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/security/credentials.h"
+
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/sync.h>
+
+#include "src/core/httpcli/httpcli.h"
+#include "src/core/support/env.h"
+#include "src/core/support/file.h"
+
+/* -- Constants. -- */
+
+#define GRPC_COMPUTE_ENGINE_DETECTION_HOST "metadata.google.internal"
+#define GRPC_GOOGLE_CREDENTIALS_ENV_VAR "GOOGLE_APPLICATION_CREDENTIALS"
+
+/* -- Default credentials. -- */
+
+static grpc_credentials *default_credentials = NULL;
+static int compute_engine_detection_done = 0;
+static gpr_mu g_mu;
+static gpr_once g_once = GPR_ONCE_INIT;
+
+static void init_default_credentials(void) {
+  gpr_mu_init(&g_mu);
+}
+
+typedef struct {
+  gpr_cv cv;
+  gpr_mu mu;
+  int is_done;
+  int success;
+} compute_engine_detector;
+
+static void on_compute_engine_detection_http_response(
+    void *user_data, const grpc_httpcli_response *response) {
+  compute_engine_detector *detector = (compute_engine_detector *)user_data;
+  if (response != NULL && response->status == 200 && response->hdr_count > 0) {
+    /* Internet providers can return a generic response to all requests, so
+       it is necessary to check that metadata header is present also. */
+    size_t i;
+    for (i = 0; i < response->hdr_count; i++) {
+      grpc_httpcli_header *header = &response->hdrs[i];
+      if (!strcmp(header->key, "Metadata-Flavor") &&
+          !strcmp(header->value, "Google")) {
+        detector->success = 1;
+        break;
+      }
+    }
+  }
+  gpr_mu_lock(&detector->mu);
+  detector->is_done = 1;
+  gpr_mu_unlock(&detector->mu);
+  gpr_cv_signal(&detector->cv);
+}
+
+static int is_stack_running_on_compute_engine(void) {
+  compute_engine_detector detector;
+  grpc_httpcli_request request;
+
+  /* The http call is local. If it takes more than one sec, it is for sure not
+     on compute engine. */
+  gpr_timespec max_detection_delay = {1, 0};
+
+  gpr_mu_init(&detector.mu);
+  gpr_cv_init(&detector.cv);
+  detector.is_done = 0;
+  detector.success = 0;
+
+  memset(&request, 0, sizeof(grpc_httpcli_request));
+  request.host = GRPC_COMPUTE_ENGINE_DETECTION_HOST;
+  request.path = "/";
+
+  grpc_httpcli_get(&request, gpr_time_add(gpr_now(), max_detection_delay),
+                   on_compute_engine_detection_http_response, &detector);
+
+  /* Block until we get the response. This is not ideal but this should only be
+     called once for the lifetime of the process by the default credentials. */
+  gpr_mu_lock(&detector.mu);
+  while (!detector.is_done) {
+    gpr_cv_wait(&detector.cv, &detector.mu, gpr_inf_future);
+  }
+  gpr_mu_unlock(&detector.mu);
+
+  gpr_mu_destroy(&detector.mu);
+  gpr_cv_destroy(&detector.cv);
+  return detector.success;
+}
+
+/* Takes ownership of creds_path if not NULL. */
+static grpc_credentials *create_jwt_creds_from_path(char *creds_path) {
+  grpc_credentials *result = NULL;
+  gpr_slice creds_data;
+  int file_ok = 0;
+  if (creds_path == NULL) return NULL;
+  creds_data = gpr_load_file(creds_path, &file_ok);
+  gpr_free(creds_path);
+  if (file_ok) {
+    result = grpc_jwt_credentials_create(
+        (const char *)GPR_SLICE_START_PTR(creds_data),
+        grpc_max_auth_token_lifetime);
+    gpr_slice_unref(creds_data);
+  }
+  return result;
+}
+
+grpc_credentials *grpc_default_credentials_create(void) {
+  grpc_credentials *result = NULL;
+  int serving_cached_credentials = 0;
+  gpr_once_init(&g_once, init_default_credentials);
+
+  gpr_mu_lock(&g_mu);
+
+  if (default_credentials != NULL) {
+    result = default_credentials;
+    serving_cached_credentials = 1;
+    goto end;
+  }
+
+  /* First, try the environment variable. */
+  result =
+      create_jwt_creds_from_path(gpr_getenv(GRPC_GOOGLE_CREDENTIALS_ENV_VAR));
+  if (result != NULL) goto end;
+
+  /* Then the well-known file. */
+  result = create_jwt_creds_from_path(
+      grpc_get_well_known_credentials_file_path());
+  if (result != NULL) goto end;
+
+  /* At last try to see if we're on compute engine (do the detection only once
+     since it requires a network test). */
+  if (!compute_engine_detection_done) {
+    int need_compute_engine_creds = is_stack_running_on_compute_engine();
+    compute_engine_detection_done = 1;
+    if (need_compute_engine_creds) {
+      result = grpc_compute_engine_credentials_create();
+    }
+  }
+
+end:
+  if (!serving_cached_credentials && result != NULL) {
+    /* Blend with default ssl credentials and add a global reference so that it
+       can be cached and re-served. */
+    result = grpc_composite_credentials_create(
+        grpc_ssl_credentials_create(NULL, NULL), result);
+    GPR_ASSERT(result != NULL);
+    default_credentials = grpc_credentials_ref(result);
+  }
+  gpr_mu_unlock(&g_mu);
+  return result;
+}