libandroidfw: introduce ExecuteBinary (POSIX only)

Introduce a wrapper around fork and exec.

Test: make libandroidfw_tests
Change-Id: Iff0de5319bb6bb101a3fbef6413dfb4e77198f11

4 files changed, 205 insertions, 0 deletions

diff --git a/libs/androidfw/Android.bp b/libs/androidfw/Android.bp
index e39926beee41..172970a924dd 100644
--- a/libs/androidfw/Android.bp
+++ b/libs/androidfw/Android.bp
@@ -48,6 +48,7 @@ cc_library {
         "LocaleData.cpp",
         "misc.cpp",
         "ObbFile.cpp",
+        "PosixUtils.cpp",
         "ResourceTypes.cpp",
         "ResourceUtils.cpp",
         "StreamingZipInflater.cpp",
@@ -152,6 +153,7 @@ cc_test {
             srcs: [
                 "tests/BackupData_test.cpp",
                 "tests/ObbFile_test.cpp",
+                "tests/PosixUtils_test.cpp",
             ],
             shared_libs: common_test_libs + ["libui"],
         },
diff --git a/libs/androidfw/PosixUtils.cpp b/libs/androidfw/PosixUtils.cpp
new file mode 100644
index 000000000000..df0dd7ce463d
--- /dev/null
+++ b/libs/androidfw/PosixUtils.cpp
@@ -0,0 +1,112 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#ifdef _WIN32
+// nothing to see here
+#else
+#include <memory>
+#include <string>
+#include <vector>
+
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include "android-base/logging.h"
+
+#include "androidfw/PosixUtils.h"
+
+namespace {
+
+std::unique_ptr<std::string> ReadFile(int fd) {
+  std::unique_ptr<std::string> str(new std::string());
+  char buf[1024];
+  ssize_t r;
+  while ((r = read(fd, buf, sizeof(buf))) > 0) {
+    str->append(buf, r);
+  }
+  if (r != 0) {
+    return nullptr;
+  }
+  return str;
+}
+
+}
+
+namespace android {
+namespace util {
+
+std::unique_ptr<ProcResult> ExecuteBinary(const std::vector<std::string>& argv) {
+  int stdout[2];  // stdout[0] read, stdout[1] write
+  if (pipe(stdout) != 0) {
+    PLOG(ERROR) << "pipe";
+    return nullptr;
+  }
+
+  int stderr[2];  // stdout[0] read, stdout[1] write
+  if (pipe(stderr) != 0) {
+    PLOG(ERROR) << "pipe";
+    close(stdout[0]);
+    close(stdout[1]);
+    return nullptr;
+  }
+
+  char const** argv0 = (char const**)malloc(sizeof(char*) * (argv.size() + 1));
+  for (size_t i = 0; i < argv.size(); i++) {
+    argv0[i] = argv[i].c_str();
+  }
+  argv0[argv.size()] = nullptr;
+  switch (fork()) {
+    case -1: // error
+      free(argv0);
+      PLOG(ERROR) << "fork";
+      return nullptr;
+    case 0: // child
+      close(stdout[0]);
+      if (dup2(stdout[1], STDOUT_FILENO) == -1) {
+        abort();
+      }
+      close(stderr[0]);
+      if (dup2(stderr[1], STDERR_FILENO) == -1) {
+        abort();
+      }
+      execvp(argv0[0], const_cast<char* const*>(argv0));
+      PLOG(ERROR) << "execv";
+      abort();
+    default: // parent
+      free(argv0);
+      close(stdout[1]);
+      close(stderr[1]);
+      int status;
+      wait(&status);
+      if (!WIFEXITED(status)) {
+          return nullptr;
+      }
+      std::unique_ptr<ProcResult> result(new ProcResult());
+      result->status = status;
+      const auto out = ReadFile(stdout[0]);
+      result->stdout = out ? *out : "";
+      close(stdout[0]);
+      const auto err = ReadFile(stderr[0]);
+      result->stderr = err ? *err : "";
+      close(stderr[0]);
+      return result;
+  }
+}
+
+} // namespace util
+} // namespace android
+#endif
diff --git a/libs/androidfw/include/androidfw/PosixUtils.h b/libs/androidfw/include/androidfw/PosixUtils.h
new file mode 100644
index 000000000000..8fc3ee2733c7
--- /dev/null
+++ b/libs/androidfw/include/androidfw/PosixUtils.h
@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * 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 <memory>
+#include <string>
+#include <vector>
+
+namespace android {
+namespace util {
+
+struct ProcResult {
+  int status;
+  std::string stdout;
+  std::string stderr;
+};
+
+// Fork, exec and wait for an external process. Return nullptr if the process could not be launched,
+// otherwise a ProcResult containing the external process' exit status and captured stdout and
+// stderr.
+std::unique_ptr<ProcResult> ExecuteBinary(const std::vector<std::string>& argv);
+
+} // namespace util
+} // namespace android
diff --git a/libs/androidfw/tests/PosixUtils_test.cpp b/libs/androidfw/tests/PosixUtils_test.cpp
new file mode 100644
index 000000000000..cf97f87a4163
--- /dev/null
+++ b/libs/androidfw/tests/PosixUtils_test.cpp
@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * 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 <utility>
+
+#include "androidfw/PosixUtils.h"
+
+#include "TestHelpers.h"
+
+using ::testing::IsNull;
+using ::testing::NotNull;
+
+namespace android {
+namespace util {
+
+TEST(PosixUtilsTest, AbsolutePathToBinary) {
+  const auto result = ExecuteBinary({"/bin/date", "--help"});
+  ASSERT_THAT(result, NotNull());
+  ASSERT_EQ(result->status, 0);
+  ASSERT_EQ(result->stdout.find("usage: date "), 0);
+}
+
+TEST(PosixUtilsTest, RelativePathToBinary) {
+  const auto result = ExecuteBinary({"date", "--help"});
+  ASSERT_THAT(result, NotNull());
+  ASSERT_EQ(result->status, 0);
+  ASSERT_EQ(result->stdout.find("usage: date "), 0);
+}
+
+TEST(PosixUtilsTest, BadParameters) {
+  const auto result = ExecuteBinary({"/bin/date", "--this-parameter-is-not-supported"});
+  ASSERT_THAT(result, NotNull());
+  ASSERT_NE(result->status, 0);
+}
+
+TEST(PosixUtilsTest, NoSuchBinary) {
+  const auto result = ExecuteBinary({"/this/binary/does/not/exist"});
+  ASSERT_THAT(result, IsNull());
+}
+
+} // android
+} // util