Add GetUserFromPid() to libpsl

And clean up some tests.

src/libpsl-native/src/CMakeLists.txt

@@ -1,6 +1,7 @@
 add_library(psl-native SHARED
   getstat.cpp
   getpwuid.cpp
+  getuserfrompid.cpp
   getfileowner.cpp
   getcurrentprocessorid.cpp
   getusername.cpp

src/libpsl-native/src/getuserfrompid.cpp

@@ -0,0 +1,47 @@
+#include <string>
+#include <sstream>
+#include <errno.h>
+#include <sys/sysctl.h>
+#include "pal.h"
+#include "getfileowner.h"
+#include "getpwuid.h"
+#include "getuserfrompid.h"
+
+char* GetUserFromPid(pid_t pid)
+{
+
+#if defined(__linux__)
+
+    // Get effective owner of pid from procfs
+    std::stringstream ss;
+    ss << "/proc/" << pid;
+    std::string path;
+    ss >> path;
+
+    return GetFileOwner(path.c_str());
+
+#elif defined(__APPLE__) && defined(__MACH__)
+
+    // Get effective owner of pid from sysctl
+    struct kinfo_proc oldp;
+    size_t oldlenp = sizeof(oldp);
+    int name[] = {CTL_KERN, KERN_PROC, KERN_PROC_PID, pid};
+    u_int namelen = sizeof(name)/sizeof(int);
+
+    // Read-only query
+    int ret = sysctl(name, namelen, &oldp, &oldlenp, NULL, 0);
+    if (ret != 0 || oldlenp == 0)
+    {
+        errno = ERROR_GEN_FAILURE;
+        return NULL;
+    }
+
+    return GetPwUid(oldp.kp_eproc.e_ucred.cr_uid);
+
+#else
+
+    return NULL;
+
+#endif
+
+}

src/libpsl-native/src/getuserfrompid.h

@@ -0,0 +1,9 @@
+#pragma once
+
+#include "pal.h"
+
+PAL_BEGIN_EXTERNC
+
+char* GetUserFromPid(pid_t pid);
+
+PAL_END_EXTERNC

src/libpsl-native/test/CMakeLists.txt

@@ -3,6 +3,7 @@ add_subdirectory(googletest)
 add_executable(psl-native-test
   test-getfileowner.cpp
   test-locale.cpp
+  test-getuserfrompid.cpp
   test-getcurrentprocessid.cpp
   test-getusername.cpp
   test-getcomputername.cpp

src/libpsl-native/test/test-getfileowner.cpp

@@ -7,25 +7,18 @@
 #include <unistd.h>
 #include "getfileowner.h"
 
-using namespace std;
-
-//! Test fixture for GetFileOwner
-class GetFileOwnerTest : public ::testing::Test
+TEST(GetFileOwnerTest, CanGetOwnerOfRoot)
 {
-};
-
-TEST_F(GetFileOwnerTest, CanGetOwnerOfRoot)
-{
-    ASSERT_STREQ(GetFileOwner("/"), "root");
+    EXPECT_STREQ(GetFileOwner("/"), "root");
 }
 
-TEST_F(GetFileOwnerTest, CannotGetOwnerOfFakeFile)
+TEST(GetFileOwnerTest, CannotGetOwnerOfFakeFile)
 {
     EXPECT_STREQ(GetFileOwner("SomeMadeUpFileNameThatDoesNotExist"), NULL);
     EXPECT_EQ(errno, ERROR_FILE_NOT_FOUND);
 }
 
-TEST_F(GetFileOwnerTest, ReturnsNullForNullInput)
+TEST(GetFileOwnerTest, ReturnsNullForNullInput)
 {
     EXPECT_STREQ(GetFileOwner(NULL), NULL);
     EXPECT_EQ(errno, ERROR_INVALID_PARAMETER);

src/libpsl-native/test/test-getuserfrompid.cpp

@@ -0,0 +1,13 @@
+//! @file test-getuserfrompid.cpp
+//! @author Andrew Schwartzmeyer <andschwa@microsoft.com>
+//! @brief Unit tests for GetUserFromPid
+
+#include <gtest/gtest.h>
+#include <pwd.h>
+#include "getuserfrompid.h"
+
+TEST(GetUserFromPid, Success)
+{
+    char* expected = getpwuid(geteuid())->pw_name;
+    EXPECT_STREQ(GetUserFromPid(getpid()), expected);
+}

src/libpsl-native/test/test-getusername.cpp

@@ -2,9 +2,6 @@
 //! @author Andrew Schwartzmeyer <andschwa@microsoft.com>
 //! @brief Unit tests for GetUserName
 
-#include <string>
-#include <vector>
-#include <unistd.h>
 #include <gtest/gtest.h>
 #include <pwd.h>
 #include "getusername.h"
@@ -12,6 +9,5 @@
 TEST(GetUserName, Success)
 {
     char* expected = getpwuid(geteuid())->pw_name;
-    ASSERT_TRUE(expected != NULL);
-    ASSERT_EQ(GetUserName(), std::string(expected));
+    EXPECT_STREQ(GetUserName(), expected);
 }