Add GetFileOwner

src/libpsl-native/src/CMakeLists.txt

@@ -1,5 +1,6 @@
 add_library(psl-native SHARED
   getstat.cpp
+  getfileowner.cpp
   getcurrentprocessorid.cpp
   getusername.cpp
   getcomputername.cpp

src/libpsl-native/src/getfileowner.cpp

@@ -0,0 +1,105 @@
+//! @file getfileowner.cpp
+//! @author Andrew Schwartzmeyer <andschwa@microsoft.com>
+//! @brief returns the owner of a file
+
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <pwd.h>
+#include <string.h>
+#include <unistd.h>
+#include "getstat.h"
+#include "getfileowner.h"
+
+//! @brief GetFileOwner returns the owner of a file
+//!
+//! GetFileOwner
+//!
+//! @param[in] fileName
+//! @parblock
+//! A pointer to the buffer that contains the file name
+//!
+//! char* is marshaled as an LPStr, which on Linux is UTF-8.
+//! @endparblock
+//!
+//! @exception errno Passes these errors via errno to GetLastError:
+//! - ERROR_INVALID_PARAMETER: parameter is not valid
+//! - ERROR_FILE_NOT_FOUND: file does not exist
+//! - ERROR_ACCESS_DENIED: access is denied
+//! - ERROR_INVALID_ADDRESS: attempt to access invalid address
+//! - ERROR_STOPPED_ON_SYMLINK: too many symbolic links
+//! - ERROR_GEN_FAILURE: I/O error occurred
+//! - ERROR_INVALID_NAME: file provided is not a symbolic link
+//! - ERROR_INVALID_FUNCTION: incorrect function
+//! - ERROR_BAD_PATH_NAME: pathname is too long
+//! - ERROR_OUTOFMEMORY insufficient kernal memory
+//!
+//! @retval file owner, or NULL if unsuccessful
+//!
+char* GetFileOwner(const char* fileName)
+{
+    int32_t ret = 0;
+    errno = 0;
+
+    if (!fileName)
+    {
+        errno = ERROR_INVALID_PARAMETER;
+        return NULL;
+    }
+
+    struct stat fileStat;
+    ret = GetStat(fileName, &fileStat);
+    if (ret != 0)
+    {
+        return NULL;
+    }
+
+    struct passwd pwd;
+    struct passwd* result = NULL;
+    char* buf;
+
+    int buflen = sysconf(_SC_GETPW_R_SIZE_MAX);
+    if (buflen < 1)
+    {
+        buflen = 2048;
+    }
+
+allocate:
+    buf = (char*)calloc(buflen, sizeof(char));
+
+    ret = getpwuid_r(fileStat.st_uid, &pwd, buf, buflen, &result);
+
+    if (ret != 0)
+    {
+        switch(errno)
+        {
+        case ERANGE:
+            free(buf);
+            buflen *= 2;
+            goto allocate;
+        case ENOENT:
+        case ESRCH:
+        case EBADF:
+        case EPERM:
+            errno = ERROR_NO_SUCH_USER;
+            break;
+        case ENOMEM:
+            errno = ERROR_OUTOFMEMORY;
+            break;
+       default:
+            errno = ERROR_GEN_FAILURE;
+        }
+        return NULL;
+    }
+
+    // no result
+    if (result == NULL)
+    {
+        return NULL;
+    }
+
+    size_t userlen = strnlen(pwd.pw_name, buflen);
+    char* username = strndup(pwd.pw_name, userlen);
+    free(buf);
+    return username;
+}

src/libpsl-native/src/getfileowner.h

@@ -0,0 +1,9 @@
+#pragma once
+
+#include "pal.h"
+
+PAL_BEGIN_EXTERNC
+
+char* GetFileOwner(const char* fileName);
+
+PAL_END_EXTERNC