[tracker-miners: 2/4] tracker-extract: Use libz to process ps.gz files

[Sam Thursfield <sthursfield src gnome org>]

commit 3752c094f108ad7bca0fd429505126c52bc60a4b
Author: Andrea Azzarone <andrea azzarone canonical com>
Date:   Tue Apr 23 12:01:54 2019 +0100

    tracker-extract: Use libz to process ps.gz files
    
    Process ps.gz files using GZlibDecompressor instead of spawing gunzip. Because
    tracker-extract runs the file parsers inside a seccomp sandbox, spawning an
    external process during parsing is not a good idea because it leaves us with
    little control on which syscalls are used.
    
    Closes: https://gitlab.gnome.org/GNOME/tracker-miners/issues/61

 src/tracker-extract/tracker-extract-ps.c | 203 ++++++++-----------------------
 1 file changed, 51 insertions(+), 152 deletions(-)
---
diff --git a/src/tracker-extract/tracker-extract-ps.c b/src/tracker-extract/tracker-extract-ps.c
index 6d59e3d2f..207a32a89 100644
--- a/src/tracker-extract/tracker-extract-ps.c
+++ b/src/tracker-extract/tracker-extract-ps.c
@@ -18,13 +18,7 @@
  * Boston, MA  02110-1301, USA.
  */
 
-#include "config.h"
-
-#include <fcntl.h>
-#include <string.h>
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <unistd.h>
+#include <config.h>
 
 #include <glib.h>
 #include <glib/gstdio.h>
@@ -101,43 +95,30 @@ date_to_iso8601 (const gchar *date)
 }
 
 static TrackerResource *
-extract_ps_from_filestream (FILE *f)
+extract_ps_from_inputstream (GInputStream *stream)
 {
        TrackerResource *metadata;
+       g_autoptr(GDataInputStream) data_stream = NULL;
        gchar *line;
-       gsize length;
-       gssize read_char;
-       gsize accum;
-       gsize max_bytes;
-
-       line = NULL;
-       length = 0;
+       gsize length, accum, max_bytes;
+       g_autoptr(GError) error = NULL;
 
        metadata = tracker_resource_new (NULL);
        tracker_resource_add_uri (metadata, "rdf:type", "nfo:PaginatedTextDocument");
 
+       data_stream = g_data_input_stream_new (stream);
+
        /* 20 MiB should be enough! (original safe limit) */
        accum = 0;
        max_bytes = 20u << 20;
 
-       /* Reuse the same buffer for all lines. Must be dynamically allocated with
-        * malloc family methods as getline() may re-size it with realloc() */
-       length = 1024;
-       line = g_malloc (length);
-
-       /* Halt the whole when one of these conditions is met:
-        *  a) Reached max bytes to read
-        *  b) No more lines to read
-        */
        while ((accum < max_bytes) &&
-              (read_char = tracker_getline (&line, &length, f)) != -1) {
+              (line = g_data_input_stream_read_line (data_stream, &length, NULL, &error)) != NULL) {
                gboolean pageno_atend = FALSE;
                gboolean header_finished = FALSE;
 
                /* Update accumulated bytes read */
-               accum += read_char;
-
-               line[read_char - 1] = '\0';  /* overwrite '\n' char */
+               accum += length;
 
                if (!header_finished && strncmp (line, "%%Copyright:", 12) == 0) {
                        tracker_resource_set_string (metadata, "nie:copyright", line + 13);
@@ -148,13 +129,11 @@ extract_ps_from_filestream (FILE *f)
                        tracker_resource_set_relation (metadata, "nco:creator", creator);
                        g_object_unref (creator);
                } else if (!header_finished && strncmp (line, "%%CreationDate:", 15) == 0) {
-                       gchar *date;
+                       g_autofree gchar *date = NULL;
 
                        date = date_to_iso8601 (line + 16);
-                       if (date) {
+                       if (date)
                                tracker_resource_set_string (metadata, "nie:contentCreated", date);
-                               g_free (date);
-                       }
                } else if (strncmp (line, "%%Pages:", 8) == 0) {
                        if (strcmp (line + 9, "(atend)") == 0) {
                                pageno_atend = TRUE;
@@ -168,141 +147,66 @@ extract_ps_from_filestream (FILE *f)
                        header_finished = TRUE;
 
                        if (!pageno_atend) {
+                               g_free (line);
                                break;
                        }
                }
-       }
 
-       /* Deallocate the buffer */
-       if (line) {
                g_free (line);
        }
 
+       if (error != NULL)
+               g_warning ("Unexpected lack of content trying to read a line: %s", error->message);
+
        return metadata;
 }
 
-
-
 static TrackerResource *
-extract_ps (const gchar          *uri)
+extract_ps (const gchar *uri)
 {
-       TrackerResource *metadata;
-       FILE *f;
-       gchar *filename;
+       g_autoptr(GFile) file = NULL;
+       g_autoptr(GInputStream) stream = NULL;
+       g_autoptr(GError) error = NULL;
 
-       filename = g_filename_from_uri (uri, NULL, NULL);
-       f = tracker_file_open (filename);
-       g_free (filename);
+       g_debug ("Extracting PS '%s'...", uri);
 
-       if (!f) {
+       file = g_file_new_for_uri (uri);
+
+       stream = G_INPUT_STREAM (g_file_read (file, NULL, &error));
+       if (stream == NULL) {
+               g_warning ("Could't not read file %s: %s", uri, error->message);
                return NULL;
        }
 
-       /* Extract from filestream! */
-       g_debug ("Extracting PS '%s'...", uri);
-       metadata = extract_ps_from_filestream (f);
-
-       tracker_file_close (f, FALSE);
-
-       return metadata;
+       return extract_ps_from_inputstream (stream);
 }
 
 #ifdef USING_UNZIPPSFILES
 
-#include <errno.h>
-#include <sys/time.h>
-#include <sys/resource.h>
+#include <zlib.h>
 
-static void
-spawn_child_func (gpointer user_data)
+static TrackerResource *
+extract_ps_gz (const gchar *uri)
 {
-       struct rlimit cpu_limit;
-       gint timeout = GPOINTER_TO_INT (user_data);
+       g_autoptr(GFile) file = NULL;
+       g_autoptr(GInputStream) stream, cstream = NULL;
+       g_autoptr(GConverter) converter = NULL;
+       g_autoptr(GError) error = NULL;
 
-       if (timeout > 0) {
-               /* set cpu limit */
-               getrlimit (RLIMIT_CPU, &cpu_limit);
-               cpu_limit.rlim_cur = timeout;
-               cpu_limit.rlim_max = timeout + 1;
-
-               if (setrlimit (RLIMIT_CPU, &cpu_limit) != 0) {
-                       g_critical ("Failed to set resource limit for CPU");
-               }
-
-               /* Have this as a precaution in cases where cpu limit has not
-                * been reached due to spawned app sleeping.
-                */
-               alarm (timeout + 2);
-       }
-
-       /* Set child's niceness to 19 */
-       errno = 0;
+       g_debug ("Extracting PS '%s'...", uri);
 
-       /* nice() uses attribute "warn_unused_result" and so complains
-        * if we do not check its returned value. But it seems that
-        * since glibc 2.2.4, nice() can return -1 on a successful call
-        * so we have to check value of errno too. Stupid...
-        */
-       if (nice (19) == -1 && errno) {
-               g_warning ("Failed to set nice value");
-       }
-}
+       file = g_file_new_for_uri (uri);
 
-static TrackerResource *
-extract_ps_gz (const gchar          *uri)
-{
-       TrackerResource *metadata = NULL;
-       FILE *fz;
-       gint fdz;
-       const gchar *argv[4];
-       gchar *filename;
-       GError *error = NULL;
-
-       filename = g_filename_from_uri (uri, NULL, NULL);
-
-       /* TODO: we should be using libz for this instead */
-
-       argv[0] = "gunzip";
-       argv[1] = "-c";
-       argv[2] = filename;
-       argv[3] = NULL;
-
-       /* Fork & spawn to gunzip the file */
-       if (!g_spawn_async_with_pipes (g_get_tmp_dir (),
-                                      (gchar **) argv,
-                                      NULL,
-                                      G_SPAWN_SEARCH_PATH | G_SPAWN_STDERR_TO_DEV_NULL,
-                                      spawn_child_func,
-                                      GINT_TO_POINTER (10),
-                                      NULL,
-                                      NULL,
-                                      &fdz,
-                                      NULL,
-                                      &error)) {
-               g_warning ("Couldn't fork & spawn to gunzip '%s': %s",
-                          uri, error ? error->message : NULL);
-               g_clear_error (&error);
-       }
-       /* Get FILE from FD */
-       else if ((fz = fdopen (fdz, "r")) == NULL) {
-               g_warning ("Couldn't open FILE from FD (%s)...", uri);
-               close (fdz);
-       }
-       /* Extract from filestream! */
-       else
-       {
-               g_debug ("Extracting compressed PS '%s'...", uri);
-               metadata = extract_ps_from_filestream (fz);
-#ifdef HAVE_POSIX_FADVISE
-               if (posix_fadvise (fdz, 0, 0, POSIX_FADV_DONTNEED) != 0)
-                       g_warning ("posix_fadvise() call failed: %m");
-#endif /* HAVE_POSIX_FADVISE */
-               fclose (fz);
+       stream = G_INPUT_STREAM (g_file_read (file, NULL, &error));
+       if (stream == NULL) {
+               g_warning ("Could't not read file %s: %s", uri, error->message);
+               return NULL;
        }
 
-       g_free (filename);
+       converter = G_CONVERTER (g_zlib_decompressor_new (G_ZLIB_COMPRESSOR_FORMAT_GZIP));
+       cstream = g_converter_input_stream_new (stream, converter);
 
-       return metadata;
+       return extract_ps_from_inputstream (cstream);
 }
 
 #endif /* USING_UNZIPPSFILES */
@@ -312,28 +216,23 @@ tracker_extract_get_metadata (TrackerExtractInfo *info)
 {
        TrackerResource *metadata;
        GFile *file;
-       gchar *uri;
+       g_autofree gchar *uri = NULL;
+       const char *mimetype;
 
        file = tracker_extract_info_get_file (info);
        uri = g_file_get_uri (file);
+       mimetype = tracker_extract_info_get_mimetype (info);
 
-       {
+       if (strcmp (mimetype, "application/x-gzpostscript") == 0) {
 #ifdef USING_UNZIPPSFILES
-               const char *mimetype;
-
-               mimetype = tracker_extract_info_get_mimetype (info);
-
-               if (strcmp (mimetype, "application/x-gzpostscript") == 0) {
-                       metadata = extract_ps_gz (uri);
-               } else
+               metadata = extract_ps_gz (uri);
+#else
+               metadata = NULL;
 #endif /* USING_UNZIPPSFILES */
-               {
-                       metadata = extract_ps (uri);
-               }
+       } else {
+               metadata = extract_ps (uri);
        }
 
-       g_free (uri);
-
        if (metadata) {
                tracker_extract_info_set_resource (info, metadata);
                g_object_unref (metadata);