Improve diagnostics for tar archive processing faults.

diff --git a/ChangeLog b/ChangeLog
index 1372d29..3409db7 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,21 @@
+2013-06-27  Keith Marshall  <keithmarshall@users.sourceforge.net>
+
+       Improve diagnostics for tar archive processing faults.
+
+       * src/pkgproc.h (TAR_ARCHIVE_FORMAT_ERROR): New constant; define it.
+       (TAR_ARCHIVE_DATA_READ_ERROR, TAR_ARCHIVE_DATA_WRITE_ERROR): Likewise.
+
+       * src/tarproc.cpp (dmh_notify_archive_data_exhausted): New static
+       inline function; implement it.
+       (pkgTarArchiveProcessor::GetArchiveEntry) [short header]: Use it.
+       (pkgArchiveProcessor::ExtractFile) [TAR_ARCHIVE_DATA_READ_ERROR]:
+       Likewise, use it here; also explicitlycheck for, and diagnose...
+       [TAR_ARCHIVE_DATA_WRITE_ERROR]: ...this; also add a further catch all
+       case, to diagnose any other unexpected condition.
+       (pkgTarArchiveProcessor::GetArchiveEntry) [bad checksum]: Diagnose it.
+       (pkgTarArchiveProcessor::Process): Return appropriate status codes.
+       (pkgTarArchiveProcessor::ProcessEntityData): Likewise.
+
 2013-06-24  Keith Marshall  <keithmarshall@users.sourceforge.net>
 
        Facilitate version synchronisation for mingw-get-setup.

diff --git a/src/pkgproc.h b/src/pkgproc.h
index 9d104ad..964d8d7 100644 (file)
--- a/src/pkgproc.h
+++ b/src/pkgproc.h
@@ -137,7 +137,7 @@ union tar_archive_header
  */
 #define TAR_ENTITY_TYPE_FILE           '0'
 #define TAR_ENTITY_TYPE_LINK           '1'
-#define TAR_ENTITY_TYPE_SYMLINK                '2'
+#define TAR_ENTITY_TYPE_SYMLINK        '2'
 #define TAR_ENTITY_TYPE_CHRDEV         '3'
 #define TAR_ENTITY_TYPE_BLKDEV         '4'
 #define TAR_ENTITY_TYPE_DIRECTORY      '5'
@@ -146,7 +146,13 @@ union tar_archive_header
 /* Some older style tar archives may use '\0' as an alternative to '0',
  * to identify an archive entry representing a regular file.
  */
-#define TAR_ENTITY_TYPE_ALTFILE                '\0'
+#define TAR_ENTITY_TYPE_ALTFILE        '\0'
+
+/* Specify classification codes for tar archive processing errors.
+ */
+#define TAR_ARCHIVE_DATA_READ_ERROR    -1
+#define TAR_ARCHIVE_DATA_WRITE_ERROR   -2
+#define TAR_ARCHIVE_FORMAT_ERROR       -3
 
 class pkgTarArchiveProcessor : public pkgArchiveProcessor
 {

diff --git a/src/tarproc.cpp b/src/tarproc.cpp
index eef9e3a..800d94f 100644 (file)
--- a/src/tarproc.cpp
+++ b/src/tarproc.cpp
@@ -68,6 +68,15 @@ int pkgArchiveProcessor::CreateExtractionDirectory( const char *pathname )
   return status;
 }
 
+static inline int dmh_notify_archive_data_exhausted( const char *context )
+{
+  /* Helper function to emit "premature end of archive" diagnostics.
+   */
+  return dmh_notify( DMH_ERROR,
+      "unexpected end of archive reading %s record\n", context
+    );
+}
+
 inline int pkgArchiveProcessor::SetOutputStream( const char *name, int mode )
 {
   /* Wrapper method to facilitate the set up of output streams
@@ -98,6 +107,19 @@ int pkgArchiveProcessor::ExtractFile( int fd, const char *pathname, int status )
        */
       unlink( pathname );
       dmh_notify( DMH_ERROR, "%s: extraction failed\n", pathname );
+      switch( status )
+      {
+       case TAR_ARCHIVE_DATA_READ_ERROR:
+         dmh_notify_archive_data_exhausted( "content" );
+         break;
+
+       case TAR_ARCHIVE_DATA_WRITE_ERROR:
+         dmh_notify( DMH_ERROR, "write error extracting file content\n" );
+         break;
+
+       default:
+         dmh_notify( DMH_ERROR, "unexpected fault; status = %d\n", status );
+      }
     }
   }
   /* Finally, we pass the original status value back to the caller.
@@ -249,9 +271,10 @@ int pkgTarArchiveProcessor::GetArchiveEntry()
 
   if( count < sizeof( header ) )
   {
-    /* Failed to read a complete header; return error code.
+    /* Failed to read a complete header; diagnose and return error code.
      */
-    return -1;
+    dmh_notify_archive_data_exhausted( "header" );
+    return TAR_ARCHIVE_DATA_READ_ERROR;
   }
 
   while( count-- )
@@ -280,9 +303,16 @@ int pkgTarArchiveProcessor::GetArchiveEntry()
       }
       /* After computing the checksum for a non-zero header,
        * verify it against the value recorded in the checksum field;
-       * return +1 for a successful match, or -2 for failure.
+       * return +1 for a successful match...
+       */
+      if( sum == octval( header.field.chksum ) )
+               return 1;
+
+      /* ...otherwise diagnose checksum validation failure, and
+       * return the fault status.
        */
-      return (sum == octval( header.field.chksum )) ? 1 : -2;
+      dmh_notify( DMH_ERROR, "checksum validation failed\n" );
+      return TAR_ARCHIVE_FORMAT_ERROR;
     }
 
   /* If we get to here, then the inner loop was never entered;
@@ -297,7 +327,8 @@ int pkgTarArchiveProcessor::Process()
   /* Generic method for reading tar archives, and extracting their
    * content; loops over each archive entry in turn...
    */
-  while( GetArchiveEntry() > 0 )
+  int status;
+  while( (status = GetArchiveEntry()) > 0 )
   {
     char *prefix = *header.field.prefix ? header.field.prefix : NULL;
     char *name = header.field.name;
@@ -312,14 +343,19 @@ int pkgTarArchiveProcessor::Process()
     {
       /* Extract the full pathname from the data of this entry.
        */
-      longname = EntityDataAsString();
-      if( !longname )
+      if( (longname = EntityDataAsString()) == NULL )
+      {
         dmh_notify( DMH_ERROR, "Unable to read a long name entry\n" );
+       return TAR_ARCHIVE_FORMAT_ERROR;
+      }
 
       /* Read the entry for which this long name is intended.
        */
       if( GetArchiveEntry() <= 0 )
+      {
         dmh_notify( DMH_ERROR, "Expected a new entry after a long name entry\n" );
+       return TAR_ARCHIVE_FORMAT_ERROR;
+      }
 
       /* Use the previously determined long name as the pathname for this entry.
        */
@@ -448,7 +484,7 @@ int pkgTarArchiveProcessor::ProcessEntityData( int fd )
        * Failure to fully populate the transfer buffer, (i.e. a short
        * read), indicates a corrupt archive; bail out immediately.
        */
-      return -1;
+      return TAR_ARCHIVE_DATA_READ_ERROR;
 
     /* When the number of actual data bytes expected is fewer than the
      * total number of bytes in the transfer buffer...
@@ -470,7 +506,7 @@ int pkgTarArchiveProcessor::ProcessEntityData( int fd )
        * An extraction error occurred; set the status code to
        * indicate failure.
        */
-      status = -2;
+      status = TAR_ARCHIVE_DATA_WRITE_ERROR;
 
     /* Adjust the count of remaining unprocessed data bytes, and begin
      * a new processing cycle, to capture any which may be present.