[hurd] 67/70: exec: remove support for transparently ungziping executables

[Samuel Thibault]

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sthibault pushed a commit to branch upstream
in repository hurd.

commit b2e27fcee4cec98ffc39273ecfaa73aace9da2c3
Author: Justus Winter <address@hidden>
Date:   Thu Aug 15 18:41:51 2013 +0200

    exec: remove support for transparently ungziping executables
    
    Remove support for transparently ungziping executables from the exec
    server. The code in question makes the exec server unnecessarily
    complex and since the exec server is an essential process, crashing it
    makes /hurd/init crash the whole system.
    
    Since the gzip code is not thread-safe, all access to it is
    serialized, so there is a trivial way for one user to delay another
    users gzipped executables for some unspecified time.
    
    This can be accomplished by padding any program with easily compressed
    data, zipping it and executing it. Using such a program as an passive
    translator and then triggering its execution by the filesystem
    translator also stalls any requests to that filesystem (observed using
    the libdiskfs-based ext2fs).
    
    Since compressed executables cannot be mapped into the memory, they
    have to be uncompressed into allocated memory first. This is slower
    and any user with access to the exec server can make it allocate
    arbitrary amounts of memory. If the Hurd had proper memory accounting,
    this would probably be a way around it.
    
    So the compression support in exec seemingly creates various issues
    for little value, at least with the abundance of nonvolatile memory
    available today.
    
    * exec/Makefile: Remove gzip related files.
    * exec/exec.c: Remove anything #ifdef GZIPped.
    * exec/unzip.c: Move to libstore.
    * exec/crypt.h: Likewise.
    * exec/gzip.h: Likewise.
    * exec/inflate.c: Likewise.
    * exec/tailor.h: Likewise.
    * exec/util.c: Likewise.
    * libstore/Makefile: Remove the vpath magic for looking up the zip
      stuff.
---
 exec/Makefile                |    6 +-
 exec/exec.c                  |  138 ------------------------------------------
 libstore/Makefile            |    4 --
 {exec => libstore}/crypt.h   |    0
 {exec => libstore}/gzip.h    |    0
 {exec => libstore}/inflate.c |    0
 {exec => libstore}/tailor.h  |    0
 {exec => libstore}/unzip.c   |    0
 {exec => libstore}/util.c    |    0
 9 files changed, 1 insertion(+), 147 deletions(-)

diff --git a/exec/Makefile b/exec/Makefile
index 11d2875..890ee4b 100644
--- a/exec/Makefile
+++ b/exec/Makefile
@@ -21,12 +21,8 @@ dir := exec
 makemode := server
 
 SRCS = exec.c main.c hashexec.c hostarch.c
-#       $(gzip-sources)
 OBJS = main.o hostarch.o exec.o hashexec.o \
        execServer.o exec_startupServer.o
-#       $(gzip-objects)
-gzip-sources = unzip.c util.c inflate.c
-gzip-objects = $(gzip-sources:%.c=%.o)
 
 target = exec
 #targets = exec exec.static
@@ -38,6 +34,6 @@ exec-MIGSFLAGS = -imacros $(srcdir)/execmutations.h
 
 include ../Makeconf
 
-CPPFLAGS += # -DGZIP -DBFD
+CPPFLAGS += # -DBFD
 
 exec.static exec: $(OBJS) $(library_deps)
diff --git a/exec/exec.c b/exec/exec.c
index 201e629..fad9492 100644
--- a/exec/exec.c
+++ b/exec/exec.c
@@ -4,9 +4,6 @@
    Written by Roland McGrath.
 
    Can exec ELF format directly.
-   #ifdef GZIP
-   Can gunzip executables into core on the fly.
-   #endif
 
 This file is part of the GNU Hurd.
 
@@ -45,10 +42,6 @@ pthread_rwlock_t std_lock = PTHREAD_RWLOCK_INITIALIZER;
 
 #define        b2he()  a2he (errno)
 
-#ifdef GZIP
-static void check_gzip (struct execdata *);
-#endif
-
 /* Zero the specified region but don't crash the server if it faults.  */
 
 #include <hurd/sigpreempt.h>
@@ -720,118 +713,6 @@ load (task_t usertask, struct execdata *e)
   finish_mapping (e);
 }
 
-#ifdef GZIP
-/* Check the file for being a gzip'd image.  Return with ENOEXEC means not
-   a valid gzip file; return with another error means lossage in decoding;
-   return with zero means the file was uncompressed into memory which E now
-   points to, and `check' can be run again.  */
-
-static void
-check_gzip (struct execdata *earg)
-{
-  struct execdata *e = earg;
-  /* Entry points to unzip engine.  */
-  int get_method (int);
-  void unzip (int, int);
-  extern long int bytes_out;
-  /* Callbacks from unzip for I/O and error interface.  */
-  extern int (*unzip_read) (char *buf, size_t maxread);
-  extern void (*unzip_write) (const char *buf, size_t nwrite);
-  extern void (*unzip_read_error) (void);
-  extern void (*unzip_error) (const char *msg);
-
-  char *zipdata = NULL;
-  size_t zipdatasz = 0;
-  FILE *zipout = NULL;
-  jmp_buf ziperr;
-  off_t zipread_pos = 0;
-  int zipread (char *buf, size_t maxread)
-    {
-      char *contents = map (e, zipread_pos, 1);
-      size_t n;
-      if (contents == NULL)
-       {
-         errno = e->error;
-         return -1;
-       }
-      n = MIN (maxread, map_buffer (e) + map_fsize (e) - contents);
-      errno = hurd_safe_copyin (buf, contents, n); /* XXX/fault */
-      if (errno)
-        longjmp (ziperr, 2);
-        
-      zipread_pos += n;
-      return n;
-    }
-  void zipwrite (const char *buf, size_t nwrite)
-    {
-      if (fwrite (buf, nwrite, 1, zipout) != 1)
-       longjmp (ziperr, 1);
-    }
-  void ziprderr (void)
-    {
-      errno = ENOEXEC;
-      longjmp (ziperr, 2);
-    }
-  void ziperror (const char *msg)
-    {
-      errno = ENOEXEC;
-      longjmp (ziperr, 2);
-    }
-
-  unzip_read = zipread;
-  unzip_write = zipwrite;
-  unzip_read_error = ziprderr;
-  unzip_error = ziperror;
-
-  if (setjmp (ziperr))
-    {
-      /* Error in unzipping jumped out.  */
-      if (zipout)
-       {
-         fclose (zipout);
-         free (zipdata);
-       }
-      e->error = errno;
-      return;
-    }
-
-  if (get_method (0) != 0)
-    {
-      /* Not a happy gzip file.  */
-      e->error = ENOEXEC;
-      return;
-    }
-
-  /* Matched gzip magic number.  Ready to unzip.
-     Set up the output stream and let 'er rip.  */
-
-  zipout = open_memstream (&zipdata, &zipdatasz);
-  if (! zipout)
-    {
-      e->error = errno;
-      return;
-    }
-
-  /* Call the gunzip engine.  */
-  bytes_out = 0;
-  unzip (17, 23);              /* Arguments ignored.  */
-
-  /* The output is complete.  Clean up the stream and store its resultant
-     buffer and size in the execdata as the file contents.  */
-  fclose (zipout);
-
-  /* Clean up the old exec file stream's state.
-     Now that we have the contents all in memory (in E->file_data),
-     nothing will in fact ever try to use E->stream again.  */
-  finish (e, 0);
-
-  /* Prepare the stream state to use the file contents already in memory.  */
-  e->file_data = zipdata;
-  e->file_size = zipdatasz;
-  prepare_in_memory (e);
-}
-#endif
-
 
 static inline void *
 servercopy (void *arg, mach_msg_type_number_t argsize, boolean_t argcopy,
@@ -889,25 +770,6 @@ do_exec (file_t file,
 
       /* Check the file for validity first.  */
       check (e);
-
-#ifdef GZIP
-      if (e->error == ENOEXEC)
-       {
-         /* See if it is a compressed image.  */
-         static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
-         /* The gzip code is really cheesy, not even close to thread-safe.
-            So we serialize all uses of it.  */
-         pthread_mutex_lock (&lock);
-         e->error = 0;
-         check_gzip (e);
-         pthread_mutex_unlock (&lock);
-         if (e->error == 0)
-           /* The file was uncompressed into memory, and now E describes the
-              uncompressed image rather than the actual file.  Check it again
-              for a valid magic number.  */
-           check (e);
-       }
-#endif
     }
 
 
diff --git a/libstore/Makefile b/libstore/Makefile
index eafdd0a..607940b 100644
--- a/libstore/Makefile
+++ b/libstore/Makefile
@@ -60,10 +60,6 @@ OBJS = $(SRCS:.c=.o) $(GUNZIP_OBJS) $(BUNZIP2_OBJS)
 
 include ../Makeconf
 
-# Look for zip stuff
-vpath %.c $(srcdir)/../exec
-CPPFLAGS += -I$(srcdir)/../exec
-
 module-CPPFLAGS = -D'STORE_SONAME_SUFFIX=".so.$(hurd-version)"'
 module-DEPS = $(..)config.make
 
diff --git a/exec/crypt.h b/libstore/crypt.h
similarity index 100%
rename from exec/crypt.h
rename to libstore/crypt.h
diff --git a/exec/gzip.h b/libstore/gzip.h
similarity index 100%
rename from exec/gzip.h
rename to libstore/gzip.h
diff --git a/exec/inflate.c b/libstore/inflate.c
similarity index 100%
rename from exec/inflate.c
rename to libstore/inflate.c
diff --git a/exec/tailor.h b/libstore/tailor.h
similarity index 100%
rename from exec/tailor.h
rename to libstore/tailor.h
diff --git a/exec/unzip.c b/libstore/unzip.c
similarity index 100%
rename from exec/unzip.c
rename to libstore/unzip.c
diff --git a/exec/util.c b/libstore/util.c
similarity index 100%
rename from exec/util.c
rename to libstore/util.c

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