gnupg/util/secmem.c

/* secmem.c  -	memory allocation from a secure heap
 *	Copyright (C) 1998, 1999, 2000 Free Software Foundation, Inc.
 *
 * This file is part of GnuPG.
 *
 * GnuPG is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * GnuPG is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
 */

#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <stdarg.h>
#include <unistd.h>
#if defined(HAVE_MLOCK) || defined(HAVE_MMAP)
  #include <sys/mman.h>
  #include <sys/types.h>
  #include <fcntl.h>
  #ifdef USE_CAPABILITIES
    #include <sys/capability.h>
  #endif
  #ifdef HAVE_PLOCK
    #include <sys/lock.h>
  #endif
#endif

#include "types.h"
#include "memory.h"
#include "util.h"
#include "i18n.h"

#if defined(MAP_ANON) && !defined(MAP_ANONYMOUS)
  #define MAP_ANONYMOUS MAP_ANON
#endif
/* It seems that Slackware 7.1 does not know about EPERM */
#if !defined(EPERM) && defined(ENOMEM)
  #define EPERM  ENOMEM
#endif


#define DEFAULT_POOLSIZE 16384

typedef struct memblock_struct MEMBLOCK;
struct memblock_struct {
    unsigned size;
    union {
	MEMBLOCK *next;
	PROPERLY_ALIGNED_TYPE aligned;
    } u;
};



static void  *pool;
static volatile int pool_okay; /* may be checked in an atexit function */
static volatile int pool_is_mmapped;
static size_t poolsize; /* allocated length */
static size_t poollen;	/* used length */
static MEMBLOCK *unused_blocks;
static unsigned max_alloced;
static unsigned cur_alloced;
static unsigned max_blocks;
static unsigned cur_blocks;
static int disable_secmem;
static int show_warning;
static int no_warning;
static int suspend_warning;


static void
print_warn(void)
{
  if (!no_warning)
    {
      log_info(_("Warning: using insecure memory!\n"));
      log_info(_("please see http://www.gnupg.org/faq.html "
		 "for more information\n"));
    }
}


static void
lock_pool( void *p, size_t n )
{
  #if defined(USE_CAPABILITIES) && defined(HAVE_MLOCK)
    int err;

    cap_set_proc( cap_from_text("cap_ipc_lock+ep") );
    err = mlock( p, n );
    if( err && errno )
	err = errno;
    cap_set_proc( cap_from_text("cap_ipc_lock+p") );

    if( err ) {
	if( errno != EPERM
	  #ifdef EAGAIN  /* OpenBSD returns this */
	    && errno != EAGAIN
	  #endif
	  #ifdef ENOSYS  /* Some SCOs return this (function not implemented) */
	    && errno != ENOSYS
	  #endif
          #ifdef ENOMEM  /* Linux can return this */
            && errno != ENOMEM
          #endif
	  )
	    log_error("can't lock memory: %s\n", strerror(err));
	show_warning = 1;
    }

  #elif defined(HAVE_MLOCK)
    uid_t uid;
    int err;

    uid = getuid();

  #ifdef HAVE_BROKEN_MLOCK
    /* ick. but at least we get secured memory. about to lock
       entire data segment. */
  #ifdef HAVE_PLOCK
    err = plock( DATLOCK );
    if( err && errno )
        err = errno;
#else /*!HAVE_PLOCK*/
    if( uid ) {
	errno = EPERM;
	err = errno;
    }
    else {
	err = mlock( p, n );
	if( err && errno )
	    err = errno;
    }
  #endif /*!HAVE_PLOCK*/
  #else
    err = mlock( p, n );
    if( err && errno )
	err = errno;
  #endif

    if( uid && !geteuid() ) {
	/* check that we really dropped the privs.
	 * Note: setuid(0) should always fail */
	if( setuid( uid ) || getuid() != geteuid() || !setuid(0) )
	    log_fatal("failed to reset uid: %s\n", strerror(errno));
    }

    if( err ) {
	if( errno != EPERM
	  #ifdef EAGAIN  /* OpenBSD returns this */
	    && errno != EAGAIN
	  #endif
	  #ifdef ENOSYS  /* Some SCOs return this (function not implemented) */
	    && errno != ENOSYS
	  #endif
          #ifdef ENOMEM  /* Linux can return this */
            && errno != ENOMEM
          #endif
	  )
	    log_error("can't lock memory: %s\n", strerror(err));
	show_warning = 1;
    }

  #elif defined ( __QNX__ )
    /* QNX does not page at all, so the whole secure memory stuff does
     * not make much sense.  However it is still of use because it
     * wipes out the memory on a free().
     * Therefore it is sufficient to suppress the warning
     */
  #elif defined (HAVE_DOSISH_SYSTEM)
    /* It does not make sense to print such a warning, given the fact that 
     * this whole Windows !@#$% and their user base are inherently insecure
     */
  #elif defined (__riscos__)
    /* no virtual memory on RISC OS, so no pages are swapped to disc,
     * besides we don't have mmap, so we don't use it! ;-)
     * But don't complain, as explained above.
     */
  #else
    log_info("Please note that you don't have secure memory on this system\n");
  #endif
}


static void
init_pool( size_t n)
{
    size_t pgsize;

    poolsize = n;

    if( disable_secmem )
	log_bug("secure memory is disabled");

  #ifdef HAVE_GETPAGESIZE
    pgsize = getpagesize();
  #else
    pgsize = 4096;
  #endif

  #if HAVE_MMAP
    poolsize = (poolsize + pgsize -1 ) & ~(pgsize-1);
    #ifdef MAP_ANONYMOUS
       pool = mmap( 0, poolsize, PROT_READ|PROT_WRITE,
				 MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
    #else /* map /dev/zero instead */
    {	int fd;

	fd = open("/dev/zero", O_RDWR);
	if( fd == -1 ) {
	    log_error("can't open /dev/zero: %s\n", strerror(errno) );
	    pool = (void*)-1;
	}
	else {
	    pool = mmap( 0, poolsize, PROT_READ|PROT_WRITE,
				      MAP_PRIVATE, fd, 0);
	}
    }
    #endif
    if( pool == (void*)-1 )
	log_info("can't mmap pool of %u bytes: %s - using malloc\n",
			    (unsigned)poolsize, strerror(errno));
    else {
	pool_is_mmapped = 1;
	pool_okay = 1;
    }

  #endif
    if( !pool_okay ) {
	pool = malloc( poolsize );
	if( !pool )
	    log_fatal("can't allocate memory pool of %u bytes\n",
						       (unsigned)poolsize);
	else
	    pool_okay = 1;
    }
    lock_pool( pool, poolsize );
    poollen = 0;
}


/* concatenate unused blocks */
static void
compress_pool(void)
{
    /* fixme: we really should do this */
}

void
secmem_set_flags( unsigned flags )
{
    int was_susp = suspend_warning;

    no_warning = flags & 1;
    suspend_warning = flags & 2;

    /* and now issue the warning if it is not longer suspended */
    if( was_susp && !suspend_warning && show_warning ) {
	show_warning = 0;
	print_warn();
    }
}

unsigned
secmem_get_flags(void)
{
    unsigned flags;

    flags  = no_warning      ? 1:0;
    flags |= suspend_warning ? 2:0;
    return flags;
}

void
secmem_init( size_t n )
{
    if( !n ) {
#ifndef __riscos__
      #ifdef USE_CAPABILITIES
	/* drop all capabilities */
	cap_set_proc( cap_from_text("all-eip") );

      #elif !defined(HAVE_DOSISH_SYSTEM)
	uid_t uid;

	disable_secmem=1;
	uid = getuid();
	if( uid != geteuid() ) {
	    if( setuid( uid ) || getuid() != geteuid() || !setuid(0) )
		log_fatal("failed to drop setuid\n" );
	}
      #endif
#endif /* !__riscos__ */
    }
    else {
	if( n < DEFAULT_POOLSIZE )
	    n = DEFAULT_POOLSIZE;
	if( !pool_okay )
	    init_pool(n);
	else
	    log_error("Oops, secure memory pool already initialized\n");
    }
}


void *
secmem_malloc( size_t size )
{
    MEMBLOCK *mb, *mb2;
    int compressed=0;

    if( !pool_okay ) {
	log_info(
	 _("operation is not possible without initialized secure memory\n"));
	log_info(_("(you may have used the wrong program for this task)\n"));
	exit(2);
    }
    if( show_warning && !suspend_warning ) {
	show_warning = 0;
	print_warn();
    }

    /* blocks are always a multiple of 32 */
    size += sizeof(MEMBLOCK);
    size = ((size + 31) / 32) * 32;

  retry:
    /* try to get it from the used blocks */
    for(mb = unused_blocks,mb2=NULL; mb; mb2=mb, mb = mb->u.next )
	if( mb->size >= size ) {
	    if( mb2 )
		mb2->u.next = mb->u.next;
	    else
		unused_blocks = mb->u.next;
	    goto leave;
	}
    /* allocate a new block */
    if( (poollen + size <= poolsize) ) {
	mb = (void*)((char*)pool + poollen);
	poollen += size;
	mb->size = size;
    }
    else if( !compressed ) {
	compressed=1;
	compress_pool();
	goto retry;
    }
    else
	return NULL;

  leave:
    cur_alloced += mb->size;
    cur_blocks++;
    if( cur_alloced > max_alloced )
	max_alloced = cur_alloced;
    if( cur_blocks > max_blocks )
	max_blocks = cur_blocks;

    return &mb->u.aligned.c;
}


void *
secmem_realloc( void *p, size_t newsize )
{
    MEMBLOCK *mb;
    size_t size;
    void *a;

    mb = (MEMBLOCK*)((char*)p - ((size_t) &((MEMBLOCK*)0)->u.aligned.c));
    size = mb->size;
    if( newsize < size )
	return p; /* it is easier not to shrink the memory */
    a = secmem_malloc( newsize );
    if ( a ) {
        memcpy(a, p, size);
        memset((char*)a+size, 0, newsize-size);
        secmem_free(p);
    }
    return a;
}


void
secmem_free( void *a )
{
    MEMBLOCK *mb;
    size_t size;

    if( !a )
	return;

    mb = (MEMBLOCK*)((char*)a - ((size_t) &((MEMBLOCK*)0)->u.aligned.c));
    size = mb->size;
    /* This does not make much sense: probably this memory is held in the
     * cache. We do it anyway: */
    memset(mb, 0xff, size );
    memset(mb, 0xaa, size );
    memset(mb, 0x55, size );
    memset(mb, 0x00, size );
    mb->size = size;
    mb->u.next = unused_blocks;
    unused_blocks = mb;
    cur_blocks--;
    cur_alloced -= size;
}

int
m_is_secure( const void *p )
{
    return p >= pool && p < (void*)((char*)pool+poolsize);
}



/****************
 * Warning:  This code might be called by an interrupt handler
 *	     and frankly, there should really be such a handler,
 *	     to make sure that the memory is wiped out.
 *	     We hope that the OS wipes out mlocked memory after
 *	     receiving a SIGKILL - it really should do so, otherwise
 *	     there is no chance to get the secure memory cleaned.
 */
void
secmem_term()
{
    if( !pool_okay )
	return;

    memset( pool, 0xff, poolsize);
    memset( pool, 0xaa, poolsize);
    memset( pool, 0x55, poolsize);
    memset( pool, 0x00, poolsize);
  #if HAVE_MMAP
    if( pool_is_mmapped )
	munmap( pool, poolsize );
  #endif
    pool = NULL;
    pool_okay = 0;
    poolsize=0;
    poollen=0;
    unused_blocks=NULL;
}


void
secmem_dump_stats()
{
    if( disable_secmem )
	return;
    fprintf(stderr,
		"secmem usage: %u/%u bytes in %u/%u blocks of pool %lu/%lu\n",
		cur_alloced, max_alloced, cur_blocks, max_blocks,
		(ulong)poollen, (ulong)poolsize );
}