- djm@cvs.openbsd.org 2007/05/17 07:55:29

     [sftp-server.c]
     bz#1286 stop reading and processing commands when input or output buffer
     is nearly full, otherwise sftp-server would happily try to grow the
     input/output buffers past the maximum supported by the buffer API and
     promptly fatal()
     based on patch from Thue Janus Kristensen; feedback & ok dtucker@

2 files changed, 27 insertions, 7 deletions

diff --git a/ChangeLog b/ChangeLog
index c189c7810..2bc077cf7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -15,6 +15,13 @@
    - djm@cvs.openbsd.org 2007/05/17 07:50:31
      [log.c]
      save and restore errno when logging; ok deraadt@
+   - djm@cvs.openbsd.org 2007/05/17 07:55:29
+     [sftp-server.c]
+     bz#1286 stop reading and processing commands when input or output buffer
+     is nearly full, otherwise sftp-server would happily try to grow the
+     input/output buffers past the maximum supported by the buffer API and
+     promptly fatal()
+     based on patch from Thue Janus Kristensen; feedback & ok dtucker@
 
 20070509
  - (tim) [configure.ac] Bug #1287: Add missing test for ucred.h.
@@ -2915,4 +2922,4 @@
    OpenServer 6 and add osr5bigcrypt support so when someone migrates
    passwords between UnixWare and OpenServer they will still work. OK dtucker@
 
-$Id: ChangeLog,v 1.4664 2007/05/20 05:08:15 dtucker Exp $
+$Id: ChangeLog,v 1.4665 2007/05/20 05:09:04 dtucker Exp $
diff --git a/sftp-server.c b/sftp-server.c
index d68584b52..76edebc5a 100644
--- a/sftp-server.c
+++ b/sftp-server.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sftp-server.c,v 1.72 2007/04/18 01:12:43 stevesk Exp $ */
+/* $OpenBSD: sftp-server.c,v 1.73 2007/05/17 07:55:29 djm Exp $ */
 /*
  * Copyright (c) 2000-2004 Markus Friedl.  All rights reserved.
  *
@@ -1214,7 +1214,7 @@ main(int argc, char **argv)
         int in, out, max, ch, skipargs = 0, log_stderr = 0;
         ssize_t len, olen, set_size;
         SyslogFacility log_facility = SYSLOG_FACILITY_AUTH;
-        char *cp;
+        char *cp, buf[4*4096];
 
         extern char *optarg;
         extern char *__progname;
@@ -1298,7 +1298,15 @@ main(int argc, char **argv)
                 memset(rset, 0, set_size);
                 memset(wset, 0, set_size);
 
-                FD_SET(in, rset);
+                /*
+                 * Ensure that we can read a full buffer and handle
+                 * the worst-case length packet it can generate,
+                 * otherwise apply backpressure by stopping reads.
+                 */
+                if (buffer_check_alloc(&iqueue, sizeof(buf)) &&
+                    buffer_check_alloc(&oqueue, SFTP_MAX_MSG_LENGTH))
+                        FD_SET(in, rset);
+
                 olen = buffer_len(&oqueue);
                 if (olen > 0)
                         FD_SET(out, wset);
@@ -1312,7 +1320,6 @@ main(int argc, char **argv)
 
                 /* copy stdin to iqueue */
                 if (FD_ISSET(in, rset)) {
-                        char buf[4*4096];
                         len = read(in, buf, sizeof buf);
                         if (len == 0) {
                                 debug("read eof");
@@ -1334,7 +1341,13 @@ main(int argc, char **argv)
                                 buffer_consume(&oqueue, len);
                         }
                 }
-                /* process requests from client */
-                process();
+
+                /*
+                 * Process requests from client if we can fit the results
+                 * into the output buffer, otherwise stop processing input
+                 * and let the output queue drain.
+                 */
+                if (buffer_check_alloc(&oqueue, SFTP_MAX_MSG_LENGTH))
+                        process();
         }
 }