Обсуждение: BUG #8540: Avoid sscanf buffer overflow

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BUG #8540: Avoid sscanf buffer overflow

От
jackie.qq.chang@gmail.com
Дата:
The following bug has been logged on the website:

Bug reference:      8540
Logged by:          Jackie Chang
Email address:      jackie.qq.chang@gmail.com
PostgreSQL version: 9.3.1
Operating system:   Any
Description:

sscanf can set the maximum length of string read. If such a number is not
provided, it's vulnerable to buffer overflow.


Diff is:


diff --git a/contrib/pg_upgrade/option.c b/contrib/pg_upgrade/option.c
index 250aeb8..293ef1c 100644
--- a/contrib/pg_upgrade/option.c
+++ b/contrib/pg_upgrade/option.c
@@ -443,7 +443,7 @@ get_sock_dir(ClusterInfo *cluster, bool live_check)
                 {
                     cluster->sockdir = pg_malloc(MAXPGPATH);
                     /* strip off newline */
-                    sscanf(line, "%s\n", cluster->sockdir);
+                    sscanf(line, "%1023s\n", cluster->sockdir);
                 }
             }
             fclose(fp);
diff --git a/src/backend/access/transam/xlog.c
b/src/backend/access/transam/xlog.c
index 06f5eb0..560230f 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -10029,7 +10029,7 @@ do_pg_stop_backup(char *labelfile, bool
waitforarchive, TimeLineID *stoptli_p)
      * Read and parse the START WAL LOCATION line (this code is pretty crude,
      * but we are not expecting any variability in the file format).
      */
-    if (sscanf(labelfile, "START WAL LOCATION: %X/%X (file %24s)%c",
+    if (sscanf(labelfile, "START WAL LOCATION: %X/%X (file %63s)%c",
                &hi, &lo, startxlogfilename,
                &ch) != 4 || ch != '\n')
         ereport(ERROR,
diff --git a/src/bin/pg_dump/pg_backup_directory.c
b/src/bin/pg_dump/pg_backup_directory.c
index f803186..48e0db9 100644
--- a/src/bin/pg_dump/pg_backup_directory.c
+++ b/src/bin/pg_dump/pg_backup_directory.c
@@ -452,7 +452,7 @@ _LoadBlobs(ArchiveHandle *AH, RestoreOptions *ropt)
         char        fname[MAXPGPATH];
         char        path[MAXPGPATH];

-        if (sscanf(line, "%u %s\n", &oid, fname) != 2)
+        if (sscanf(line, "%u %1023s\n", &oid, fname) != 2)
             exit_horribly(modulename, "invalid line in large object TOC file \"%s\":
\"%s\"\n",
                           fname, line);

Re: BUG #8540: Avoid sscanf buffer overflow

От
Bruce Momjian
Дата:
On Sat, Oct 19, 2013 at 09:49:05PM +0000, jackie.qq.chang@gmail.com wrote:
> The following bug has been logged on the website:
>
> Bug reference:      8540
> Logged by:          Jackie Chang
> Email address:      jackie.qq.chang@gmail.com
> PostgreSQL version: 9.3.1
> Operating system:   Any
> Description:
>
> sscanf can set the maximum length of string read. If such a number is not
> provided, it's vulnerable to buffer overflow.

I have looked at your patch and I wasn't happy to be adding a hard-coded
constant based on a macro definition.  What I did do with the attached,
applied patch is to remove the use of sscanf in pg_upgrade, and add a C
comment in pg_dump explaining why the scanf can't overflow.  I didn't
see increasing the xlog.c length as useful.

For pg_dump it would be nice from a sanity perspective if we could do:

    sscanf(str, "%" CppAsString2(MAXPGPATH-1) "s\n", ...

but there is no way to string-ify a macro while also computing it during
preprocessing.

--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + Everyone has their own god. +

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