Patch from Scott McKellar to repair srfsh buffer overflow:

The potential overflow occurs in handle_introspection(), which in the
existing code uses sprintf() to insert some user-supplied input into a
fixed length buffer, without checking the length of the user-supplied
input.

There's always more than one way to fix this sort of thing.  For
example I could have formatted into a growing_buffer.  Instead, I
chose to calculate the necessary buffer size and then declare a
variable-length buffer.  That way I avoid two mallocs and two frees.

I tested this change by inserting some temporary printfs to capture
the commands being sent to parse_request().  The outputs before and
after the change were identical.

There's at least one more such potential overflow that I haven't
addressed yet.  It's near the top of handle_login(), where we
use sprintf() to insert a username into a fixed length buffer.
There may be others that I haven't noticed yet.

Scott McKellar
http://home.swbell.net/mck9/ct/

git-svn-id: svn://svn.open-ils.org/OpenSRF/trunk@1038 9efc2488-bf62-4759-914b-345cdb29e865

diff --git a/src/srfsh/srfsh.c b/src/srfsh/srfsh.c
index 37a767b..6c4cb54 100644 (file)
--- a/src/srfsh/srfsh.c
+++ b/src/srfsh/srfsh.c
@@ -324,25 +324,30 @@ static int parse_request( char* request ) {
 
 static int handle_introspect(char* words[]) {
 
-       if(words[1] && words[2]) {
-               fprintf(stderr, "--> %s\n", words[1]);
-               char buf[256];
-               memset(buf,0,256);
-               sprintf( buf, "request %s opensrf.system.method %s", words[1], words[2] );
+       if( ! words[1] )
+               return 0;
+
+       fprintf(stderr, "--> %s\n", words[1]);
+
+       // Build a command in a suitably-sized
+       // buffer and then parse it
+       
+       size_t len;
+       if( words[2] ) {
+               static const char text[] = "request %s opensrf.system.method %s";
+               len = sizeof( text ) + strlen( words[1] ) + strlen( words[2] );
+               char buf[len];
+               sprintf( buf, text, words[1], words[2] );
                return parse_request( buf );
 
        } else {
-       
-               if(words[1]) {
-                       fprintf(stderr, "--> %s\n", words[1]);
-                       char buf[256];
-                       memset(buf,0,256);
-                       sprintf( buf, "request %s opensrf.system.method.all", words[1] );
-                       return parse_request( buf );
-               }
-       }
+               static const char text[] = "request %s opensrf.system.method.all";
+               len = sizeof( text ) + strlen( words[1] );
+               char buf[len];
+               sprintf( buf, text, words[1] );
+               return parse_request( buf );
 
-       return 0;
+       }
 }