[PATCH] Use temporary buffer for generating Uxxx names to avoid overflow

[Alan Coopersmith]

Instead of sprintf()'ing a 4 character string to a char [4] buffer,
and leaving the trailing '\0' to overwrite into the next entry,
snprintf() to a 5 character temp buffer and memcpy the 4 characters
to the right place.

Fixes parfait errors:
Error: Buffer overflow at xkbcomp-1.0.4/misc.c:393
        in function 'ComputeKbdDefaults' [Standard C Library pattern matching]
       In sprintf related dereference of xkb->names->keys[i].name
        with index not less than '4'
       Destination array size is 4 bytes, data to be written is 4 bytes
Error: Buffer overflow at xkbcomp-1.0.4/misc.c:402
        in function 'ComputeKbdDefaults' [Standard C Library pattern matching]
       In sprintf related dereference of xkb->names->keys[i].name
        with index not less than '4'
       Destination array size is 4 bytes, data to be written is 4 bytes

[This bug was found by the Parfait bug checking tool.
  For more information see http://research.sun.com/projects/parfait ]

Signed-off-by: Alan Coopersmith <alan.coopersmith at sun.com>
---
 misc.c |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/misc.c b/misc.c
index 0e4f61d..4990a74 100644
--- a/misc.c
+++ b/misc.c
@@ -383,6 +383,7 @@ ComputeKbdDefaults(XkbDescPtr xkb)
     register int i, tmp, nUnknown;
     KeyNameDesc *name;
     KeySym *syms;
+    char tmpname[XkbKeyNameLength + 1];

     if ((xkb->names == NULL) || (xkb->names->keys == NULL))
     {
@@ -430,8 +431,10 @@ ComputeKbdDefaults(XkbDescPtr xkb)
                             ACTION2("Using <U%03d> for key %d\n",
                                     nUnknown, i);
                         }
-                        sprintf(xkb->names->keys[i].name, "U%03d",
-                                nUnknown++);
+                        snprintf(tmpname, sizeof(tmpname), "U%03d",
+                                 nUnknown++);
+                        memcpy(xkb->names->keys[i].name, tmpname,
+                               XkbKeyNameLength);
                     }
                     break;
                 }
@@ -442,7 +445,9 @@ ComputeKbdDefaults(XkbDescPtr xkb)
                 {
                     WARN1("Key %d does not match any defaults\n", i);
                     ACTION1("Using name <U%03d>\n", nUnknown);
-                    sprintf(xkb->names->keys[i].name, "U%03d", nUnknown++);
+                    snprintf(tmpname, sizeof(tmpname), "U%03d", nUnknown++);
+                    memcpy(xkb->names->keys[i].name, tmpname,
+                           XkbKeyNameLength);
                 }
             }
         }
-- 
1.5.6.5