gzsig: avoid endless loop on input error

[Tobias Stoeckmann]

Hi,

while skipping some header sections of a *.gz file, gzsig uses the
function getc without taking a possible EOF return value into account.

On error, the tool should obviously stop with an error message, therefore
leaving sign() or verify() with -1.


Tobias

Index: sign.c
===================================================================
RCS file: /cvs/src/usr.bin/gzsig/sign.c,v
retrieving revision 1.9
diff -u -p -r1.9 sign.c
--- sign.c      12 Oct 2007 19:52:06 -0000      1.9
+++ sign.c      9 Mar 2013 22:41:53 -0000
@@ -114,12 +114,12 @@ embed_signature(struct key *key, FILE *f
        offset = ftell(fin);
 
        if (gh.flags & GZIP_FNAME) {
-               while (getc(fin) != '\0')
-                       ;
+               if (skip_string(fin))
+                       return (-1);
        }
        if (gh.flags & GZIP_FCOMMENT) {
-               while (getc(fin) != '\0')
-                       ;
+               if (skip_string(fin))
+                       return (-1);
        }
        if (gh.flags & GZIP_FENCRYPT) {
                if (fread(buf, 1, GZIP_FENCRYPT_LEN, fin) != GZIP_FENCRYPT_LEN)
Index: util.c
===================================================================
RCS file: /cvs/src/usr.bin/gzsig/util.c,v
retrieving revision 1.2
diff -u -p -r1.2 util.c
--- util.c      28 May 2005 08:07:45 -0000      1.2
+++ util.c      9 Mar 2013 22:41:53 -0000
@@ -62,6 +62,17 @@ copy_permissions(char *srcfile, char *ds
        return (0);
 }
 
+int
+skip_string(FILE *fin)
+{
+       int c;
+
+       while ((c = getc(fin)) != '\0')
+               if (c == EOF)
+                       return (-1);
+       return (0);
+}
+
 void
 fatal(int status, const char *fmt, ...)
 {
Index: util.h
===================================================================
RCS file: /cvs/src/usr.bin/gzsig/util.h,v
retrieving revision 1.2
diff -u -p -r1.2 util.h
--- util.h      28 May 2005 08:07:45 -0000      1.2
+++ util.h      9 Mar 2013 22:41:53 -0000
@@ -34,6 +34,7 @@
 #ifndef UTIL_H
 
 int            copy_permissions(char *srcfile, char *dstfile);
+int            skip_string(FILE *fin);
 void           fatal(int status, const char *fmt, ...);
 
 #endif /* UTIL_H */
Index: verify.c
===================================================================
RCS file: /cvs/src/usr.bin/gzsig/verify.c,v
retrieving revision 1.7
diff -u -p -r1.7 verify.c
--- verify.c    12 Oct 2007 19:52:06 -0000      1.7
+++ verify.c    9 Mar 2013 22:41:53 -0000
@@ -105,12 +105,12 @@ verify_signature(struct key *key, FILE *
        }
        /* Skip over any options. */
        if (gh.flags & GZIP_FNAME) {
-               while (getc(fin) != '\0')
-                       ;
+               if (skip_string(fin))
+                       return (-1);
        }
        if (gh.flags & GZIP_FCOMMENT) {
-               while (getc(fin) != '\0')
-                       ;
+               if (skip_string(fin))
+                       return (-1);
        }
        if (gh.flags & GZIP_FENCRYPT &&
            fread(buf, 1, GZIP_FENCRYPT_LEN, fin) != GZIP_FENCRYPT_LEN)