From f715b9e156dfa99ae829fc694e5a0abd23ef97d7 Mon Sep 17 00:00:00 2001
From: Werner Koch <wk@gnupg.org>
Date: Tue, 25 Nov 2014 11:47:28 +0100
Subject: [PATCH] Fix buffer overflow in ksba_oid_to_str.
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* src/oid.c (ksba_oid_to_str): Fix unsigned underflow.

* tests/Makefile.am (noinst_PROGRAMS): Move t-oid to ..
(TESTS): here.
* tests/t-oid.c (test_oid_to_str): New.
(main): Run the new tests by default.  The former functionality
requires the use of one of the new options.
--

The code has an obvious error by not considering invalid encoding for
arc-2.  A first byte of 0x80 can be used to make a value of less then
80 and we then subtract 80 from that value as required by the OID
encoding rules.  Due to the unsigned integer this results in a pretty
long value which won't fit anymore into the allocated buffer.

The fix is obvious.  Also added a few simple test cases.  Note that we
keep on using sprintf instead of snprintf because managing the
remaining length of the buffer would probably be more error prone than
assuring that the buffer is large enough.  Getting rid of sprintf
altogether by using direct conversion along with membuf_t like code
might be possible.

Reported-by: Hanno BÃ¶ck
Signed-off-by: Werner Koch <wk@gnupg.org>
---
 src/oid.c          |    2 ++
 tests/Makefile.am  |    4 +--
 tests/t-dnparser.c |    2 +-
 tests/t-oid.c      |   97 ++++++++++++++++++++++++++++++++++++++++++++++++++--
 4 files changed, 99 insertions(+), 6 deletions(-)

Index: libksba-1.3.0/src/oid.c
===================================================================
--- libksba-1.3.0.orig/src/oid.c	2014-12-10 11:16:54.484367960 +0100
+++ libksba-1.3.0/src/oid.c	2014-12-10 11:16:55.764382099 +0100
@@ -94,6 +94,8 @@ ksba_oid_to_str (const char *buffer, siz
         val <<= 7;
         val |= buf[n] & 0x7f;
       }
+    if (val < 80)
+      goto badoid;
     val -= 80;
     sprintf (p, "2.%lu", val);
     p += strlen (p);
Index: libksba-1.3.0/tests/Makefile.am
===================================================================
--- libksba-1.3.0.orig/tests/Makefile.am	2014-12-10 11:16:55.764382099 +0100
+++ libksba-1.3.0/tests/Makefile.am	2014-12-10 11:17:57.483061228 +0100
@@ -39,12 +39,12 @@ EXTRA_DIST = $(test_certs) samples/READM
 BUILT_SOURCES = oidtranstbl.h
 CLEANFILES = oidtranstbl.h
 
-TESTS = cert-basic t-crl-parser t-dnparser
+TESTS = cert-basic t-crl-parser t-dnparser t-oid
 
 AM_CFLAGS = $(GPG_ERROR_CFLAGS)
 
 noinst_HEADERS = t-common.h
-noinst_PROGRAMS = $(TESTS) t-cms-parser t-crl-parser t-dnparser t-ocsp t-oid
+noinst_PROGRAMS = $(TESTS) t-cms-parser t-crl-parser t-dnparser t-ocsp
 LDADD = ../src/libksba.la $(GPG_ERROR_LIBS)
 
 t_ocsp_SOURCES = t-ocsp.c sha1.c
Index: libksba-1.3.0/tests/t-dnparser.c
===================================================================
--- libksba-1.3.0.orig/tests/t-dnparser.c	2014-12-10 11:16:54.485367971 +0100
+++ libksba-1.3.0/tests/t-dnparser.c	2014-12-10 11:16:55.764382099 +0100
@@ -144,7 +144,7 @@ main (int argc, char **argv)
       if (!feof (stdin))
         fail ("read error or input too large");
 
-      fail ("no yet implemented");
+      fail ("not yet implemented");
 
     }
   else if (argc == 2 && !strcmp (argv[1], "--to-der") )
Index: libksba-1.3.0/tests/t-oid.c
===================================================================
--- libksba-1.3.0.orig/tests/t-oid.c	2014-12-10 11:16:54.485367971 +0100
+++ libksba-1.3.0/tests/t-oid.c	2014-12-10 11:16:55.765382110 +0100
@@ -27,6 +27,9 @@
 
 #include "../src/ksba.h"
 
+#define PGM "t-oid"
+#define BADOID "1.3.6.1.4.1.11591.2.12242973"
+
 
 static void *
 read_into_buffer (FILE *fp, size_t *r_length)
@@ -68,23 +71,104 @@ read_into_buffer (FILE *fp, size_t *r_le
 }
 
 
+static void
+test_oid_to_str (void)
+{
+  struct {
+    unsigned int binlen;
+    unsigned char *bin;
+    char *str;
+  } tests[] = {
+
+    {  7, "\x02\x82\x06\x01\x0A\x0C\x00",
+       "0.2.262.1.10.12.0"
+    },
+    {  7, "\x02\x82\x06\x01\x0A\x0C\x01",
+       "0.2.262.1.10.12.1"
+    },
+    {  7, "\x2A\x86\x48\xCE\x38\x04\x01",
+       "1.2.840.10040.4.1"
+    },
+    {  7, "\x2A\x86\x48\xCE\x38\x04\x03",
+       "1.2.840.10040.4.3"
+    },
+    { 10, "\x2B\x06\x01\x04\x01\xDA\x47\x02\x01\x01",
+      "1.3.6.1.4.1.11591.2.1.1"
+    },
+    {  3, "\x55\x1D\x0E",
+       "2.5.29.14"
+    },
+    {  9, "\x80\x02\x70\x50\x25\x46\xfd\x0c\xc0",
+       BADOID
+    },
+    {  1, "\x80",
+       BADOID
+    },
+    {  2, "\x81\x00",
+       "2.48"
+    },
+    {  2, "\x81\x01",
+       "2.49"
+    },
+    {  2, "\x81\x7f",
+       "2.175"
+    },
+    {  2, "\x81\x80",  /* legal encoding? */
+       "2.48"
+    },
+    {  2, "\x81\x81\x01",  /* legal encoding? */
+       "2.49"
+    },
+    {  0, "",
+       ""
+    },
+
+    { 0, NULL, NULL }
+  };
+  int tidx;
+  char *str;
+
+  for (tidx=0; tests[tidx].bin; tidx++)
+    {
+      str = ksba_oid_to_str (tests[tidx].bin, tests[tidx].binlen);
+      if (!str)
+        {
+          perror ("ksba_oid_to_str failed");
+          exit (1);
+        }
+      if (strcmp (tests[tidx].str, str))
+        {
+          fprintf (stderr, "ksba_oid_to_str test %d failed\n", tidx);
+          fprintf (stderr, "  got=%s\n", str);
+          fprintf (stderr, " want=%s\n", tests[tidx].str);
+          exit (1);
+        }
+    }
+}
+
 
 int
 main (int argc, char **argv)
 {
   gpg_error_t err;
+
   if (argc)
     {
       argc--;
       argv++;
     }
 
-  if (argc)
+
+  if (!argc)
+    {
+      test_oid_to_str ();
+    }
+  else if (!strcmp (*argv, "--from-str"))
     {
       unsigned char *buffer;
       size_t n, buflen;
 
-      for ( ;argc ; argc--, argv++)
+      for (argv++,argc-- ; argc; argc--, argv++)
         {
           err = ksba_oid_from_str (*argv, &buffer, &buflen);
           if (err)
@@ -100,18 +184,25 @@ main (int argc, char **argv)
           free (buffer);
         }
     }
-  else
+  else if (!strcmp (*argv, "--to-str"))
     {
       char *buffer;
       size_t buflen;
       char *result;
 
+      argv++;argc--;
+
       buffer = read_into_buffer (stdin, &buflen);
       result = ksba_oid_to_str (buffer, buflen);
       free (buffer);
       printf ("%s\n", result? result:"[malloc failed]");
       free (result);
     }
+  else
+    {
+      fputs ("usage: "PGM" [--from-str|--to-str]\n", stderr);
+      return 1;
+    }
 
   return 0;
 }
