Permit nested ASN1 string encoding but with a maximum depth to avoid

stack overflow.

diff --git a/CHANGES b/CHANGES
index 514193682366656fba4a116d5cf0eb95a6f6a83f..8455d94d986009c0f021e3d29d4066ffc8e38569 100644 (file)
--- a/CHANGES
+++ b/CHANGES
@@ -4,6 +4,10 @@
 
  Changes between 0.9.8j and 0.9.8k  [xx XXX xxxx]
 
+  *) Permit restricted recursion of ASN1 strings. This is needed in practice
+     to handle some structures.
+     [Steve Henson]
+
   *) Improve efficiency of mem_gets: don't search whole buffer each time
      for a '\n'
      [Jeremy Shapiro <jnshapir@us.ibm.com>]

diff --git a/crypto/asn1/tasn_dec.c b/crypto/asn1/tasn_dec.c
index ced641698ebd9ede3977a9e72f90b1c7d56d458b..05129f229c738d59f76216eaa1e517881955ee67 100644 (file)
--- a/crypto/asn1/tasn_dec.c
+++ b/crypto/asn1/tasn_dec.c
@@ -69,7 +69,7 @@ static int asn1_check_eoc(const unsigned char **in, long len);
 static int asn1_find_end(const unsigned char **in, long len, char inf);
 
 static int asn1_collect(BUF_MEM *buf, const unsigned char **in, long len,
-                               char inf, int tag, int aclass);
+                       char inf, int tag, int aclass, int depth);
 
 static int collect_data(BUF_MEM *buf, const unsigned char **p, long plen);
 
@@ -878,7 +878,7 @@ static int asn1_d2i_ex_primitive(ASN1_VALUE **pval,
                 * internally irrespective of the type. So instead just check
                 * for UNIVERSAL class and ignore the tag.
                 */
-               if (!asn1_collect(&buf, &p, plen, inf, -1, V_ASN1_UNIVERSAL))
+               if (!asn1_collect(&buf, &p, plen, inf, -1, V_ASN1_UNIVERSAL, 0))
                        {
                        free_cont = 1;
                        goto err;
@@ -1128,8 +1128,18 @@ static int asn1_find_end(const unsigned char **in, long len, char inf)
  * if it is indefinite length.
  */
 
+#ifndef ASN1_MAX_STRING_NEST
+/* This determines how many levels of recursion are permitted in ASN1
+ * string types. If it is not limited stack overflows can occur. If set
+ * to zero no recursion is allowed at all. Although zero should be adequate
+ * examples exist that require a value of 1. So 5 should be more than enough.
+ */
+#define ASN1_MAX_STRING_NEST 5
+#endif
+
+
 static int asn1_collect(BUF_MEM *buf, const unsigned char **in, long len,
-                               char inf, int tag, int aclass)
+                       char inf, int tag, int aclass, int depth)
        {
        const unsigned char *p, *q;
        long plen;
@@ -1171,13 +1181,15 @@ static int asn1_collect(BUF_MEM *buf, const unsigned char **in, long len,
                /* If indefinite length constructed update max length */
                if (cst)
                        {
-#ifdef OPENSSL_ALLOW_NESTED_ASN1_STRINGS
-                       if (!asn1_collect(buf, &p, plen, ininf, tag, aclass))
+                       if (depth >= ASN1_MAX_STRING_NEST)
+                               {
+                               ASN1err(ASN1_F_ASN1_COLLECT,
+                                       ASN1_R_NESTED_ASN1_STRING);
+                               return 0;
+                               }
+                       if (!asn1_collect(buf, &p, plen, ininf, tag, aclass,
+                                               depth + 1))
                                return 0;
-#else
-                       ASN1err(ASN1_F_ASN1_COLLECT, ASN1_R_NESTED_ASN1_STRING);
-                       return 0;
-#endif
                        }
                else if (plen && !collect_data(buf, &p, plen))
                        return 0;