1 files changed, 23 insertions, 0 deletions

diff --git a/src/lib/libcrypto/asn1/a_bitstr.c b/src/lib/libcrypto/asn1/a_bitstr.c
index 0fb9ce0c2a..34179960b8 100644
--- a/src/lib/libcrypto/asn1/a_bitstr.c
+++ b/src/lib/libcrypto/asn1/a_bitstr.c
@@ -223,3 +223,26 @@ int ASN1_BIT_STRING_get_bit(ASN1_BIT_STRING *a, int n)
         return((a->data[w]&v) != 0);
         }
 
+/*
+ * Checks if the given bit string contains only bits specified by 
+ * the flags vector. Returns 0 if there is at least one bit set in 'a'
+ * which is not specified in 'flags', 1 otherwise.
+ * 'len' is the length of 'flags'.
+ */
+int ASN1_BIT_STRING_check(ASN1_BIT_STRING *a,
+                          unsigned char *flags, int flags_len)
+        {
+        int i, ok;
+        /* Check if there is one bit set at all. */
+        if (!a || !a->data) return 1;
+
+        /* Check each byte of the internal representation of the bit string. */
+        ok = 1;
+        for (i = 0; i < a->length && ok; ++i)
+                {
+                unsigned char mask = i < flags_len ? ~flags[i] : 0xff;
+                /* We are done if there is an unneeded bit set. */
+                ok = (a->data[i] & mask) == 0;
+                }
+        return ok;
+        }