asn1: fix out-of-bounds read in decoding constructed objects

* OpenSSL::ASN1.{decode,decode_all,traverse}: have a bug of
  out-of-bounds read. int_ossl_asn1_decode0_cons() does not give the
  correct available length to ossl_asn1_decode() when decoding the
  inner components of a constructed object. This can cause
  out-of-bounds read if a crafted input given.

Reference: https://hackerone.com/reports/170316
https://github.com/ruby/openssl/commit/1648afef33c1d97fb203c82291b8a61269e85d3b



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_3@59800 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

4 files changed, 43 insertions, 8 deletions

diff --git a/ChangeLog b/ChangeLog
index 6f52c2d098..fb4ba3c204 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,16 @@
+Sat Sep  9 23:05:31 2017  Kazuki Yamaguchi <k@rhe.jp>
+
+	asn1: fix out-of-bounds read in decoding constructed objects
+
+	* OpenSSL::ASN1.{decode,decode_all,traverse}: have a bug of
+	  out-of-bounds read. int_ossl_asn1_decode0_cons() does not give the
+	  correct available length to ossl_asn1_decode() when decoding the
+	  inner components of a constructed object. This can cause
+	  out-of-bounds read if a crafted input given.
+
+	Reference: https://hackerone.com/reports/170316
+	https://github.com/ruby/openssl/commit/1648afef33c1d97fb203c82291b8a61269e85d3b
+
 Sat Sep  9 22:57:24 2017  SHIBATA Hiroshi  <hsbt@ruby-lang.org>
 
 	* ext/json: bump to version 1.8.3.1. [Backport #13853]
diff --git a/ext/openssl/ossl_asn1.c b/ext/openssl/ossl_asn1.c
index 89da5949b8..444440125c 100644
--- a/ext/openssl/ossl_asn1.c
+++ b/ext/openssl/ossl_asn1.c
@@ -870,19 +870,18 @@ int_ossl_asn1_decode0_cons(unsigned char **pp, long max_len, long length,
 {
     VALUE value, asn1data, ary;
     int infinite;
-    long off = *offset;
+    long available_len, off = *offset;
 
     infinite = (j == 0x21);
     ary = rb_ary_new();
 
-    while (length > 0 || infinite) {
+    available_len = infinite ? max_len : length;
+    while (available_len > 0) {
 	long inner_read = 0;
-	value = ossl_asn1_decode0(pp, max_len, &off, depth + 1, yield, &inner_read);
+	value = ossl_asn1_decode0(pp, available_len, &off, depth + 1, yield, &inner_read);
 	*num_read += inner_read;
-	max_len -= inner_read;
+	available_len -= inner_read;
 	rb_ary_push(ary, value);
-	if (length > 0)
-	    length -= inner_read;
 
 	if (infinite &&
 	    NUM2INT(ossl_asn1_get_tag(value)) == V_ASN1_EOC &&
@@ -973,7 +972,7 @@ ossl_asn1_decode0(unsigned char **pp, long length, long *offset, int depth,
     if(j & V_ASN1_CONSTRUCTED) {
 	*pp += hlen;
 	off += hlen;
-	asn1data = int_ossl_asn1_decode0_cons(pp, length, len, &off, depth, yield, j, tag, tag_class, &inner_read);
+	asn1data = int_ossl_asn1_decode0_cons(pp, length - hlen, len, &off, depth, yield, j, tag, tag_class, &inner_read);
 	inner_read += hlen;
     }
     else {
diff --git a/test/openssl/test_asn1.rb b/test/openssl/test_asn1.rb
index fd2118d808..109fd95fd4 100644
--- a/test/openssl/test_asn1.rb
+++ b/test/openssl/test_asn1.rb
@@ -596,6 +596,29 @@ rEzBQ0F9dUyqQ9gyRg8KHhDfv9HzT1d/rnUZMkoombwYBRIUChGCYV0GnJcan2Zm
     assert_equal(false, asn1.value[3].infinite_length)
   end
 
+  def test_decode_constructed_overread
+    test = %w{ 31 06 31 02 30 02 05 00 }
+    #                          ^ <- invalid
+    raw = [test.join].pack("H*")
+    ret = []
+    assert_raise(OpenSSL::ASN1::ASN1Error) {
+      OpenSSL::ASN1.traverse(raw) { |x| ret << x }
+    }
+    assert_equal 2, ret.size
+    assert_equal 17, ret[0][6]
+    assert_equal 17, ret[1][6]
+
+    test = %w{ 31 80 30 03 00 00 }
+    #                    ^ <- invalid
+    raw = [test.join].pack("H*")
+    ret = []
+    assert_raise(OpenSSL::ASN1::ASN1Error) {
+      OpenSSL::ASN1.traverse(raw) { |x| ret << x }
+    }
+    assert_equal 1, ret.size
+    assert_equal 17, ret[0][6]
+  end
+
   private
 
   def assert_universal(tag, asn1)
diff --git a/version.h b/version.h
index 949ea42fd0..f67d12fb44 100644
--- a/version.h
+++ b/version.h
@@ -1,6 +1,6 @@
 #define RUBY_VERSION "2.3.5"
 #define RUBY_RELEASE_DATE "2017-09-09"
-#define RUBY_PATCHLEVEL 368
+#define RUBY_PATCHLEVEL 369
 
 #define RUBY_RELEASE_YEAR 2017
 #define RUBY_RELEASE_MONTH 9