1 files changed, 220 insertions, 0 deletions

diff --git a/src/lib/libssl/bs_ber.c b/src/lib/libssl/bs_ber.c
new file mode 100644
index 0000000000..b94b63e37e
--- /dev/null
+++ b/src/lib/libssl/bs_ber.c
@@ -0,0 +1,220 @@
+/*      $OpenBSD: bs_ber.c,v 1.1 2015/02/06 09:36:16 doug Exp $ */
+/*
+ * Copyright (c) 2014, Google Inc.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+ * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+ * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
+
+#include <string.h>
+
+#include <openssl/opensslconf.h>
+
+#include "bytestring.h"
+
+/* kMaxDepth is a just a sanity limit. The code should be such that the length
+ * of the input being processes always decreases. None the less, a very large
+ * input could otherwise cause the stack to overflow. */
+static const unsigned kMaxDepth = 2048;
+
+/* cbs_find_ber walks an ASN.1 structure in |orig_in| and sets |*ber_found|
+ * depending on whether an indefinite length element was found. The value of
+ * |in| is not changed. It returns one on success (i.e. |*ber_found| was set)
+ * and zero on error. */
+static int cbs_find_ber(CBS *orig_in, char *ber_found, unsigned depth) {
+  CBS in;
+
+  if (depth > kMaxDepth) {
+    return 0;
+  }
+
+  CBS_init(&in, CBS_data(orig_in), CBS_len(orig_in));
+  *ber_found = 0;
+
+  while (CBS_len(&in) > 0) {
+    CBS contents;
+    unsigned tag;
+    size_t header_len;
+
+    if (!CBS_get_any_asn1_element(&in, &contents, &tag, &header_len)) {
+      return 0;
+    }
+    if (CBS_len(&contents) == header_len &&
+        header_len > 0 &&
+        CBS_data(&contents)[header_len-1] == 0x80) {
+      *ber_found = 1;
+      return 1;
+    }
+    if (tag & CBS_ASN1_CONSTRUCTED) {
+      if (!CBS_skip(&contents, header_len) ||
+          !cbs_find_ber(&contents, ber_found, depth + 1)) {
+        return 0;
+      }
+    }
+  }
+
+  return 1;
+}
+
+/* is_primitive_type returns true if |tag| likely a primitive type. Normally
+ * one can just test the "constructed" bit in the tag but, in BER, even
+ * primitive tags can have the constructed bit if they have indefinite
+ * length. */
+static char is_primitive_type(unsigned tag) {
+  return (tag & 0xc0) == 0 &&
+         (tag & 0x1f) != (CBS_ASN1_SEQUENCE & 0x1f) &&
+         (tag & 0x1f) != (CBS_ASN1_SET & 0x1f);
+}
+
+/* is_eoc returns true if |header_len| and |contents|, as returned by
+ * |CBS_get_any_asn1_element|, indicate an "end of contents" (EOC) value. */
+static char is_eoc(size_t header_len, CBS *contents) {
+  return header_len == 2 && CBS_len(contents) == 2 &&
+         memcmp(CBS_data(contents), "\x00\x00", 2) == 0;
+}
+
+/* cbs_convert_ber reads BER data from |in| and writes DER data to |out|. If
+ * |squash_header| is set then the top-level of elements from |in| will not
+ * have their headers written. This is used when concatenating the fragments of
+ * an indefinite length, primitive value. If |looking_for_eoc| is set then any
+ * EOC elements found will cause the function to return after consuming it.
+ * It returns one on success and zero on error. */
+static int cbs_convert_ber(CBS *in, CBB *out, char squash_header,
+                           char looking_for_eoc, unsigned depth) {
+  if (depth > kMaxDepth) {
+    return 0;
+  }
+
+  while (CBS_len(in) > 0) {
+    CBS contents;
+    unsigned tag;
+    size_t header_len;
+    CBB *out_contents, out_contents_storage;
+
+    if (!CBS_get_any_asn1_element(in, &contents, &tag, &header_len)) {
+      return 0;
+    }
+    out_contents = out;
+
+    if (CBS_len(&contents) == header_len) {
+      if (is_eoc(header_len, &contents)) {
+        return looking_for_eoc;
+      }
+
+      if (header_len > 0 && CBS_data(&contents)[header_len - 1] == 0x80) {
+        /* This is an indefinite length element. If it's a SEQUENCE or SET then
+         * we just need to write the out the contents as normal, but with a
+         * concrete length prefix.
+         *
+         * If it's a something else then the contents will be a series of BER
+         * elements of the same type which need to be concatenated. */
+        const char context_specific = (tag & 0xc0) == 0x80;
+        char squash_child_headers = is_primitive_type(tag);
+
+        /* This is a hack, but it sufficies to handle NSS's output. If we find
+         * an indefinite length, context-specific tag with a definite, primtive
+         * tag inside it, then we assume that the context-specific tag is
+         * implicit and the tags within are fragments of a primitive type that
+         * need to be concatenated. */
+        if (context_specific && (tag & CBS_ASN1_CONSTRUCTED)) {
+          CBS in_copy, inner_contents;
+          unsigned inner_tag;
+          size_t inner_header_len;
+
+          CBS_init(&in_copy, CBS_data(in), CBS_len(in));
+          if (!CBS_get_any_asn1_element(&in_copy, &inner_contents, &inner_tag,
+                                        &inner_header_len)) {
+            return 0;
+          }
+          if (CBS_len(&inner_contents) > inner_header_len &&
+              is_primitive_type(inner_tag)) {
+            squash_child_headers = 1;
+          }
+        }
+
+        if (!squash_header) {
+          unsigned out_tag = tag;
+          if (squash_child_headers) {
+            out_tag &= ~CBS_ASN1_CONSTRUCTED;
+          }
+          if (!CBB_add_asn1(out, &out_contents_storage, out_tag)) {
+            return 0;
+          }
+          out_contents = &out_contents_storage;
+        }
+
+        if (!cbs_convert_ber(in, out_contents,
+                             squash_child_headers,
+                             1 /* looking for eoc */, depth + 1)) {
+          return 0;
+        }
+        if (out_contents != out && !CBB_flush(out)) {
+          return 0;
+        }
+        continue;
+      }
+    }
+
+    if (!squash_header) {
+      if (!CBB_add_asn1(out, &out_contents_storage, tag)) {
+        return 0;
+      }
+      out_contents = &out_contents_storage;
+    }
+
+    if (!CBS_skip(&contents, header_len)) {
+      return 0;
+    }
+
+    if (tag & CBS_ASN1_CONSTRUCTED) {
+      if (!cbs_convert_ber(&contents, out_contents, 0 /* don't squash header */,
+                           0 /* not looking for eoc */, depth + 1)) {
+        return 0;
+      }
+    } else {
+      if (!CBB_add_bytes(out_contents, CBS_data(&contents),
+                         CBS_len(&contents))) {
+        return 0;
+      }
+    }
+
+    if (out_contents != out && !CBB_flush(out)) {
+      return 0;
+    }
+  }
+
+  return looking_for_eoc == 0;
+}
+
+int CBS_asn1_ber_to_der(CBS *in, uint8_t **out, size_t *out_len) {
+  CBB cbb;
+
+  /* First, do a quick walk to find any indefinite-length elements. Most of the
+   * time we hope that there aren't any and thus we can quickly return. */
+  char conversion_needed;
+  if (!cbs_find_ber(in, &conversion_needed, 0)) {
+    return 0;
+  }
+
+  if (!conversion_needed) {
+    *out = NULL;
+    *out_len = 0;
+    return 1;
+  }
+
+  CBB_init(&cbb, CBS_len(in));
+  if (!cbs_convert_ber(in, &cbb, 0, 0, 0)) {
+    CBB_cleanup(&cbb);
+    return 0;
+  }
+
+  return CBB_finish(&cbb, out, out_len);
+}