Initial commit of BoringSSL for Android.

6 files changed, 1702 insertions, 0 deletions

diff --git a/src/crypto/bytestring/CMakeLists.txt b/src/crypto/bytestring/CMakeLists.txt
new file mode 100644
index 0000000..8d6be7b
--- /dev/null
+++ b/src/crypto/bytestring/CMakeLists.txt
@@ -0,0 +1,19 @@
+include_directories(. .. ../../include)
+
+add_library(
+  bytestring
+
+  OBJECT
+
+  ber.c
+  cbs.c
+  cbb.c
+)
+
+add_executable(
+  bytestring_test
+
+  bytestring_test.c
+)
+
+target_link_libraries(bytestring_test crypto)
diff --git a/src/crypto/bytestring/ber.c b/src/crypto/bytestring/ber.c
new file mode 100644
index 0000000..2729fa1
--- /dev/null
+++ b/src/crypto/bytestring/ber.c
@@ -0,0 +1,219 @@
+/* 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 <openssl/bytestring.h>
+
+#include <string.h>
+
+#include "internal.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);
+}
diff --git a/src/crypto/bytestring/bytestring_test.c b/src/crypto/bytestring/bytestring_test.c
new file mode 100644
index 0000000..cd0155e
--- /dev/null
+++ b/src/crypto/bytestring/bytestring_test.c
@@ -0,0 +1,655 @@
+/* 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 <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <openssl/crypto.h>
+#include <openssl/bytestring.h>
+
+#include "internal.h"
+#include "../internal.h"
+
+
+static int test_skip(void) {
+  static const uint8_t kData[] = {1, 2, 3};
+  CBS data;
+
+  CBS_init(&data, kData, sizeof(kData));
+  return CBS_len(&data) == 3 &&
+      CBS_skip(&data, 1) &&
+      CBS_len(&data) == 2 &&
+      CBS_skip(&data, 2) &&
+      CBS_len(&data) == 0 &&
+      !CBS_skip(&data, 1);
+}
+
+static int test_get_u(void) {
+  static const uint8_t kData[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
+  uint8_t u8;
+  uint16_t u16;
+  uint32_t u32;
+  CBS data;
+
+  CBS_init(&data, kData, sizeof(kData));
+  return CBS_get_u8(&data, &u8) &&
+    u8 == 1 &&
+    CBS_get_u16(&data, &u16) &&
+    u16 == 0x203 &&
+    CBS_get_u24(&data, &u32) &&
+    u32 == 0x40506 &&
+    CBS_get_u32(&data, &u32) &&
+    u32 == 0x708090a &&
+    !CBS_get_u8(&data, &u8);
+}
+
+static int test_get_prefixed(void) {
+  static const uint8_t kData[] = {1, 2, 0, 2, 3, 4, 0, 0, 3, 3, 2, 1};
+  uint8_t u8;
+  uint16_t u16;
+  uint32_t u32;
+  CBS data, prefixed;
+
+  CBS_init(&data, kData, sizeof(kData));
+  return CBS_get_u8_length_prefixed(&data, &prefixed) &&
+    CBS_len(&prefixed) == 1 &&
+    CBS_get_u8(&prefixed, &u8) &&
+    u8 == 2 &&
+    CBS_get_u16_length_prefixed(&data, &prefixed) &&
+    CBS_len(&prefixed) == 2 &&
+    CBS_get_u16(&prefixed, &u16) &&
+    u16 == 0x304 &&
+    CBS_get_u24_length_prefixed(&data, &prefixed) &&
+    CBS_len(&prefixed) == 3 &&
+    CBS_get_u24(&prefixed, &u32) &&
+    u32 == 0x30201;
+}
+
+static int test_get_prefixed_bad(void) {
+  static const uint8_t kData1[] = {2, 1};
+  static const uint8_t kData2[] = {0, 2, 1};
+  static const uint8_t kData3[] = {0, 0, 2, 1};
+  CBS data, prefixed;
+
+  CBS_init(&data, kData1, sizeof(kData1));
+  if (CBS_get_u8_length_prefixed(&data, &prefixed)) {
+    return 0;
+  }
+
+  CBS_init(&data, kData2, sizeof(kData2));
+  if (CBS_get_u16_length_prefixed(&data, &prefixed)) {
+    return 0;
+  }
+
+  CBS_init(&data, kData3, sizeof(kData3));
+  if (CBS_get_u24_length_prefixed(&data, &prefixed)) {
+    return 0;
+  }
+
+  return 1;
+}
+
+static int test_get_asn1(void) {
+  static const uint8_t kData1[] = {0x30, 2, 1, 2};
+  static const uint8_t kData2[] = {0x30, 3, 1, 2};
+  static const uint8_t kData3[] = {0x30, 0x80};
+  static const uint8_t kData4[] = {0x30, 0x81, 1, 1};
+  static const uint8_t kData5[] = {0x30, 0x82, 0, 1, 1};
+  static const uint8_t kData6[] = {0xa1, 3, 0x4, 1, 1};
+  static const uint8_t kData7[] = {0xa1, 3, 0x4, 2, 1};
+  static const uint8_t kData8[] = {0xa1, 3, 0x2, 1, 1};
+  static const uint8_t kData9[] = {0xa1, 3, 0x2, 1, 0xff};
+
+  CBS data, contents;
+  int present;
+  uint64_t value;
+
+  CBS_init(&data, kData1, sizeof(kData1));
+  if (CBS_peek_asn1_tag(&data, 0x1) ||
+      !CBS_peek_asn1_tag(&data, 0x30)) {
+    return 0;
+  }
+  if (!CBS_get_asn1(&data, &contents, 0x30) ||
+      CBS_len(&contents) != 2 ||
+      memcmp(CBS_data(&contents), "\x01\x02", 2) != 0) {
+    return 0;
+  }
+
+  CBS_init(&data, kData2, sizeof(kData2));
+  /* data is truncated */
+  if (CBS_get_asn1(&data, &contents, 0x30)) {
+    return 0;
+  }
+
+  CBS_init(&data, kData3, sizeof(kData3));
+  /* zero byte length of length */
+  if (CBS_get_asn1(&data, &contents, 0x30)) {
+    return 0;
+  }
+
+  CBS_init(&data, kData4, sizeof(kData4));
+  /* long form mistakenly used. */
+  if (CBS_get_asn1(&data, &contents, 0x30)) {
+    return 0;
+  }
+
+  CBS_init(&data, kData5, sizeof(kData5));
+  /* length takes too many bytes. */
+  if (CBS_get_asn1(&data, &contents, 0x30)) {
+    return 0;
+  }
+
+  CBS_init(&data, kData1, sizeof(kData1));
+  /* wrong tag. */
+  if (CBS_get_asn1(&data, &contents, 0x31)) {
+    return 0;
+  }
+
+  CBS_init(&data, NULL, 0);
+  /* peek at empty data. */
+  if (CBS_peek_asn1_tag(&data, 0x30)) {
+    return 0;
+  }
+
+  CBS_init(&data, NULL, 0);
+  /* optional elements at empty data. */
+  if (!CBS_get_optional_asn1(&data, &contents, &present, 0xa0) ||
+      present ||
+      !CBS_get_optional_asn1_octet_string(&data, &contents, &present, 0xa0) ||
+      present ||
+      CBS_len(&contents) != 0 ||
+      !CBS_get_optional_asn1_octet_string(&data, &contents, NULL, 0xa0) ||
+      CBS_len(&contents) != 0 ||
+      !CBS_get_optional_asn1_uint64(&data, &value, 0xa0, 42) ||
+      value != 42) {
+    return 0;
+  }
+
+  CBS_init(&data, kData6, sizeof(kData6));
+  /* optional element. */
+  if (!CBS_get_optional_asn1(&data, &contents, &present, 0xa0) ||
+      present ||
+      !CBS_get_optional_asn1(&data, &contents, &present, 0xa1) ||
+      !present ||
+      CBS_len(&contents) != 3 ||
+      memcmp(CBS_data(&contents), "\x04\x01\x01", 3) != 0) {
+    return 0;
+  }
+
+  CBS_init(&data, kData6, sizeof(kData6));
+  /* optional octet string. */
+  if (!CBS_get_optional_asn1_octet_string(&data, &contents, &present, 0xa0) ||
+      present ||
+      CBS_len(&contents) != 0 ||
+      !CBS_get_optional_asn1_octet_string(&data, &contents, &present, 0xa1) ||
+      !present ||
+      CBS_len(&contents) != 1 ||
+      CBS_data(&contents)[0] != 1) {
+    return 0;
+  }
+
+  CBS_init(&data, kData7, sizeof(kData7));
+  /* invalid optional octet string. */
+  if (CBS_get_optional_asn1_octet_string(&data, &contents, &present, 0xa1)) {
+    return 0;
+  }
+
+  CBS_init(&data, kData8, sizeof(kData8));
+  /* optional octet string. */
+  if (!CBS_get_optional_asn1_uint64(&data, &value, 0xa0, 42) ||
+      value != 42 ||
+      !CBS_get_optional_asn1_uint64(&data, &value, 0xa1, 42) ||
+      value != 1) {
+    return 0;
+  }
+
+  CBS_init(&data, kData9, sizeof(kData9));
+  /* invalid optional integer. */
+  if (CBS_get_optional_asn1_uint64(&data, &value, 0xa1, 42)) {
+    return 0;
+  }
+
+  return 1;
+}
+
+static int test_get_optional_asn1_bool(void) {
+  CBS data;
+  int val;
+
+  static const uint8_t kTrue[] = {0x0a, 3, CBS_ASN1_BOOLEAN, 1, 0xff};
+  static const uint8_t kFalse[] = {0x0a, 3, CBS_ASN1_BOOLEAN, 1, 0x00};
+  static const uint8_t kInvalid[] = {0x0a, 3, CBS_ASN1_BOOLEAN, 1, 0x01};
+
+  CBS_init(&data, NULL, 0);
+  val = 2;
+  if (!CBS_get_optional_asn1_bool(&data, &val, 0x0a, 0) ||
+      val != 0) {
+    return 0;
+  }
+
+  CBS_init(&data, kTrue, sizeof(kTrue));
+  val = 2;
+  if (!CBS_get_optional_asn1_bool(&data, &val, 0x0a, 0) ||
+      val != 1) {
+    return 0;
+  }
+
+  CBS_init(&data, kFalse, sizeof(kFalse));
+  val = 2;
+  if (!CBS_get_optional_asn1_bool(&data, &val, 0x0a, 1) ||
+      val != 0) {
+    return 0;
+  }
+
+  CBS_init(&data, kInvalid, sizeof(kInvalid));
+  if (CBS_get_optional_asn1_bool(&data, &val, 0x0a, 1)) {
+    return 0;
+  }
+
+  return 1;
+}
+
+static int test_cbb_basic(void) {
+  static const uint8_t kExpected[] = {1, 2, 3, 4, 5, 6, 7, 8};
+  uint8_t *buf;
+  size_t buf_len;
+  int ok;
+  CBB cbb;
+
+  if (!CBB_init(&cbb, 100)) {
+    return 0;
+  }
+  CBB_cleanup(&cbb);
+
+  if (!CBB_init(&cbb, 0) ||
+      !CBB_add_u8(&cbb, 1) ||
+      !CBB_add_u16(&cbb, 0x203) ||
+      !CBB_add_u24(&cbb, 0x40506) ||
+      !CBB_add_bytes(&cbb, (const uint8_t*) "\x07\x08", 2) ||
+      !CBB_finish(&cbb, &buf, &buf_len)) {
+    return 0;
+  }
+
+  ok = buf_len == sizeof(kExpected) && memcmp(buf, kExpected, buf_len) == 0;
+  free(buf);
+  return ok;
+}
+
+static int test_cbb_fixed(void) {
+  CBB cbb;
+  uint8_t buf[1];
+  uint8_t *out_buf;
+  size_t out_size;
+
+  if (!CBB_init_fixed(&cbb, NULL, 0) ||
+      CBB_add_u8(&cbb, 1) ||
+      !CBB_finish(&cbb, &out_buf, &out_size) ||
+      out_buf != NULL ||
+      out_size != 0) {
+    return 0;
+  }
+
+  if (!CBB_init_fixed(&cbb, buf, 1) ||
+      !CBB_add_u8(&cbb, 1) ||
+      CBB_add_u8(&cbb, 2) ||
+      !CBB_finish(&cbb, &out_buf, &out_size) ||
+      out_buf != buf ||
+      out_size != 1 ||
+      buf[0] != 1) {
+    return 0;
+  }
+
+  return 1;
+}
+
+static int test_cbb_finish_child(void) {
+  CBB cbb, child;
+  uint8_t *out_buf;
+  size_t out_size;
+
+  if (!CBB_init(&cbb, 16) ||
+      !CBB_add_u8_length_prefixed(&cbb, &child) ||
+      CBB_finish(&child, &out_buf, &out_size) ||
+      !CBB_finish(&cbb, &out_buf, &out_size) ||
+      out_size != 1 ||
+      out_buf[0] != 0) {
+    return 0;
+  }
+
+  free(out_buf);
+  return 1;
+}
+
+static int test_cbb_prefixed(void) {
+  static const uint8_t kExpected[] = {0, 1, 1, 0, 2, 2, 3, 0, 0, 3,
+                                      4, 5, 6, 5, 4, 1, 0, 1, 2};
+  uint8_t *buf;
+  size_t buf_len;
+  CBB cbb, contents, inner_contents, inner_inner_contents;
+  int ok;
+
+  if (!CBB_init(&cbb, 0) ||
+      !CBB_add_u8_length_prefixed(&cbb, &contents) ||
+      !CBB_add_u8_length_prefixed(&cbb, &contents) ||
+      !CBB_add_u8(&contents, 1) ||
+      !CBB_add_u16_length_prefixed(&cbb, &contents) ||
+      !CBB_add_u16(&contents, 0x203) ||
+      !CBB_add_u24_length_prefixed(&cbb, &contents) ||
+      !CBB_add_u24(&contents, 0x40506) ||
+      !CBB_add_u8_length_prefixed(&cbb, &contents) ||
+      !CBB_add_u8_length_prefixed(&contents, &inner_contents) ||
+      !CBB_add_u8(&inner_contents, 1) ||
+      !CBB_add_u16_length_prefixed(&inner_contents, &inner_inner_contents) ||
+      !CBB_add_u8(&inner_inner_contents, 2) ||
+      !CBB_finish(&cbb, &buf, &buf_len)) {
+    return 0;
+  }
+
+  ok = buf_len == sizeof(kExpected) && memcmp(buf, kExpected, buf_len) == 0;
+  free(buf);
+  return ok;
+}
+
+static int test_cbb_misuse(void) {
+  CBB cbb, child, contents;
+  uint8_t *buf;
+  size_t buf_len;
+
+  if (!CBB_init(&cbb, 0) ||
+      !CBB_add_u8_length_prefixed(&cbb, &child) ||
+      !CBB_add_u8(&child, 1) ||
+      !CBB_add_u8(&cbb, 2)) {
+    return 0;
+  }
+
+  /* Since we wrote to |cbb|, |child| is now invalid and attempts to write to
+   * it should fail. */
+  if (CBB_add_u8(&child, 1) ||
+      CBB_add_u16(&child, 1) ||
+      CBB_add_u24(&child, 1) ||
+      CBB_add_u8_length_prefixed(&child, &contents) ||
+      CBB_add_u16_length_prefixed(&child, &contents) ||
+      CBB_add_asn1(&child, &contents, 1) ||
+      CBB_add_bytes(&child, (const uint8_t*) "a", 1)) {
+    fprintf(stderr, "CBB operation on invalid CBB did not fail.\n");
+    return 0;
+  }
+
+  if (!CBB_finish(&cbb, &buf, &buf_len) ||
+      buf_len != 3 ||
+      memcmp(buf, "\x01\x01\x02", 3) != 0) {
+    return 0;
+  }
+
+  free(buf);
+
+  return 1;
+}
+
+static int test_cbb_asn1(void) {
+  static const uint8_t kExpected[] = {0x30, 3, 1, 2, 3};
+  uint8_t *buf, *test_data;
+  size_t buf_len;
+  CBB cbb, contents, inner_contents;
+
+  if (!CBB_init(&cbb, 0) ||
+      !CBB_add_asn1(&cbb, &contents, 0x30) ||
+      !CBB_add_bytes(&contents, (const uint8_t*) "\x01\x02\x03", 3) ||
+      !CBB_finish(&cbb, &buf, &buf_len)) {
+    return 0;
+  }
+
+  if (buf_len != sizeof(kExpected) || memcmp(buf, kExpected, buf_len) != 0) {
+    return 0;
+  }
+  free(buf);
+
+  test_data = malloc(100000);
+  memset(test_data, 0x42, 100000);
+
+  if (!CBB_init(&cbb, 0) ||
+      !CBB_add_asn1(&cbb, &contents, 0x30) ||
+      !CBB_add_bytes(&contents, test_data, 130) ||
+      !CBB_finish(&cbb, &buf, &buf_len)) {
+    return 0;
+  }
+
+  if (buf_len != 3 + 130 ||
+      memcmp(buf, "\x30\x81\x82", 3) != 0 ||
+      memcmp(buf + 3, test_data, 130) != 0) {
+    return 0;
+  }
+  free(buf);
+
+  if (!CBB_init(&cbb, 0) ||
+      !CBB_add_asn1(&cbb, &contents, 0x30) ||
+      !CBB_add_bytes(&contents, test_data, 1000) ||
+      !CBB_finish(&cbb, &buf, &buf_len)) {
+    return 0;
+  }
+
+  if (buf_len != 4 + 1000 ||
+      memcmp(buf, "\x30\x82\x03\xe8", 4) != 0 ||
+      memcmp(buf + 4, test_data, 1000)) {
+    return 0;
+  }
+  free(buf);
+
+  if (!CBB_init(&cbb, 0) ||
+      !CBB_add_asn1(&cbb, &contents, 0x30) ||
+      !CBB_add_asn1(&contents, &inner_contents, 0x30) ||
+      !CBB_add_bytes(&inner_contents, test_data, 100000) ||
+      !CBB_finish(&cbb, &buf, &buf_len)) {
+    return 0;
+  }
+
+  if (buf_len != 5 + 5 + 100000 ||
+      memcmp(buf, "\x30\x83\x01\x86\xa5\x30\x83\x01\x86\xa0", 10) != 0 ||
+      memcmp(buf + 10, test_data, 100000)) {
+    return 0;
+  }
+  free(buf);
+
+  free(test_data);
+  return 1;
+}
+
+static int do_ber_convert(const char *name,
+                          const uint8_t *der_expected, size_t der_len,
+                          const uint8_t *ber, size_t ber_len) {
+  CBS in;
+  uint8_t *out;
+  size_t out_len;
+
+  CBS_init(&in, ber, ber_len);
+  if (!CBS_asn1_ber_to_der(&in, &out, &out_len)) {
+    fprintf(stderr, "%s: CBS_asn1_ber_to_der failed.\n", name);
+    return 0;
+  }
+
+  if (out == NULL) {
+    if (ber_len != der_len ||
+        memcmp(der_expected, ber, ber_len) != 0) {
+      fprintf(stderr, "%s: incorrect unconverted result.\n", name);
+      return 0;
+    }
+
+    return 1;
+  }
+
+  if (out_len != der_len ||
+      memcmp(out, der_expected, der_len) != 0) {
+    fprintf(stderr, "%s: incorrect converted result.\n", name);
+    return 0;
+  }
+
+  free(out);
+  return 1;
+}
+
+static int test_ber_convert(void) {
+  static const uint8_t kSimpleBER[] = {0x01, 0x01, 0x00};
+
+  /* kIndefBER contains a SEQUENCE with an indefinite length. */
+  static const uint8_t kIndefBER[] = {0x30, 0x80, 0x01, 0x01, 0x02, 0x00, 0x00};
+  static const uint8_t kIndefDER[] = {0x30, 0x03, 0x01, 0x01, 0x02};
+
+  /* kOctetStringBER contains an indefinite length OCTETSTRING with two parts.
+   * These parts need to be concatenated in DER form. */
+  static const uint8_t kOctetStringBER[] = {0x24, 0x80, 0x04, 0x02, 0,    1,
+                                            0x04, 0x02, 2,    3,    0x00, 0x00};
+  static const uint8_t kOctetStringDER[] = {0x04, 0x04, 0, 1, 2, 3};
+
+  /* kNSSBER is part of a PKCS#12 message generated by NSS that uses indefinite
+   * length elements extensively. */
+  static const uint8_t kNSSBER[] = {
+      0x30, 0x80, 0x02, 0x01, 0x03, 0x30, 0x80, 0x06, 0x09, 0x2a, 0x86, 0x48,
+      0x86, 0xf7, 0x0d, 0x01, 0x07, 0x01, 0xa0, 0x80, 0x24, 0x80, 0x04, 0x04,
+      0x01, 0x02, 0x03, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x30, 0x39,
+      0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2b, 0x0e, 0x03, 0x02, 0x1a, 0x05,
+      0x00, 0x04, 0x14, 0x84, 0x98, 0xfc, 0x66, 0x33, 0xee, 0xba, 0xe7, 0x90,
+      0xc1, 0xb6, 0xe8, 0x8f, 0xfe, 0x1d, 0xc5, 0xa5, 0x97, 0x93, 0x3e, 0x04,
+      0x10, 0x38, 0x62, 0xc6, 0x44, 0x12, 0xd5, 0x30, 0x00, 0xf8, 0xf2, 0x1b,
+      0xf0, 0x6e, 0x10, 0x9b, 0xb8, 0x02, 0x02, 0x07, 0xd0, 0x00, 0x00,
+  };
+
+  static const uint8_t kNSSDER[] = {
+      0x30, 0x53, 0x02, 0x01, 0x03, 0x30, 0x13, 0x06, 0x09, 0x2a, 0x86,
+      0x48, 0x86, 0xf7, 0x0d, 0x01, 0x07, 0x01, 0xa0, 0x06, 0x04, 0x04,
+      0x01, 0x02, 0x03, 0x04, 0x30, 0x39, 0x30, 0x21, 0x30, 0x09, 0x06,
+      0x05, 0x2b, 0x0e, 0x03, 0x02, 0x1a, 0x05, 0x00, 0x04, 0x14, 0x84,
+      0x98, 0xfc, 0x66, 0x33, 0xee, 0xba, 0xe7, 0x90, 0xc1, 0xb6, 0xe8,
+      0x8f, 0xfe, 0x1d, 0xc5, 0xa5, 0x97, 0x93, 0x3e, 0x04, 0x10, 0x38,
+      0x62, 0xc6, 0x44, 0x12, 0xd5, 0x30, 0x00, 0xf8, 0xf2, 0x1b, 0xf0,
+      0x6e, 0x10, 0x9b, 0xb8, 0x02, 0x02, 0x07, 0xd0,
+  };
+
+  return do_ber_convert("kSimpleBER", kSimpleBER, sizeof(kSimpleBER),
+                        kSimpleBER, sizeof(kSimpleBER)) &&
+         do_ber_convert("kIndefBER", kIndefDER, sizeof(kIndefDER), kIndefBER,
+                        sizeof(kIndefBER)) &&
+         do_ber_convert("kOctetStringBER", kOctetStringDER,
+                        sizeof(kOctetStringDER), kOctetStringBER,
+                        sizeof(kOctetStringBER)) &&
+         do_ber_convert("kNSSBER", kNSSDER, sizeof(kNSSDER), kNSSBER,
+                        sizeof(kNSSBER));
+}
+
+typedef struct {
+  uint64_t value;
+  const char *encoding;
+  size_t encoding_len;
+} ASN1_UINT64_TEST;
+
+static const ASN1_UINT64_TEST kAsn1Uint64Tests[] = {
+  {0, "\x02\x01\x00", 3},
+  {1, "\x02\x01\x01", 3},
+  {127, "\x02\x01\x7f", 3},
+  {128, "\x02\x02\x00\x80", 4},
+  {0xdeadbeef, "\x02\x05\x00\xde\xad\xbe\xef", 7},
+  {OPENSSL_U64(0x0102030405060708),
+   "\x02\x08\x01\x02\x03\x04\x05\x06\x07\x08", 10},
+  {OPENSSL_U64(0xffffffffffffffff),
+    "\x02\x09\x00\xff\xff\xff\xff\xff\xff\xff\xff", 11},
+};
+
+typedef struct {
+  const char *encoding;
+  size_t encoding_len;
+} ASN1_INVALID_UINT64_TEST;
+
+static const ASN1_INVALID_UINT64_TEST kAsn1InvalidUint64Tests[] = {
+  /* Bad tag. */
+  {"\x03\x01\x00", 3},
+  /* Empty contents. */
+  {"\x02\x00", 2},
+  /* Negative number. */
+  {"\x02\x01\x80", 3},
+  /* Overflow */
+  {"\x02\x09\x01\x00\x00\x00\x00\x00\x00\x00\x00", 11},
+};
+
+static int test_asn1_uint64(void) {
+  size_t i;
+
+  for (i = 0; i < sizeof(kAsn1Uint64Tests) / sizeof(kAsn1Uint64Tests[0]); i++) {
+    const ASN1_UINT64_TEST *test = &kAsn1Uint64Tests[i];
+    CBS cbs;
+    uint64_t value;
+    CBB cbb;
+    uint8_t *out;
+    size_t len;
+
+    CBS_init(&cbs, (const uint8_t *)test->encoding, test->encoding_len);
+    if (!CBS_get_asn1_uint64(&cbs, &value) ||
+        CBS_len(&cbs) != 0 ||
+        value != test->value) {
+      return 0;
+    }
+
+    if (!CBB_init(&cbb, 0)) {
+      return 0;
+    }
+    if (!CBB_add_asn1_uint64(&cbb, test->value) ||
+        !CBB_finish(&cbb, &out, &len)) {
+      CBB_cleanup(&cbb);
+      return 0;
+    }
+    if (len != test->encoding_len || memcmp(out, test->encoding, len) != 0) {
+      free(out);
+      return 0;
+    }
+    free(out);
+  }
+
+  for (i = 0;
+       i < sizeof(kAsn1InvalidUint64Tests) / sizeof(kAsn1InvalidUint64Tests[0]);
+       i++) {
+    const ASN1_INVALID_UINT64_TEST *test = &kAsn1InvalidUint64Tests[i];
+    CBS cbs;
+    uint64_t value;
+
+    CBS_init(&cbs, (const uint8_t *)test->encoding, test->encoding_len);
+    if (CBS_get_asn1_uint64(&cbs, &value)) {
+      return 0;
+    }
+  }
+
+  return 1;
+}
+
+int main(void) {
+  CRYPTO_library_init();
+
+  if (!test_skip() ||
+      !test_get_u() ||
+      !test_get_prefixed() ||
+      !test_get_prefixed_bad() ||
+      !test_get_asn1() ||
+      !test_cbb_basic() ||
+      !test_cbb_fixed() ||
+      !test_cbb_finish_child() ||
+      !test_cbb_misuse() ||
+      !test_cbb_prefixed() ||
+      !test_cbb_asn1() ||
+      !test_ber_convert() ||
+      !test_asn1_uint64() ||
+      !test_get_optional_asn1_bool()) {
+    return 1;
+  }
+
+  printf("PASS\n");
+  return 0;
+}
diff --git a/src/crypto/bytestring/cbb.c b/src/crypto/bytestring/cbb.c
new file mode 100644
index 0000000..4428836
--- /dev/null
+++ b/src/crypto/bytestring/cbb.c
@@ -0,0 +1,375 @@
+/* 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 <openssl/bytestring.h>
+
+#include <assert.h>
+#include <string.h>
+
+#include <openssl/mem.h>
+
+
+static int cbb_init(CBB *cbb, uint8_t *buf, size_t cap) {
+  struct cbb_buffer_st *base;
+
+  base = OPENSSL_malloc(sizeof(struct cbb_buffer_st));
+  if (base == NULL) {
+    OPENSSL_free(buf);
+    return 0;
+  }
+
+  base->buf = buf;
+  base->len = 0;
+  base->cap = cap;
+  base->can_resize = 1;
+
+  memset(cbb, 0, sizeof(CBB));
+  cbb->base = base;
+  cbb->is_top_level = 1;
+  return 1;
+}
+
+int CBB_init(CBB *cbb, size_t initial_capacity) {
+  uint8_t *buf;
+
+  buf = OPENSSL_malloc(initial_capacity);
+  if (initial_capacity > 0 && buf == NULL) {
+    return 0;
+  }
+
+  return cbb_init(cbb, buf, initial_capacity);
+}
+
+int CBB_init_fixed(CBB *cbb, uint8_t *buf, size_t len) {
+  if (!cbb_init(cbb, buf, len)) {
+    return 0;
+  }
+
+  cbb->base->can_resize = 0;
+  return 1;
+}
+
+void CBB_cleanup(CBB *cbb) {
+  if (cbb->base) {
+    if (cbb->base->buf && cbb->base->can_resize) {
+      OPENSSL_free(cbb->base->buf);
+    }
+    OPENSSL_free(cbb->base);
+  }
+  cbb->base = NULL;
+}
+
+static int cbb_buffer_add(struct cbb_buffer_st *base, uint8_t **out,
+                          size_t len) {
+  size_t newlen;
+
+  if (base == NULL) {
+    return 0;
+  }
+
+  newlen = base->len + len;
+  if (newlen < base->len) {
+    /* Overflow */
+    return 0;
+  }
+
+  if (newlen > base->cap) {
+    size_t newcap = base->cap * 2;
+    uint8_t *newbuf;
+
+    if (!base->can_resize) {
+      return 0;
+    }
+
+    if (newcap < base->cap || newcap < newlen) {
+      newcap = newlen;
+    }
+    newbuf = OPENSSL_realloc(base->buf, newcap);
+    if (newbuf == NULL) {
+      return 0;
+    }
+
+    base->buf = newbuf;
+    base->cap = newcap;
+  }
+
+  if (out) {
+    *out = base->buf + base->len;
+  }
+  base->len = newlen;
+  return 1;
+}
+
+static int cbb_buffer_add_u(struct cbb_buffer_st *base, uint32_t v,
+                            size_t len_len) {
+  uint8_t *buf;
+  size_t i;
+
+  if (len_len == 0) {
+    return 1;
+  }
+  if (!cbb_buffer_add(base, &buf, len_len)) {
+    return 0;
+  }
+
+  for (i = len_len - 1; i < len_len; i--) {
+    buf[i] = v;
+    v >>= 8;
+  }
+  return 1;
+}
+
+int CBB_finish(CBB *cbb, uint8_t **out_data, size_t *out_len) {
+  if (!cbb->is_top_level) {
+    return 0;
+  }
+
+  if (!CBB_flush(cbb)) {
+    return 0;
+  }
+
+  if (cbb->base->can_resize && (out_data == NULL || out_len == NULL)) {
+    /* |out_data| and |out_len| can only be NULL if the CBB is fixed. */
+    return 0;
+  }
+
+  if (out_data != NULL) {
+    *out_data = cbb->base->buf;
+  }
+  if (out_len != NULL) {
+    *out_len = cbb->base->len;
+  }
+  cbb->base->buf = NULL;
+  CBB_cleanup(cbb);
+  return 1;
+}
+
+/* CBB_flush recurses and then writes out any pending length prefix. The
+ * current length of the underlying base is taken to be the length of the
+ * length-prefixed data. */
+int CBB_flush(CBB *cbb) {
+  size_t child_start, i, len;
+
+  if (cbb->base == NULL) {
+    return 0;
+  }
+
+  if (cbb->child == NULL || cbb->pending_len_len == 0) {
+    return 1;
+  }
+
+  child_start = cbb->offset + cbb->pending_len_len;
+
+  if (!CBB_flush(cbb->child) ||
+      child_start < cbb->offset ||
+      cbb->base->len < child_start) {
+    return 0;
+  }
+
+  len = cbb->base->len - child_start;
+
+  if (cbb->pending_is_asn1) {
+    /* For ASN.1 we assume that we'll only need a single byte for the length.
+     * If that turned out to be incorrect, we have to move the contents along
+     * in order to make space. */
+    size_t len_len;
+    uint8_t initial_length_byte;
+
+    assert (cbb->pending_len_len == 1);
+
+    if (len > 0xfffffffe) {
+      /* Too large. */
+      return 0;
+    } else if (len > 0xffffff) {
+      len_len = 5;
+      initial_length_byte = 0x80 | 4;
+    } else if (len > 0xffff) {
+      len_len = 4;
+      initial_length_byte = 0x80 | 3;
+    } else if (len > 0xff) {
+      len_len = 3;
+      initial_length_byte = 0x80 | 2;
+    } else if (len > 0x7f) {
+      len_len = 2;
+      initial_length_byte = 0x80 | 1;
+    } else {
+      len_len = 1;
+      initial_length_byte = len;
+      len = 0;
+    }
+
+    if (len_len != 1) {
+      /* We need to move the contents along in order to make space. */
+      size_t extra_bytes = len_len - 1;
+      if (!cbb_buffer_add(cbb->base, NULL, extra_bytes)) {
+        return 0;
+      }
+      memmove(cbb->base->buf + child_start + extra_bytes,
+              cbb->base->buf + child_start, len);
+    }
+    cbb->base->buf[cbb->offset++] = initial_length_byte;
+    cbb->pending_len_len = len_len - 1;
+  }
+
+  for (i = cbb->pending_len_len - 1; i < cbb->pending_len_len; i--) {
+    cbb->base->buf[cbb->offset + i] = len;
+    len >>= 8;
+  }
+  if (len != 0) {
+    return 0;
+  }
+
+  cbb->child->base = NULL;
+  cbb->child = NULL;
+  cbb->pending_len_len = 0;
+  cbb->pending_is_asn1 = 0;
+  cbb->offset = 0;
+
+  return 1;
+}
+
+
+static int cbb_add_length_prefixed(CBB *cbb, CBB *out_contents,
+                                   size_t len_len) {
+  uint8_t *prefix_bytes;
+
+  if (!CBB_flush(cbb)) {
+    return 0;
+  }
+
+  cbb->offset = cbb->base->len;
+  if (!cbb_buffer_add(cbb->base, &prefix_bytes, len_len)) {
+    return 0;
+  }
+
+  memset(prefix_bytes, 0, len_len);
+  memset(out_contents, 0, sizeof(CBB));
+  out_contents->base = cbb->base;
+  cbb->child = out_contents;
+  cbb->pending_len_len = len_len;
+  cbb->pending_is_asn1 = 0;
+
+  return 1;
+}
+
+int CBB_add_u8_length_prefixed(CBB *cbb, CBB *out_contents) {
+  return cbb_add_length_prefixed(cbb, out_contents, 1);
+}
+
+int CBB_add_u16_length_prefixed(CBB *cbb, CBB *out_contents) {
+  return cbb_add_length_prefixed(cbb, out_contents, 2);
+}
+
+int CBB_add_u24_length_prefixed(CBB *cbb, CBB *out_contents) {
+  return cbb_add_length_prefixed(cbb, out_contents, 3);
+}
+
+int CBB_add_asn1(CBB *cbb, CBB *out_contents, uint8_t tag) {
+  if (!CBB_flush(cbb) ||
+      !CBB_add_u8(cbb, tag)) {
+    return 0;
+  }
+
+  cbb->offset = cbb->base->len;
+  if (!CBB_add_u8(cbb, 0)) {
+    return 0;
+  }
+
+  memset(out_contents, 0, sizeof(CBB));
+  out_contents->base = cbb->base;
+  cbb->child = out_contents;
+  cbb->pending_len_len = 1;
+  cbb->pending_is_asn1 = 1;
+
+  return 1;
+}
+
+int CBB_add_bytes(CBB *cbb, const uint8_t *data, size_t len) {
+  uint8_t *dest;
+
+  if (!CBB_flush(cbb) ||
+      !cbb_buffer_add(cbb->base, &dest, len)) {
+    return 0;
+  }
+  memcpy(dest, data, len);
+  return 1;
+}
+
+int CBB_add_space(CBB *cbb, uint8_t **out_data, size_t len) {
+  if (!CBB_flush(cbb) ||
+      !cbb_buffer_add(cbb->base, out_data, len)) {
+    return 0;
+  }
+  return 1;
+}
+
+int CBB_add_u8(CBB *cbb, uint8_t value) {
+  if (!CBB_flush(cbb)) {
+    return 0;
+  }
+
+  return cbb_buffer_add_u(cbb->base, value, 1);
+}
+
+int CBB_add_u16(CBB *cbb, uint16_t value) {
+  if (!CBB_flush(cbb)) {
+    return 0;
+  }
+
+  return cbb_buffer_add_u(cbb->base, value, 2);
+}
+
+int CBB_add_u24(CBB *cbb, uint32_t value) {
+  if (!CBB_flush(cbb)) {
+    return 0;
+  }
+
+  return cbb_buffer_add_u(cbb->base, value, 3);
+}
+
+int CBB_add_asn1_uint64(CBB *cbb, uint64_t value) {
+  CBB child;
+  size_t i;
+  int started = 0;
+
+  if (!CBB_add_asn1(cbb, &child, CBS_ASN1_INTEGER)) {
+    return 0;
+  }
+
+  for (i = 0; i < 8; i++) {
+    uint8_t byte = (value >> 8*(7-i)) & 0xff;
+    if (!started) {
+      if (byte == 0) {
+        /* Don't encode leading zeros. */
+        continue;
+      }
+      /* If the high bit is set, add a padding byte to make it
+       * unsigned. */
+      if ((byte & 0x80) && !CBB_add_u8(&child, 0)) {
+        return 0;
+      }
+      started = 1;
+    }
+    if (!CBB_add_u8(&child, byte)) {
+      return 0;
+    }
+  }
+
+  /* 0 is encoded as a single 0, not the empty string. */
+  if (!started && !CBB_add_u8(&child, 0)) {
+    return 0;
+  }
+
+  return CBB_flush(cbb);
+}
diff --git a/src/crypto/bytestring/cbs.c b/src/crypto/bytestring/cbs.c
new file mode 100644
index 0000000..b417716
--- /dev/null
+++ b/src/crypto/bytestring/cbs.c
@@ -0,0 +1,388 @@
+/* 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 <openssl/buf.h>
+#include <openssl/mem.h>
+#include <openssl/bytestring.h>
+
+#include <assert.h>
+#include <string.h>
+
+#include "internal.h"
+
+
+void CBS_init(CBS *cbs, const uint8_t *data, size_t len) {
+  cbs->data = data;
+  cbs->len = len;
+}
+
+static int cbs_get(CBS *cbs, const uint8_t **p, size_t n) {
+  if (cbs->len < n) {
+    return 0;
+  }
+
+  *p = cbs->data;
+  cbs->data += n;
+  cbs->len -= n;
+  return 1;
+}
+
+int CBS_skip(CBS *cbs, size_t len) {
+  const uint8_t *dummy;
+  return cbs_get(cbs, &dummy, len);
+}
+
+const uint8_t *CBS_data(const CBS *cbs) {
+  return cbs->data;
+}
+
+size_t CBS_len(const CBS *cbs) {
+  return cbs->len;
+}
+
+int CBS_stow(const CBS *cbs, uint8_t **out_ptr, size_t *out_len) {
+  if (*out_ptr != NULL) {
+    OPENSSL_free(*out_ptr);
+    *out_ptr = NULL;
+  }
+  *out_len = 0;
+
+  if (cbs->len == 0) {
+    return 1;
+  }
+  *out_ptr = BUF_memdup(cbs->data, cbs->len);
+  if (*out_ptr == NULL) {
+    return 0;
+  }
+  *out_len = cbs->len;
+  return 1;
+}
+
+int CBS_strdup(const CBS *cbs, char **out_ptr) {
+  if (*out_ptr != NULL) {
+    OPENSSL_free(*out_ptr);
+  }
+  *out_ptr = BUF_strndup((const char*)cbs->data, cbs->len);
+  return (*out_ptr != NULL);
+}
+
+int CBS_contains_zero_byte(const CBS *cbs) {
+  return memchr(cbs->data, 0, cbs->len) != NULL;
+}
+
+int CBS_mem_equal(const CBS *cbs, const uint8_t *data, size_t len) {
+  if (len != cbs->len)
+    return 0;
+  return CRYPTO_memcmp(cbs->data, data, len) == 0;
+}
+
+static int cbs_get_u(CBS *cbs, uint32_t *out, size_t len) {
+  uint32_t result = 0;
+  size_t i;
+  const uint8_t *data;
+
+  if (!cbs_get(cbs, &data, len)) {
+    return 0;
+  }
+  for (i = 0; i < len; i++) {
+    result <<= 8;
+    result |= data[i];
+  }
+  *out = result;
+  return 1;
+}
+
+int CBS_get_u8(CBS *cbs, uint8_t *out) {
+  const uint8_t *v;
+  if (!cbs_get(cbs, &v, 1)) {
+    return 0;
+  }
+  *out = *v;
+  return 1;
+}
+
+int CBS_get_u16(CBS *cbs, uint16_t *out) {
+  uint32_t v;
+  if (!cbs_get_u(cbs, &v, 2)) {
+    return 0;
+  }
+  *out = v;
+  return 1;
+}
+
+int CBS_get_u24(CBS *cbs, uint32_t *out) {
+  return cbs_get_u(cbs, out, 3);
+}
+
+int CBS_get_u32(CBS *cbs, uint32_t *out) {
+  return cbs_get_u(cbs, out, 4);
+}
+
+int CBS_get_bytes(CBS *cbs, CBS *out, size_t len) {
+  const uint8_t *v;
+  if (!cbs_get(cbs, &v, len)) {
+    return 0;
+  }
+  CBS_init(out, v, len);
+  return 1;
+}
+
+static int cbs_get_length_prefixed(CBS *cbs, CBS *out, size_t len_len) {
+  uint32_t len;
+  if (!cbs_get_u(cbs, &len, len_len)) {
+    return 0;
+  }
+  return CBS_get_bytes(cbs, out, len);
+}
+
+int CBS_get_u8_length_prefixed(CBS *cbs, CBS *out) {
+  return cbs_get_length_prefixed(cbs, out, 1);
+}
+
+int CBS_get_u16_length_prefixed(CBS *cbs, CBS *out) {
+  return cbs_get_length_prefixed(cbs, out, 2);
+}
+
+int CBS_get_u24_length_prefixed(CBS *cbs, CBS *out) {
+  return cbs_get_length_prefixed(cbs, out, 3);
+}
+
+int CBS_get_any_asn1_element(CBS *cbs, CBS *out, unsigned *out_tag,
+                             size_t *out_header_len) {
+  uint8_t tag, length_byte;
+  CBS header = *cbs;
+  CBS throwaway;
+
+  if (out == NULL) {
+    out = &throwaway;
+  }
+
+  if (!CBS_get_u8(&header, &tag) ||
+      !CBS_get_u8(&header, &length_byte)) {
+    return 0;
+  }
+
+  if ((tag & 0x1f) == 0x1f) {
+    /* Long form tags are not supported. */
+    return 0;
+  }
+
+  if (out_tag != NULL) {
+    *out_tag = tag;
+  }
+
+  size_t len;
+  if ((length_byte & 0x80) == 0) {
+    /* Short form length. */
+    len = ((size_t) length_byte) + 2;
+    if (out_header_len != NULL) {
+      *out_header_len = 2;
+    }
+  } else {
+    /* Long form length. */
+    const size_t num_bytes = length_byte & 0x7f;
+    uint32_t len32;
+
+    if ((tag & CBS_ASN1_CONSTRUCTED) != 0 && num_bytes == 0) {
+      /* indefinite length */
+      *out_header_len = 2;
+      return CBS_get_bytes(cbs, out, 2);
+    }
+
+    if (num_bytes == 0 || num_bytes > 4) {
+      return 0;
+    }
+    if (!cbs_get_u(&header, &len32, num_bytes)) {
+      return 0;
+    }
+    if (len32 < 128) {
+      /* Length should have used short-form encoding. */
+      return 0;
+    }
+    if ((len32 >> ((num_bytes-1)*8)) == 0) {
+      /* Length should have been at least one byte shorter. */
+      return 0;
+    }
+    len = len32;
+    if (len + 2 + num_bytes < len) {
+      /* Overflow. */
+      return 0;
+    }
+    len += 2 + num_bytes;
+    if (out_header_len != NULL) {
+      *out_header_len = 2 + num_bytes;
+    }
+  }
+
+  return CBS_get_bytes(cbs, out, len);
+}
+
+static int cbs_get_asn1(CBS *cbs, CBS *out, unsigned tag_value,
+                        int skip_header) {
+  size_t header_len;
+  unsigned tag;
+  CBS throwaway;
+
+  if (out == NULL) {
+    out = &throwaway;
+  }
+
+  if (!CBS_get_any_asn1_element(cbs, out, &tag, &header_len) ||
+      tag != tag_value ||
+      (header_len > 0 &&
+       /* This ensures that the tag is either zero length or
+        * indefinite-length. */
+       CBS_len(out) == header_len &&
+       CBS_data(out)[header_len - 1] == 0x80)) {
+    return 0;
+  }
+
+  if (skip_header && !CBS_skip(out, header_len)) {
+    assert(0);
+    return 0;
+  }
+
+  return 1;
+}
+
+int CBS_get_asn1(CBS *cbs, CBS *out, unsigned tag_value) {
+  return cbs_get_asn1(cbs, out, tag_value, 1 /* skip header */);
+}
+
+int CBS_get_asn1_element(CBS *cbs, CBS *out, unsigned tag_value) {
+  return cbs_get_asn1(cbs, out, tag_value, 0 /* include header */);
+}
+
+int CBS_peek_asn1_tag(const CBS *cbs, unsigned tag_value) {
+  if (CBS_len(cbs) < 1) {
+    return 0;
+  }
+  return CBS_data(cbs)[0] == tag_value;
+}
+
+int CBS_get_asn1_uint64(CBS *cbs, uint64_t *out) {
+  CBS bytes;
+  const uint8_t *data;
+  size_t i, len;
+
+  if (!CBS_get_asn1(cbs, &bytes, CBS_ASN1_INTEGER)) {
+    return 0;
+  }
+
+  *out = 0;
+  data = CBS_data(&bytes);
+  len = CBS_len(&bytes);
+
+  if (len == 0) {
+    /* An INTEGER is encoded with at least one octet. */
+    return 0;
+  }
+
+  if ((data[0] & 0x80) != 0) {
+    /* negative number */
+    return 0;
+  }
+
+  for (i = 0; i < len; i++) {
+    if ((*out >> 56) != 0) {
+      /* Too large to represent as a uint64_t. */
+      return 0;
+    }
+    *out <<= 8;
+    *out |= data[i];
+  }
+
+  return 1;
+}
+
+int CBS_get_optional_asn1(CBS *cbs, CBS *out, int *out_present, unsigned tag) {
+  if (CBS_peek_asn1_tag(cbs, tag)) {
+    if (!CBS_get_asn1(cbs, out, tag)) {
+      return 0;
+    }
+    *out_present = 1;
+  } else {
+    *out_present = 0;
+  }
+  return 1;
+}
+
+int CBS_get_optional_asn1_octet_string(CBS *cbs, CBS *out, int *out_present,
+                                       unsigned tag) {
+  CBS child;
+  int present;
+  if (!CBS_get_optional_asn1(cbs, &child, &present, tag)) {
+    return 0;
+  }
+  if (present) {
+    if (!CBS_get_asn1(&child, out, CBS_ASN1_OCTETSTRING) ||
+        CBS_len(&child) != 0) {
+      return 0;
+    }
+  } else {
+    CBS_init(out, NULL, 0);
+  }
+  if (out_present) {
+    *out_present = present;
+  }
+  return 1;
+}
+
+int CBS_get_optional_asn1_uint64(CBS *cbs, uint64_t *out, unsigned tag,
+                                 uint64_t default_value) {
+  CBS child;
+  int present;
+  if (!CBS_get_optional_asn1(cbs, &child, &present, tag)) {
+    return 0;
+  }
+  if (present) {
+    if (!CBS_get_asn1_uint64(&child, out) ||
+        CBS_len(&child) != 0) {
+      return 0;
+    }
+  } else {
+    *out = default_value;
+  }
+  return 1;
+}
+
+int CBS_get_optional_asn1_bool(CBS *cbs, int *out, unsigned tag,
+                               int default_value) {
+  CBS child, child2;
+  int present;
+  if (!CBS_get_optional_asn1(cbs, &child, &present, tag)) {
+    return 0;
+  }
+  if (present) {
+    uint8_t boolean;
+
+    if (!CBS_get_asn1(&child, &child2, CBS_ASN1_BOOLEAN) ||
+        CBS_len(&child2) != 1 ||
+        CBS_len(&child) != 0) {
+      return 0;
+    }
+
+    boolean = CBS_data(&child2)[0];
+    if (boolean == 0) {
+      *out = 0;
+    } else if (boolean == 0xff) {
+      *out = 1;
+    } else {
+      return 0;
+    }
+  } else {
+    *out = default_value;
+  }
+  return 1;
+}
diff --git a/src/crypto/bytestring/internal.h b/src/crypto/bytestring/internal.h
new file mode 100644
index 0000000..b4ea7e5
--- /dev/null
+++ b/src/crypto/bytestring/internal.h
@@ -0,0 +1,46 @@
+/* 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. */
+
+#ifndef OPENSSL_HEADER_BYTESTRING_INTERNAL_H
+#define OPENSSL_HEADER_BYTESTRING_INTERNAL_H
+
+#include <openssl/base.h>
+
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
+
+/* CBS_asn1_ber_to_der reads an ASN.1 structure from |in|. If it finds
+ * indefinite-length elements then it attempts to convert the BER data to DER
+ * and sets |*out| and |*out_length| to describe a malloced buffer containing
+ * the DER data. Additionally, |*in| will be advanced over the ASN.1 data.
+ *
+ * If it doesn't find any indefinite-length elements then it sets |*out| to
+ * NULL and |*in| is unmodified.
+ *
+ * A sufficiently complex ASN.1 structure will break this function because it's
+ * not possible to generically convert BER to DER without knowledge of the
+ * structure itself. However, this sufficies to handle the PKCS#7 and #12 output
+ * from NSS.
+ *
+ * It returns one on success and zero otherwise. */
+OPENSSL_EXPORT int CBS_asn1_ber_to_der(CBS *in, uint8_t **out, size_t *out_len);
+
+
+#if defined(__cplusplus)
+}  /* extern C */
+#endif
+
+#endif  /* OPENSSL_HEADER_BYTESTRING_INTERNAL_H */