1 files changed, 74 insertions, 0 deletions
diff --git a/crypto/bn/bn_asn1.c b/crypto/bn/bn_asn1.c
new file mode 100644
index 00000000..81e7b897
--- /dev/null
+++ b/crypto/bn/bn_asn1.c
@@ -0,0 +1,74 @@
+/* Copyright (c) 2015, 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/bn.h>
+
+#include <openssl/bytestring.h>
+#include <openssl/err.h>
+
+
+int BN_cbs2unsigned(CBS *cbs, BIGNUM *ret) {
+  CBS child;
+  if (!CBS_get_asn1(cbs, &child, CBS_ASN1_INTEGER) ||
+      CBS_len(&child) == 0) {
+    OPENSSL_PUT_ERROR(BN, BN_cbs2unsigned, BN_R_BAD_ENCODING);
+    return 0;
+  }
+  if (CBS_data(&child)[0] & 0x80) {
+    OPENSSL_PUT_ERROR(BN, BN_cbs2unsigned, BN_R_NEGATIVE_NUMBER);
+    return 0;
+  }
+  /* INTEGERs must be minimal. */
+  if (CBS_data(&child)[0] == 0x00 &&
+      CBS_len(&child) > 1 &&
+      !(CBS_data(&child)[1] & 0x80)) {
+    OPENSSL_PUT_ERROR(BN, BN_cbs2unsigned, BN_R_BAD_ENCODING);
+    return 0;
+  }
+  return BN_bin2bn(CBS_data(&child), CBS_len(&child), ret) != NULL;
+}
+
+int BN_bn2cbb(CBB *cbb, const BIGNUM *bn) {
+  /* Negative numbers are unsupported. */
+  if (BN_is_negative(bn)) {
+    OPENSSL_PUT_ERROR(BN, BN_bn2cbb, BN_R_NEGATIVE_NUMBER);
+    return 0;
+  }
+
+  CBB child;
+  if (!CBB_add_asn1(cbb, &child, CBS_ASN1_INTEGER)) {
+    OPENSSL_PUT_ERROR(BN, BN_bn2cbb, BN_R_ENCODE_ERROR);
+    return 0;
+  }
+
+  /* The number must be padded with a leading zero if the high bit would
+   * otherwise be set (or |bn| is zero). */
+  if (BN_num_bits(bn) % 8 == 0 &&
+      !CBB_add_u8(&child, 0x00)) {
+    OPENSSL_PUT_ERROR(BN, BN_bn2cbb, BN_R_ENCODE_ERROR);
+    return 0;
+  }
+
+  uint8_t *out;
+  if (!CBB_add_space(&child, &out, BN_num_bytes(bn))) {
+    OPENSSL_PUT_ERROR(BN, BN_bn2cbb, BN_R_ENCODE_ERROR);
+    return 0;
+  }
+  BN_bn2bin(bn, out);
+  if (!CBB_flush(cbb)) {
+    OPENSSL_PUT_ERROR(BN, BN_bn2cbb, BN_R_ENCODE_ERROR);
+    return 0;
+  }
+  return 1;
+}