Extended master secret support.

This change implements support for the extended master secret. See
https://tools.ietf.org/html/draft-ietf-tls-session-hash-01
https://secure-resumption.com/

Change-Id: Ifc7327763149ab0894b4f1d48cdc35e0f1093b93
Reviewed-on: https://boringssl-review.googlesource.com/1930
Reviewed-by: David Benjamin <davidben@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>

2 files changed, 69 insertions, 1 deletions

diff --git a/crypto/bytestring/bytestring_test.c b/crypto/bytestring/bytestring_test.c
index 28dfd3a4..5ef3259f 100644
--- a/crypto/bytestring/bytestring_test.c
+++ b/crypto/bytestring/bytestring_test.c
@@ -222,6 +222,43 @@ static int test_get_asn1(void) {
   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;
@@ -604,7 +641,8 @@ int main(void) {
       !test_cbb_prefixed() ||
       !test_cbb_asn1() ||
       !test_ber_convert() ||
-      !test_asn1_uint64()) {
+      !test_asn1_uint64() ||
+      !test_get_optional_asn1_bool()) {
     return 1;
   }
 
diff --git a/crypto/bytestring/cbs.c b/crypto/bytestring/cbs.c
index ae661208..b4177162 100644
--- a/crypto/bytestring/cbs.c
+++ b/crypto/bytestring/cbs.c
@@ -356,3 +356,33 @@ int CBS_get_optional_asn1_uint64(CBS *cbs, uint64_t *out, unsigned tag,
   }
   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;
+}