Add EVP_EncodedLength.

Several callers of EVP_EncodeBlock are doing ad-hoc versions of this
function without any overflow checks.

Change-Id: I4d0cad2347ea8c44b42465e8b14b2783db69ee8f
Reviewed-on: https://boringssl-review.googlesource.com/1511
Reviewed-by: David Benjamin <davidben@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/crypto/base64/base64.c b/crypto/base64/base64.c
index 4cd95d60..2336cf53 100644
--- a/crypto/base64/base64.c
+++ b/crypto/base64/base64.c
@@ -402,3 +402,21 @@ int EVP_DecodeBlock(uint8_t *dst, const uint8_t *src, size_t src_len) {
 
   return ret;
 }
+
+int EVP_EncodedLength(size_t *out_len, size_t len) {
+  if (len + 2 < len) {
+    return 0;
+  }
+  len += 2;
+  len /= 3;
+  if (((len << 2) >> 2) != len) {
+    return 0;
+  }
+  len <<= 2;
+  if (len + 1 < len) {
+    return 0;
+  }
+  len++;
+  *out_len = len;
+  return 1;
+}