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-rw-r--r--src/tls/c_kex.cpp25
1 files changed, 23 insertions, 2 deletions
diff --git a/src/tls/c_kex.cpp b/src/tls/c_kex.cpp
index 22c0253c1..f95f74931 100644
--- a/src/tls/c_kex.cpp
+++ b/src/tls/c_kex.cpp
@@ -16,6 +16,26 @@
namespace Botan {
+namespace {
+
+SecureVector<byte> strip_leading_zeros(const MemoryRegion<byte>& input)
+ {
+ size_t leading_zeros = 0;
+
+ for(size_t i = 0; i != input.size(); ++i)
+ {
+ if(input[i] != 0)
+ break;
+ ++leading_zeros;
+ }
+
+ SecureVector<byte> output(&input[leading_zeros],
+ input.size() - leading_zeros);
+ return output;
+ }
+
+}
+
/*
* Create a new Client Key Exchange message
*/
@@ -34,7 +54,8 @@ Client_Key_Exchange::Client_Key_Exchange(Record_Writer& writer,
PK_Key_Agreement ka(priv_key, "Raw");
- pre_master = ka.derive_key(0, dh_pub->public_value()).bits_of();
+ pre_master = strip_leading_zeros(
+ ka.derive_key(0, dh_pub->public_value()).bits_of());
key_material = priv_key.public_value();
}
@@ -115,7 +136,7 @@ Client_Key_Exchange::pre_master_secret(RandomNumberGenerator& rng,
try {
PK_Key_Agreement ka(*dh_priv, "Raw");
- pre_master = ka.derive_key(0, key_material).bits_of();
+ pre_master = strip_leading_zeros(ka.derive_key(0, key_material).bits_of());
}
catch(...)
{