Check to make sure the user didn't provide two of the same has for

Comb4P. If you do this, the first N bytes are all zero, which could
expose some problems, especially if the caller truncates or is relying
on Comb4P acting like a random function.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/hash/comb4p/comb4p.cpp b/src/hash/comb4p/comb4p.cpp
index 1afc5c8e7..6ae36b9d3 100644
--- a/src/hash/comb4p/comb4p.cpp
+++ b/src/hash/comb4p/comb4p.cpp
@@ -52,6 +52,9 @@ Comb4P::Comb4P(HashFunction* h1, HashFunction* h2) :
                 comb4p_block_size(h1, h2)),
    hash1(h1), hash2(h2)
    {
+   if(hash1->name() == hash2->name())
+      throw std::invalid_argument("Comb4P: Must use two distinct hashes");
+
    if(hash1->OUTPUT_LENGTH != hash2->OUTPUT_LENGTH)
       throw std::invalid_argument("Comb4P: Incompatible hashes " +
                                   hash1->name() + " and " +