From fee6b431c27dfe98e57085650e24467c83a010ae Mon Sep 17 00:00:00 2001
From: Mirek Kratochvil <exa.exa@gmail.com>
Date: Sat, 25 Jan 2014 10:34:33 +0100
Subject: [PATCH] fmtseq: privkey internals checking

Simple size checks that prevent some segfaults from working with mangled
privkeys.
---
 src/fmtseq.cpp        | 44 +++++++++++++++++++++++++++++++++++++++++++
 src/fmtseq.h          |  1 -
 src/serialization.cpp |  3 ++-
 3 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/src/fmtseq.cpp b/src/fmtseq.cpp
index 7facc3c..b197b64 100644
--- a/src/fmtseq.cpp
+++ b/src/fmtseq.cpp
@@ -93,6 +93,45 @@ static void store_desired (privkey&priv, uint did,
 	priv.desired[did][i.pos + (1 << depth) - 2] = i.item;
 }
 
+static bool check_privkey (privkey&priv, hash_func&hf)
+{
+	size_t i, j;
+	uint ts = (1 << (priv.h + 1) ) - 2;
+
+	/*
+	 * check the content of privkey caches to prevent reading/writing
+	 * unallocated memory.
+	 */
+
+	//exist tree count is always L
+	if (priv.exist.size() != priv.l) return false;
+
+	//exist tree sizes
+	for (i = 0; i < priv.exist.size(); ++i) {
+		if (priv.exist[i].size() != ts) return false;
+
+		//exist tree hash sizes must be OK
+		for (j = 0; j < ts; ++j)
+			if (priv.exist[i][j].size()
+			    != hf.size() )
+				return false;
+	}
+
+	//check desired stuff
+	if (priv.desired_stack.size() < priv.desired.size() ) return false;
+	if (priv.desired_progress.size() < priv.desired.size() ) return false;
+
+	for (i = 0; i < priv.desired.size(); ++i) {
+		if (priv.desired[i].size() != ts) return false;
+		for (j = 0; j < ts; ++j)
+			if (priv.desired[i][j].size()
+			    != hf.size() )
+				return false;
+	}
+
+	return true;
+}
+
 static void update_privkey (privkey&priv, hash_func&hf)
 {
 	uint i, j;
@@ -330,6 +369,11 @@ int privkey::sign (const bvector& hash, bvector& sig, hash_func& hf)
 		return 2;
 	}
 
+	if (!check_privkey (*this, hf) ) {
+		err ("fmtseq: mangled privkey");
+		return 3;
+	}
+
 	uint commitments = fmtseq_commitments (hs);
 
 	bvector M2 = hash;
diff --git a/src/fmtseq.h b/src/fmtseq.h
index fca8c8e..d27cb87 100644
--- a/src/fmtseq.h
+++ b/src/fmtseq.h
@@ -105,7 +105,6 @@ public:
 		return ( (H + fmtseq_commitments (hs) ) * hf.size() * 8) + H;
 	}
 
-
 	sencode* serialize();
 	bool unserialize (sencode*);
 };
diff --git a/src/serialization.cpp b/src/serialization.cpp
index e38601a..6ce9c2e 100644
--- a/src/serialization.cpp
+++ b/src/serialization.cpp
@@ -552,7 +552,8 @@ bool fmtseq::privkey::unserialize (sencode*s)
 		desired_progress[i] = I->i;
 	}
 
-	//TODO check the sizes of everything
+	//checking the sizes and correctness of everything is a job of FMTSeq
+	//implementation that has some insight into how it works :]
 	return true;
 }