Merge pull request #347 from tresorit/fix-asn1-decoder-dos

Fix possible DoS in ASN.1 decoders (CVE-2016-9939)

2 files changed, 12 insertions, 0 deletions

diff --git a/asn.cpp b/asn.cpp
index 297ff010..2e923ef7 100644
--- a/asn.cpp
+++ b/asn.cpp
@@ -123,6 +123,8 @@ size_t BERDecodeOctetString(BufferedTransformation &bt, SecByteBlock &str)
 	size_t bc;

 	if (!BERLengthDecode(bt, bc))

 		BERDecodeError();

+	if (bc > bt.MaxRetrievable())

+		BERDecodeError();

 

 	str.New(bc);

 	if (bc != bt.Get(str, bc))

@@ -139,6 +141,8 @@ size_t BERDecodeOctetString(BufferedTransformation &bt, BufferedTransformation &
 	size_t bc;

 	if (!BERLengthDecode(bt, bc))

 		BERDecodeError();

+	if (bc > bt.MaxRetrievable())

+		BERDecodeError();

 

 	bt.TransferTo(str, bc);

 	return bc;

@@ -161,6 +165,8 @@ size_t BERDecodeTextString(BufferedTransformation &bt, std::string &str, byte as
 	size_t bc;

 	if (!BERLengthDecode(bt, bc))

 		BERDecodeError();

+	if (bc > bt.MaxRetrievable())

+		BERDecodeError();

 

 	SecByteBlock temp(bc);

 	if (bc != bt.Get(temp, bc))

@@ -188,6 +194,10 @@ size_t BERDecodeBitString(BufferedTransformation &bt, SecByteBlock &str, unsigne
 	size_t bc;

 	if (!BERLengthDecode(bt, bc))

 		BERDecodeError();

+	if (bc == 0)

+		BERDecodeError();

+	if (bc > bt.MaxRetrievable())

+		BERDecodeError();

 

 	byte unused;

 	if (!bt.Get(unused))

diff --git a/asn.h b/asn.h
index ed9de52c..33f0dd09 100644
--- a/asn.h
+++ b/asn.h
@@ -498,6 +498,8 @@ void BERDecodeUnsigned(BufferedTransformation &in, T &w, byte asnTag = INTEGER,
 	bool definite = BERLengthDecode(in, bc);

 	if (!definite)

 		BERDecodeError();

+	if (bc > in.MaxRetrievable())

+		BERDecodeError();

 

 	SecByteBlock buf(bc);