The definite long form for the length is allowed only for cases where
the definite short form cannot be used, i.e., if the length is 128 or
greater. This was not previously enforced and as such, multiple
different encoding options for the same length could have been accepted.
Perform more strict checks to reject invalid cases for the definite long
form for the length. This is needed for a compliant implementation and
this is especially important for the case of verifying DER encoded
signatures to prevent potential forging attacks.
Signed-off-by: Jouni Malinen <j@w1.fi>
The extended tag case is allowed only for tag values that are 31 or
larger (i.e., the ones that would not fit in the single octet identifier
case with five bits). Extended tag format was previously accepted even
for the values 0..31 and this would enable multiple different encodings
for the same tag value. That is not allowed for DER.
Perform more strict checks to reject invalid extended tag values. This
is needed for a compliant implementation and this is especially
important for the case of verifying DER encoded signatures to prevent
potential forging attacks.
Signed-off-by: Jouni Malinen <j@w1.fi>
The identifier octet in DER encoding includes three components. Only two
of these (Class and Tag) were checked in most cases when looking for a
specific data type. Also check the Primitive/Constructed bit to avoid
accepting invalid encoding.
This is needed for correct behavior in DER parsing and especially
important for the case of verifying DER encoded signatures to prevent
potential forging attacks.
Signed-off-by: Jouni Malinen <j@w1.fi>
This does not need to be specific to X.509, so move the BOOLEAN DER
encoding validation into asn1_get_next() to make it apply for all cases
instead of having to have the caller handle this separately.
Signed-off-by: Jouni Malinen <j@w1.fi>
Explicitly check the remaining buffer length before trying to read the
ASN.1 header values. Attempt to parse an ASN.1 header when there was not
enough buffer room for it would have started by reading one or two
octets beyond the end of the buffer before reporting invalid data at the
following explicit check for buffer room.
Signed-off-by: Jouni Malinen <j@w1.fi>
