Debian DSA-1807-1 Critical: cyrus-sasl2 Buffer Overflow Risk

James Ralston discovered that the sasl_encode64() function of cyrus-sasl2,
a free library implementing the Simple Authentication and Security Layer,
suffers from a missing null termination in certain situations. This causes
several buffer overflows in situations where cyrus-sasl2 itself requires
the string to be null terminated which can lead to denial of service or
arbitrary code execution.

Important notice (Quoting from US-CERT):
While this patch will fix currently vulnerable code, it can cause
non-vulnerable existing code to break. Here's a function prototype from
include/saslutil.h to clarify my explanation:

/* base64 encode
* in -- input data
* inlen -- input data length
* out -- output buffer (will be NUL terminated)
* outmax -- max size of output buffer
* result:
* outlen -- gets actual length of output buffer (optional)
*
* Returns SASL_OK on success, SASL_BUFOVER if result won't fit
*/
LIBSASL_API int sasl_encode64(const char *in, unsigned inlen,
char *out, unsigned outmax,
unsigned *outlen);

As...