| Description: | ASN.1 strings are represented internally within OpenSSL as an
ASN1_STRING structure which contains a buffer holding the string data
and a field holding the buffer length. This contrasts with normal C
strings which are repesented as a buffer for the string data which is
terminated with a NUL (0) byte. Although not a strict requirement,
ASN.1 strings that are parsed using OpenSSL's own "d2i" functions (and
other similar parsing functions) as well as any string whose value has
been set with the ASN1_STRING_set() function will additionally NUL
terminate the byte array in the ASN1_STRING structure. However, it is
possible for applications to directly construct valid ASN1_STRING
structures which do not NUL terminate the byte array by directly
setting the "data" and "length" fields in the ASN1_STRING array. This
can also happen by using the ASN1_STRING_set0() function. Numerous
OpenSSL functions that print ASN.1 data have been found to assume that
the ASN1_STRING byte array will be NUL terminated, even though this is
not guaranteed for strings that have been directly constructed. Where
an application requests an ASN.1 structure to be printed, and where
that ASN.1 structure contains ASN1_STRINGs that have been directly
constructed by the application without NUL terminating the "data"
field, then a read buffer overrun can occur. The same thing can also
occur during name constraints processing of certificates (for example
if a certificate has been directly constructed by the application
instead of loading it via the OpenSSL parsing functions, and the
certificate contains non NUL terminated ASN1_STRING structures). It
can also occur in the X509_get1_email(), X509_REQ_get1_email() and
X509_get1_ocsp() functions. If a malicious actor can cause an
application to directly construct an ASN1_STRING and then process it
through one of the affected OpenSSL functions then this issue could be
hit. This might result in a crash (causing a Denial of Service
attack). It could also result in the disclosure of private memory
contents (such as private keys, or sensitive plaintext). Fixed in
OpenSSL 1.1.1l (Affected 1.1.1-1.1.1k). Fixed in OpenSSL 1.0.2za
(Affected 1.0.2-1.0.2y).
|
