| Description: | The X.509 GeneralName type is a generic type for representing
different types of names. One of those name types is known as
EDIPartyName. OpenSSL provides a function GENERAL_NAME_cmp which
compares different instances of a GENERAL_NAME to see if they are
equal or not. This function behaves incorrectly when both
GENERAL_NAMEs contain an EDIPARTYNAME. A NULL pointer dereference and
a crash may occur leading to a possible denial of service attack.
OpenSSL itself uses the GENERAL_NAME_cmp function for two purposes: 1)
Comparing CRL distribution point names between an available CRL and a
CRL distribution point embedded in an X509 certificate 2) When
verifying that a timestamp response token signer matches the timestamp
authority name (exposed via the API functions TS_RESP_verify_response
and TS_RESP_verify_token) If an attacker can control both items being
compared then that attacker could trigger a crash. For example if the
attacker can trick a client or server into checking a malicious
certificate against a malicious CRL then this may occur. Note that
some applications automatically download CRLs based on a URL embedded
in a certificate. This checking happens prior to the signatures on the
certificate and CRL being verified. OpenSSL's s_server, s_client and
verify tools have support for the "-crl_download" option which
implements automatic CRL downloading and this attack has been
demonstrated to work against those tools. Note that an unrelated bug
means that affected versions of OpenSSL cannot parse or construct
correct encodings of EDIPARTYNAME. However it is possible to construct
a malformed EDIPARTYNAME that OpenSSL's parser will accept and hence
trigger this attack. All OpenSSL 1.1.1 and 1.0.2 versions are affected
by this issue. Other OpenSSL releases are out of support and have not
been checked. Fixed in OpenSSL 1.1.1i (Affected 1.1.1-1.1.1h). Fixed
in OpenSSL 1.0.2x (Affected 1.0.2-1.0.2w).
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