| Description: | Issue summary: Checking excessively long DH keys or parameters may be
very slow. Impact summary: Applications that use the functions
DH_check(), DH_check_ex() or EVP_PKEY_param_check() to check a DH key
or DH parameters may experience long delays. Where the key or
parameters that are being checked have been obtained from an untrusted
source this may lead to a Denial of Service. The function DH_check()
performs various checks on DH parameters. One of those checks confirms
that the modulus ('p' parameter) is not too large. Trying to use a
very large modulus is slow and OpenSSL will not normally use a modulus
which is over 10,000 bits in length. However the DH_check() function
checks numerous aspects of the key or parameters that have been
supplied. Some of those checks use the supplied modulus value even if
it has already been found to be too large. An application that calls
DH_check() and supplies a key or parameters obtained from an untrusted
source could be vulernable to a Denial of Service attack. The function
DH_check() is itself called by a number of other OpenSSL functions. An
application calling any of those other functions may similarly be
affected. The other functions affected by this are DH_check_ex() and
EVP_PKEY_param_check(). Also vulnerable are the OpenSSL dhparam and
pkeyparam command line applications when using the '-check' option.
The OpenSSL SSL/TLS implementation is not affected by this issue. The
OpenSSL 3.0 and 3.1 FIPS providers are not affected by this issue.
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