CVE-2023-5363

Issue summary: A bug has been identified in the processing of key and
initialisation vector (IV) lengths. This can lead to potential truncation
or overruns during the initialisation of some symmetric ciphers. Impact
summary: A truncation in the IV can result in non-uniqueness, which could
result in loss of confidentiality for some cipher modes. When calling
EVP_EncryptInit_ex2(), EVP_DecryptInit_ex2() or EVP_CipherInit_ex2() the
provided OSSL_PARAM array is processed after the key and IV have been
established. Any alterations to the key length, via the “keylen” parameter
or the IV length, via the “ivlen” parameter, within the OSSL_PARAM array
will not take effect as intended, potentially causing truncation or
overreading of these values. The following ciphers and cipher modes are
impacted: RC2, RC4, RC5, CCM, GCM and OCB. For the CCM, GCM and OCB cipher
modes, truncation of the IV can result in loss of confidentiality. For
example, when following NIST’s SP 800-38D section 8.2.1 guidance for
constructing a deterministic IV for AES in GCM mode, truncation of the
counter portion could lead to IV reuse. Both truncations and overruns of
the key and overruns of the IV will produce incorrect results and could, in
some cases, trigger a memory exception. However, these issues are not
currently assessed as security critical. Changing the key and/or IV lengths
is not considered to be a common operation and the vulnerable API was
recently introduced. Furthermore it is likely that application developers
will have spotted this problem during testing since decryption would fail
unless both peers in the communication were similarly vulnerable. For these
reasons we expect the probability of an application being vulnerable to
this to be quite low. However if an application is vulnerable then this
issue is considered very serious. For these reasons we have assessed this
issue as Moderate severity overall. 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 because the issue lies outside of the FIPS provider
boundary. OpenSSL 3.1 and 3.0 are vulnerable to this issue.

Notes