evp: process key length and iv length early if present

evp_cipher_init_internal() takes a params array argument and this is processed
late in the initialisation process for some ciphers (AEAD ones).

This means that changing the IV length as a parameter will either truncate the
IV (very bad if SP 800-38d section 8.2.1 is used) or grab extra uninitialised
bytes.

Truncation is very bad if SP 800-38d section 8.2.1 is being used to
contruct a deterministic IV.  This leads to an instant loss of confidentiality.

Grabbing extra bytes isn't so serious, it will most likely result in a bad
decryption.

Problem reported by Tony Battersby of Cybernetics.com but earlier discovered
and raised as issue #19822.

Fixes CVE-2023-5363
Fixes #19822

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Hugo Landau <hlandau@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>

1 files changed, 36 insertions, 0 deletions

diff --git a/crypto/evp/evp_enc.c b/crypto/evp/evp_enc.c
index e1d3eeef64..e9faf31057 100644
--- a/crypto/evp/evp_enc.c
+++ b/crypto/evp/evp_enc.c
@@ -233,6 +233,42 @@ static int evp_cipher_init_internal(EVP_CIPHER_CTX *ctx,
             return 0;
     }
 
+#ifndef FIPS_MODULE
+    /*
+     * Fix for CVE-2023-5363
+     * Passing in a size as part of the init call takes effect late
+     * so, force such to occur before the initialisation.
+     *
+     * The FIPS provider's internal library context is used in a manner
+     * such that this is not an issue.
+     */
+    if (params != NULL) {
+        OSSL_PARAM param_lens[3] = { OSSL_PARAM_END, OSSL_PARAM_END,
+                                     OSSL_PARAM_END };
+        OSSL_PARAM *q = param_lens;
+        const OSSL_PARAM *p;
+
+        p = OSSL_PARAM_locate_const(params, OSSL_CIPHER_PARAM_KEYLEN); 
+        if (p != NULL)
+            memcpy(q++, p, sizeof(*q));
+
+        /*
+         * Note that OSSL_CIPHER_PARAM_AEAD_IVLEN is a synomym for
+         * OSSL_CIPHER_PARAM_IVLEN so both are covered here.
+         */
+        p = OSSL_PARAM_locate_const(params, OSSL_CIPHER_PARAM_IVLEN);
+        if (p != NULL)
+            memcpy(q++, p, sizeof(*q));
+
+        if (q != param_lens) {
+            if (!EVP_CIPHER_CTX_set_params(ctx, param_lens)) {
+                ERR_raise(ERR_LIB_EVP, EVP_R_INVALID_LENGTH);
+                return 0;
+            }
+        }
+    }
+#endif
+
     if (enc) {
         if (ctx->cipher->einit == NULL) {
             ERR_raise(ERR_LIB_EVP, EVP_R_INITIALIZATION_ERROR);