[Openvpn-devel,v4,7/9] Remove cipher_kt_t and change type to const char* in API

Message ID 20211213150654.3993358-1-arne@rfc2549.org
State Accepted
Headers show
Series
  • Untitled series #1381
Related show

Commit Message

Arne Schwabe Dec. 13, 2021, 3:06 p.m.
Make the external crypto consumer oblivious to the internal cipher
type that both mbed TLS and OpenSSL use. This change is mainly done
so the cipher type that is used can be stay a const type but instead
of an SSL library type, we now use a simple string to identify a
cipher. This has the disadvantages that we do a cipher lookup every
time a function is called that needs to query properties of a cipher.
But none of these queries are in a critical path.

This patch also fixes the memory leaks introduced by the
EVP_fetch_cipher commit by always freeing the EVP_CIPHER.

This also changes kt->cipher to be always defined with the name of
the cipher. This only affects the "none" cipher cipher which was
previously represented by kt->cipher to be NULL.

Patch v2: rebase on master

Patch v3: fix errors with mbed TLS without having md_kt to const char * patch
          also applied, fix logic inversion in tls_crypt_tk

Patch v4: fix issue if cipher does not get changed by NCP that null cipher is
          then used

Signed-off-by: Arne Schwabe <arne@rfc2549.org>
---
 src/openvpn/auth_token.c               |   2 +-
 src/openvpn/crypto.c                   |  32 ++---
 src/openvpn/crypto.h                   |   4 +-
 src/openvpn/crypto_backend.h           |  77 ++++++------
 src/openvpn/crypto_mbedtls.c           |  85 ++++++++-----
 src/openvpn/crypto_mbedtls.h           |   3 -
 src/openvpn/crypto_openssl.c           | 157 ++++++++++++++++++-------
 src/openvpn/crypto_openssl.h           |  13 +-
 src/openvpn/init.c                     |  20 ++--
 src/openvpn/openssl_compat.h           |   7 ++
 src/openvpn/openvpn.h                  |   2 -
 src/openvpn/options.c                  |   9 +-
 src/openvpn/ssl.c                      |   4 +-
 src/openvpn/ssl_ncp.c                  |  24 ++--
 src/openvpn/tls_crypt.c                |   4 +-
 tests/unit_tests/openvpn/test_crypto.c |   4 +-
 tests/unit_tests/openvpn/test_ncp.c    |   6 +-
 17 files changed, 282 insertions(+), 171 deletions(-)

Comments

Gert Doering Dec. 13, 2021, 5:41 p.m. | #1
Acked-by: Gert Doering <gert@greenie.muc.de>

Thanks to Selva for the v2 review, and thanks for the timely v3 + v4.

I have tested this most thoroughly this time...

 - Linux, OpenSSL 1.1.1l   (full client + server side tests) -> OK
 - Linux, mbedTLS 2.27.0   (full client + server side tests) -> ????
 - Linux, OpenSSL 3.0.0    (full client side tests)          -> OK
 - FreeBSD, OpenSSL 1.1.1h  (fairly thorough client side tests) -> OK
 - FreeBSD, mbedTLS 2.16.11 (fairly thorough client side tests) -> 

and everything went well.

Plus, stare-at code, which also looks good (Selva's points addressed).

I have not fixed the "TYPE* x" vs. "TYPE *x" this round, as it will
lead to extra rounds of conflicts with the later patchsets.  We have
agreed on IRC to do an uncrustify run when the "frame" set (xx/21) is in.

Some observations and request for a followup patch:

 - crypto_mbedtls/cipher_ctx_init() has a sequence of events that need
   swapping

+    const mbedtls_cipher_info_t *kt = cipher_get(ciphername);
+    int key_len = kt->key_bitlen/8;
+
+    ASSERT(kt);

   ... if kt is NULL, it won't reach the ASSERT()...
   (this is unlikely to happen, so not a showstopper today, but still)

 - crypto_openssl.c has functions that do not check the return value
   of cipher_get() (e.g. cipher_kt_iv_size()) and some that do
   (e.g. cipher_kt_block_size()) - is this intentional, due to "it is
   ok to pass NULL to EVP_CIPHER_iv_length()", or an oversight?

 - cipher_kt_mode_cbc(), cipher_kt_mode_ofb_cfb() and cipher_kt_mode_aead()
   do very similar things - except that the coding style of the third
   is totally different...

 - cipher_ctx_init() ASSERTs on ciphername & ctx, but not on *kt
   - intentional and guaranteed safe?


Your patch has been applied to the master branch.

commit ce2954a0ca3f352df8d1492f5a2f2f809d309918
Author: Arne Schwabe
Date:   Mon Dec 13 16:06:53 2021 +0100

     Remove cipher_kt_t and change type to const char* in API

     Signed-off-by: Arne Schwabe <arne@rfc2549.org>
     Acked-by: Gert Doering <gert@greenie.muc.de>
     Message-Id: <20211213150654.3993358-1-arne@rfc2549.org>
     URL: https://www.mail-archive.com/search?l=mid&q=20211213150654.3993358-1-arne@rfc2549.org
     Signed-off-by: Gert Doering <gert@greenie.muc.de>


--
kind regards,

Gert Doering
Arne Schwabe Dec. 13, 2021, 6:41 p.m. | #2
Am 13.12.21 um 18:41 schrieb Gert Doering:
> Acked-by: Gert Doering <gert@greenie.muc.de>
> 
> Thanks to Selva for the v2 review, and thanks for the timely v3 + v4.
> 
> I have tested this most thoroughly this time...
> 
>   - Linux, OpenSSL 1.1.1l   (full client + server side tests) -> OK
>   - Linux, mbedTLS 2.27.0   (full client + server side tests) -> ????
>   - Linux, OpenSSL 3.0.0    (full client side tests)          -> OK
>   - FreeBSD, OpenSSL 1.1.1h  (fairly thorough client side tests) -> OK
>   - FreeBSD, mbedTLS 2.16.11 (fairly thorough client side tests) ->
> 
> and everything went well.
> 
> Plus, stare-at code, which also looks good (Selva's points addressed).
> 
> I have not fixed the "TYPE* x" vs. "TYPE *x" this round, as it will
> lead to extra rounds of conflicts with the later patchsets.  We have
> agreed on IRC to do an uncrustify run when the "frame" set (xx/21) is in.
> 
> Some observations and request for a followup patch:
> 
>   - crypto_mbedtls/cipher_ctx_init() has a sequence of events that need
>     swapping
> 
> +    const mbedtls_cipher_info_t *kt = cipher_get(ciphername);
> +    int key_len = kt->key_bitlen/8;
> +
> +    ASSERT(kt);
> 
>     ... if kt is NULL, it won't reach the ASSERT()...
>     (this is unlikely to happen, so not a showstopper today, but still)
> 
>   - crypto_openssl.c has functions that do not check the return value
>     of cipher_get() (e.g. cipher_kt_iv_size()) and some that do
>     (e.g. cipher_kt_block_size()) - is this intentional, due to "it is
>     ok to pass NULL to EVP_CIPHER_iv_length()", or an oversight?
> 
>   - cipher_kt_mode_cbc(), cipher_kt_mode_ofb_cfb() and cipher_kt_mode_aead()
>     do very similar things - except that the coding style of the third
>     is totally different...
> 
>   - cipher_ctx_init() ASSERTs on ciphername & ctx, but not on *kt
>     - intentional and guaranteed safe?

This was the same mess before but less obvious to be honest. Just now 
with instead blindly taking ctx having a cipher_get it is now become 
obvious that some of these functions expect their input to be always 
correct.

Arne

Patch

diff --git a/src/openvpn/auth_token.c b/src/openvpn/auth_token.c
index 5d5cea7f6..5c947004e 100644
--- a/src/openvpn/auth_token.c
+++ b/src/openvpn/auth_token.c
@@ -35,7 +35,7 @@  auth_token_kt(void)
 {
     struct key_type kt = { 0 };
     /* We do not encrypt our session tokens */
-    kt.cipher = NULL;
+    kt.cipher = "none";
     kt.digest = md_kt_get("SHA256");
 
     if (!kt.digest)
diff --git a/src/openvpn/crypto.c b/src/openvpn/crypto.c
index a63a26195..0b47dec44 100644
--- a/src/openvpn/crypto.c
+++ b/src/openvpn/crypto.c
@@ -680,7 +680,7 @@  crypto_adjust_frame_parameters(struct frame *frame,
         crypto_overhead += packet_id_size(packet_id_long_form);
     }
 
-    if (kt->cipher)
+    if (cipher_defined(kt->cipher))
     {
         crypto_overhead += cipher_kt_iv_size(kt->cipher);
 
@@ -710,16 +710,16 @@  crypto_max_overhead(void)
 }
 
 static void
-warn_insecure_key_type(const char *ciphername, const cipher_kt_t *cipher)
+warn_insecure_key_type(const char *ciphername)
 {
-    if (cipher_kt_insecure(cipher))
+    if (cipher_kt_insecure(ciphername))
     {
         msg(M_WARN, "WARNING: INSECURE cipher (%s) with block size less than 128"
             " bit (%d bit).  This allows attacks like SWEET32.  Mitigate by "
             "using a --cipher with a larger block size (e.g. AES-256-CBC). "
             "Support for these insecure ciphers will be removed in "
             "OpenVPN 2.6.",
-            ciphername, cipher_kt_block_size(cipher)*8);
+            ciphername, cipher_kt_block_size(ciphername)*8);
     }
 }
 
@@ -736,10 +736,10 @@  init_key_type(struct key_type *kt, const char *ciphername,
     ASSERT(authname);
 
     CLEAR(*kt);
+    kt->cipher = ciphername;
     if (strcmp(ciphername, "none") != 0)
     {
-        kt->cipher = cipher_kt_get(ciphername);
-        if (!kt->cipher)
+        if (!cipher_valid(ciphername))
         {
             msg(M_FATAL, "Cipher %s not supported", ciphername);
         }
@@ -762,7 +762,7 @@  init_key_type(struct key_type *kt, const char *ciphername,
         }
         if (warn)
         {
-            warn_insecure_key_type(ciphername, kt->cipher);
+            warn_insecure_key_type(ciphername);
         }
     }
     else
@@ -809,7 +809,7 @@  init_key_ctx(struct key_ctx *ctx, const struct key *key,
 {
     struct gc_arena gc = gc_new();
     CLEAR(*ctx);
-    if (kt->cipher)
+    if (cipher_defined(kt->cipher))
     {
 
         ctx->cipher = cipher_ctx_new();
@@ -824,7 +824,7 @@  init_key_ctx(struct key_ctx *ctx, const struct key *key,
         dmsg(D_CRYPTO_DEBUG, "%s: CIPHER block_size=%d iv_size=%d",
              prefix, cipher_kt_block_size(kt->cipher),
              cipher_kt_iv_size(kt->cipher));
-        warn_insecure_key_type(ciphername, kt->cipher);
+        warn_insecure_key_type(ciphername);
     }
     if (kt->digest)
     {
@@ -912,7 +912,7 @@  key_is_zero(struct key *key, const struct key_type *kt)
 bool
 check_key(struct key *key, const struct key_type *kt)
 {
-    if (kt->cipher)
+    if (cipher_defined(kt->cipher))
     {
         /*
          * Check for zero key
@@ -1622,22 +1622,22 @@  get_random(void)
 }
 
 void
-print_cipher(const cipher_kt_t *cipher)
+print_cipher(const char *ciphername)
 {
     printf("%s  (%d bit key, ",
-           cipher_kt_name(cipher),
-           cipher_kt_key_size(cipher) * 8);
+           cipher_kt_name(ciphername),
+           cipher_kt_key_size(ciphername) * 8);
 
-    if (cipher_kt_block_size(cipher) == 1)
+    if (cipher_kt_block_size(ciphername) == 1)
     {
         printf("stream cipher");
     }
     else
     {
-        printf("%d bit block", cipher_kt_block_size(cipher) * 8);
+        printf("%d bit block", cipher_kt_block_size(ciphername) * 8);
     }
 
-    if (!cipher_kt_mode_cbc(cipher))
+    if (!cipher_kt_mode_cbc(ciphername))
     {
         printf(", TLS client/server mode only");
     }
diff --git a/src/openvpn/crypto.h b/src/openvpn/crypto.h
index 1e2ca3cb0..af94b0eb5 100644
--- a/src/openvpn/crypto.h
+++ b/src/openvpn/crypto.h
@@ -138,7 +138,7 @@  struct sha256_digest {
  */
 struct key_type
 {
-    const cipher_kt_t *cipher;  /**< Cipher static parameters */
+    const char *cipher;         /**< const name of the cipher */
     const md_kt_t *digest;      /**< Message digest static parameters */
 };
 
@@ -473,7 +473,7 @@  void prng_bytes(uint8_t *output, int len);
 long int get_random(void);
 
 /** Print a cipher list entry */
-void print_cipher(const cipher_kt_t *cipher);
+void print_cipher(const char *cipher);
 
 void test_crypto(struct crypto_options *co, struct frame *f);
 
diff --git a/src/openvpn/crypto_backend.h b/src/openvpn/crypto_backend.h
index cc3e40400..e3da5c957 100644
--- a/src/openvpn/crypto_backend.h
+++ b/src/openvpn/crypto_backend.h
@@ -188,114 +188,115 @@  void cipher_des_encrypt_ecb(const unsigned char key[DES_KEY_LENGTH],
 #define MAX_CIPHER_KEY_LENGTH 64
 
 /**
- * Return cipher parameters, based on the given cipher name. The
- * contents of these parameters are library-specific, and can be used to
- * initialise encryption/decryption.
+ * Returns if the cipher is valid, based on the given cipher name.
  *
- * @param ciphername    Name of the cipher to retrieve parameters for (e.g.
+ * @param ciphername    Name of the cipher to check for validity (e.g.
  *                      \c AES-128-CBC). Will be translated to the library name
  *                      from the openvpn config name if needed.
  *
- * @return              A statically allocated structure containing parameters
- *                      for the given cipher, or NULL if no matching parameters
- *                      were found.
+ * @return              if the cipher is valid
  */
-const cipher_kt_t *cipher_kt_get(const char *ciphername);
+bool cipher_valid(const char *ciphername);
 
 /**
- * Retrieve a string describing the cipher (e.g. \c AES-128-CBC).
+ * Checks if the cipher is defined and is not the null (none) cipher
+ *
+ * @param ciphername    Name of the cipher to check if it is defined, may not
+ *                      be NULL
+ * @return              The cipher is defined and not the null (none) cipher
+ */
+static inline bool cipher_defined(const char *ciphername)
+{
+    ASSERT(ciphername);
+    return strcmp(ciphername, "none") != 0;
+}
+
+/**
+ * Retrieve a normalised string describing the cipher (e.g. \c AES-128-CBC).
  * The returned name is normalised to the OpenVPN config name in case the
  * name differs from the name used by the crypto library.
  *
- * Returns [null-cipher] in case the cipher_kt is NULL.
+ * Returns [null-cipher] in case the ciphername is none. NULL if the cipher
+ * is not valid.
  *
- * @param cipher_kt     Static cipher parameters
+ * @param ciphername     Name of the cipher
  *
  * @return a statically allocated string describing the cipher.
  */
-const char *cipher_kt_name(const cipher_kt_t *cipher_kt);
+const char *cipher_kt_name(const char *ciphername);
 
 /**
  * Returns the size of keys used by the cipher, in bytes. If the cipher has a
  * variable key size, return the default key size.
  *
- * @param cipher_kt     Static cipher parameters
+ * @param ciphername    Cipher name to lookup
  *
  * @return              (Default) size of keys used by the cipher, in bytes.
  */
-int cipher_kt_key_size(const cipher_kt_t *cipher_kt);
+int cipher_kt_key_size(const char *ciphername);
 
 /**
  * Returns the size of the IV used by the cipher, in bytes, or 0 if no IV is
  * used.
  *
- * @param cipher_kt     Static cipher parameters
+ * @param ciphername    cipher name to lookup
  *
  * @return              Size of the IV, in bytes, or 0 if the cipher does not
  *                      use an IV.
  */
-int cipher_kt_iv_size(const cipher_kt_t *cipher_kt);
+int cipher_kt_iv_size(const char *ciphername);
 
 /**
  * Returns the block size of the cipher, in bytes.
  *
- * @param cipher_kt     Static cipher parameters
+ * @param ciphername    cipher name
  *
  * @return              Block size, in bytes.
  */
-int cipher_kt_block_size(const cipher_kt_t *cipher_kt);
+int cipher_kt_block_size(const char *ciphername);
 
 /**
  * Returns the MAC tag size of the cipher, in bytes.
  *
- * @param ctx           Static cipher parameters.
+ * @param ciphername    Name of the cipher
  *
  * @return              Tag size in bytes, or 0 if the tag size could not be
  *                      determined.
  */
-int cipher_kt_tag_size(const cipher_kt_t *cipher_kt);
+int cipher_kt_tag_size(const char *ciphername);
 
 /**
  * Returns true if we consider this cipher to be insecure.
  */
-bool cipher_kt_insecure(const cipher_kt_t *cipher);
+bool cipher_kt_insecure(const char *ciphername);
 
-/**
- * Returns the mode that the cipher runs in.
- *
- * @param cipher_kt     Static cipher parameters. May not be NULL.
- *
- * @return              Cipher mode, either \c OPENVPN_MODE_CBC, \c
- *                      OPENVPN_MODE_OFB or \c OPENVPN_MODE_CFB
- */
-int cipher_kt_mode(const cipher_kt_t *cipher_kt);
 
 /**
  * Check if the supplied cipher is a supported CBC mode cipher.
  *
- * @param cipher        Static cipher parameters.
+ * @param ciphername    cipher name
  *
  * @return              true iff the cipher is a CBC mode cipher.
  */
-bool cipher_kt_mode_cbc(const cipher_kt_t *cipher);
+bool cipher_kt_mode_cbc(const char *ciphername);
 
 /**
  * Check if the supplied cipher is a supported OFB or CFB mode cipher.
  *
- * @param cipher        Static cipher parameters.
+ * @param ciphername    cipher name
  *
  * @return              true iff the cipher is a OFB or CFB mode cipher.
  */
-bool cipher_kt_mode_ofb_cfb(const cipher_kt_t *cipher);
+bool cipher_kt_mode_ofb_cfb(const char *ciphername);
 
 /**
  * Check if the supplied cipher is a supported AEAD mode cipher.
  *
- * @param cipher        Static cipher parameters.
+ * @param ciphername    name of the cipher
  *
  * @return              true iff the cipher is a AEAD mode cipher.
  */
-bool cipher_kt_mode_aead(const cipher_kt_t *cipher);
+bool cipher_kt_mode_aead(const char *ciphername);
 
 
 /**
@@ -323,12 +324,12 @@  void cipher_ctx_free(cipher_ctx_t *ctx);
  *
  * @param ctx           Cipher context. May not be NULL
  * @param key           Buffer containing the key to use
- * @param kt            Static cipher parameters to use
+ * @param ciphername    Ciphername of the cipher to use
  * @param enc           Whether to encrypt or decrypt (either
  *                      \c MBEDTLS_OP_ENCRYPT or \c MBEDTLS_OP_DECRYPT).
  */
 void cipher_ctx_init(cipher_ctx_t *ctx, const uint8_t *key,
-                     const cipher_kt_t *kt, int enc);
+                     const char *cipername, int enc);
 
 /**
  * Returns the size of the IV used by the cipher, in bytes, or 0 if no IV is
diff --git a/src/openvpn/crypto_mbedtls.c b/src/openvpn/crypto_mbedtls.c
index 8acf0e184..c3e18a1bc 100644
--- a/src/openvpn/crypto_mbedtls.c
+++ b/src/openvpn/crypto_mbedtls.c
@@ -169,11 +169,11 @@  show_available_ciphers(void)
 
     while (*ciphers != 0)
     {
-        const cipher_kt_t *info = mbedtls_cipher_info_from_type(*ciphers);
-        if (info && !cipher_kt_insecure(info)
-            && (cipher_kt_mode_aead(info) || cipher_kt_mode_cbc(info)))
+        const mbedtls_cipher_info_t *info = mbedtls_cipher_info_from_type(*ciphers);
+        if (info && !cipher_kt_insecure(info->name)
+            && (cipher_kt_mode_aead(info->name) || cipher_kt_mode_cbc(info->name)))
         {
-            print_cipher(info);
+            print_cipher(info->name);
         }
         ciphers++;
     }
@@ -183,11 +183,11 @@  show_available_ciphers(void)
     ciphers = mbedtls_cipher_list();
     while (*ciphers != 0)
     {
-        const cipher_kt_t *info = mbedtls_cipher_info_from_type(*ciphers);
-        if (info && cipher_kt_insecure(info)
-            && (cipher_kt_mode_aead(info) || cipher_kt_mode_cbc(info)))
+        const mbedtls_cipher_info_t *info = mbedtls_cipher_info_from_type(*ciphers);
+        if (info && cipher_kt_insecure(info->name)
+            && (cipher_kt_mode_aead(info->name) || cipher_kt_mode_cbc(info->name)))
         {
-            print_cipher(info);
+            print_cipher(info->name);
         }
         ciphers++;
     }
@@ -390,17 +390,22 @@  rand_bytes(uint8_t *output, int len)
  * Generic cipher key type functions
  *
  */
-
-
-const mbedtls_cipher_info_t *
-cipher_kt_get(const char *ciphername)
+static const mbedtls_cipher_info_t *
+cipher_get(const char* ciphername)
 {
-    const mbedtls_cipher_info_t *cipher = NULL;
-
     ASSERT(ciphername);
 
+    const mbedtls_cipher_info_t *cipher = NULL;
+
     ciphername = translate_cipher_name_from_openvpn(ciphername);
     cipher = mbedtls_cipher_info_from_string(ciphername);
+    return cipher;
+}
+
+bool
+cipher_valid(const char *ciphername)
+{
+    const mbedtls_cipher_info_t *cipher = cipher_get(ciphername);
 
     if (NULL == cipher)
     {
@@ -416,12 +421,13 @@  cipher_kt_get(const char *ciphername)
         return NULL;
     }
 
-    return cipher;
+    return cipher != NULL;
 }
 
 const char *
-cipher_kt_name(const mbedtls_cipher_info_t *cipher_kt)
+cipher_kt_name(const char *ciphername)
 {
+    const mbedtls_cipher_info_t *cipher_kt = cipher_get(ciphername);
     if (NULL == cipher_kt)
     {
         return "[null-cipher]";
@@ -431,8 +437,10 @@  cipher_kt_name(const mbedtls_cipher_info_t *cipher_kt)
 }
 
 int
-cipher_kt_key_size(const mbedtls_cipher_info_t *cipher_kt)
+cipher_kt_key_size(const char *ciphername)
 {
+    const mbedtls_cipher_info_t *cipher_kt = cipher_get(ciphername);
+
     if (NULL == cipher_kt)
     {
         return 0;
@@ -442,8 +450,10 @@  cipher_kt_key_size(const mbedtls_cipher_info_t *cipher_kt)
 }
 
 int
-cipher_kt_iv_size(const mbedtls_cipher_info_t *cipher_kt)
+cipher_kt_iv_size(const char *ciphername)
 {
+    const mbedtls_cipher_info_t *cipher_kt = cipher_get(ciphername);
+
     if (NULL == cipher_kt)
     {
         return 0;
@@ -452,8 +462,9 @@  cipher_kt_iv_size(const mbedtls_cipher_info_t *cipher_kt)
 }
 
 int
-cipher_kt_block_size(const mbedtls_cipher_info_t *cipher_kt)
+cipher_kt_block_size(const char *ciphername)
 {
+    const mbedtls_cipher_info_t *cipher_kt = cipher_get(ciphername);
     if (NULL == cipher_kt)
     {
         return 0;
@@ -462,9 +473,9 @@  cipher_kt_block_size(const mbedtls_cipher_info_t *cipher_kt)
 }
 
 int
-cipher_kt_tag_size(const mbedtls_cipher_info_t *cipher_kt)
+cipher_kt_tag_size(const char *ciphername)
 {
-    if (cipher_kt && cipher_kt_mode_aead(cipher_kt))
+    if (cipher_kt_mode_aead(ciphername))
     {
         return OPENVPN_AEAD_TAG_LENGTH;
     }
@@ -472,16 +483,22 @@  cipher_kt_tag_size(const mbedtls_cipher_info_t *cipher_kt)
 }
 
 bool
-cipher_kt_insecure(const mbedtls_cipher_info_t *cipher_kt)
+cipher_kt_insecure(const char *ciphername)
 {
-    return !(cipher_kt_block_size(cipher_kt) >= 128 / 8
+    const mbedtls_cipher_info_t *cipher_kt = cipher_get(ciphername);
+    if (!cipher_kt)
+    {
+        return true;
+    }
+
+    return !(cipher_kt_block_size(ciphername) >= 128 / 8
 #ifdef MBEDTLS_CHACHAPOLY_C
              || cipher_kt->type == MBEDTLS_CIPHER_CHACHA20_POLY1305
 #endif
              );
 }
 
-int
+static int
 cipher_kt_mode(const mbedtls_cipher_info_t *cipher_kt)
 {
     ASSERT(NULL != cipher_kt);
@@ -489,21 +506,24 @@  cipher_kt_mode(const mbedtls_cipher_info_t *cipher_kt)
 }
 
 bool
-cipher_kt_mode_cbc(const cipher_kt_t *cipher)
+cipher_kt_mode_cbc(const char *ciphername)
 {
+    const mbedtls_cipher_info_t *cipher = cipher_get(ciphername);
     return cipher && cipher_kt_mode(cipher) == OPENVPN_MODE_CBC;
 }
 
 bool
-cipher_kt_mode_ofb_cfb(const cipher_kt_t *cipher)
+cipher_kt_mode_ofb_cfb(const char *ciphername)
 {
+    const mbedtls_cipher_info_t *cipher = cipher_get(ciphername);
     return cipher && (cipher_kt_mode(cipher) == OPENVPN_MODE_OFB
                       || cipher_kt_mode(cipher) == OPENVPN_MODE_CFB);
 }
 
 bool
-cipher_kt_mode_aead(const cipher_kt_t *cipher)
+cipher_kt_mode_aead(const char *ciphername)
 {
+    const mbedtls_cipher_info_t *cipher = cipher_get(ciphername);
     return cipher && (cipher_kt_mode(cipher) == OPENVPN_MODE_GCM
 #ifdef MBEDTLS_CHACHAPOLY_C
                       || cipher_kt_mode(cipher) == MBEDTLS_MODE_CHACHAPOLY
@@ -535,13 +555,16 @@  cipher_ctx_free(mbedtls_cipher_context_t *ctx)
 
 void
 cipher_ctx_init(mbedtls_cipher_context_t *ctx, const uint8_t *key,
-                const mbedtls_cipher_info_t *kt, const mbedtls_operation_t operation)
+                const char *ciphername, const mbedtls_operation_t operation)
 {
-    ASSERT(NULL != kt && NULL != ctx);
-    int key_len = cipher_kt_key_size(kt);
-
+    ASSERT(NULL != ciphername && NULL != ctx);
     CLEAR(*ctx);
 
+    const mbedtls_cipher_info_t *kt = cipher_get(ciphername);
+    int key_len = kt->key_bitlen/8;
+
+    ASSERT(kt);
+
     if (!mbed_ok(mbedtls_cipher_setup(ctx, kt)))
     {
         msg(M_FATAL, "mbed TLS cipher context init #1");
diff --git a/src/openvpn/crypto_mbedtls.h b/src/openvpn/crypto_mbedtls.h
index b2e9eceab..b9d03f2f9 100644
--- a/src/openvpn/crypto_mbedtls.h
+++ b/src/openvpn/crypto_mbedtls.h
@@ -33,9 +33,6 @@ 
 #include <mbedtls/md.h>
 #include <mbedtls/ctr_drbg.h>
 
-/** Generic cipher key type %context. */
-typedef mbedtls_cipher_info_t cipher_kt_t;
-
 /** Generic message digest key type %context. */
 typedef mbedtls_md_info_t md_kt_t;
 
diff --git a/src/openvpn/crypto_openssl.c b/src/openvpn/crypto_openssl.c
index e28e2f43a..01893e2f9 100644
--- a/src/openvpn/crypto_openssl.c
+++ b/src/openvpn/crypto_openssl.c
@@ -311,7 +311,7 @@  cipher_name_cmp(const void *a, const void *b)
     const EVP_CIPHER *const *cipher_a = a;
     const EVP_CIPHER *const *cipher_b = b;
 
-    return strcmp(cipher_kt_name(*cipher_a), cipher_kt_name(*cipher_b));
+    return strcmp(EVP_CIPHER_get0_name(*cipher_a), EVP_CIPHER_get0_name(*cipher_b));
 }
 
 struct collect_ciphers {
@@ -322,6 +322,10 @@  struct collect_ciphers {
 
 static void collect_ciphers(EVP_CIPHER *cipher, void *list)
 {
+    if (!cipher)
+    {
+        return;
+    }
     struct collect_ciphers* cipher_list = list;
     if (cipher_list->num == SIZE(cipher_list->list))
     {
@@ -329,11 +333,13 @@  static void collect_ciphers(EVP_CIPHER *cipher, void *list)
         return;
     }
 
-    if (cipher && (cipher_kt_mode_cbc(cipher)
+    const char *ciphername = EVP_CIPHER_get0_name(cipher);
+
+    if (ciphername && (cipher_kt_mode_cbc(ciphername)
 #ifdef ENABLE_OFB_CFB_MODE
-        || cipher_kt_mode_ofb_cfb(cipher)
+        || cipher_kt_mode_ofb_cfb(ciphername)
 #endif
-        || cipher_kt_mode_aead(cipher)
+        || cipher_kt_mode_aead(ciphername)
     ))
     {
         cipher_list->list[cipher_list->num++] = cipher;
@@ -361,7 +367,7 @@  show_available_ciphers(void)
         const EVP_CIPHER *cipher = EVP_get_cipherbynid(nid);
         /* We cast the const away so we can keep the function prototype
          * compatible with EVP_CIPHER_do_all_provided */
-        collect_ciphers((EVP_CIPHER *)cipher, &cipher_list);
+        collect_ciphers((EVP_CIPHER *) cipher, &cipher_list);
     }
 #endif
 
@@ -370,9 +376,9 @@  show_available_ciphers(void)
 
     for (size_t i = 0; i < cipher_list.num; i++)
     {
-        if (!cipher_kt_insecure(cipher_list.list[i]))
+        if (!cipher_kt_insecure(EVP_CIPHER_get0_name(cipher_list.list[i])))
         {
-            print_cipher(cipher_list.list[i]);
+            print_cipher(EVP_CIPHER_get0_name(cipher_list.list[i]));
         }
     }
 
@@ -380,9 +386,9 @@  show_available_ciphers(void)
            "and are therefore deprecated.  Do not use unless you have to.\n\n");
     for (int i = 0; i < cipher_list.num; i++)
     {
-        if (cipher_kt_insecure(cipher_list.list[i]))
+        if (cipher_kt_insecure(EVP_CIPHER_get0_name(cipher_list.list[i])))
         {
-            print_cipher(cipher_list.list[i]);
+            print_cipher(EVP_CIPHER_get0_name(cipher_list.list[i]));
         }
     }
     printf("\n");
@@ -556,11 +562,10 @@  rand_bytes(uint8_t *output, int len)
  *
  */
 
-
-const EVP_CIPHER *
-cipher_kt_get(const char *ciphername)
+static evp_cipher_type *
+cipher_get(const char *ciphername)
 {
-    const EVP_CIPHER *cipher = NULL;
+    evp_cipher_type *cipher = NULL;
 
     ASSERT(ciphername);
 
@@ -569,7 +574,6 @@  cipher_kt_get(const char *ciphername)
 
     if (NULL == cipher)
     {
-        crypto_msg(D_LOW, "Cipher algorithm '%s' not found", ciphername);
         return NULL;
     }
 
@@ -596,32 +600,67 @@  cipher_kt_get(const char *ciphername)
     return cipher;
 }
 
+bool cipher_valid(const char *ciphername)
+{
+    evp_cipher_type *cipher = cipher_get(ciphername);
+    bool valid = (cipher != NULL);
+    if (!valid)
+    {
+        crypto_msg(D_LOW, "Cipher algorithm '%s' not found", ciphername);
+    }
+    EVP_CIPHER_free(cipher);
+    return valid;
+}
+
+bool cipher_var_key_size(const char *ciphername)
+{
+    evp_cipher_type *cipher = cipher_get(ciphername);
+    bool ret = EVP_CIPHER_flags(cipher) & EVP_CIPH_VARIABLE_LENGTH;
+    EVP_CIPHER_free(cipher);
+    return ret;
+}
+
+
 const char *
-cipher_kt_name(const EVP_CIPHER *cipher_kt)
+cipher_kt_name(const char *ciphername)
 {
-    if (NULL == cipher_kt)
+    ASSERT(ciphername);
+    if (strcmp("none", ciphername) == 0)
     {
         return "[null-cipher]";
     }
 
+    evp_cipher_type *cipher_kt = cipher_get(ciphername);
+    if (!cipher_kt)
+    {
+        return NULL;
+    }
+
     const char *name = EVP_CIPHER_name(cipher_kt);
+    EVP_CIPHER_free(cipher_kt);
     return translate_cipher_name_to_openvpn(name);
 }
 
 int
-cipher_kt_key_size(const EVP_CIPHER *cipher_kt)
+cipher_kt_key_size(const char *ciphername)
 {
-    return EVP_CIPHER_key_length(cipher_kt);
+    evp_cipher_type *cipher = cipher_get(ciphername);
+    int size = EVP_CIPHER_key_length(cipher);
+    EVP_CIPHER_free(cipher);
+    return size;
 }
 
 int
-cipher_kt_iv_size(const EVP_CIPHER *cipher_kt)
+cipher_kt_iv_size(const char *ciphername)
 {
-    return EVP_CIPHER_iv_length(cipher_kt);
+    evp_cipher_type *cipher = cipher_get(ciphername);
+    int ivsize = EVP_CIPHER_iv_length(cipher);
+    EVP_CIPHER_free(cipher);
+    return ivsize;
 }
 
 int
-cipher_kt_block_size(const EVP_CIPHER *cipher)
+cipher_kt_block_size(const char *ciphername)
 {
     /*
      * OpenSSL reports OFB/CFB/GCM cipher block sizes as '1 byte'.  To work
@@ -632,7 +671,12 @@  cipher_kt_block_size(const EVP_CIPHER *cipher)
     char *name = NULL;
     char *mode_str = NULL;
     const char *orig_name = NULL;
-    const EVP_CIPHER *cbc_cipher = NULL;
+    evp_cipher_type *cbc_cipher = NULL;
+    evp_cipher_type *cipher = cipher_get(ciphername);
+    if (!cipher)
+    {
+        return 0;
+    }
 
     int block_size = EVP_CIPHER_block_size(cipher);
 
@@ -651,21 +695,23 @@  cipher_kt_block_size(const EVP_CIPHER *cipher)
 
     strcpy(mode_str, "-CBC");
 
-    cbc_cipher = EVP_CIPHER_fetch(NULL,translate_cipher_name_from_openvpn(name), NULL);
+    cbc_cipher = EVP_CIPHER_fetch(NULL, translate_cipher_name_from_openvpn(name), NULL);
     if (cbc_cipher)
     {
         block_size = EVP_CIPHER_block_size(cbc_cipher);
     }
 
 cleanup:
+    EVP_CIPHER_free(cbc_cipher);
+    EVP_CIPHER_free(cipher);
     free(name);
     return block_size;
 }
 
 int
-cipher_kt_tag_size(const EVP_CIPHER *cipher_kt)
+cipher_kt_tag_size(const char *ciphername)
 {
-    if (cipher_kt_mode_aead(cipher_kt))
+    if (cipher_kt_mode_aead(ciphername))
     {
         return OPENVPN_AEAD_TAG_LENGTH;
     }
@@ -676,13 +722,26 @@  cipher_kt_tag_size(const EVP_CIPHER *cipher_kt)
 }
 
 bool
-cipher_kt_insecure(const EVP_CIPHER *cipher)
+cipher_kt_insecure(const char *ciphername)
 {
-    return !(cipher_kt_block_size(cipher) >= 128 / 8
+
+    if (cipher_kt_block_size(ciphername) >= 128 / 8)
+    {
+        return false;
+    }
 #ifdef NID_chacha20_poly1305
-             || EVP_CIPHER_nid(cipher) == NID_chacha20_poly1305
+    evp_cipher_type *cipher = cipher_get(ciphername);
+    if (cipher)
+    {
+        bool ischachapoly = (EVP_CIPHER_nid(cipher) == NID_chacha20_poly1305);
+        EVP_CIPHER_free(cipher);
+        if (ischachapoly)
+        {
+            return false;
+        }
+    }
 #endif
-             );
+    return true;
 }
 
 int
@@ -693,44 +752,56 @@  cipher_kt_mode(const EVP_CIPHER *cipher_kt)
 }
 
 bool
-cipher_kt_mode_cbc(const cipher_kt_t *cipher)
+cipher_kt_mode_cbc(const char *ciphername)
 {
-    return cipher && cipher_kt_mode(cipher) == OPENVPN_MODE_CBC
+    evp_cipher_type *cipher = cipher_get(ciphername);
+
+    bool ret = cipher && (cipher_kt_mode(cipher) == OPENVPN_MODE_CBC
            /* Exclude AEAD cipher modes, they require a different API */
 #ifdef EVP_CIPH_FLAG_CTS
            && !(EVP_CIPHER_flags(cipher) & EVP_CIPH_FLAG_CTS)
 #endif
-           && !(EVP_CIPHER_flags(cipher) & EVP_CIPH_FLAG_AEAD_CIPHER);
+           && !(EVP_CIPHER_flags(cipher) & EVP_CIPH_FLAG_AEAD_CIPHER));
+    EVP_CIPHER_free(cipher);
+    return ret;
 }
 
 bool
-cipher_kt_mode_ofb_cfb(const cipher_kt_t *cipher)
+cipher_kt_mode_ofb_cfb(const char *ciphername)
 {
-    return cipher && (cipher_kt_mode(cipher) == OPENVPN_MODE_OFB
+    evp_cipher_type *cipher = cipher_get(ciphername);
+    bool ofb_cfb = cipher && (cipher_kt_mode(cipher) == OPENVPN_MODE_OFB
                       || cipher_kt_mode(cipher) == OPENVPN_MODE_CFB)
-           /* Exclude AEAD cipher modes, they require a different API */
-           && !(EVP_CIPHER_flags(cipher) & EVP_CIPH_FLAG_AEAD_CIPHER);
+                      /* Exclude AEAD cipher modes, they require a different API */
+                      && !(EVP_CIPHER_flags(cipher) & EVP_CIPH_FLAG_AEAD_CIPHER);
+    EVP_CIPHER_free(cipher);
+    return ofb_cfb;
 }
 
 bool
-cipher_kt_mode_aead(const cipher_kt_t *cipher)
+cipher_kt_mode_aead(const char *ciphername)
 {
+    bool isaead = false;
+
+    evp_cipher_type *cipher = cipher_get(ciphername);
     if (cipher)
     {
         if (EVP_CIPHER_mode(cipher) == OPENVPN_MODE_GCM)
         {
-            return true;
+            isaead = true;
         }
 
 #ifdef NID_chacha20_poly1305
         if (EVP_CIPHER_nid(cipher) == NID_chacha20_poly1305)
         {
-            return true;
+            isaead =  true;
         }
 #endif
     }
 
-    return false;
+    EVP_CIPHER_free(cipher);
+
+    return isaead;
 }
 
 /*
@@ -755,9 +826,10 @@  cipher_ctx_free(EVP_CIPHER_CTX *ctx)
 
 void
 cipher_ctx_init(EVP_CIPHER_CTX *ctx, const uint8_t *key,
-                const EVP_CIPHER *kt, int enc)
+                const char *ciphername, int enc)
 {
-    ASSERT(NULL != kt && NULL != ctx);
+    ASSERT(NULL != ciphername && NULL != ctx);
+    evp_cipher_type *kt = cipher_get(ciphername);
 
     EVP_CIPHER_CTX_reset(ctx);
     if (!EVP_CipherInit(ctx, kt, NULL, NULL, enc))
@@ -769,6 +841,7 @@  cipher_ctx_init(EVP_CIPHER_CTX *ctx, const uint8_t *key,
         crypto_msg(M_FATAL, "EVP cipher init #2");
     }
 
+    EVP_CIPHER_free(kt);
     /* make sure we used a big enough key */
     ASSERT(EVP_CIPHER_CTX_key_length(ctx) <= EVP_CIPHER_key_length(kt));
 }
diff --git a/src/openvpn/crypto_openssl.h b/src/openvpn/crypto_openssl.h
index 6eb16a906..3371d07e7 100644
--- a/src/openvpn/crypto_openssl.h
+++ b/src/openvpn/crypto_openssl.h
@@ -37,10 +37,6 @@ 
 #include <openssl/provider.h>
 #endif
 
-
-/** Generic cipher key type %context. */
-typedef EVP_CIPHER cipher_kt_t;
-
 /** Generic message digest key type %context. */
 typedef EVP_MD md_kt_t;
 
@@ -66,6 +62,15 @@  typedef struct {
 typedef OSSL_PROVIDER provider_t;
 #endif
 
+/* In OpenSSL 3.0 the method that returns EVP_CIPHER, the cipher needs to be
+ * freed afterwards, thus needing a non-const type. In constrast OpenSSL 1.1.1
+ * and lower returns a const type, needing a const type */
+#if OPENSSL_VERSION_NUMBER < 0x30000000L
+typedef const EVP_CIPHER evp_cipher_type;
+#else
+typedef EVP_CIPHER evp_cipher_type;
+#endif
+
 /** Maximum length of an IV */
 #define OPENVPN_MAX_IV_LENGTH   EVP_MAX_IV_LENGTH
 
diff --git a/src/openvpn/init.c b/src/openvpn/init.c
index 4fee7f49f..bb9dce778 100644
--- a/src/openvpn/init.c
+++ b/src/openvpn/init.c
@@ -2529,7 +2529,7 @@  frame_finalize_options(struct context *c, const struct options *o)
      * Set adjustment factor for buffer alignment when no
      * cipher is used.
      */
-    if (!CIPHER_ENABLED(c))
+    if (!cipher_defined(c->c1.ks.key_type.cipher))
     {
         frame_align_to_extra_frame(&c->c2.frame);
         frame_or_align_flags(&c->c2.frame,
@@ -2660,6 +2660,7 @@  do_init_tls_wrap_key(struct context *c)
         CLEAR(c->c1.ks.tls_auth_key_type);
         if (!streq(options->authname, "none"))
         {
+            c->c1.ks.tls_auth_key_type.cipher = "none";
             c->c1.ks.tls_auth_key_type.digest = md_kt_get(options->authname);
         }
         else
@@ -2762,16 +2763,19 @@  do_init_crypto_tls_c1(struct context *c)
         * Note that BF-CBC will still be part of the OCC string to retain
         * backwards compatibility with older clients.
         */
-        if (!streq(options->ciphername, "BF-CBC")
-            || tls_item_in_cipher_list("BF-CBC", options->ncp_ciphers)
-            || options->enable_ncp_fallback)
+        const char* ciphername = options->ciphername;
+        if (streq(options->ciphername, "BF-CBC")
+            && !tls_item_in_cipher_list("BF-CBC", options->ncp_ciphers)
+            && !options->enable_ncp_fallback)
         {
-            /* Do not warn if the if the cipher is used only in OCC */
-            bool warn = options->enable_ncp_fallback;
-            init_key_type(&c->c1.ks.key_type, options->ciphername, options->authname,
-                          true, warn);
+            ciphername = "none";
         }
 
+        /* Do not warn if the cipher is used only in OCC */
+        bool warn = options->enable_ncp_fallback;
+        init_key_type(&c->c1.ks.key_type, ciphername, options->authname,
+                      true, warn);
+
         /* initialize tls-auth/crypt/crypt-v2 key */
         do_init_tls_wrap_key(c);
 
diff --git a/src/openvpn/openssl_compat.h b/src/openvpn/openssl_compat.h
index 54fd5d60f..dcc210c79 100644
--- a/src/openvpn/openssl_compat.h
+++ b/src/openvpn/openssl_compat.h
@@ -757,6 +757,7 @@  int EVP_PKEY_get_group_name(EVP_PKEY *pkey, char *gname, size_t gname_sz,
 
 #if OPENSSL_VERSION_NUMBER < 0x30000000L
 #define EVP_MD_get0_name EVP_MD_name
+#define EVP_CIPHER_get0_name EVP_CIPHER_name
 #define EVP_CIPHER_CTX_get_mode EVP_CIPHER_CTX_mode
 
 /* Mimics the functions but only when the default context without
@@ -776,6 +777,12 @@  EVP_MD_fetch(void *ctx, const char *algorithm, const char *properties)
     ASSERT(!properties);
     return EVP_get_digestbyname(algorithm);
 }
+
+static inline void
+EVP_CIPHER_free(const EVP_CIPHER *cipher)
+{
+    /* OpenSSL 1.1.1 and lower use only const EVP_CIPHER, nothing to free */
+}
 #endif /* OPENSSL_VERSION_NUMBER < 0x30000000L */
 
 #endif /* OPENSSL_COMPAT_H_ */
diff --git a/src/openvpn/openvpn.h b/src/openvpn/openvpn.h
index 84477837e..aff63aef1 100644
--- a/src/openvpn/openvpn.h
+++ b/src/openvpn/openvpn.h
@@ -529,8 +529,6 @@  struct context
                                           |(c->options.tls_auth_file ? md_kt_size(c->c1.ks.key_type.digest) : 0), \
                                           gc)
 
-#define CIPHER_ENABLED(c) (c->c1.ks.key_type.cipher != NULL)
-
 /* this represents "disabled peer-id" */
 #define MAX_PEER_ID 0xFFFFFF
 
diff --git a/src/openvpn/options.c b/src/openvpn/options.c
index ac13412a4..b840b767b 100644
--- a/src/openvpn/options.c
+++ b/src/openvpn/options.c
@@ -3084,7 +3084,7 @@  options_postprocess_setdefault_ncpciphers(struct options *o)
         /* custom --data-ciphers set, keep list */
         return;
     }
-    else if (cipher_kt_get("CHACHA20-POLY1305"))
+    else if (cipher_valid("CHACHA20-POLY1305"))
     {
         o->ncp_ciphers = "AES-256-GCM:AES-128-GCM:CHACHA20-POLY1305";
     }
@@ -3979,7 +3979,7 @@  options_string(const struct options *o,
         /* Skip resolving BF-CBC to allow SSL libraries without BF-CBC
          * to work here in the default configuration */
         const char *ciphername = o->ciphername;
-        int keysize;
+        int keysize = 0;
 
         if (strcmp(o->ciphername, "BF-CBC") == 0)
         {
@@ -3990,7 +3990,10 @@  options_string(const struct options *o,
         {
             init_key_type(&kt, o->ciphername, o->authname, true, false);
             ciphername = cipher_kt_name(kt.cipher);
-            keysize = cipher_kt_key_size(kt.cipher) * 8;
+            if (cipher_defined(o->ciphername))
+            {
+                keysize = cipher_kt_key_size(kt.cipher) * 8;
+            }
         }
         /* Only announce the cipher to our peer if we are willing to
          * support it */
diff --git a/src/openvpn/ssl.c b/src/openvpn/ssl.c
index 81b2a1afd..05096ee0a 100644
--- a/src/openvpn/ssl.c
+++ b/src/openvpn/ssl.c
@@ -281,9 +281,9 @@  tls_get_cipher_name_pair(const char *cipher_name, size_t len)
  *                      May *not* be NULL.
  */
 static void
-tls_limit_reneg_bytes(const cipher_kt_t *cipher, int *reneg_bytes)
+tls_limit_reneg_bytes(const char *ciphername, int *reneg_bytes)
 {
-    if (cipher && cipher_kt_insecure(cipher))
+    if (cipher_kt_insecure(ciphername))
     {
         if (*reneg_bytes == -1) /* Not user-specified */
         {
diff --git a/src/openvpn/ssl_ncp.c b/src/openvpn/ssl_ncp.c
index 4b95406e9..ce82e8951 100644
--- a/src/openvpn/ssl_ncp.c
+++ b/src/openvpn/ssl_ncp.c
@@ -105,8 +105,7 @@  mutate_ncp_cipher_list(const char *list, struct gc_arena *gc)
     while (token)
     {
         /*
-         * Going through a roundtrip by using cipher_kt_get/cipher_kt_name
-         * (and translate_cipher_name_from_openvpn/
+         * Going cipher_kt_name (and translate_cipher_name_from_openvpn/
          * translate_cipher_name_to_openvpn) also normalises the cipher name,
          * e.g. replacing AeS-128-gCm with AES-128-GCM
          *
@@ -114,15 +113,16 @@  mutate_ncp_cipher_list(const char *list, struct gc_arena *gc)
          * OpenVPN will only warn if they are not found (and remove them from
          * the list)
          */
-
         bool optional = false;
         if (token[0] == '?')
         {
             token++;
             optional = true;
         }
-        const cipher_kt_t *ktc = cipher_kt_get(token);
-        if (strcmp(token, "none") == 0)
+
+        const bool nonecipher = (strcmp(token, "none") == 0);
+
+        if (nonecipher)
         {
             msg(M_WARN, "WARNING: cipher 'none' specified for --data-ciphers. "
                         "This allows negotiation of NO encryption and "
@@ -130,7 +130,7 @@  mutate_ncp_cipher_list(const char *list, struct gc_arena *gc)
                         "over the network! "
                         "PLEASE DO RECONSIDER THIS SETTING!");
         }
-        if (!ktc && strcmp(token, "none") != 0)
+        if (!nonecipher && !cipher_valid(token))
         {
             const char* optstr = optional ? "optional ": "";
             msg(M_WARN, "Unsupported %scipher in --data-ciphers: %s", optstr, token);
@@ -138,8 +138,8 @@  mutate_ncp_cipher_list(const char *list, struct gc_arena *gc)
         }
         else
         {
-            const char *ovpn_cipher_name = cipher_kt_name(ktc);
-            if (ktc == NULL)
+            const char *ovpn_cipher_name = cipher_kt_name(token);
+            if (nonecipher)
             {
                 /* NULL resolves to [null-cipher] but we need none for
                  * data-ciphers */
@@ -466,17 +466,17 @@  p2p_mode_ncp(struct tls_multi *multi, struct tls_session *session)
     if (!common_cipher)
     {
         struct buffer out = alloc_buf_gc(128, &gc);
-        const cipher_kt_t *cipher = session->opt->key_type.cipher;
-
         /* at this point we do not really know if our fallback is
          * not enabled or if we use 'none' cipher as fallback, so
          * keep this ambiguity here and print fallback-cipher: none
          */
 
         const char *fallback_name = "none";
-        if (cipher)
+        const char *ciphername = session->opt->key_type.cipher;
+
+        if (cipher_defined(ciphername))
         {
-            fallback_name = cipher_kt_name(cipher);
+            fallback_name = cipher_kt_name(ciphername);
         }
 
         buf_printf(&out, "(not negotiated, fallback-cipher: %s)", fallback_name);
diff --git a/src/openvpn/tls_crypt.c b/src/openvpn/tls_crypt.c
index 80ed9684e..841261329 100644
--- a/src/openvpn/tls_crypt.c
+++ b/src/openvpn/tls_crypt.c
@@ -51,10 +51,10 @@  static struct key_type
 tls_crypt_kt(void)
 {
     struct key_type kt;
-    kt.cipher = cipher_kt_get("AES-256-CTR");
+    kt.cipher = "AES-256-CTR";
     kt.digest = md_kt_get("SHA256");
 
-    if (!kt.cipher)
+    if (!cipher_valid(kt.cipher))
     {
         msg(M_WARN, "ERROR: --tls-crypt requires AES-256-CTR support.");
         return (struct key_type) { 0 };
diff --git a/tests/unit_tests/openvpn/test_crypto.c b/tests/unit_tests/openvpn/test_crypto.c
index 42632c72b..344817eef 100644
--- a/tests/unit_tests/openvpn/test_crypto.c
+++ b/tests/unit_tests/openvpn/test_crypto.c
@@ -72,7 +72,7 @@  crypto_pem_encode_decode_loopback(void **state)
 static void
 test_translate_cipher(const char *ciphername, const char *openvpn_name)
 {
-    const cipher_kt_t *cipher = cipher_kt_get(ciphername);
+    bool cipher = cipher_valid(ciphername);
 
     /* Empty cipher is fine */
     if (!cipher)
@@ -80,7 +80,7 @@  test_translate_cipher(const char *ciphername, const char *openvpn_name)
         return;
     }
 
-    const char *kt_name = cipher_kt_name(cipher);
+    const char *kt_name = cipher_kt_name(ciphername);
 
     assert_string_equal(kt_name, openvpn_name);
 }
diff --git a/tests/unit_tests/openvpn/test_ncp.c b/tests/unit_tests/openvpn/test_ncp.c
index f4c28ffdf..f3d7ed20a 100644
--- a/tests/unit_tests/openvpn/test_ncp.c
+++ b/tests/unit_tests/openvpn/test_ncp.c
@@ -59,8 +59,8 @@  static void
 test_check_ncp_ciphers_list(void **state)
 {
     struct gc_arena gc = gc_new();
-    bool have_chacha = cipher_kt_get("CHACHA20-POLY1305");
-    bool have_blowfish = cipher_kt_get("BF-CBC");
+    bool have_chacha = cipher_valid("CHACHA20-POLY1305");
+    bool have_blowfish = cipher_valid("BF-CBC");
 
     assert_string_equal(mutate_ncp_cipher_list("none", &gc), "none");
     assert_string_equal(mutate_ncp_cipher_list("AES-256-GCM:none", &gc),
@@ -100,7 +100,7 @@  test_check_ncp_ciphers_list(void **state)
 
     /* For testing that with OpenSSL 1.1.0+ that also accepts ciphers in
      * a different spelling the normalised cipher output is the same */
-    bool have_chacha_mixed_case = cipher_kt_get("ChaCha20-Poly1305");
+    bool have_chacha_mixed_case = cipher_valid("ChaCha20-Poly1305");
     if (have_chacha_mixed_case)
     {
         assert_string_equal(mutate_ncp_cipher_list("AES-128-CBC:ChaCha20-Poly1305", &gc),