diff --git a/ChangeLog.d/mbedtls_ssl_set_hostname.txt b/ChangeLog.d/mbedtls_ssl_set_hostname.txt
new file mode 100644
index 0000000..f5f0fa7
--- /dev/null
+++ b/ChangeLog.d/mbedtls_ssl_set_hostname.txt
@@ -0,0 +1,15 @@
+Default behavior changes
+   * In TLS clients, if mbedtls_ssl_set_hostname() has not been called,
+     mbedtls_ssl_handshake() now fails with
+     MBEDTLS_ERR_SSL_CERTIFICATE_VERIFICATION_WITHOUT_HOSTNAME
+     if certificate-based authentication of the server is attempted.
+     This is because authenticating a server without knowing what name
+     to expect is usually insecure.
+
+Security
+   * Note that TLS clients should generally call mbedtls_ssl_set_hostname()
+     if they use certificate authentication (i.e. not pre-shared keys).
+     Otherwise, in many scenarios, the server could be impersonated.
+     The library will now prevent the handshake and return
+     MBEDTLS_ERR_SSL_CERTIFICATE_VERIFICATION_WITHOUT_HOSTNAME
+     if mbedtls_ssl_set_hostname() has not been called.
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index e0c0eae..3154024 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -169,6 +169,39 @@
 #define MBEDTLS_ERR_SSL_VERSION_MISMATCH                  -0x5F00
 /** Invalid value in SSL config */
 #define MBEDTLS_ERR_SSL_BAD_CONFIG                        -0x5E80
+/* Error space gap */
+/** Attempt to verify a certificate without an expected hostname.
+ * This is usually insecure.
+ *
+ * In TLS clients, when a client authenticates a server through its
+ * certificate, the client normally checks three things:
+ * - the certificate chain must be valid;
+ * - the chain must start from a trusted CA;
+ * - the certificate must cover the server name that is expected by the client.
+ *
+ * Omitting any of these checks is generally insecure, and can allow a
+ * malicious server to impersonate a legitimate server.
+ *
+ * The third check may be safely skipped in some unusual scenarios,
+ * such as networks where eavesdropping is a risk but not active attacks,
+ * or a private PKI where the client equally trusts all servers that are
+ * accredited by the root CA.
+ *
+ * You should call mbedtls_ssl_set_hostname() with the expected server name
+ * before starting a TLS handshake on a client (unless the client is
+ * set up to only use PSK-based authentication, which does not rely on the
+ * host name). If you have determined that server name verification is not
+ * required for security in your scenario, call mbedtls_ssl_set_hostname()
+ * with \p NULL as the server name.
+ *
+ * This error is raised if all of the following conditions are met:
+ *
+ * - A TLS client is configured with the authentication mode
+ *   #MBEDTLS_SSL_VERIFY_REQUIRED (default).
+ * - Certificate authentication is enabled.
+ * - The client does not call mbedtls_ssl_set_hostname().
+ */
+#define MBEDTLS_ERR_SSL_CERTIFICATE_VERIFICATION_WITHOUT_HOSTNAME  -0x5D80
 
 /*
  * Constants from RFC 8446 for TLS 1.3 PSK modes
@@ -1295,8 +1328,8 @@
 #endif /* MBEDTLS_SSL_SERVER_NAME_INDICATION && MBEDTLS_SSL_CLI_C */
 
 #if defined(MBEDTLS_SSL_EARLY_DATA) && defined(MBEDTLS_SSL_ALPN) && defined(MBEDTLS_SSL_SRV_C)
-    char *ticket_alpn;                      /*!< ALPN negotiated in the session
-                                                 during which the ticket was generated. */
+    char *MBEDTLS_PRIVATE(ticket_alpn);           /*!< ALPN negotiated in the session
+                                                       during which the ticket was generated. */
 #endif
 
 #if defined(MBEDTLS_HAVE_TIME) && defined(MBEDTLS_SSL_CLI_C)
@@ -1669,6 +1702,14 @@
      * Miscellaneous
      */
     int MBEDTLS_PRIVATE(state);                  /*!< SSL handshake: current state     */
+
+    /** Mask of `MBEDTLS_SSL_CONTEXT_FLAG_XXX`.
+     * See `mbedtls_ssl_context_flags_t` in ssl_misc.h.
+     *
+     * This field is not saved by mbedtls_ssl_session_save().
+     */
+    uint32_t MBEDTLS_PRIVATE(flags);
+
 #if defined(MBEDTLS_SSL_RENEGOTIATION)
     int MBEDTLS_PRIVATE(renego_status);          /*!< Initial, in progress, pending?   */
     int MBEDTLS_PRIVATE(renego_records_seen);    /*!< Records since renego request, or with DTLS,
@@ -1974,6 +2015,17 @@
  * \note           The PSA crypto subsystem must have been initialized by
  *                 calling psa_crypto_init() before calling this function.
  *
+ * \note           After setting up a client context, if certificate-based
+ *                 authentication is enabled, you should call
+ *                 mbedtls_ssl_set_hostname() to specifiy the expected
+ *                 name of the server. Otherwise, if server authentication
+ *                 is required (which is the case by default) and the
+ *                 selected key exchange involves a certificate (i.e. is not
+ *                 based on a pre-shared key), the certificate authentication
+ *                 will fail. See
+ *                 #MBEDTLS_ERR_SSL_CERTIFICATE_VERIFICATION_WITHOUT_HOSTNAME
+ *                 for more information.
+ *
  * \param ssl      SSL context
  * \param conf     SSL configuration to use
  *
@@ -3885,16 +3937,29 @@
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
 /**
  * \brief          Set or reset the hostname to check against the received
- *                 server certificate. It sets the ServerName TLS extension,
- *                 too, if that extension is enabled. (client-side only)
+ *                 peer certificate. On a client, this also sets the
+ *                 ServerName TLS extension, if that extension is enabled.
+ *                 On a TLS 1.3 client, this also sets the server name in
+ *                 the session resumption ticket, if that feature is enabled.
  *
  * \param ssl      SSL context
- * \param hostname the server hostname, may be NULL to clear hostname
-
- * \note           Maximum hostname length MBEDTLS_SSL_MAX_HOST_NAME_LEN.
+ * \param hostname The server hostname. This may be \c NULL to clear
+ *                 the hostname.
  *
- * \return         0 if successful, MBEDTLS_ERR_SSL_ALLOC_FAILED on
- *                 allocation failure, MBEDTLS_ERR_SSL_BAD_INPUT_DATA on
+ * \note           Maximum hostname length #MBEDTLS_SSL_MAX_HOST_NAME_LEN.
+ *
+ * \note           If the hostname is \c NULL on a client, then the server
+ *                 is not authenticated: it only needs to have a valid
+ *                 certificate, not a certificate matching its name.
+ *                 Therefore you should always call this function on a client,
+ *                 unless the connection is set up to only allow
+ *                 pre-shared keys, or in scenarios where server
+ *                 impersonation is not a concern. See the documentation of
+ *                 #MBEDTLS_ERR_SSL_CERTIFICATE_VERIFICATION_WITHOUT_HOSTNAME
+ *                 for more details.
+ *
+ * \return         0 if successful, #MBEDTLS_ERR_SSL_ALLOC_FAILED on
+ *                 allocation failure, #MBEDTLS_ERR_SSL_BAD_INPUT_DATA on
  *                 too long input hostname.
  *
  *                 Hostname set to the one provided on success (cleared
diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index 9f91861..fd01aac 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -51,6 +51,22 @@
 #define MBEDTLS_SSL_ECP_RESTARTABLE_ENABLED
 #endif
 
+/** Flag values for mbedtls_ssl_context::flags. */
+typedef enum {
+    /** Set if mbedtls_ssl_set_hostname() has been called. */
+    MBEDTLS_SSL_CONTEXT_FLAG_HOSTNAME_SET = 1,
+} mbedtls_ssl_context_flags_t;
+
+/** Flags from ::mbedtls_ssl_context_flags_t to keep in
+ * mbedtls_ssl_session_reset().
+ *
+ * The flags that are in this list are kept until explicitly updated or
+ * until mbedtls_ssl_free(). The flags that are not listed here are
+ * reset to 0 in mbedtls_ssl_session_reset().
+ */
+#define MBEDTLS_SSL_CONTEXT_FLAGS_KEEP_AT_SESSION       \
+    (MBEDTLS_SSL_CONTEXT_FLAG_HOSTNAME_SET)
+
 #define MBEDTLS_SSL_INITIAL_HANDSHAKE           0
 #define MBEDTLS_SSL_RENEGOTIATION_IN_PROGRESS   1   /* In progress */
 #define MBEDTLS_SSL_RENEGOTIATION_DONE          2   /* Done or aborted */
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 60f2e1c..0b072e6 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -1411,6 +1411,7 @@
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
 
     ssl->state = MBEDTLS_SSL_HELLO_REQUEST;
+    ssl->flags &= MBEDTLS_SSL_CONTEXT_FLAGS_KEEP_AT_SESSION;
     ssl->tls_version = ssl->conf->max_tls_version;
 
     mbedtls_ssl_session_reset_msg_layer(ssl, partial);
@@ -2515,6 +2516,31 @@
 }
 
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
+
+#if defined(MBEDTLS_SSL_HANDSHAKE_WITH_CERT_ENABLED)
+/** Whether mbedtls_ssl_set_hostname() has been called.
+ *
+ * \param[in]   ssl     SSL context
+ *
+ * \return \c 1 if mbedtls_ssl_set_hostname() has been called on \p ssl
+ *         (including `mbedtls_ssl_set_hostname(ssl, NULL)`),
+ *         otherwise \c 0.
+ */
+static int mbedtls_ssl_has_set_hostname_been_called(
+    const mbedtls_ssl_context *ssl)
+{
+    return (ssl->flags & MBEDTLS_SSL_CONTEXT_FLAG_HOSTNAME_SET) != 0;
+}
+#endif
+
+static void mbedtls_ssl_free_hostname(mbedtls_ssl_context *ssl)
+{
+    if (ssl->hostname != NULL) {
+        mbedtls_zeroize_and_free(ssl->hostname, strlen(ssl->hostname));
+    }
+    ssl->hostname = NULL;
+}
+
 int mbedtls_ssl_set_hostname(mbedtls_ssl_context *ssl, const char *hostname)
 {
     /* Initialize to suppress unnecessary compiler warning */
@@ -2532,10 +2558,7 @@
 
     /* Now it's clear that we will overwrite the old hostname,
      * so we can free it safely */
-
-    if (ssl->hostname != NULL) {
-        mbedtls_zeroize_and_free(ssl->hostname, strlen(ssl->hostname));
-    }
+    mbedtls_ssl_free_hostname(ssl);
 
     /* Passing NULL as hostname shall clear the old one */
 
@@ -2552,6 +2575,8 @@
         ssl->hostname[hostname_len] = '\0';
     }
 
+    ssl->flags |= MBEDTLS_SSL_CONTEXT_FLAG_HOSTNAME_SET;
+
     return 0;
 }
 #endif /* MBEDTLS_X509_CRT_PARSE_C */
@@ -5294,9 +5319,7 @@
     }
 
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
-    if (ssl->hostname != NULL) {
-        mbedtls_zeroize_and_free(ssl->hostname, strlen(ssl->hostname));
-    }
+    mbedtls_ssl_free_hostname(ssl);
 #endif
 
 #if defined(MBEDTLS_SSL_DTLS_HELLO_VERIFY) && defined(MBEDTLS_SSL_SRV_C)
@@ -8844,6 +8867,25 @@
     return ret;
 }
 
+static int get_hostname_for_verification(mbedtls_ssl_context *ssl,
+                                         const char **hostname)
+{
+    if (!mbedtls_ssl_has_set_hostname_been_called(ssl)) {
+        MBEDTLS_SSL_DEBUG_MSG(1, ("Certificate verification without having set hostname"));
+        if (mbedtls_ssl_conf_get_endpoint(ssl->conf) == MBEDTLS_SSL_IS_CLIENT &&
+            ssl->conf->authmode == MBEDTLS_SSL_VERIFY_REQUIRED) {
+            return MBEDTLS_ERR_SSL_CERTIFICATE_VERIFICATION_WITHOUT_HOSTNAME;
+        }
+    }
+
+    *hostname = ssl->hostname;
+    if (*hostname == NULL) {
+        MBEDTLS_SSL_DEBUG_MSG(2, ("Certificate verification without CN verification"));
+    }
+
+    return 0;
+}
+
 int mbedtls_ssl_verify_certificate(mbedtls_ssl_context *ssl,
                                    int authmode,
                                    mbedtls_x509_crt *chain,
@@ -8869,7 +8911,13 @@
         p_vrfy = ssl->conf->p_vrfy;
     }
 
-    int ret = 0;
+    const char *hostname = "";
+    int ret = get_hostname_for_verification(ssl, &hostname);
+    if (ret != 0) {
+        MBEDTLS_SSL_DEBUG_RET(1, "get_hostname_for_verification", ret);
+        return ret;
+    }
+
     int have_ca_chain_or_callback = 0;
 #if defined(MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK)
     if (ssl->conf->f_ca_cb != NULL) {
@@ -8882,7 +8930,7 @@
             ssl->conf->f_ca_cb,
             ssl->conf->p_ca_cb,
             ssl->conf->cert_profile,
-            ssl->hostname,
+            hostname,
             &ssl->session_negotiate->verify_result,
             f_vrfy, p_vrfy);
     } else
@@ -8909,7 +8957,7 @@
             chain,
             ca_chain, ca_crl,
             ssl->conf->cert_profile,
-            ssl->hostname,
+            hostname,
             &ssl->session_negotiate->verify_result,
             f_vrfy, p_vrfy, rs_ctx);
     }
diff --git a/programs/ssl/ssl_client2.c b/programs/ssl/ssl_client2.c
index f009a31..fa61c6c 100644
--- a/programs/ssl/ssl_client2.c
+++ b/programs/ssl/ssl_client2.c
@@ -68,6 +68,7 @@
 #define DFL_MAX_VERSION         -1
 #define DFL_SHA1                -1
 #define DFL_AUTH_MODE           -1
+#define DFL_SET_HOSTNAME        1
 #define DFL_MFL_CODE            MBEDTLS_SSL_MAX_FRAG_LEN_NONE
 #define DFL_TRUNC_HMAC          -1
 #define DFL_RECSPLIT            -1
@@ -403,6 +404,9 @@
 #define USAGE2 \
     "    auth_mode=%%s        default: (library default: none)\n" \
     "                        options: none, optional, required\n" \
+    "    set_hostname=%%s     call mbedtls_ssl_set_hostname()?" \
+    "                        options: no, server_name, NULL\n" \
+    "                        default: server_name (but ignored if certs disabled)\n"  \
     USAGE_IO                                                \
     USAGE_KEY_OPAQUE                                        \
     USAGE_CA_CALLBACK                                       \
@@ -505,6 +509,8 @@
     int max_version;            /* maximum protocol version accepted        */
     int allow_sha1;             /* flag for SHA-1 support                   */
     int auth_mode;              /* verify mode for connection               */
+    int set_hostname;           /* call mbedtls_ssl_set_hostname()?         */
+                                /* 0=no, 1=yes, -1=NULL */
     unsigned char mfl_code;     /* code for maximum fragment length         */
     int trunc_hmac;             /* negotiate truncated hmac or not          */
     int recsplit;               /* enable record splitting?                 */
@@ -953,6 +959,7 @@
     opt.max_version         = DFL_MAX_VERSION;
     opt.allow_sha1          = DFL_SHA1;
     opt.auth_mode           = DFL_AUTH_MODE;
+    opt.set_hostname        = DFL_SET_HOSTNAME;
     opt.mfl_code            = DFL_MFL_CODE;
     opt.trunc_hmac          = DFL_TRUNC_HMAC;
     opt.recsplit            = DFL_RECSPLIT;
@@ -1344,6 +1351,16 @@
             } else {
                 goto usage;
             }
+        } else if (strcmp(p, "set_hostname") == 0) {
+            if (strcmp(q, "no") == 0) {
+                opt.set_hostname = 0;
+            } else if (strcmp(q, "server_name") == 0) {
+                opt.set_hostname = 1;
+            } else if (strcmp(q, "NULL") == 0) {
+                opt.set_hostname = -1;
+            } else {
+                goto usage;
+            }
         } else if (strcmp(p, "max_frag_len") == 0) {
             if (strcmp(q, "512") == 0) {
                 opt.mfl_code = MBEDTLS_SSL_MAX_FRAG_LEN_512;
@@ -2052,10 +2069,24 @@
 #endif /* MBEDTLS_SSL_DTLS_SRTP */
 
 #if defined(MBEDTLS_SSL_HANDSHAKE_WITH_CERT_ENABLED)
-    if ((ret = mbedtls_ssl_set_hostname(&ssl, opt.server_name)) != 0) {
-        mbedtls_printf(" failed\n  ! mbedtls_ssl_set_hostname returned %d\n\n",
-                       ret);
-        goto exit;
+    switch (opt.set_hostname) {
+        case -1:
+            if ((ret = mbedtls_ssl_set_hostname(&ssl, NULL)) != 0) {
+                mbedtls_printf(" failed\n  ! mbedtls_ssl_set_hostname returned %d\n\n",
+                               ret);
+                goto exit;
+            }
+            break;
+        case 0:
+            /* Skip the call */
+            break;
+        default:
+            if ((ret = mbedtls_ssl_set_hostname(&ssl, opt.server_name)) != 0) {
+                mbedtls_printf(" failed\n  ! mbedtls_ssl_set_hostname returned %d\n\n",
+                               ret);
+                goto exit;
+            }
+            break;
     }
 #endif
 
diff --git a/programs/ssl/ssl_test_common_source.c b/programs/ssl/ssl_test_common_source.c
index 6c7eed5..e194b58 100644
--- a/programs/ssl/ssl_test_common_source.c
+++ b/programs/ssl/ssl_test_common_source.c
@@ -315,7 +315,7 @@
 };
 #endif /* MBEDTLS_X509_CRT_PARSE_C */
 
-#if defined(MBEDTLS_X509_CRT_PARSE_C)
+#if defined(MBEDTLS_SSL_HANDSHAKE_WITH_CERT_ENABLED)
 /** Functionally equivalent to mbedtls_x509_crt_verify_info, see that function
  *  for more info.
  */
@@ -350,9 +350,7 @@
     return (int) (size - n);
 #endif /* MBEDTLS_X509_REMOVE_INFO */
 }
-#endif /* MBEDTLS_X509_CRT_PARSE_C */
 
-#if defined(MBEDTLS_SSL_HANDSHAKE_WITH_CERT_ENABLED)
 static void mbedtls_print_supported_sig_algs(void)
 {
     mbedtls_printf("supported signature algorithms:\n");
diff --git a/programs/ssl/ssl_test_lib.h b/programs/ssl/ssl_test_lib.h
index a8387d7..3bbddd7 100644
--- a/programs/ssl/ssl_test_lib.h
+++ b/programs/ssl/ssl_test_lib.h
@@ -243,8 +243,8 @@
  * - free the provided PK context and re-initilize it as an opaque PK context
  *   wrapping the PSA key imported in the above step.
  *
- * \param[in/out] pk    On input the non-opaque PK context which contains the
- *                      key to be wrapped. On output the re-initialized PK
+ * \param[in,out] pk    On input, the non-opaque PK context which contains the
+ *                      key to be wrapped. On output, the re-initialized PK
  *                      context which represents the opaque version of the one
  *                      provided as input.
  * \param[in] psa_alg   The primary algorithm that will be associated to the
diff --git a/tests/src/test_helpers/ssl_helpers.c b/tests/src/test_helpers/ssl_helpers.c
index 44e07ef..b89ca21 100644
--- a/tests/src/test_helpers/ssl_helpers.c
+++ b/tests/src/test_helpers/ssl_helpers.c
@@ -855,6 +855,10 @@
     ret = mbedtls_ssl_setup(&(ep->ssl), &(ep->conf));
     TEST_ASSERT(ret == 0);
 
+    if (MBEDTLS_SSL_IS_CLIENT == endpoint_type) {
+        ret = mbedtls_ssl_set_hostname(&(ep->ssl), "localhost");
+    }
+
 #if defined(MBEDTLS_SSL_PROTO_DTLS) && defined(MBEDTLS_SSL_SRV_C)
     if (endpoint_type == MBEDTLS_SSL_IS_SERVER && dtls_context != NULL) {
         mbedtls_ssl_conf_dtls_cookies(&(ep->conf), NULL, NULL, NULL);
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index 23b692c..8a44687 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -476,6 +476,11 @@
     esac
 
     case " $CMD_LINE " in
+        *\ ca_callback=1\ *)
+            requires_config_enabled MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK;;
+    esac
+
+    case " $CMD_LINE " in
         *"programs/ssl/dtls_client "*|\
         *"programs/ssl/ssl_client1 "*)
             requires_config_enabled MBEDTLS_CTR_DRBG_C
@@ -2217,7 +2222,6 @@
             "$P_CLI" \
             0
 
-requires_config_enabled MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK
 run_test    "CA callback on client" \
             "$P_SRV debug_level=3" \
             "$P_CLI ca_callback=1 debug_level=3 " \
@@ -2226,7 +2230,6 @@
             -S "error" \
             -C "error"
 
-requires_config_enabled MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK
 requires_config_enabled MBEDTLS_X509_CRT_PARSE_C
 requires_hash_alg SHA_256
 run_test    "CA callback on server" \
@@ -5935,6 +5938,215 @@
             -C "X509 - Certificate verification failed" \
             -C "SSL - No CA Chain is set, but required to operate"
 
+# The next few tests check what happens if the server has a valid certificate
+# that does not match its name (impersonation).
+
+run_test "Authentication: hostname match, client required" \
+         "$P_SRV" \
+         "$P_CLI auth_mode=required server_name=localhost debug_level=2" \
+         0 \
+         -C "does not match with the expected CN" \
+         -C "Certificate verification without having set hostname" \
+         -C "Certificate verification without CN verification" \
+         -C "x509_verify_cert() returned -" \
+         -C "! mbedtls_ssl_handshake returned" \
+         -C "X509 - Certificate verification failed"
+
+run_test "Authentication: hostname match, client required, CA callback" \
+         "$P_SRV" \
+         "$P_CLI auth_mode=required server_name=localhost debug_level=3 ca_callback=1" \
+         0 \
+         -C "does not match with the expected CN" \
+         -C "Certificate verification without having set hostname" \
+         -C "Certificate verification without CN verification" \
+         -c "use CA callback for X.509 CRT verification" \
+         -C "x509_verify_cert() returned -" \
+         -C "! mbedtls_ssl_handshake returned" \
+         -C "X509 - Certificate verification failed"
+
+run_test "Authentication: hostname mismatch (wrong), client required" \
+         "$P_SRV" \
+         "$P_CLI auth_mode=required server_name=wrong-name debug_level=1" \
+         1 \
+         -c "does not match with the expected CN" \
+         -c "x509_verify_cert() returned -" \
+         -c "! mbedtls_ssl_handshake returned" \
+         -c "X509 - Certificate verification failed"
+
+run_test "Authentication: hostname mismatch (empty), client required" \
+         "$P_SRV" \
+         "$P_CLI auth_mode=required server_name= debug_level=1" \
+         1 \
+         -c "does not match with the expected CN" \
+         -c "x509_verify_cert() returned -" \
+         -c "! mbedtls_ssl_handshake returned" \
+         -c "X509 - Certificate verification failed"
+
+run_test "Authentication: hostname mismatch (truncated), client required" \
+         "$P_SRV" \
+         "$P_CLI auth_mode=required server_name=localhos debug_level=1" \
+         1 \
+         -c "does not match with the expected CN" \
+         -c "x509_verify_cert() returned -" \
+         -c "! mbedtls_ssl_handshake returned" \
+         -c "X509 - Certificate verification failed"
+
+run_test "Authentication: hostname mismatch (last char), client required" \
+         "$P_SRV" \
+         "$P_CLI auth_mode=required server_name=localhoss debug_level=1" \
+         1 \
+         -c "does not match with the expected CN" \
+         -c "x509_verify_cert() returned -" \
+         -c "! mbedtls_ssl_handshake returned" \
+         -c "X509 - Certificate verification failed"
+
+run_test "Authentication: hostname mismatch (trailing), client required" \
+         "$P_SRV" \
+         "$P_CLI auth_mode=required server_name=localhostt debug_level=1" \
+         1 \
+         -c "does not match with the expected CN" \
+         -c "x509_verify_cert() returned -" \
+         -c "! mbedtls_ssl_handshake returned" \
+         -c "X509 - Certificate verification failed"
+
+run_test "Authentication: hostname mismatch, client optional" \
+         "$P_SRV" \
+         "$P_CLI auth_mode=optional server_name=wrong-name debug_level=2" \
+         0 \
+         -c "does not match with the expected CN" \
+         -c "x509_verify_cert() returned -" \
+         -C "X509 - Certificate verification failed"
+
+run_test "Authentication: hostname mismatch, client none" \
+         "$P_SRV" \
+         "$P_CLI auth_mode=none server_name=wrong-name debug_level=2" \
+         0 \
+         -C "does not match with the expected CN" \
+         -C "Certificate verification without having set hostname" \
+         -C "Certificate verification without CN verification" \
+         -C "x509_verify_cert() returned -" \
+         -C "X509 - Certificate verification failed"
+
+run_test "Authentication: hostname null, client required" \
+         "$P_SRV" \
+         "$P_CLI auth_mode=required set_hostname=NULL debug_level=2" \
+         0 \
+         -C "does not match with the expected CN" \
+         -C "Certificate verification without having set hostname" \
+         -c "Certificate verification without CN verification" \
+         -C "x509_verify_cert() returned -" \
+         -C "! mbedtls_ssl_handshake returned" \
+         -C "X509 - Certificate verification failed"
+
+run_test "Authentication: hostname null, client optional" \
+         "$P_SRV" \
+         "$P_CLI auth_mode=optional set_hostname=NULL debug_level=2" \
+         0 \
+         -C "does not match with the expected CN" \
+         -C "Certificate verification without having set hostname" \
+         -c "Certificate verification without CN verification" \
+         -C "x509_verify_cert() returned -" \
+         -C "X509 - Certificate verification failed"
+
+run_test "Authentication: hostname null, client none" \
+         "$P_SRV" \
+         "$P_CLI auth_mode=none set_hostname=NULL debug_level=2" \
+         0 \
+         -C "does not match with the expected CN" \
+         -C "Certificate verification without having set hostname" \
+         -C "Certificate verification without CN verification" \
+         -C "x509_verify_cert() returned -" \
+         -C "X509 - Certificate verification failed"
+
+run_test "Authentication: hostname unset, client required" \
+         "$P_SRV" \
+         "$P_CLI auth_mode=required set_hostname=no debug_level=2" \
+         1 \
+         -C "does not match with the expected CN" \
+         -c "Certificate verification without having set hostname" \
+         -C "Certificate verification without CN verification" \
+         -c "get_hostname_for_verification() returned -" \
+         -C "x509_verify_cert() returned -" \
+         -c "! mbedtls_ssl_handshake returned" \
+         -C "X509 - Certificate verification failed"
+
+run_test "Authentication: hostname unset, client required, CA callback" \
+         "$P_SRV" \
+         "$P_CLI auth_mode=required set_hostname=no debug_level=3 ca_callback=1" \
+         1 \
+         -C "does not match with the expected CN" \
+         -c "Certificate verification without having set hostname" \
+         -C "Certificate verification without CN verification" \
+         -c "get_hostname_for_verification() returned -" \
+         -C "use CA callback for X.509 CRT verification" \
+         -C "x509_verify_cert() returned -" \
+         -c "! mbedtls_ssl_handshake returned" \
+         -C "X509 - Certificate verification failed"
+
+run_test "Authentication: hostname unset, client optional" \
+         "$P_SRV" \
+         "$P_CLI auth_mode=optional set_hostname=no debug_level=2" \
+         0 \
+         -C "does not match with the expected CN" \
+         -c "Certificate verification without having set hostname" \
+         -c "Certificate verification without CN verification" \
+         -C "x509_verify_cert() returned -" \
+         -C "X509 - Certificate verification failed"
+
+run_test "Authentication: hostname unset, client none" \
+         "$P_SRV" \
+         "$P_CLI auth_mode=none set_hostname=no debug_level=2" \
+         0 \
+         -C "does not match with the expected CN" \
+         -C "Certificate verification without having set hostname" \
+         -C "Certificate verification without CN verification" \
+         -C "x509_verify_cert() returned -" \
+         -C "X509 - Certificate verification failed"
+
+run_test "Authentication: hostname unset, client default, server picks cert, 1.2" \
+         "$P_SRV force_version=tls12 force_ciphersuite=TLS-ECDHE-ECDSA-WITH-AES-128-CCM-8" \
+         "$P_CLI psk=73776f726466697368 psk_identity=foo set_hostname=no debug_level=2" \
+         1 \
+         -C "does not match with the expected CN" \
+         -c "Certificate verification without having set hostname" \
+         -C "Certificate verification without CN verification" \
+         -c "get_hostname_for_verification() returned -" \
+         -C "x509_verify_cert() returned -" \
+         -C "X509 - Certificate verification failed"
+
+requires_config_enabled MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL_ENABLED
+run_test "Authentication: hostname unset, client default, server picks cert, 1.3" \
+         "$P_SRV force_version=tls13 tls13_kex_modes=ephemeral" \
+         "$P_CLI psk=73776f726466697368 psk_identity=foo set_hostname=no debug_level=2" \
+         1 \
+         -C "does not match with the expected CN" \
+         -c "Certificate verification without having set hostname" \
+         -C "Certificate verification without CN verification" \
+         -c "get_hostname_for_verification() returned -" \
+         -C "x509_verify_cert() returned -" \
+         -C "X509 - Certificate verification failed"
+
+run_test "Authentication: hostname unset, client default, server picks PSK, 1.2" \
+         "$P_SRV force_version=tls12 force_ciphersuite=TLS-PSK-WITH-AES-128-CCM-8 psk=73776f726466697368 psk_identity=foo" \
+         "$P_CLI psk=73776f726466697368 psk_identity=foo set_hostname=no debug_level=2" \
+         0 \
+         -C "does not match with the expected CN" \
+         -C "Certificate verification without having set hostname" \
+         -C "Certificate verification without CN verification" \
+         -C "x509_verify_cert() returned -" \
+         -C "X509 - Certificate verification failed"
+
+requires_config_enabled MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK_ENABLED
+run_test "Authentication: hostname unset, client default, server picks PSK, 1.3" \
+         "$P_SRV force_version=tls13 tls13_kex_modes=psk psk=73776f726466697368 psk_identity=foo" \
+         "$P_CLI psk=73776f726466697368 psk_identity=foo set_hostname=no debug_level=2" \
+         0 \
+         -C "does not match with the expected CN" \
+         -C "Certificate verification without having set hostname" \
+         -C "Certificate verification without CN verification" \
+         -C "x509_verify_cert() returned -" \
+         -C "X509 - Certificate verification failed"
+
 # The purpose of the next two tests is to test the client's behaviour when receiving a server
 # certificate with an unsupported elliptic curve. This should usually not happen because
 # the client informs the server about the supported curves - it does, though, in the
@@ -6279,7 +6491,6 @@
 # Tests for auth_mode, using CA callback, these are duplicated from the authentication tests
 # When updating these tests, modify the matching authentication tests accordingly
 
-requires_config_enabled MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK
 run_test    "Authentication, CA callback: server badcert, client required" \
             "$P_SRV crt_file=$DATA_FILES_PATH/server5-badsign.crt \
              key_file=$DATA_FILES_PATH/server5.key" \
@@ -6291,7 +6502,6 @@
             -c "! mbedtls_ssl_handshake returned" \
             -c "X509 - Certificate verification failed"
 
-requires_config_enabled MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK
 run_test    "Authentication, CA callback: server badcert, client optional" \
             "$P_SRV crt_file=$DATA_FILES_PATH/server5-badsign.crt \
              key_file=$DATA_FILES_PATH/server5.key" \
@@ -6303,7 +6513,6 @@
             -C "! mbedtls_ssl_handshake returned" \
             -C "X509 - Certificate verification failed"
 
-requires_config_enabled MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK
 run_test    "Authentication, CA callback: server badcert, client none" \
             "$P_SRV crt_file=$DATA_FILES_PATH/server5-badsign.crt \
              key_file=$DATA_FILES_PATH/server5.key" \
@@ -6322,7 +6531,6 @@
 # occasion (to be fixed). If that bug's fixed, the test needs to be altered to use a
 # different means to have the server ignoring the client's supported curve list.
 
-requires_config_enabled MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK
 run_test    "Authentication, CA callback: server ECDH p256v1, client required, p256v1 unsupported" \
             "$P_SRV debug_level=1 key_file=$DATA_FILES_PATH/server5.key \
              crt_file=$DATA_FILES_PATH/server5.ku-ka.crt" \
@@ -6333,7 +6541,6 @@
             -c "! Certificate verification flags" \
             -C "bad server certificate (ECDH curve)" # Expect failure at earlier verification stage
 
-requires_config_enabled MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK
 run_test    "Authentication, CA callback: server ECDH p256v1, client optional, p256v1 unsupported" \
             "$P_SRV debug_level=1 key_file=$DATA_FILES_PATH/server5.key \
              crt_file=$DATA_FILES_PATH/server5.ku-ka.crt" \
@@ -6344,7 +6551,6 @@
             -c "! Certificate verification flags"\
             -c "bad server certificate (ECDH curve)" # Expect failure only at ECDH params check
 
-requires_config_enabled MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK
 requires_any_configs_enabled $TLS1_2_KEY_EXCHANGES_WITH_CERT
 run_test    "Authentication, CA callback: client SHA384, server required" \
             "$P_SRV ca_callback=1 debug_level=3 auth_mode=required" \
@@ -6356,7 +6562,6 @@
             -c "Supported Signature Algorithm found: 04 " \
             -c "Supported Signature Algorithm found: 05 "
 
-requires_config_enabled MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK
 requires_any_configs_enabled $TLS1_2_KEY_EXCHANGES_WITH_CERT
 run_test    "Authentication, CA callback: client SHA256, server required" \
             "$P_SRV ca_callback=1 debug_level=3 auth_mode=required" \
@@ -6368,7 +6573,6 @@
             -c "Supported Signature Algorithm found: 04 " \
             -c "Supported Signature Algorithm found: 05 "
 
-requires_config_enabled MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK
 run_test    "Authentication, CA callback: client badcert, server required" \
             "$P_SRV ca_callback=1 debug_level=3 auth_mode=required" \
             "$P_CLI debug_level=3 crt_file=$DATA_FILES_PATH/server5-badsign.crt \
@@ -6390,7 +6594,6 @@
 # detect that its write end of the connection is closed and abort
 # before reading the alert message.
 
-requires_config_enabled MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK
 run_test    "Authentication, CA callback: client cert not trusted, server required" \
             "$P_SRV ca_callback=1 debug_level=3 auth_mode=required" \
             "$P_CLI debug_level=3 crt_file=$DATA_FILES_PATH/server5-selfsigned.crt \
@@ -6408,7 +6611,6 @@
             -s "! mbedtls_ssl_handshake returned" \
             -s "X509 - Certificate verification failed"
 
-requires_config_enabled MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK
 run_test    "Authentication, CA callback: client badcert, server optional" \
             "$P_SRV ca_callback=1 debug_level=3 auth_mode=optional" \
             "$P_CLI debug_level=3 crt_file=$DATA_FILES_PATH/server5-badsign.crt \
@@ -6429,7 +6631,6 @@
 
 requires_config_value_equals "MBEDTLS_X509_MAX_INTERMEDIATE_CA" $MAX_IM_CA
 requires_full_size_output_buffer
-requires_config_enabled MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK
 run_test    "Authentication, CA callback: server max_int chain, client default" \
             "$P_SRV crt_file=$DATA_FILES_PATH/dir-maxpath/c09.pem \
                     key_file=$DATA_FILES_PATH/dir-maxpath/09.key" \
@@ -6440,7 +6641,6 @@
 
 requires_config_value_equals "MBEDTLS_X509_MAX_INTERMEDIATE_CA" $MAX_IM_CA
 requires_full_size_output_buffer
-requires_config_enabled MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK
 run_test    "Authentication, CA callback: server max_int+1 chain, client default" \
             "$P_SRV crt_file=$DATA_FILES_PATH/dir-maxpath/c10.pem \
                     key_file=$DATA_FILES_PATH/dir-maxpath/10.key" \
@@ -6451,7 +6651,6 @@
 
 requires_config_value_equals "MBEDTLS_X509_MAX_INTERMEDIATE_CA" $MAX_IM_CA
 requires_full_size_output_buffer
-requires_config_enabled MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK
 run_test    "Authentication, CA callback: server max_int+1 chain, client optional" \
             "$P_SRV crt_file=$DATA_FILES_PATH/dir-maxpath/c10.pem \
                     key_file=$DATA_FILES_PATH/dir-maxpath/10.key" \
@@ -6463,7 +6662,6 @@
 
 requires_config_value_equals "MBEDTLS_X509_MAX_INTERMEDIATE_CA" $MAX_IM_CA
 requires_full_size_output_buffer
-requires_config_enabled MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK
 run_test    "Authentication, CA callback: client max_int+1 chain, server optional" \
             "$P_SRV ca_callback=1 debug_level=3 ca_file=$DATA_FILES_PATH/dir-maxpath/00.crt auth_mode=optional" \
             "$P_CLI crt_file=$DATA_FILES_PATH/dir-maxpath/c10.pem \
@@ -6474,7 +6672,6 @@
 
 requires_config_value_equals "MBEDTLS_X509_MAX_INTERMEDIATE_CA" $MAX_IM_CA
 requires_full_size_output_buffer
-requires_config_enabled MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK
 run_test    "Authentication, CA callback: client max_int+1 chain, server required" \
             "$P_SRV ca_callback=1 debug_level=3 ca_file=$DATA_FILES_PATH/dir-maxpath/00.crt auth_mode=required" \
             "$P_CLI crt_file=$DATA_FILES_PATH/dir-maxpath/c10.pem \
@@ -6485,7 +6682,6 @@
 
 requires_config_value_equals "MBEDTLS_X509_MAX_INTERMEDIATE_CA" $MAX_IM_CA
 requires_full_size_output_buffer
-requires_config_enabled MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK
 run_test    "Authentication, CA callback: client max_int chain, server required" \
             "$P_SRV ca_callback=1 debug_level=3 ca_file=$DATA_FILES_PATH/dir-maxpath/00.crt auth_mode=required" \
             "$P_CLI crt_file=$DATA_FILES_PATH/dir-maxpath/c09.pem \