Merge branch 'wip/dueno/external-psk-importer' into 'master'HEADmaster

psk: Add basic support for RFC 9258 external PSK importer interface

Closes #1355

See merge request gnutls/gnutls!1741

20 files changed, 791 insertions, 86 deletions

diff --git a/.gitignore b/.gitignore
index b474c09f41..2b0725526e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -623,6 +623,7 @@ tests/privkey-keygen
 tests/privkey-verify-broken
 tests/protocol-set-allowlist
 tests/psk-file
+tests/psk-importer
 tests/pskself
 tests/pskself2
 tests/pubkey-import-export
diff --git a/NEWS b/NEWS
index 5f6e45a814..2f46982ed9 100644
--- a/NEWS
+++ b/NEWS
@@ -14,6 +14,20 @@ See the end for copying conditions.
    extension without payload, the behavior can be reverted with the
    %NO_SHUFFLE_EXTENSIONS priority keyword.
 
+** libgnutls: Add support for RFC 9258 external PSK importer.
+   This enables to deploy the same PSK across multiple TLS versions
+   (TLS 1.2 and TLS 1.3) in a secure manner. To use, the application
+   needs to set up a callback that formats the PSK identity using
+   gnutls_psk_format_imported_identity().
+
+** API and ABI modifications:
+gnutls_psk_client_credentials_function3: New typedef
+gnutls_psk_server_credentials_function3: New typedef
+gnutls_psk_set_server_credentials_function3: New function
+gnutls_psk_set_client_credentials_function3: New function
+gnutls_psk_format_imported_identity: New function
+GNUTLS_PSK_KEY_EXT: New enum member of gnutls_psk_key_flags
+
 * Version 3.8.0 (released 2023-02-09)
 
 ** libgnutls: Fix a Bleichenbacher oracle in the TLS RSA key exchange.
diff --git a/devel/libgnutls.abignore b/devel/libgnutls.abignore
index c19dce38e1..7ed194a515 100644
--- a/devel/libgnutls.abignore
+++ b/devel/libgnutls.abignore
@@ -70,3 +70,15 @@ name = drbg_aes_reseed
 
 # The following should be removed in the new release, after updating the
 # abi-dump repository:
+[suppress_function]
+name = gnutls_psk_set_server_credentials_function3
+
+[suppress_function]
+name = gnutls_psk_set_client_credentials_function3
+
+[suppress_function]
+name = gnutls_psk_format_imported_identity
+
+[suppress_type]
+name = gnutls_psk_key_flags
+changed_enumerators = GNUTLS_PSK_KEY_EXT
diff --git a/devel/symbols.last b/devel/symbols.last
index bd0de671fd..3500a8292b 100644
--- a/devel/symbols.last
+++ b/devel/symbols.last
@@ -17,6 +17,7 @@ GNUTLS_3_7_3@GNUTLS_3_7_3
 GNUTLS_3_7_4@GNUTLS_3_7_4
 GNUTLS_3_7_5@GNUTLS_3_7_5
 GNUTLS_3_7_7@GNUTLS_3_7_7
+GNUTLS_3_8_1@GNUTLS_3_8_1
 _gnutls_global_init_skip@GNUTLS_3_4
 gnutls_aead_cipher_decrypt@GNUTLS_3_4
 gnutls_aead_cipher_decryptv2@GNUTLS_3_6_10
@@ -680,6 +681,7 @@ gnutls_protocol_set_enabled@GNUTLS_3_7_3
 gnutls_psk_allocate_client_credentials@GNUTLS_3_4
 gnutls_psk_allocate_server_credentials@GNUTLS_3_4
 gnutls_psk_client_get_hint@GNUTLS_3_4
+gnutls_psk_format_imported_identity@GNUTLS_3_8_1
 gnutls_psk_free_client_credentials@GNUTLS_3_4
 gnutls_psk_free_server_credentials@GNUTLS_3_4
 gnutls_psk_server_get_username2@GNUTLS_3_6_13
@@ -687,10 +689,12 @@ gnutls_psk_server_get_username@GNUTLS_3_4
 gnutls_psk_set_client_credentials2@GNUTLS_3_6_13
 gnutls_psk_set_client_credentials@GNUTLS_3_4
 gnutls_psk_set_client_credentials_function2@GNUTLS_3_6_13
+gnutls_psk_set_client_credentials_function3@GNUTLS_3_8_1
 gnutls_psk_set_client_credentials_function@GNUTLS_3_4
 gnutls_psk_set_params_function@GNUTLS_3_4
 gnutls_psk_set_server_credentials_file@GNUTLS_3_4
 gnutls_psk_set_server_credentials_function2@GNUTLS_3_6_13
+gnutls_psk_set_server_credentials_function3@GNUTLS_3_8_1
 gnutls_psk_set_server_credentials_function@GNUTLS_3_4
 gnutls_psk_set_server_credentials_hint@GNUTLS_3_4
 gnutls_psk_set_server_dh_params@GNUTLS_3_4
diff --git a/doc/Makefile.am b/doc/Makefile.am
index 6cfd6097ad..20e25dfa4e 100644
--- a/doc/Makefile.am
+++ b/doc/Makefile.am
@@ -1772,6 +1772,8 @@ FUNCS += functions/gnutls_psk_allocate_server_credentials
 FUNCS += functions/gnutls_psk_allocate_server_credentials.short
 FUNCS += functions/gnutls_psk_client_get_hint
 FUNCS += functions/gnutls_psk_client_get_hint.short
+FUNCS += functions/gnutls_psk_format_imported_identity
+FUNCS += functions/gnutls_psk_format_imported_identity.short
 FUNCS += functions/gnutls_psk_free_client_credentials
 FUNCS += functions/gnutls_psk_free_client_credentials.short
 FUNCS += functions/gnutls_psk_free_server_credentials
@@ -1788,6 +1790,8 @@ FUNCS += functions/gnutls_psk_set_client_credentials_function
 FUNCS += functions/gnutls_psk_set_client_credentials_function.short
 FUNCS += functions/gnutls_psk_set_client_credentials_function2
 FUNCS += functions/gnutls_psk_set_client_credentials_function2.short
+FUNCS += functions/gnutls_psk_set_client_credentials_function3
+FUNCS += functions/gnutls_psk_set_client_credentials_function3.short
 FUNCS += functions/gnutls_psk_set_params_function
 FUNCS += functions/gnutls_psk_set_params_function.short
 FUNCS += functions/gnutls_psk_set_server_credentials_file
@@ -1796,6 +1800,8 @@ FUNCS += functions/gnutls_psk_set_server_credentials_function
 FUNCS += functions/gnutls_psk_set_server_credentials_function.short
 FUNCS += functions/gnutls_psk_set_server_credentials_function2
 FUNCS += functions/gnutls_psk_set_server_credentials_function2.short
+FUNCS += functions/gnutls_psk_set_server_credentials_function3
+FUNCS += functions/gnutls_psk_set_server_credentials_function3.short
 FUNCS += functions/gnutls_psk_set_server_credentials_hint
 FUNCS += functions/gnutls_psk_set_server_credentials_hint.short
 FUNCS += functions/gnutls_psk_set_server_dh_params
diff --git a/doc/manpages/Makefile.am b/doc/manpages/Makefile.am
index 27cf77a57e..24ca59888f 100644
--- a/doc/manpages/Makefile.am
+++ b/doc/manpages/Makefile.am
@@ -732,6 +732,7 @@ APIMANS += gnutls_protocol_set_enabled.3
 APIMANS += gnutls_psk_allocate_client_credentials.3
 APIMANS += gnutls_psk_allocate_server_credentials.3
 APIMANS += gnutls_psk_client_get_hint.3
+APIMANS += gnutls_psk_format_imported_identity.3
 APIMANS += gnutls_psk_free_client_credentials.3
 APIMANS += gnutls_psk_free_server_credentials.3
 APIMANS += gnutls_psk_server_get_username.3
@@ -740,10 +741,12 @@ APIMANS += gnutls_psk_set_client_credentials.3
 APIMANS += gnutls_psk_set_client_credentials2.3
 APIMANS += gnutls_psk_set_client_credentials_function.3
 APIMANS += gnutls_psk_set_client_credentials_function2.3
+APIMANS += gnutls_psk_set_client_credentials_function3.3
 APIMANS += gnutls_psk_set_params_function.3
 APIMANS += gnutls_psk_set_server_credentials_file.3
 APIMANS += gnutls_psk_set_server_credentials_function.3
 APIMANS += gnutls_psk_set_server_credentials_function2.3
+APIMANS += gnutls_psk_set_server_credentials_function3.3
 APIMANS += gnutls_psk_set_server_credentials_hint.3
 APIMANS += gnutls_psk_set_server_dh_params.3
 APIMANS += gnutls_psk_set_server_known_dh_params.3
diff --git a/lib/auth/dhe_psk.c b/lib/auth/dhe_psk.c
index ab5eddd16a..14cf5ba918 100644
--- a/lib/auth/dhe_psk.c
+++ b/lib/auth/dhe_psk.c
@@ -103,7 +103,7 @@ static int gen_ecdhe_psk_client_kx(gnutls_session_t session,
 	if (cred == NULL)
 		return gnutls_assert_val(GNUTLS_E_INSUFFICIENT_CREDENTIALS);
 
-	ret = _gnutls_find_psk_key(session, cred, &username, &key, &free);
+	ret = _gnutls_find_psk_key(session, cred, &username, &key, NULL, &free);
 	if (ret < 0)
 		return gnutls_assert_val(ret);
 
@@ -146,7 +146,7 @@ static int gen_dhe_psk_client_kx(gnutls_session_t session,
 	if (cred == NULL)
 		return gnutls_assert_val(GNUTLS_E_INSUFFICIENT_CREDENTIALS);
 
-	ret = _gnutls_find_psk_key(session, cred, &username, &key, &free);
+	ret = _gnutls_find_psk_key(session, cred, &username, &key, NULL, &free);
 	if (ret < 0)
 		return gnutls_assert_val(ret);
 
@@ -308,7 +308,7 @@ static int proc_dhe_psk_client_kx(gnutls_session_t session, uint8_t *data,
 	data += username.size + 2;
 
 	ret = _gnutls_psk_pwd_find_entry(session, info->username,
-					 info->username_len, &psk_key);
+					 info->username_len, &psk_key, NULL);
 	if (ret < 0)
 		return gnutls_assert_val(ret);
 
@@ -374,7 +374,7 @@ static int proc_ecdhe_psk_client_kx(gnutls_session_t session, uint8_t *data,
 	/* should never fail. It will always return a key even if it is
 	 * a random one */
 	ret = _gnutls_psk_pwd_find_entry(session, info->username,
-					 info->username_len, &psk_key);
+					 info->username_len, &psk_key, NULL);
 	if (ret < 0)
 		return gnutls_assert_val(ret);
 
diff --git a/lib/auth/psk.c b/lib/auth/psk.c
index 17206f69c5..8ddb239823 100644
--- a/lib/auth/psk.c
+++ b/lib/auth/psk.c
@@ -136,7 +136,7 @@ int _gnutls_gen_psk_client_kx(gnutls_session_t session, gnutls_buffer_st *data)
 		return GNUTLS_E_INTERNAL_ERROR;
 	}
 
-	ret = _gnutls_find_psk_key(session, cred, &username, &key, &free);
+	ret = _gnutls_find_psk_key(session, cred, &username, &key, NULL, &free);
 	if (ret < 0)
 		return gnutls_assert_val(ret);
 
@@ -224,7 +224,7 @@ static int _gnutls_proc_psk_client_kx(gnutls_session_t session, uint8_t *data,
 		return gnutls_assert_val(ret);
 
 	ret = _gnutls_psk_pwd_find_entry(session, info->username,
-					 info->username_len, &psk_key);
+					 info->username_len, &psk_key, NULL);
 	if (ret < 0)
 		return gnutls_assert_val(ret);
 
diff --git a/lib/auth/psk.h b/lib/auth/psk.h
index 06d7913c85..9e1f94b1fe 100644
--- a/lib/auth/psk.h
+++ b/lib/auth/psk.h
@@ -36,19 +36,20 @@
 typedef struct gnutls_psk_client_credentials_st {
 	gnutls_datum_t username;
 	gnutls_datum_t key;
-	gnutls_psk_client_credentials_function2 *get_function;
-	gnutls_psk_client_credentials_function *get_function_legacy;
+	gnutls_psk_client_credentials_function3 *get_function;
+	gnutls_psk_client_credentials_function2 *get_function2;
+	gnutls_psk_client_credentials_function *get_function1;
 	/* TLS 1.3 - The HMAC algorithm to use to compute the binder values */
 	const mac_entry_st *binder_algo;
 } psk_client_credentials_st;
 
 typedef struct gnutls_psk_server_credentials_st {
 	char *password_file;
-	/* callback function, instead of reading the
-	 * password files.
+	/* callback functions, instead of reading the password files.
 	 */
-	gnutls_psk_server_credentials_function2 *pwd_callback;
-	gnutls_psk_server_credentials_function *pwd_callback_legacy;
+	gnutls_psk_server_credentials_function3 *pwd_callback;
+	gnutls_psk_server_credentials_function2 *pwd_callback2;
+	gnutls_psk_server_credentials_function *pwd_callback1;
 
 	/* For DHE_PSK */
 	gnutls_dh_params_t dh_params;
diff --git a/lib/auth/psk_passwd.c b/lib/auth/psk_passwd.c
index 70f59c7738..eff339dd17 100644
--- a/lib/auth/psk_passwd.c
+++ b/lib/auth/psk_passwd.c
@@ -149,7 +149,8 @@ static int _randomize_psk(gnutls_datum_t *psk)
  * If the user doesn't exist a random password is returned instead.
  */
 int _gnutls_psk_pwd_find_entry(gnutls_session_t session, const char *username,
-			       uint16_t username_len, gnutls_datum_t *psk)
+			       uint16_t username_len, gnutls_datum_t *psk,
+			       gnutls_psk_key_flags *flags)
 {
 	gnutls_psk_server_credentials_t cred;
 	FILE *fp;
@@ -170,8 +171,7 @@ int _gnutls_psk_pwd_find_entry(gnutls_session_t session, const char *username,
 	 * set, use it.
 	 */
 	if (cred->pwd_callback != NULL) {
-		ret = cred->pwd_callback(session, &username_datum, psk);
-
+		ret = cred->pwd_callback(session, &username_datum, psk, flags);
 		if (ret == 1) { /* the user does not exist */
 			ret = _randomize_psk(psk);
 			if (ret < 0) {
@@ -212,6 +212,9 @@ int _gnutls_psk_pwd_find_entry(gnutls_session_t session, const char *username,
 				ret = GNUTLS_E_SRP_PWD_ERROR;
 				goto cleanup;
 			}
+			if (flags) {
+				*flags = 0;
+			}
 			ret = 0;
 			goto cleanup;
 		}
@@ -224,6 +227,9 @@ int _gnutls_psk_pwd_find_entry(gnutls_session_t session, const char *username,
 		goto cleanup;
 	}
 
+	if (flags) {
+		*flags = 0;
+	}
 	ret = 0;
 cleanup:
 	if (fp != NULL)
@@ -241,7 +247,7 @@ cleanup:
 int _gnutls_find_psk_key(gnutls_session_t session,
 			 gnutls_psk_client_credentials_t cred,
 			 gnutls_datum_t *username, gnutls_datum_t *key,
-			 int *free)
+			 gnutls_psk_key_flags *flags, int *free)
 {
 	int ret;
 
@@ -252,11 +258,14 @@ int _gnutls_find_psk_key(gnutls_session_t session,
 		username->size = cred->username.size;
 		key->data = cred->key.data;
 		key->size = cred->key.size;
+		if (flags) {
+			*flags = 0;
+		}
 	} else if (cred->get_function != NULL) {
-		ret = cred->get_function(session, username, key);
-
-		if (ret)
+		ret = cred->get_function(session, username, key, flags);
+		if (ret) {
 			return gnutls_assert_val(ret);
+		}
 
 		*free = 1;
 	} else
diff --git a/lib/auth/psk_passwd.h b/lib/auth/psk_passwd.h
index 18ac72b34b..2f270cc377 100644
--- a/lib/auth/psk_passwd.h
+++ b/lib/auth/psk_passwd.h
@@ -25,11 +25,12 @@
 
 /* this is locally allocated. It should be freed using the provided function */
 int _gnutls_psk_pwd_find_entry(gnutls_session_t, const char *username,
-			       uint16_t username_len, gnutls_datum_t *key);
+			       uint16_t username_len, gnutls_datum_t *key,
+			       gnutls_psk_key_flags *flags);
 
 int _gnutls_find_psk_key(gnutls_session_t session,
 			 gnutls_psk_client_credentials_t cred,
 			 gnutls_datum_t *username, gnutls_datum_t *key,
-			 int *free);
+			 gnutls_psk_key_flags *flags, int *free);
 
 #endif /* GNUTLS_LIB_AUTH_PSK_PASSWD_H */
diff --git a/lib/auth/rsa_psk.c b/lib/auth/rsa_psk.c
index e9e99761cf..6e3fbbda82 100644
--- a/lib/auth/rsa_psk.c
+++ b/lib/auth/rsa_psk.c
@@ -193,7 +193,7 @@ static int _gnutls_gen_rsa_psk_client_kx(gnutls_session_t session,
 		return GNUTLS_E_INSUFFICIENT_CREDENTIALS;
 	}
 
-	ret = _gnutls_find_psk_key(session, cred, &username, &key, &free);
+	ret = _gnutls_find_psk_key(session, cred, &username, &key, NULL, &free);
 	if (ret < 0)
 		return gnutls_assert_val(ret);
 
@@ -382,7 +382,8 @@ static int _gnutls_proc_rsa_psk_client_kx(gnutls_session_t session,
 	/* find the key of this username
 	 */
 	ret = _gnutls_psk_pwd_find_entry(session, info->username,
-					 strlen(info->username), &pwd_psk);
+					 strlen(info->username), &pwd_psk,
+					 NULL);
 	if (ret < 0) {
 		gnutls_assert();
 		goto cleanup;
diff --git a/lib/ext/pre_shared_key.c b/lib/ext/pre_shared_key.c
index 44797bb5ad..f632f972bc 100644
--- a/lib/ext/pre_shared_key.c
+++ b/lib/ext/pre_shared_key.c
@@ -35,6 +35,14 @@
 #include <ext/pre_shared_key.h>
 #include <assert.h>
 
+inline static bool
+have_psk_credentials(const gnutls_psk_client_credentials_t cred,
+		     gnutls_session_t session)
+{
+	return (cred->get_function || cred->username.data) &&
+	       session->internals.priorities->have_psk;
+}
+
 static int compute_psk_from_ticket(const tls13_ticket_st *ticket,
 				   gnutls_datum_t *key)
 {
@@ -61,16 +69,45 @@ static int compute_psk_from_ticket(const tls13_ticket_st *ticket,
 	return ret;
 }
 
+enum binder_type {
+	BINDER_EXT,
+	BINDER_RES,
+	BINDER_IMP
+};
+
+static const char *get_binder_label(enum binder_type type, size_t *size)
+{
+	static const char ext_label[] = EXT_BINDER_LABEL;
+	static const char res_label[] = RES_BINDER_LABEL;
+	static const char imp_label[] = IMP_BINDER_LABEL;
+	const char *label;
+
+	switch (type) {
+	case BINDER_EXT:
+		label = ext_label;
+		*size = sizeof(ext_label) - 1;
+		break;
+	case BINDER_RES:
+		label = res_label;
+		*size = sizeof(res_label) - 1;
+		break;
+	case BINDER_IMP:
+		label = imp_label;
+		*size = sizeof(imp_label) - 1;
+		break;
+	default:
+		assert(0);
+	}
+
+	return label;
+}
+
 static int compute_binder_key(const mac_entry_st *prf, const uint8_t *key,
-			      size_t keylen, bool resuming, void *out)
+			      size_t keylen, enum binder_type type, void *out)
 {
 	int ret;
-	const char ext_label[] = EXT_BINDER_LABEL;
-	const size_t ext_label_len = sizeof(ext_label) - 1;
-	const char res_label[] = RES_BINDER_LABEL;
-	const size_t res_label_len = sizeof(res_label) - 1;
-	const char *label = resuming ? res_label : ext_label;
-	size_t label_len = resuming ? res_label_len : ext_label_len;
+	size_t label_len;
+	const char *label = get_binder_label(type, &label_len);
 	uint8_t tmp_key[MAX_HASH_SIZE];
 
 	/* Compute HKDF-Extract(0, psk) */
@@ -90,8 +127,8 @@ static int compute_binder_key(const mac_entry_st *prf, const uint8_t *key,
 static int compute_psk_binder(gnutls_session_t session, const mac_entry_st *prf,
 			      unsigned binders_length, int exts_length,
 			      int ext_offset, const gnutls_datum_t *psk,
-			      const gnutls_datum_t *client_hello, bool resuming,
-			      void *out)
+			      const gnutls_datum_t *client_hello,
+			      enum binder_type type, void *out)
 {
 	int ret;
 	unsigned client_hello_pos, extensions_len_pos;
@@ -176,8 +213,7 @@ static int compute_psk_binder(gnutls_session_t session, const mac_entry_st *prf,
 		}
 	}
 
-	ret = compute_binder_key(prf, psk->data, psk->size, resuming,
-				 binder_key);
+	ret = compute_binder_key(prf, psk->data, psk->size, type, binder_key);
 	if (ret < 0) {
 		gnutls_assert();
 		goto error;
@@ -264,6 +300,172 @@ int _gnutls_generate_early_secrets_for_psk(gnutls_session_t session)
 	return 0;
 }
 
+/**
+ * gnutls_psk_format_imported_identity:
+ * @identity: external identity
+ * @context: optional contextual information
+ * @version: protocol version to which the PSK is imported
+ * @hash: hash algorithm used for KDF
+ * @imported_identity: where the imported identity is stored
+ *
+ * This formats an external PSK identity @identity into an imported
+ * form, described in RFC 9258 as ImportedIdentity.
+ *
+ * Upon success, the data field of @imported_identity is allocated
+ * using gnutls_malloc() and the caller must free the memory after
+ * use.
+ *
+ * Returns: %GNUTLS_E_SUCCESS (0) on success, otherwise a negative error code.
+ * Since: 3.8.1
+ */
+int gnutls_psk_format_imported_identity(const gnutls_datum_t *identity,
+					const gnutls_datum_t *context,
+					gnutls_protocol_t version,
+					gnutls_digest_algorithm_t hash,
+					gnutls_datum_t *imported_identity)
+{
+	gnutls_buffer_st buf;
+	const version_entry_st *ver = version_to_entry(version);
+	const mac_entry_st *prf = hash_to_entry(hash);
+	uint16_t target_protocol;
+	uint16_t target_kdf;
+	int ret;
+
+	_gnutls_buffer_init(&buf);
+
+	/* external_identity */
+	ret = _gnutls_buffer_append_data_prefix(&buf, 16, identity->data,
+						identity->size);
+	if (ret < 0) {
+		goto error;
+	}
+
+	/* context */
+	ret = _gnutls_buffer_append_data_prefix(&buf, 16, context->data,
+						context->size);
+	if (ret < 0) {
+		goto error;
+	}
+
+	/* target_protocol */
+	target_protocol = ver->major << 8 | ver->minor;
+	ret = _gnutls_buffer_append_prefix(&buf, 16, target_protocol);
+	if (ret < 0) {
+		goto error;
+	}
+
+	/* target_kdf */
+	switch (prf->id) {
+	case GNUTLS_MAC_SHA256:
+		target_kdf = 0x0001;
+		break;
+	case GNUTLS_MAC_SHA384:
+		target_kdf = 0x0002;
+		break;
+	default:
+		ret = gnutls_assert_val(GNUTLS_E_UNKNOWN_HASH_ALGORITHM);
+		goto error;
+	}
+	ret = _gnutls_buffer_append_prefix(&buf, 16, target_kdf);
+	if (ret < 0) {
+		goto error;
+	}
+
+	ret = _gnutls_buffer_to_datum(&buf, imported_identity, 0);
+	if (ret < 0) {
+		goto error;
+	}
+	return 0;
+
+error:
+	_gnutls_buffer_clear(&buf);
+	return ret;
+}
+
+static int derive_ipsk(const mac_entry_st *prf,
+		       const gnutls_datum_t *imported_identity,
+		       const gnutls_datum_t *epsk, uint8_t ipsk[MAX_HASH_SIZE])
+{
+	uint8_t epskx[MAX_HASH_SIZE];
+	uint8_t hashed_identity[MAX_HASH_SIZE];
+	int ret;
+
+	/* epskx = HKDF-Extract(0, epsk) */
+	ret = _tls13_init_secret2(prf, epsk->data, epsk->size, epskx);
+	if (ret < 0) {
+		return ret;
+	}
+	ret = gnutls_hash_fast((gnutls_digest_algorithm_t)prf->id,
+			       imported_identity->data, imported_identity->size,
+			       hashed_identity);
+	if (ret < 0) {
+		return ret;
+	}
+	/* ipskx = HKDF-Expand-Label(epskx, "derived psk", Hash(ImportedIdentity), L) */
+	return _tls13_expand_secret2(prf, DERIVED_PSK_LABEL,
+				     sizeof(DERIVED_PSK_LABEL) - 1,
+				     hashed_identity, prf->output_size, epskx,
+				     prf->output_size, ipsk);
+}
+
+/* This does the opposite of gnutls_psk_format_imported_identity.
+ * Note that this does not allocate memory, and the data field of
+ * identity and context must not be freed.
+ */
+static int parse_imported_identity(const gnutls_datum_t *imported_identity,
+				   gnutls_datum_t *identity,
+				   gnutls_datum_t *context,
+				   gnutls_protocol_t *version,
+				   gnutls_digest_algorithm_t *hash)
+{
+	uint16_t target_protocol;
+	uint16_t target_kdf;
+	gnutls_buffer_st buf;
+	size_t size;
+	int ret;
+
+	_gnutls_ro_buffer_from_datum(&buf, (gnutls_datum_t *)imported_identity);
+
+	/* external_identity */
+	ret = _gnutls_buffer_pop_datum_prefix16(&buf, identity);
+	if (ret < 0) {
+		return ret;
+	}
+
+	/* context */
+	ret = _gnutls_buffer_pop_datum_prefix16(&buf, context);
+	if (ret < 0) {
+		return ret;
+	}
+
+	/* target_protocol */
+	ret = _gnutls_buffer_pop_prefix16(&buf, &size, 0);
+	if (ret < 0) {
+		return ret;
+	}
+	target_protocol = size;
+	*version = _gnutls_version_get((target_protocol >> 8) & 0xFF,
+				       target_protocol & 0xFF);
+
+	/* target_kdf */
+	ret = _gnutls_buffer_pop_prefix16(&buf, &size, 0);
+	if (ret < 0) {
+		return ret;
+	}
+	target_kdf = size;
+	switch (target_kdf) {
+	case 0x0001:
+		*hash = GNUTLS_DIG_SHA256;
+		break;
+	case 0x0002:
+		*hash = GNUTLS_DIG_SHA384;
+		break;
+	default:
+		return gnutls_assert_val(GNUTLS_E_UNKNOWN_HASH_ALGORITHM);
+	}
+	return 0;
+}
+
 static int client_send_params(gnutls_session_t session, gnutls_buffer_t extdata,
 			      const gnutls_psk_client_credentials_t cred)
 {
@@ -282,11 +484,12 @@ static int client_send_params(gnutls_session_t session, gnutls_buffer_t extdata,
 	psk_auth_info_t info = NULL;
 	unsigned psk_id_len = 0;
 	unsigned binders_len, binders_pos;
+	bool imported = false;
 	tls13_ticket_st *ticket = &session->internals.tls13_ticket;
 
 	if (((session->internals.flags & GNUTLS_NO_TICKETS) ||
 	     session->internals.tls13_ticket.ticket.data == NULL) &&
-	    (!cred || !_gnutls_have_psk_credentials(cred, session))) {
+	    (!cred || !have_psk_credentials(cred, session))) {
 		return 0;
 	}
 
@@ -353,8 +556,9 @@ static int client_send_params(gnutls_session_t session, gnutls_buffer_t extdata,
 	}
 
 ignore_ticket:
-	if (cred && _gnutls_have_psk_credentials(cred, session)) {
+	if (cred && have_psk_credentials(cred, session)) {
 		gnutls_datum_t tkey;
+		gnutls_psk_key_flags flags;
 
 		if (cred->binder_algo == NULL) {
 			gnutls_assert();
@@ -366,7 +570,7 @@ ignore_ticket:
 		prf_psk = cred->binder_algo;
 
 		ret = _gnutls_find_psk_key(session, cred, &username, &tkey,
-					   &free_username);
+					   &flags, &free_username);
 		if (ret < 0) {
 			gnutls_assert();
 			goto cleanup;
@@ -390,6 +594,50 @@ ignore_ticket:
 			user_key.size = tkey.size;
 		}
 
+		if (flags & GNUTLS_PSK_KEY_EXT) {
+			uint8_t ipsk[MAX_HASH_SIZE];
+			gnutls_datum_t imported_identity = { NULL, 0 };
+			gnutls_datum_t context = { NULL, 0 };
+			gnutls_protocol_t version;
+			gnutls_digest_algorithm_t hash;
+			const version_entry_st *vers;
+
+			ret = parse_imported_identity(&username,
+						      &imported_identity,
+						      &context, &version,
+						      &hash);
+			if (ret < 0) {
+				gnutls_assert();
+				goto cleanup;
+			}
+
+			vers = version_to_entry(version);
+			if (unlikely(!vers || !vers->tls13_sem)) {
+				gnutls_assert();
+				goto cleanup;
+			}
+			if (hash != MAC_TO_DIG(prf_psk->id)) {
+				gnutls_assert();
+				goto cleanup;
+			}
+
+			ret = derive_ipsk(prf_psk, &username, &user_key, ipsk);
+			if (ret < 0) {
+				gnutls_assert();
+				goto cleanup;
+			}
+
+			_gnutls_free_datum(&user_key);
+			ret = _gnutls_set_datum(&user_key, ipsk,
+						prf_psk->output_size);
+			zeroize_key(ipsk, sizeof(ipsk));
+			if (ret < 0) {
+				gnutls_assert();
+				goto cleanup;
+			}
+			imported = true;
+		}
+
 		ret = _gnutls_auth_info_init(session, GNUTLS_CRD_PSK,
 					     sizeof(psk_auth_info_st), 1);
 		if (ret < 0) {
@@ -457,7 +705,8 @@ ignore_ticket:
 
 		ret = compute_psk_binder(session, prf_res, binders_len,
 					 binders_pos, ext_offset, &rkey,
-					 &client_hello, 1, binder_value);
+					 &client_hello, BINDER_RES,
+					 binder_value);
 		if (ret < 0) {
 			gnutls_assert();
 			goto cleanup;
@@ -498,7 +747,9 @@ ignore_ticket:
 
 		ret = compute_psk_binder(session, prf_psk, binders_len,
 					 binders_pos, ext_offset, &user_key,
-					 &client_hello, 0, binder_value);
+					 &client_hello,
+					 imported ? BINDER_IMP : BINDER_EXT,
+					 binder_value);
 		if (ret < 0) {
 			gnutls_assert();
 			goto cleanup;
@@ -574,7 +825,7 @@ static int server_recv_params(gnutls_session_t session,
 	/* These values should be set properly when session ticket is accepted. */
 	uint32_t ticket_age = UINT32_MAX;
 	struct timespec ticket_creation_time = { 0, 0 };
-	bool resuming;
+	enum binder_type binder_type;
 	bool refuse_early_data = false;
 
 	ret = _gnutls13_psk_ext_parser_init(&psk_parser, data, len);
@@ -625,22 +876,69 @@ static int server_recv_params(gnutls_session_t session,
 
 			tls13_ticket_deinit(&ticket_data);
 
-			resuming = 1;
+			binder_type = BINDER_RES;
 			break;
 		} else if (pskcred && psk.ob_ticket_age == 0 &&
 			   psk.identity.size > 0 &&
 			   psk.identity.size <= MAX_USERNAME_SIZE) {
+			gnutls_psk_key_flags flags;
+			uint8_t ipsk[MAX_HASH_SIZE];
+
 			prf = pskcred->binder_algo;
 
 			/* this fails only on configuration errors; as such we always
 			 * return its error code in that case */
 			ret = _gnutls_psk_pwd_find_entry(
 				session, (char *)psk.identity.data,
-				psk.identity.size, &key);
-			if (ret < 0)
+				psk.identity.size, &key, &flags);
+			if (ret < 0) {
 				return gnutls_assert_val(ret);
+			}
+
+			if (flags & GNUTLS_PSK_KEY_EXT) {
+				gnutls_datum_t imported_identity = { NULL, 0 };
+				gnutls_datum_t context = { NULL, 0 };
+				gnutls_protocol_t version;
+				gnutls_digest_algorithm_t hash;
+				const version_entry_st *vers;
 
-			resuming = 0;
+				ret = parse_imported_identity(
+					&psk.identity, &imported_identity,
+					&context, &version, &hash);
+				if (ret < 0) {
+					gnutls_assert();
+					goto fail;
+				}
+
+				vers = version_to_entry(version);
+				if (unlikely(!vers || !vers->tls13_sem)) {
+					gnutls_assert();
+					goto fail;
+				}
+				if (hash != MAC_TO_DIG(prf->id)) {
+					gnutls_assert();
+					goto fail;
+				}
+
+				ret = derive_ipsk(prf, &psk.identity, &key,
+						  ipsk);
+				_gnutls_free_temp_key_datum(&key);
+				if (ret < 0) {
+					gnutls_assert();
+					goto fail;
+				}
+				ret = _gnutls_set_datum(&key, ipsk,
+							prf->output_size);
+				zeroize_key(ipsk, sizeof(ipsk));
+				if (ret < 0) {
+					gnutls_assert();
+					goto fail;
+				}
+
+				binder_type = BINDER_IMP;
+			} else {
+				binder_type = BINDER_EXT;
+			}
 			break;
 		}
 	}
@@ -667,7 +965,7 @@ static int server_recv_params(gnutls_session_t session,
 
 	/* Compute the binder value for this PSK */
 	ret = compute_psk_binder(session, prf, psk_parser.binders_len + 2, 0, 0,
-				 &key, &full_client_hello, resuming,
+				 &key, &full_client_hello, binder_type,
 				 binder_value);
 	if (ret < 0) {
 		gnutls_assert();
@@ -691,7 +989,7 @@ static int server_recv_params(gnutls_session_t session,
 
 	/* save the username in psk_auth_info to make it available
 	 * using gnutls_psk_server_get_username() */
-	if (!resuming) {
+	if (binder_type != BINDER_RES) {
 		assert(psk.identity.size <= MAX_USERNAME_SIZE);
 
 		ret = _gnutls_auth_info_init(session, GNUTLS_CRD_PSK,
@@ -760,10 +1058,12 @@ static int server_recv_params(gnutls_session_t session,
 	/* Reference the selected pre-shared key */
 	session->key.binders[0].psk.data = key.data;
 	session->key.binders[0].psk.size = key.size;
+	key.data = NULL;
+	key.size = 0;
 
 	session->key.binders[0].idx = psk_index;
 	session->key.binders[0].prf = prf;
-	session->key.binders[0].resumption = resuming;
+	session->key.binders[0].resumption = binder_type == BINDER_RES;
 
 	ret = _gnutls_generate_early_secrets_for_psk(session);
 	if (ret < 0) {
@@ -771,10 +1071,8 @@ static int server_recv_params(gnutls_session_t session,
 		goto fail;
 	}
 
-	return 0;
-
 fail:
-	gnutls_free(key.data);
+	_gnutls_free_datum(&key);
 	return ret;
 }
 
diff --git a/lib/ext/pre_shared_key.h b/lib/ext/pre_shared_key.h
index 496d275a7f..f6a088c614 100644
--- a/lib/ext/pre_shared_key.h
+++ b/lib/ext/pre_shared_key.h
@@ -9,17 +9,6 @@
 
 extern const hello_ext_entry_st ext_mod_pre_shared_key;
 
-inline static unsigned
-_gnutls_have_psk_credentials(const gnutls_psk_client_credentials_t cred,
-			     gnutls_session_t session)
-{
-	if ((cred->get_function || cred->username.data) &&
-	    session->internals.priorities->have_psk)
-		return 1;
-	else
-		return 0;
-}
-
 int _gnutls_generate_early_secrets_for_psk(gnutls_session_t session);
 
 #endif /* GNUTLS_LIB_EXT_PRE_SHARED_KEY_H */
diff --git a/lib/handshake-defs.h b/lib/handshake-defs.h
index 1b0c250e75..51aa5d2369 100644
--- a/lib/handshake-defs.h
+++ b/lib/handshake-defs.h
@@ -25,10 +25,12 @@
 #define EARLY_TRAFFIC_LABEL "c e traffic"
 #define EXT_BINDER_LABEL "ext binder"
 #define RES_BINDER_LABEL "res binder"
+#define IMP_BINDER_LABEL "imp binder"
 #define EARLY_EXPORTER_MASTER_LABEL "e exp master"
 #define HANDSHAKE_CLIENT_TRAFFIC_LABEL "c hs traffic"
 #define HANDSHAKE_SERVER_TRAFFIC_LABEL "s hs traffic"
 #define DERIVED_LABEL "derived"
+#define DERIVED_PSK_LABEL "derived psk"
 #define APPLICATION_CLIENT_TRAFFIC_LABEL "c ap traffic"
 #define APPLICATION_SERVER_TRAFFIC_LABEL "s ap traffic"
 #define APPLICATION_TRAFFIC_UPDATE "traffic upd"
diff --git a/lib/includes/gnutls/gnutls.h.in b/lib/includes/gnutls/gnutls.h.in
index f4c003dcde..ec132cb5c3 100644
--- a/lib/includes/gnutls/gnutls.h.in
+++ b/lib/includes/gnutls/gnutls.h.in
@@ -2533,12 +2533,14 @@ typedef struct gnutls_psk_client_credentials_st *gnutls_psk_client_credentials_t
  * gnutls_psk_key_flags:
  * @GNUTLS_PSK_KEY_RAW: PSK-key in raw format.
  * @GNUTLS_PSK_KEY_HEX: PSK-key in hex format.
+ * @GNUTLS_PSK_KEY_EXT: PSK-key is external and to be imported.
  *
  * Enumeration of different PSK key flags.
  */
 typedef enum gnutls_psk_key_flags {
 	GNUTLS_PSK_KEY_RAW = 0,
-	GNUTLS_PSK_KEY_HEX
+	GNUTLS_PSK_KEY_HEX = 1 << 0,
+	GNUTLS_PSK_KEY_EXT = 1 << 1
 } gnutls_psk_key_flags;
 
 void gnutls_psk_free_client_credentials(gnutls_psk_client_credentials_t sc);
@@ -2570,12 +2572,24 @@ typedef int gnutls_psk_server_credentials_function(gnutls_session_t,
 						   gnutls_datum_t *key);
 typedef int gnutls_psk_server_credentials_function2(
 	gnutls_session_t, const gnutls_datum_t *username, gnutls_datum_t *key);
+typedef int gnutls_psk_server_credentials_function3(
+	gnutls_session_t, const gnutls_datum_t *username, gnutls_datum_t *key,
+	gnutls_psk_key_flags *flags);
 void gnutls_psk_set_server_credentials_function(
 	gnutls_psk_server_credentials_t cred,
 	gnutls_psk_server_credentials_function *func);
 void gnutls_psk_set_server_credentials_function2(
 	gnutls_psk_server_credentials_t cred,
 	gnutls_psk_server_credentials_function2 *func);
+void gnutls_psk_set_server_credentials_function3(
+	gnutls_psk_server_credentials_t cred,
+	gnutls_psk_server_credentials_function3 *func);
+
+int gnutls_psk_format_imported_identity(const gnutls_datum_t *identity,
+					const gnutls_datum_t *context,
+					gnutls_protocol_t version,
+					gnutls_digest_algorithm_t hash,
+					gnutls_datum_t *imported_identity);
 
 typedef int gnutls_psk_client_credentials_function(gnutls_session_t,
 						   char **username,
@@ -2583,12 +2597,18 @@ typedef int gnutls_psk_client_credentials_function(gnutls_session_t,
 typedef int gnutls_psk_client_credentials_function2(gnutls_session_t,
 						    gnutls_datum_t *username,
 						    gnutls_datum_t *key);
+typedef int gnutls_psk_client_credentials_function3(
+	gnutls_session_t, gnutls_datum_t *username, gnutls_datum_t *key,
+	gnutls_psk_key_flags *flags);
 void gnutls_psk_set_client_credentials_function(
 	gnutls_psk_client_credentials_t cred,
 	gnutls_psk_client_credentials_function *func);
 void gnutls_psk_set_client_credentials_function2(
 	gnutls_psk_client_credentials_t cred,
 	gnutls_psk_client_credentials_function2 *func);
+void gnutls_psk_set_client_credentials_function3(
+	gnutls_psk_client_credentials_t cred,
+	gnutls_psk_client_credentials_function3 *func);
 
 int gnutls_hex_encode(const gnutls_datum_t *data, char *result,
 		      size_t *result_size);
diff --git a/lib/libgnutls.map b/lib/libgnutls.map
index 72e425c3a0..fae2070dfc 100644
--- a/lib/libgnutls.map
+++ b/lib/libgnutls.map
@@ -1409,6 +1409,16 @@ GNUTLS_3_7_7
 	*;
 } GNUTLS_3_7_5;
 
+GNUTLS_3_8_1
+{
+ global:
+	gnutls_psk_set_server_credentials_function3;
+	gnutls_psk_set_client_credentials_function3;
+	gnutls_psk_format_imported_identity;
+ local:
+	*;
+} GNUTLS_3_7_7;
+
 GNUTLS_FIPS140_3_4 {
   global:
 	gnutls_cipher_self_test;
diff --git a/lib/psk.c b/lib/psk.c
index ac8c7751ce..8d1db2fe7a 100644
--- a/lib/psk.c
+++ b/lib/psk.c
@@ -280,9 +280,9 @@ int gnutls_psk_set_server_credentials_hint(gnutls_psk_server_credentials_t res,
 	return 0;
 }
 
-static int call_server_callback_legacy(gnutls_session_t session,
-				       const gnutls_datum_t *username,
-				       gnutls_datum_t *key)
+static int call_server_callback1(gnutls_session_t session,
+				 const gnutls_datum_t *username,
+				 gnutls_datum_t *key)
 {
 	gnutls_psk_server_credentials_t cred =
 		(gnutls_psk_server_credentials_t)_gnutls_get_cred(
@@ -290,8 +290,29 @@ static int call_server_callback_legacy(gnutls_session_t session,
 	if (unlikely(cred == NULL))
 		return gnutls_assert_val(-1);
 
-	return cred->pwd_callback_legacy(session, (const char *)username->data,
-					 key);
+	return cred->pwd_callback1(session, (const char *)username->data, key);
+}
+
+static int call_server_callback2(gnutls_session_t session,
+				 const gnutls_datum_t *username,
+				 gnutls_datum_t *key,
+				 gnutls_psk_key_flags *flags)
+{
+	gnutls_psk_server_credentials_t cred;
+	int ret;
+
+	cred = (gnutls_psk_server_credentials_t)_gnutls_get_cred(
+		session, GNUTLS_CRD_PSK);
+	if (unlikely(cred == NULL))
+		return gnutls_assert_val(-1);
+
+	ret = cred->pwd_callback2(session, username, key);
+	if (ret >= 0) {
+		if (flags) {
+			*flags = 0;
+		}
+	}
+	return ret;
 }
 
 /**
@@ -318,8 +339,9 @@ void gnutls_psk_set_server_credentials_function(
 	gnutls_psk_server_credentials_t cred,
 	gnutls_psk_server_credentials_function *func)
 {
-	cred->pwd_callback_legacy = func;
-	cred->pwd_callback = call_server_callback_legacy;
+	cred->pwd_callback1 = func;
+	cred->pwd_callback2 = call_server_callback1;
+	cred->pwd_callback = call_server_callback2;
 }
 
 /**
@@ -349,31 +371,88 @@ void gnutls_psk_set_server_credentials_function2(
 	gnutls_psk_server_credentials_t cred,
 	gnutls_psk_server_credentials_function2 func)
 {
+	cred->pwd_callback1 = NULL;
+	cred->pwd_callback2 = func;
+	cred->pwd_callback = call_server_callback2;
+}
+
+/**
+ * gnutls_psk_set_server_credentials_function3:
+ * @cred: is a #gnutls_psk_server_credentials_t type.
+ * @func: is the callback function
+ *
+ * This function can be used to set a callback to retrieve the user's PSK credentials.
+ * The callback's function form is:
+ * int (*callback)(gnutls_session_t, const gnutls_datum_t* username,
+ *  gnutls_datum_t* key, gnutls_psk_key_flags *flags);
+ *
+ * This callback function has the same semantics as that of
+ * gnutls_psk_set_server_credentials_function2(), but it returns flags
+ * associated with the key.  The callback may import external PSK
+ * using the method described in RFC 9258 by using
+ * gnutls_psk_format_imported_identity().
+ *
+ * @username contains the actual username.
+ * The @key must be filled in using the gnutls_malloc().
+ *
+ * In case the callback returned a negative number then gnutls will
+ * assume that the username does not exist.
+ *
+ * The callback function will only be called once per handshake.  The
+ * callback function should return 0 on success, while -1 indicates
+ * an error.
+ **/
+void gnutls_psk_set_server_credentials_function3(
+	gnutls_psk_server_credentials_t cred,
+	gnutls_psk_server_credentials_function3 func)
+{
+	cred->pwd_callback1 = NULL;
+	cred->pwd_callback2 = NULL;
 	cred->pwd_callback = func;
-	cred->pwd_callback_legacy = NULL;
 }
 
-static int call_client_callback_legacy(gnutls_session_t session,
-				       gnutls_datum_t *username,
-				       gnutls_datum_t *key)
+static int call_client_callback1(gnutls_session_t session,
+				 gnutls_datum_t *username, gnutls_datum_t *key)
 {
+	gnutls_psk_client_credentials_t cred;
 	int ret;
 	char *user_p;
-	gnutls_psk_client_credentials_t cred =
-		(gnutls_psk_client_credentials_t)_gnutls_get_cred(
-			session, GNUTLS_CRD_PSK);
+
+	cred = (gnutls_psk_client_credentials_t)_gnutls_get_cred(
+		session, GNUTLS_CRD_PSK);
 	if (unlikely(cred == NULL))
 		return gnutls_assert_val(-1);
 
-	ret = cred->get_function_legacy(session, &user_p, key);
+	ret = cred->get_function1(session, &user_p, key);
+	if (ret >= 0) {
+		username->data = (uint8_t *)user_p;
+		username->size = strlen(user_p);
+	}
+
+	return ret;
+}
+
+static int call_client_callback2(gnutls_session_t session,
+				 gnutls_datum_t *username, gnutls_datum_t *key,
+				 gnutls_psk_key_flags *flags)
+{
+	gnutls_psk_client_credentials_t cred;
+	int ret;
+
+	cred = (gnutls_psk_client_credentials_t)_gnutls_get_cred(
+		session, GNUTLS_CRD_PSK);
+	if (unlikely(cred == NULL))
+		return gnutls_assert_val(-1);
 
-	if (ret)
-		goto end;
+	ret = cred->get_function2(session, username, key);
+	if (ret < 0) {
+		return ret;
+	}
 
-	username->data = (uint8_t *)user_p;
-	username->size = strlen(user_p);
+	if (flags) {
+		*flags = 0;
+	}
 
-end:
 	return ret;
 }
 
@@ -402,8 +481,9 @@ void gnutls_psk_set_client_credentials_function(
 	gnutls_psk_client_credentials_t cred,
 	gnutls_psk_client_credentials_function *func)
 {
-	cred->get_function = call_client_callback_legacy;
-	cred->get_function_legacy = func;
+	cred->get_function1 = func;
+	cred->get_function2 = call_client_callback1;
+	cred->get_function = call_client_callback2;
 }
 
 /**
@@ -434,8 +514,45 @@ void gnutls_psk_set_client_credentials_function2(
 	gnutls_psk_client_credentials_t cred,
 	gnutls_psk_client_credentials_function2 *func)
 {
+	cred->get_function1 = NULL;
+	cred->get_function2 = func;
+	cred->get_function = call_client_callback2;
+}
+
+/**
+ * gnutls_psk_set_client_credentials_function3:
+ * @cred: is a #gnutls_psk_server_credentials_t type.
+ * @func: is the callback function
+ *
+ * This function can be used to set a callback to retrieve the username and
+ * password for client PSK authentication.
+ * The callback's function form is:
+ * int (*callback)(gnutls_session_t, gnutls_datum_t* username,
+ *  gnutls_datum_t* key, gnutls_datum_t* context, gnutls_psk_key_flags *flags);
+ *
+ * This callback function has the same semantics as that of
+ * gnutls_psk_set_client_credentials_function2(), but it returns flags
+ * associated with the key.  The callback may import external PSK
+ * using the method described in RFC 9258 by using
+ * gnutls_psk_format_imported_identity().
+ *
+ * The data field of @username, @key, and @context must be allocated
+ * using gnutls_malloc().  The @username should be an ASCII string or
+ * UTF-8 string. In case of a UTF-8 string it is recommended to be
+ * following the PRECIS framework for usernames (rfc8265).
+ *
+ * The callback function will be called once per handshake.
+ *
+ * The callback function should return 0 on success.
+ * -1 indicates an error.
+ **/
+void gnutls_psk_set_client_credentials_function3(
+	gnutls_psk_client_credentials_t cred,
+	gnutls_psk_client_credentials_function3 *func)
+{
+	cred->get_function1 = NULL;
+	cred->get_function2 = NULL;
 	cred->get_function = func;
-	cred->get_function_legacy = NULL;
 }
 
 /**
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 48c694409f..86acb4c277 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -234,7 +234,8 @@ ctests += mini-record-2 simple gnutls_hmac_fast set_pkcs12_cred cert certuniquei
 	 set_x509_ocsp_multi_cli kdf-api keylog-func handshake-write \
 	 x509cert-dntypes id-on-xmppAddr tls13-compat-mode ciphersuite-name \
 	 x509-upnconstraint xts-key-check cipher-padding pkcs7-verify-double-free \
-	 fips-rsa-sizes tls12-rehandshake-ticket pathbuf tls-force-ems
+	 fips-rsa-sizes tls12-rehandshake-ticket pathbuf tls-force-ems \
+	 psk-importer
 
 ctests += tls-channel-binding
 
diff --git a/tests/psk-importer.c b/tests/psk-importer.c
new file mode 100644
index 0000000000..84c35338aa
--- /dev/null
+++ b/tests/psk-importer.c
@@ -0,0 +1,216 @@
+/*
+ * Copyright (C) 2004-2012 Free Software Foundation, Inc.
+ * Copyright (C) 2013 Adam Sampson <ats@offog.org>
+ * Copyright (C) 2019 Free Software Foundation, Inc.
+ * Copyright (C) 2023 Red Hat, Inc.
+ *
+ * Author: Simon Josefsson, Ander Juaristi, Daiki Ueno
+ *
+ * This file is part of GnuTLS.
+ *
+ * GnuTLS is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * GnuTLS is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GnuTLS.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/* This tests the external PSK importer interface (RFC 9258).  */
+/* Parts copied from pskself.c.  */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <string.h>
+#include <gnutls/gnutls.h>
+
+#include "utils.h"
+#include "eagain-common.h"
+
+const char *side = "";
+
+static void tls_log_func(int level, const char *str)
+{
+	fprintf(stderr, "%s|<%d>| %s", side, level, str);
+}
+
+#define MAX_BUF 1024
+#define MSG "Hello TLS"
+
+static const gnutls_datum_t identity = { (unsigned char *)"\xCA\xFE\xCA\xFE",
+					 4 };
+static const gnutls_datum_t context = { (unsigned char *)"\xDE\xAD\xBE\xEF",
+					4 };
+
+static const uint8_t expected_imported_identity[] = { 0x00, 0x04, 0xca, 0xfe,
+						      0xca, 0xfe, 0x00, 0x04,
+						      0xde, 0xad, 0xbe, 0xef,
+						      0x03, 0x04, 0x00, 0x01 };
+
+static int server_pskfunc(gnutls_session_t session,
+			  const gnutls_datum_t *username, gnutls_datum_t *key,
+			  gnutls_psk_key_flags *flags)
+{
+	gnutls_datum_t imported_identity = { NULL, 0 };
+
+	int ret;
+
+	if (debug)
+		printf("psk: Got username with length %d\n", username->size);
+
+	key->data = gnutls_malloc(4);
+	key->data[0] = 0xDE;
+	key->data[1] = 0xAD;
+	key->data[2] = 0xBE;
+	key->data[3] = 0xEF;
+	key->size = 4;
+
+	ret = gnutls_psk_format_imported_identity(&identity, &context,
+						  GNUTLS_TLS1_3,
+						  GNUTLS_DIG_SHA256,
+						  &imported_identity);
+	if (ret < 0) {
+		return -1;
+	}
+
+	if (imported_identity.size != sizeof(expected_imported_identity) ||
+	    memcmp(imported_identity.data, expected_imported_identity,
+		   imported_identity.size)) {
+		gnutls_free(imported_identity.data);
+		printf("Unexpected imported identity\n");
+		return -1;
+	}
+	gnutls_free(imported_identity.data);
+
+	if (flags) {
+		*flags = GNUTLS_PSK_KEY_EXT;
+	}
+
+	return 0;
+}
+
+static int client_pskfunc(gnutls_session_t session, gnutls_datum_t *username,
+			  gnutls_datum_t *key, gnutls_psk_key_flags *flags)
+{
+	int ret;
+
+	ret = gnutls_psk_format_imported_identity(&identity, &context,
+						  GNUTLS_TLS1_3,
+						  GNUTLS_DIG_SHA256, username);
+	if (ret < 0) {
+		return -1;
+	}
+
+	key->data = gnutls_malloc(4);
+	key->data[0] = 0xDE;
+	key->data[1] = 0xAD;
+	key->data[2] = 0xBE;
+	key->data[3] = 0xEF;
+	key->size = 4;
+
+	*flags = GNUTLS_PSK_KEY_EXT;
+
+	return 0;
+}
+
+static void run_test(const char *prio)
+{
+	/* Server stuff. */
+	gnutls_psk_server_credentials_t server_pskcred;
+	gnutls_session_t server;
+	int sret;
+
+	/* Client stuff. */
+	gnutls_psk_client_credentials_t client_pskcred;
+	gnutls_session_t client;
+	int cret;
+
+	char buffer[MAX_BUF + 1];
+	int transferred = 0;
+
+	gnutls_datum_t psk_username;
+
+	success("%s\n", prio);
+
+	gnutls_global_set_log_function(tls_log_func);
+	if (debug)
+		gnutls_global_set_log_level(4711);
+
+	/* Init server */
+	gnutls_psk_allocate_server_credentials(&server_pskcred);
+	gnutls_psk_set_server_credentials_function3(server_pskcred,
+						    server_pskfunc);
+	gnutls_init(&server, GNUTLS_SERVER);
+	gnutls_priority_set_direct(server, prio, NULL);
+	gnutls_credentials_set(server, GNUTLS_CRD_PSK, server_pskcred);
+	gnutls_transport_set_push_function(server, server_push);
+	gnutls_transport_set_pull_function(server, server_pull);
+	gnutls_transport_set_ptr(server, server);
+
+	/* Init client */
+	gnutls_psk_allocate_client_credentials(&client_pskcred);
+	gnutls_psk_set_client_credentials_function3(client_pskcred,
+						    client_pskfunc);
+	gnutls_init(&client, GNUTLS_CLIENT);
+	gnutls_priority_set_direct(client, prio, NULL);
+	gnutls_credentials_set(client, GNUTLS_CRD_PSK, client_pskcred);
+	gnutls_transport_set_push_function(client, client_push);
+	gnutls_transport_set_pull_function(client, client_pull);
+	gnutls_transport_set_ptr(client, client);
+
+	HANDSHAKE(client, server);
+
+	if (debug) {
+		success("server: Handshake was completed\n");
+
+		if (gnutls_psk_server_get_username(server))
+			fail("server: gnutls_psk_server_get_username() should have returned NULL\n");
+		if (gnutls_psk_server_get_username2(server, &psk_username) < 0)
+			fail("server: Could not get PSK username\n");
+
+		if (psk_username.size != sizeof(expected_imported_identity) ||
+		    memcmp(psk_username.data, expected_imported_identity,
+			   sizeof(expected_imported_identity)))
+			fail("server: Unexpected PSK username\n");
+
+		success("server: PSK username length: %d\n", psk_username.size);
+	}
+
+	TRANSFER(client, server, MSG, strlen(MSG), buffer, MAX_BUF);
+	TRANSFER(server, client, MSG, strlen(MSG), buffer, MAX_BUF);
+
+	gnutls_bye(server, GNUTLS_SHUT_WR);
+	gnutls_bye(client, GNUTLS_SHUT_WR);
+
+	gnutls_deinit(server);
+	gnutls_deinit(client);
+
+	gnutls_psk_free_server_credentials(server_pskcred);
+	gnutls_psk_free_client_credentials(client_pskcred);
+
+	reset_buffers();
+}
+
+void doit(void)
+{
+	global_init();
+	run_test("NORMAL:-VERS-ALL:+VERS-TLS1.3:+PSK");
+	run_test(
+		"NORMAL:-VERS-ALL:+VERS-TLS1.3:-GROUP-ALL:+GROUP-FFDHE2048:+DHE-PSK");
+	run_test(
+		"NORMAL:-VERS-ALL:+VERS-TLS1.3:-GROUP-ALL:+GROUP-SECP256R1:+ECDHE-PSK");
+
+	gnutls_global_deinit();
+}