Adding upstream version 1:2.3.19.1+dfsg1.upstream/1%2.3.19.1+dfsg1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1242 insertions, 0 deletions

diff --git a/src/plugins/mail-crypt/mail-crypt-key.c b/src/plugins/mail-crypt/mail-crypt-key.c
new file mode 100644
index 0000000..22c86e3
--- /dev/null
+++ b/src/plugins/mail-crypt/mail-crypt-key.c
@@ -0,0 +1,1242 @@
+/* Copyright (c) 2015-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "str.h"
+#include "dict.h"
+#include "array.h"
+#include "var-expand.h"
+#include "mail-storage.h"
+#include "mailbox-attribute.h"
+#include "mail-crypt-common.h"
+#include "mail-crypt-key.h"
+#include "mail-crypt-plugin.h"
+#include "mail-user.h"
+#include "hex-binary.h"
+#include "safe-memset.h"
+#include "base64.h"
+#include "sha2.h"
+
+struct mail_crypt_key_cache_entry {
+	struct mail_crypt_key_cache_entry *next;
+
+	char *pubid;
+	/* this is lazily initialized */
+	struct dcrypt_keypair pair;
+};
+
+static
+int mail_crypt_get_key_cache(struct mail_crypt_key_cache_entry *cache,
+			     const char *pubid,
+			     struct dcrypt_private_key **privkey_r,
+			     struct dcrypt_public_key **pubkey_r)
+{
+	for(struct mail_crypt_key_cache_entry *ent = cache;
+	    ent != NULL; ent = ent->next)
+	{
+		if (strcmp(pubid, ent->pubid) == 0) {
+			if (privkey_r != NULL && ent->pair.priv != NULL) {
+				dcrypt_key_ref_private(ent->pair.priv);
+				*privkey_r = ent->pair.priv;
+				return 1;
+			} else if (pubkey_r != NULL && ent->pair.pub != NULL) {
+				dcrypt_key_ref_public(ent->pair.pub);
+				*pubkey_r = ent->pair.pub;
+				return 1;
+			} else if ((privkey_r == NULL && pubkey_r == NULL) ||
+				   (ent->pair.priv == NULL &&
+				   ent->pair.pub == NULL)) {
+				i_unreached();
+			}
+		}
+	}
+	return 0;
+}
+
+static
+void mail_crypt_put_key_cache(struct mail_crypt_key_cache_entry **cache,
+			      const char *pubid,
+			      struct dcrypt_private_key *privkey,
+			      struct dcrypt_public_key *pubkey)
+{
+	for(struct mail_crypt_key_cache_entry *ent = *cache;
+	    ent != NULL; ent = ent->next)
+	{
+		if (strcmp(pubid, ent->pubid) == 0) {
+			if (privkey != NULL) {
+				if (ent->pair.priv == NULL) {
+					ent->pair.priv = privkey;
+					dcrypt_key_ref_private(ent->pair.priv);
+				}
+			} else if (pubkey != NULL) {
+				if (ent->pair.pub == NULL) {
+					ent->pair.pub = pubkey;
+					dcrypt_key_ref_public(ent->pair.pub);
+				}
+			} else
+				i_unreached();
+			return;
+		}
+	}
+
+	/* not found */
+	struct mail_crypt_key_cache_entry *ent =
+		i_new(struct mail_crypt_key_cache_entry, 1);
+	ent->pubid = i_strdup(pubid);
+	ent->pair.priv = privkey;
+	ent->pair.pub = pubkey;
+	if (ent->pair.priv != NULL)
+		dcrypt_key_ref_private(ent->pair.priv);
+	if (ent->pair.pub != NULL)
+		dcrypt_key_ref_public(ent->pair.pub);
+
+	if (*cache == NULL) {
+		*cache = ent;
+	} else {
+		ent->next = *cache;
+		*cache = ent;
+	}
+}
+
+void mail_crypt_key_cache_destroy(struct mail_crypt_key_cache_entry **cache)
+{
+	struct mail_crypt_key_cache_entry *next, *cur = *cache;
+
+	*cache = NULL;
+
+	while(cur != NULL) {
+		next = cur->next;
+		i_free(cur->pubid);
+		if (cur->pair.priv != NULL)
+			dcrypt_key_unref_private(&cur->pair.priv);
+		if (cur->pair.pub != NULL)
+			dcrypt_key_unref_public(&cur->pair.pub);
+		i_free(cur);
+		cur = next;
+	}
+}
+
+int mail_crypt_private_key_id_match(struct dcrypt_private_key *key,
+				     const char *pubid, const char **error_r)
+{
+	i_assert(key != NULL);
+	buffer_t *key_id = t_str_new(MAIL_CRYPT_HASH_BUF_SIZE);
+	if (!dcrypt_key_id_private(key, MAIL_CRYPT_KEY_ID_ALGORITHM, key_id,
+				   error_r))
+		return -1;
+	const char *hash = binary_to_hex(key_id->data, key_id->used);
+	if (strcmp(pubid, hash) == 0) return 1;
+
+	buffer_set_used_size(key_id, 0);
+	if (!dcrypt_key_id_private_old(key, key_id, error_r)) {
+		return -1;
+	}
+	hash = binary_to_hex(key_id->data, key_id->used);
+
+	if (strcmp(pubid, hash) != 0) {
+		*error_r = t_strdup_printf("Key %s does not match given ID %s",
+					   hash, pubid);
+		return 0;
+	}
+	return 1;		
+}
+
+int mail_crypt_public_key_id_match(struct dcrypt_public_key *key,
+				   const char *pubid, const char **error_r)
+{
+	i_assert(key != NULL);
+	buffer_t *key_id = t_str_new(MAIL_CRYPT_HASH_BUF_SIZE);
+	if (!dcrypt_key_id_public(key, MAIL_CRYPT_KEY_ID_ALGORITHM, key_id,
+				  error_r))
+		return -1;
+	const char *hash = binary_to_hex(key_id->data, key_id->used);
+	if (strcmp(pubid, hash) == 0) return 1;
+
+	buffer_set_used_size(key_id, 0);
+	if (!dcrypt_key_id_public_old(key, key_id, error_r)) {
+		return -1;
+	}
+	hash = binary_to_hex(key_id->data, key_id->used);
+
+	if (strcmp(pubid, hash) != 0) {
+		*error_r = t_strdup_printf("Key %s does not match given ID %s",
+					   hash, pubid);
+		return 0;
+	}
+	return 1;
+}
+
+static
+int mail_crypt_env_get_private_key(struct mail_user *user, const char *pubid,
+				   struct dcrypt_private_key **key_r,
+				   const char **error_r)
+{
+	struct mail_crypt_global_keys global_keys;
+	int ret = 0;
+	if (mail_crypt_global_keys_load(user, "mail_crypt", &global_keys,
+					TRUE, error_r) < 0) {
+		mail_crypt_global_keys_free(&global_keys);
+		return -1;
+	}
+
+	/* see if we got a key */
+	struct dcrypt_private_key *key =
+		mail_crypt_global_key_find(&global_keys, pubid);
+
+	if (key != NULL) {
+		dcrypt_key_ref_private(key);
+		*key_r = key;
+		ret = 1;
+	}
+
+	mail_crypt_global_keys_free(&global_keys);
+
+	return ret;
+}
+
+static
+const char *mail_crypt_get_key_path(bool user_key, bool public, const char *pubid)
+{
+	const char *ret = t_strdup_printf("%s%s%s",
+				user_key ? USER_CRYPT_PREFIX :
+					  BOX_CRYPT_PREFIX,
+				public ? PUBKEYS_PREFIX :
+					  PRIVKEYS_PREFIX,
+				pubid);
+	return ret;
+}
+
+static
+int mail_crypt_decrypt_private_key(struct mailbox *box, const char *pubid,
+				   const char *data,
+				   struct dcrypt_private_key **key_r,
+				   const char **error_r)
+{
+	enum dcrypt_key_kind key_kind;
+	enum dcrypt_key_encryption_type enc_type;
+	const char *enc_hash = NULL, *key_hash = NULL, *pw = NULL;
+	struct dcrypt_private_key *key = NULL, *dec_key = NULL;
+	struct mail_user *user = mail_storage_get_user(mailbox_get_storage(box));
+	int ret = 0;
+
+	i_assert(pubid != NULL);
+	i_assert(data != NULL);
+
+	/* see what the key needs for decrypting */
+	if (!dcrypt_key_string_get_info(data, NULL, NULL, &key_kind,
+					&enc_type, &enc_hash, &key_hash, error_r)) {
+		return -1;
+	}
+
+	if (key_kind != DCRYPT_KEY_KIND_PRIVATE) {
+		*error_r = t_strdup_printf("Cannot use key %s: "
+					   "Expected private key, got public key",
+					   pubid);
+		return -1;
+	}
+
+	if (key_hash != NULL && strcmp(key_hash, pubid) != 0) {
+		*error_r = t_strdup_printf("Cannot use key %s: "
+					   "Incorrect key hash %s stored",
+					   pubid,
+					   key_hash);
+		return -1;
+	}
+
+	/* see if it needs decrypting */
+	if (enc_type == DCRYPT_KEY_ENCRYPTION_TYPE_NONE) {
+		/* no key or password */
+	} else if (enc_type == DCRYPT_KEY_ENCRYPTION_TYPE_PASSWORD) {
+		pw = mail_user_plugin_getenv(user, MAIL_CRYPT_USERENV_PASSWORD);
+		if (pw == NULL) {
+			*error_r = t_strdup_printf("Cannot decrypt key %s: "
+						   "Password not available",
+						   pubid);
+			return -1;
+		}
+	} else if (enc_type == DCRYPT_KEY_ENCRYPTION_TYPE_KEY) {
+		if ((ret = mail_crypt_user_get_private_key(user, enc_hash,
+							   &dec_key, error_r)) <= 0) {
+			/* last resort, look at environment */
+			if (ret == 0 && (ret = mail_crypt_env_get_private_key(user, enc_hash,
+								  &dec_key, error_r)) == 0) {
+				*error_r = t_strdup_printf("Cannot decrypt key %s: "
+							   "Private key %s not available:",
+							   pubid, enc_hash);
+				return -1;
+			} else if (ret < 0) {
+				*error_r =  t_strdup_printf("Cannot decrypt key %s: %s",
+							    pubid, *error_r);
+				return ret;
+			}
+		}
+	}
+
+	bool res = dcrypt_key_load_private(&key, data, pw, dec_key, error_r);
+
+	if (dec_key != NULL)
+		dcrypt_key_unref_private(&dec_key);
+
+	if (!res)
+		return -1;
+
+	if (mail_crypt_private_key_id_match(key, pubid, error_r) <= 0) {
+		if (key != NULL)
+			dcrypt_key_unref_private(&key);
+		return -1;
+	}
+
+	i_assert(key != NULL);
+
+	*key_r = key;
+
+	return 1;
+}
+
+int mail_crypt_get_private_key(struct mailbox *box, const char *pubid,
+				bool user_key, bool shared,
+				struct dcrypt_private_key **key_r,
+				const char **error_r)
+{
+	struct mail_user *user = mail_storage_get_user(mailbox_get_storage(box));
+	struct mail_crypt_user *muser = mail_crypt_get_mail_crypt_user(user);
+
+	/* check cache */
+	if (mail_crypt_get_key_cache(muser->key_cache, pubid, key_r, NULL) > 0) {
+		return 1;
+	}
+
+	struct mail_attribute_value value;
+	struct dcrypt_private_key *key;
+	int ret;
+	const char *attr_name = mail_crypt_get_key_path(user_key, FALSE, pubid);
+
+	if ((ret = mailbox_attribute_get(box,
+					 shared ? MAIL_ATTRIBUTE_TYPE_SHARED :
+						  MAIL_ATTRIBUTE_TYPE_PRIVATE,
+					 attr_name, &value)) <= 0) {
+		if (ret < 0) {
+			*error_r = t_strdup_printf("mailbox_attribute_get(%s, %s%s) failed: %s",
+						   mailbox_get_vname(box),
+						   shared ? "/shared/" :
+							    "/priv/",
+						   attr_name,
+						   mailbox_get_last_internal_error(box, NULL));
+		}
+		return ret;
+	}
+
+	if ((ret = mail_crypt_decrypt_private_key(box, pubid, value.value,
+						  &key, error_r)) <= 0)
+		return ret;
+
+	i_assert(key != NULL);
+
+	mail_crypt_put_key_cache(&muser->key_cache, pubid, key, NULL);
+
+	*key_r = key;
+
+	return 1;
+}
+
+int mail_crypt_user_get_private_key(struct mail_user *user, const char *pubid,
+				    struct dcrypt_private_key **key_r,
+				    const char **error_r)
+{
+	struct mail_namespace *ns = mail_namespace_find_inbox(user->namespaces);
+	struct mailbox *box = mailbox_alloc(ns->list, "INBOX",
+					    MAILBOX_FLAG_READONLY);
+	struct mail_attribute_value value;
+	int ret;
+
+	/* try retrieve currently active user key */
+	if (mailbox_open(box) < 0) {
+		*error_r = t_strdup_printf("mailbox_open(%s) failed: %s",
+					   "INBOX",
+					   mailbox_get_last_internal_error(box, NULL));
+		return -1;
+	}
+
+	if (pubid == NULL) {
+		if ((ret = mailbox_attribute_get(box, MAIL_ATTRIBUTE_TYPE_SHARED,
+						 USER_CRYPT_PREFIX ACTIVE_KEY_NAME,
+						 &value)) <= 0) {
+			if (ret < 0) {
+				*error_r = t_strdup_printf("mailbox_attribute_get(%s, /shared/%s) failed: %s",
+							   mailbox_get_vname(box),
+							   USER_CRYPT_PREFIX ACTIVE_KEY_NAME,
+							   mailbox_get_last_internal_error(box, NULL));
+			}
+		} else {
+			pubid = value.value;
+			ret = 1;
+		}
+	} else
+		ret = 1;
+
+	/* try to open key */
+	if (ret > 0)
+		ret = mail_crypt_get_private_key(box, pubid, TRUE, FALSE,
+						 key_r, error_r);
+	mailbox_free(&box);
+	return ret;
+}
+
+int mail_crypt_box_get_private_key(struct mailbox *box,
+				   struct dcrypt_private_key **key_r,
+				   const char **error_r)
+{
+	struct mail_attribute_value value;
+	int ret;
+	/* get active key */
+	if ((ret = mailbox_attribute_get(box, MAIL_ATTRIBUTE_TYPE_SHARED,
+					 BOX_CRYPT_PREFIX ACTIVE_KEY_NAME, &value)) <= 0) {
+		if (ret < 0) {
+			*error_r = t_strdup_printf("mailbox_attribute_get(%s, /shared/%s) failed: %s",
+						   mailbox_get_vname(box),
+						   USER_CRYPT_PREFIX ACTIVE_KEY_NAME,
+						   mailbox_get_last_internal_error(box, NULL));
+		}
+		return ret;
+	}
+
+	return mail_crypt_get_private_key(box, value.value,
+					  FALSE, FALSE,
+					  key_r, error_r);
+}
+
+static
+int mail_crypt_set_private_key(struct mailbox_transaction_context *t,
+				bool user_key, bool shared, const char *pubid,
+				struct dcrypt_public_key *enc_key,
+				struct dcrypt_private_key *key,
+				const char **error_r)
+{
+	/* folder keys must be encrypted with some other key,
+	   unless they are shared keys */
+	i_assert(user_key || shared || enc_key != NULL);
+
+	buffer_t *data = t_str_new(MAIL_CRYPT_KEY_BUF_SIZE);
+	const char *pw = NULL;
+	const char *algo = NULL;
+	struct mail_user *user = mail_storage_get_user(
+					mailbox_get_storage(
+						mailbox_transaction_get_mailbox(t)));
+	const char *attr_name = mail_crypt_get_key_path(user_key, FALSE, pubid);
+	struct mail_attribute_value value;
+	int ret;
+
+	if (enc_key != NULL) {
+		algo = MAIL_CRYPT_KEY_CIPHER;
+	} else if (user_key &&
+		   (pw = mail_user_plugin_getenv(user,MAIL_CRYPT_USERENV_PASSWORD))
+			!= NULL) {
+		algo = MAIL_CRYPT_PW_CIPHER;
+	}
+
+	/* export key */
+	if (!dcrypt_key_store_private(key, DCRYPT_FORMAT_DOVECOT, algo, data,
+				      pw, enc_key, error_r)) {
+		return -1;
+	}
+
+	/* store it */
+	value.value_stream = NULL;
+	value.value = str_c(data);
+	value.last_change = 0;
+
+	if ((ret = mailbox_attribute_set(t,
+					 shared ? MAIL_ATTRIBUTE_TYPE_SHARED :
+						  MAIL_ATTRIBUTE_TYPE_PRIVATE,
+					 attr_name,
+					 &value)) < 0) {
+		*error_r = t_strdup_printf("mailbox_attribute_set(%s, %s/%s) failed: %s",
+			   mailbox_get_vname(mailbox_transaction_get_mailbox(t)),
+			   shared ? "/shared" : "/priv",
+			   attr_name,
+			   mailbox_get_last_internal_error(
+				mailbox_transaction_get_mailbox(t), NULL));
+	}
+
+	safe_memset(buffer_get_modifiable_data(data, NULL), 0, data->used);
+
+	return ret;
+}
+
+int mail_crypt_user_set_private_key(struct mail_user *user, const char *pubid,
+				    struct dcrypt_private_key *key,
+				    const char **error_r)
+{
+	struct mail_namespace *ns = mail_namespace_find_inbox(user->namespaces);
+	struct mailbox *box = mailbox_alloc(ns->list, "INBOX",
+					    MAILBOX_FLAG_READONLY);
+	struct dcrypt_private_key *env_key = NULL;
+	struct dcrypt_public_key *enc_key = NULL;
+	struct mailbox_transaction_context *t;
+	int ret;
+
+	if ((ret = mail_crypt_env_get_private_key(user, NULL, &env_key,
+						  error_r)) < 0) {
+		return -1;
+	} else if (ret > 0) {
+		dcrypt_key_convert_private_to_public(env_key, &enc_key);
+		dcrypt_key_unref_private(&env_key);
+	}
+
+	if (mail_user_plugin_getenv(user, MAIL_CRYPT_REQUIRE_ENCRYPTED_USER_KEY) != NULL &&
+	    mail_user_plugin_getenv(user, MAIL_CRYPT_USERENV_PASSWORD) == NULL &&
+	    mail_user_plugin_getenv(user, MAIL_CRYPT_USERENV_KEY) == NULL)
+	{
+		*error_r = MAIL_CRYPT_REQUIRE_ENCRYPTED_USER_KEY " set, cannot "
+			   "generate user keypair without password or key";
+		return -1;
+	}
+
+	if (mailbox_open(box) < 0) {
+		*error_r = t_strdup_printf("mailbox_open(%s) failed: %s",
+					   "INBOX",
+					   mailbox_get_last_internal_error(box, NULL));
+		return -1;
+	}
+
+	t = mailbox_transaction_begin(box, 0, __func__);
+
+	if ((ret = mail_crypt_set_private_key(t, TRUE, FALSE, pubid, enc_key, key,
+					      error_r)) < 0) {
+		mailbox_transaction_rollback(&t);
+	} else if ((ret = mailbox_transaction_commit(&t)) < 0) {
+		*error_r = t_strdup_printf("mailbox_transaction_commit(%s) failed: %s",
+					  mailbox_get_vname(box),
+					  mailbox_get_last_internal_error(box, NULL));
+	}
+
+	mailbox_free(&box);
+
+	return ret;
+}
+
+int mail_crypt_box_set_private_key(struct mailbox *box, const char *pubid,
+				   struct dcrypt_private_key *key,
+				   struct dcrypt_public_key *user_key,
+				   const char **error_r)
+{
+	int ret;
+	struct mailbox_transaction_context *t;
+
+	t = mailbox_transaction_begin(box, 0, __func__);
+	if ((ret = mail_crypt_set_private_key(t, FALSE, FALSE, pubid, user_key,
+					      key, error_r)) < 0) {
+		mailbox_transaction_rollback(&t);
+	} else if ((ret = mailbox_transaction_commit(&t)) < 0) {
+		*error_r = t_strdup_printf("mailbox_transaction_commit(%s) failed: %s",
+					  mailbox_get_vname(box),
+					  mailbox_get_last_internal_error(box, NULL));
+	}
+
+	return ret;
+}
+
+static
+int mail_crypt_get_public_key(struct mailbox *box, const char *pubid,
+			      bool user_key, struct dcrypt_public_key **key_r,
+			      const char **error_r)
+{
+	struct mail_user *user = mail_storage_get_user(mailbox_get_storage(box));
+	struct mail_crypt_user *muser = mail_crypt_get_mail_crypt_user(user);
+
+	/* check cache */
+	if (mail_crypt_get_key_cache(muser->key_cache, pubid, NULL, key_r) > 0) {
+		return 1;
+	}
+
+	enum dcrypt_key_kind key_kind;
+	const char *key_hash = NULL;
+	struct dcrypt_public_key *key;
+	struct mail_attribute_value value;
+	int ret;
+	const char *attr_name = mail_crypt_get_key_path(user_key, TRUE, pubid);
+
+	if ((ret = mailbox_attribute_get(box,
+					 MAIL_ATTRIBUTE_TYPE_SHARED,
+					 attr_name, &value)) <= 0) {
+		if (ret < 0) {
+			*error_r = t_strdup_printf("mailbox_attribute_get(%s, %s) failed: %s",
+						   mailbox_get_vname(box),
+						   attr_name,
+						   mailbox_get_last_internal_error(box, NULL));
+		}
+		return ret;
+	}
+
+	if (!dcrypt_key_string_get_info(value.value, NULL, NULL, &key_kind,
+					NULL, NULL, &key_hash, error_r)) {
+		return -1;
+	}
+
+	if (key_kind != DCRYPT_KEY_KIND_PUBLIC) {
+		*error_r = t_strdup_printf("Cannot use key %s: "
+					   "Expected public key, got private key",
+					   pubid);
+		return -1;
+	}
+
+	if (key_hash != NULL && strcmp(key_hash, pubid) != 0) {
+		*error_r = t_strdup_printf("Cannot use key %s: "
+					   "Incorrect key hash %s stored",
+					   pubid, key_hash);
+		return -1;
+	}
+
+	/* load the key */
+	if (!dcrypt_key_load_public(&key, value.value, error_r)) {
+		return -1;
+	}
+
+	if (pubid != NULL &&
+	    mail_crypt_public_key_id_match(key, pubid, error_r) <= 0) {
+		dcrypt_key_unref_public(&key);
+		return -1;
+	}
+
+	mail_crypt_put_key_cache(&muser->key_cache, pubid, NULL, key);
+
+	*key_r = key;
+
+	return 1;
+}
+
+int mail_crypt_user_get_public_key(struct mail_user *user,
+				   struct dcrypt_public_key **key_r,
+				   const char **error_r)
+{
+	struct mail_namespace *ns = mail_namespace_find_inbox(user->namespaces);
+	struct mailbox *box = mailbox_alloc(ns->list, "INBOX",
+					    MAILBOX_FLAG_READONLY);
+	struct mail_attribute_value value;
+	int ret;
+
+	/* try retrieve currently active user key */
+	if (mailbox_open(box) < 0) {
+		*error_r = t_strdup_printf("mailbox_open(%s) failed: %s",
+					   "INBOX",
+					   mailbox_get_last_internal_error(box, NULL));
+		return -1;
+	}
+
+	if ((ret = mailbox_attribute_get(box, MAIL_ATTRIBUTE_TYPE_SHARED,
+					 USER_CRYPT_PREFIX ACTIVE_KEY_NAME,
+					 &value)) <= 0) {
+		if (ret < 0) {
+			*error_r = t_strdup_printf("mailbox_attribute_get(%s, /shared/%s) failed: %s",
+						   mailbox_get_vname(box),
+						   USER_CRYPT_PREFIX ACTIVE_KEY_NAME,
+						   mailbox_get_last_internal_error(box, NULL));
+		}
+	} else {
+		ret = mail_crypt_get_public_key(box, value.value, TRUE, key_r, error_r);
+	}
+
+	mailbox_free(&box);
+	return ret;
+}
+
+int mail_crypt_box_get_public_key(struct mailbox *box,
+				  struct dcrypt_public_key **key_r,
+				  const char **error_r)
+{
+	struct mail_attribute_value value;
+	int ret;
+
+	if ((ret = mailbox_attribute_get(box, MAIL_ATTRIBUTE_TYPE_SHARED,
+					 BOX_CRYPT_PREFIX ACTIVE_KEY_NAME,
+					 &value)) <= 0) {
+		if (ret < 0) {
+			*error_r = t_strdup_printf("mailbox_attribute_get(%s, /shared/%s) failed: %s",
+						   mailbox_get_vname(box),
+						   BOX_CRYPT_PREFIX ACTIVE_KEY_NAME,
+						   mailbox_get_last_internal_error(box, NULL));
+		}
+		return ret;
+	}
+	return mail_crypt_get_public_key(box, value.value, FALSE, key_r, error_r);
+}
+
+static
+int mail_crypt_set_public_key(struct mailbox_transaction_context *t,
+			      bool user_key, const char *pubid,
+			      struct dcrypt_public_key *key,
+			      const char **error_r)
+{
+	buffer_t *data = t_str_new(MAIL_CRYPT_KEY_BUF_SIZE);
+	const char *attr_name = mail_crypt_get_key_path(user_key, TRUE, pubid);
+	struct mail_attribute_value value;
+
+	/* export key */
+	if (!dcrypt_key_store_public(key, DCRYPT_FORMAT_DOVECOT, data,
+				     error_r)) {
+		return -1;
+	}
+
+	/* store it */
+	value.value_stream = NULL;
+	value.value = str_c(data);
+	value.last_change = 0;
+
+	if (mailbox_attribute_set(t,
+				  MAIL_ATTRIBUTE_TYPE_SHARED,
+				  attr_name,
+				  &value) < 0) {
+		*error_r = t_strdup_printf("mailbox_attribute_set(%s, %s/%s) failed: %s",
+			   mailbox_get_vname(mailbox_transaction_get_mailbox(t)),
+			   "/shared",
+			   attr_name,
+			   mailbox_get_last_internal_error(
+				mailbox_transaction_get_mailbox(t), NULL));
+		return -1;
+	}
+
+	return 0;
+}
+
+int mail_crypt_user_set_public_key(struct mail_user *user, const char *pubid,
+				  struct dcrypt_public_key *key,
+				  const char **error_r)
+{
+	struct mail_namespace *ns = mail_namespace_find_inbox(user->namespaces);
+	struct mailbox *box = mailbox_alloc(ns->list, "INBOX",
+					    MAILBOX_FLAG_READONLY);
+	struct mailbox_transaction_context *t;
+	struct mail_attribute_value value;
+	int ret;
+
+	/* try retrieve currently active user key */
+	if (mailbox_open(box) < 0) {
+		*error_r = t_strdup_printf("mailbox_open(%s) failed: %s",
+					   "INBOX",
+					   mailbox_get_last_internal_error(box, NULL));
+		return -1;
+	}
+
+	t = mailbox_transaction_begin(box, 0, __func__);
+
+	if ((ret = mail_crypt_set_public_key(t, TRUE, pubid, key,
+					     error_r)) == 0) {
+		value.value_stream = NULL;
+		value.value = pubid;
+		value.last_change = 0;
+
+		if ((ret = mailbox_attribute_set(t, MAIL_ATTRIBUTE_TYPE_SHARED,
+						 USER_CRYPT_PREFIX ACTIVE_KEY_NAME,
+						 &value)) < 0) {
+			*error_r = t_strdup_printf("mailbox_attribute_set(%s, /shared/%s) failed: %s",
+						   mailbox_get_vname(box),
+						   USER_CRYPT_PREFIX ACTIVE_KEY_NAME,
+						   mailbox_get_last_internal_error(box, NULL));
+		}
+	}
+
+	if (ret < 0) {
+		mailbox_transaction_rollback(&t);
+	} else if (mailbox_transaction_commit(&t) < 0) {
+		*error_r = t_strdup_printf("mailbox_transaction_commit(%s) failed: %s",
+					  mailbox_get_vname(box),
+					  mailbox_get_last_internal_error(box, NULL));
+		ret = -1;
+	}
+
+	mailbox_free(&box);
+
+	return ret;
+}
+
+int mail_crypt_box_set_public_key(struct mailbox *box, const char *pubid,
+				  struct dcrypt_public_key *key,
+				  const char **error_r)
+{
+	int ret;
+	struct mailbox_transaction_context *t;
+	struct mail_attribute_value value;
+
+	t = mailbox_transaction_begin(box, 0, __func__);
+	if ((ret = mail_crypt_set_public_key(t, FALSE, pubid, key,
+					     error_r)) == 0) {
+		value.value_stream = NULL;
+		value.value = pubid;
+		value.last_change = 0;
+
+		if ((ret = mailbox_attribute_set(t, MAIL_ATTRIBUTE_TYPE_SHARED,
+						 BOX_CRYPT_PREFIX ACTIVE_KEY_NAME,
+						 &value)) < 0) {
+			*error_r = t_strdup_printf("mailbox_attribute_set(%s, /shared/%s) failed: %s",
+						   mailbox_get_vname(box),
+						   BOX_CRYPT_PREFIX ACTIVE_KEY_NAME,
+						   mailbox_get_last_internal_error(box, NULL));
+		}
+	}
+
+	if (ret < 0) {
+		mailbox_transaction_rollback(&t);
+	} else if (mailbox_transaction_commit(&t) < 0) {
+		*error_r = t_strdup_printf("mailbox_transaction_commit(%s) failed: %s",
+					  mailbox_get_vname(box),
+					  mailbox_get_last_internal_error(box, NULL));
+		ret = -1;
+	}
+
+	return ret;
+
+}
+
+static
+int mail_crypt_user_set_keys(struct mail_user *user,
+			     const char *pubid,
+			     struct dcrypt_private_key *privkey,
+			     struct dcrypt_public_key *pubkey,
+			     const char **error_r)
+{
+	if (mail_crypt_user_set_private_key(user, pubid, privkey, error_r) < 0)
+		return -1;
+	if (mail_crypt_user_set_public_key(user, pubid, pubkey, error_r) < 0)
+		return -1;
+	return 0;
+}
+
+static
+int mail_crypt_box_set_keys(struct mailbox *box,
+			    const char *pubid,
+			    struct dcrypt_private_key *privkey,
+			    struct dcrypt_public_key *user_key,
+			    struct dcrypt_public_key *pubkey,
+			    const char **error_r)
+{
+	if (mail_crypt_box_set_private_key(box, pubid, privkey, user_key,
+					   error_r) < 0)
+		return -1;
+	if (mail_crypt_box_set_public_key(box, pubid, pubkey, error_r) < 0)
+		return -1;
+	return 0;
+}
+
+int mail_crypt_box_get_shared_key(struct mailbox *box,
+				  const char *pubid,
+				  struct dcrypt_private_key **key_r,
+				  const char **error_r)
+{
+	struct mail_user *user = mail_storage_get_user(mailbox_get_storage(box));
+	struct mail_crypt_user *muser = mail_crypt_get_mail_crypt_user(user);
+
+	struct dcrypt_private_key *key = NULL;
+	struct mail_attribute_value value;
+	int ret;
+
+	/* check cache */
+	if (mail_crypt_get_key_cache(muser->key_cache, pubid, key_r, NULL) > 0) {
+		return 1;
+	}
+
+	const char *hexname =
+		binary_to_hex((const unsigned char*)user->username,
+			      strlen(user->username));
+
+	const char *attr_name = t_strdup_printf(BOX_CRYPT_PREFIX
+						PRIVKEYS_PREFIX"%s/%s",
+						hexname,
+						pubid);
+
+	if ((ret = mailbox_attribute_get(box,
+					MAIL_ATTRIBUTE_TYPE_SHARED,
+					attr_name, &value)) <= 0) {
+		if (ret < 0) {
+			*error_r = t_strdup_printf("mailbox_attribute_get(%s, %s) failed: %s",
+						mailbox_get_vname(box),
+						attr_name,
+						mailbox_get_last_internal_error(box, NULL));
+			return ret;
+		}
+		return mail_crypt_get_private_key(box, pubid, FALSE, TRUE, key_r,
+						  error_r);
+	} else {
+		if ((ret = mail_crypt_decrypt_private_key(box, pubid, value.value,
+							  &key, error_r)) <= 0)
+			return ret;
+	}
+
+	mail_crypt_put_key_cache(&muser->key_cache, pubid, key, NULL);
+
+	*key_r = key;
+
+	return 1;
+}
+
+int mail_crypt_box_set_shared_key(struct mailbox_transaction_context *t,
+				  const char *pubid,
+				  struct dcrypt_private_key *privkey,
+				  const char *target_uid,
+				  struct dcrypt_public_key *user_key,
+				  const char **error_r)
+{
+	struct mail_attribute_value value;
+	buffer_t *data = t_str_new(MAIL_CRYPT_KEY_BUF_SIZE);
+	int ret;
+	const char *attr_name;
+	const char *algo = NULL;
+
+	i_assert(target_uid == NULL || user_key != NULL);
+
+	if (target_uid != NULL) {
+		/* hash target UID */
+		algo = MAIL_CRYPT_KEY_CIPHER;
+		const char *hexname =
+			binary_to_hex((const unsigned char*)target_uid,
+				      strlen(target_uid));
+		attr_name = t_strdup_printf(BOX_CRYPT_PREFIX
+					    PRIVKEYS_PREFIX"%s/%s",
+					    hexname,
+					    pubid);
+	} else {
+		attr_name = t_strdup_printf(BOX_CRYPT_PREFIX
+					    PRIVKEYS_PREFIX"%s",
+					    pubid);
+	}
+
+	if (!dcrypt_key_store_private(privkey, DCRYPT_FORMAT_DOVECOT,
+				      algo, data,
+				      NULL, user_key, error_r)) {
+		return -1;
+	}
+	
+	value.value_stream = NULL;
+	value.value = str_c(data);
+	value.last_change = 0;
+
+	if ((ret = mailbox_attribute_set(t, MAIL_ATTRIBUTE_TYPE_SHARED,
+					 attr_name, &value)) < 0) {
+		*error_r = t_strdup_printf("mailbox_attribute_set(%s, /shared/%s) failed: %s",
+					   mailbox_get_vname(
+						mailbox_transaction_get_mailbox(t)),
+					   attr_name,
+					   mailbox_get_last_internal_error(
+						mailbox_transaction_get_mailbox(t),
+						NULL));
+	}
+
+	safe_memset(buffer_get_modifiable_data(data, NULL), 0, data->used);
+
+	return ret;
+}
+
+int mail_crypt_box_unset_shared_key(struct mailbox_transaction_context *t,
+				    const char *pubid,
+				    const char *target_uid,
+				    const char **error_r)
+{
+	int ret;
+
+	const char *hexname =
+		binary_to_hex((const unsigned char*)target_uid,
+			      strlen(target_uid));
+
+	const char *attr_name = t_strdup_printf(BOX_CRYPT_PREFIX
+						PRIVKEYS_PREFIX"%s/%s",
+						hexname,
+						pubid);
+
+	if ((ret = mailbox_attribute_unset(t, MAIL_ATTRIBUTE_TYPE_SHARED,
+					   attr_name)) <= 0) {
+		if (ret < 0) {
+			 *error_r = t_strdup_printf("mailbox_attribute_unset(%s, "
+						    " /shared/%s): failed: %s",
+						    mailbox_get_vname(
+						    mailbox_transaction_get_mailbox(t)),
+						    attr_name,
+						    mailbox_get_last_internal_error(
+						    mailbox_transaction_get_mailbox(t),
+						    NULL));
+		}
+	}
+
+	return ret;
+}
+
+static
+int mail_crypt_generate_keypair(const char *curve,
+				struct dcrypt_keypair *pair_r,
+				const char **pubid_r,
+				const char **error_r)
+{
+	if (curve == NULL) {
+		*error_r = MAIL_CRYPT_USERENV_CURVE " not set, cannot generate EC key";
+		return -1;
+	}
+
+	if (!dcrypt_keypair_generate(pair_r, DCRYPT_KEY_EC, 0, curve, error_r)) {
+		return -1;
+	}
+
+	buffer_t *key_id = t_str_new(MAIL_CRYPT_HASH_BUF_SIZE);
+	if (!dcrypt_key_id_public(pair_r->pub, MAIL_CRYPT_KEY_ID_ALGORITHM, key_id,
+				  error_r)) {
+		dcrypt_keypair_unref(pair_r);
+		return -1;
+	}
+
+	*pubid_r = binary_to_hex(key_id->data, key_id->used);
+
+	return 0;
+}
+
+int mail_crypt_user_generate_keypair(struct mail_user *user,
+				     struct dcrypt_keypair *pair,
+				     const char **pubid_r,
+				     const char **error_r)
+{
+	struct mail_crypt_user *muser = mail_crypt_get_mail_crypt_user(user);
+	const char *curve = mail_user_plugin_getenv(user, MAIL_CRYPT_USERENV_CURVE);
+
+	if (mail_crypt_generate_keypair(curve, pair, pubid_r, error_r) < 0) {
+		return -1;
+	}
+
+	if (mail_crypt_user_set_keys(user, *pubid_r,
+				     pair->priv, pair->pub, error_r) < 0) {
+		dcrypt_keypair_unref(pair);
+		return -1;
+	}
+
+	mail_crypt_put_key_cache(&muser->key_cache, *pubid_r, pair->priv, pair->pub);
+
+	return 0;
+}
+
+int mail_crypt_box_generate_keypair(struct mailbox *box,
+				    struct dcrypt_keypair *pair,
+				    struct dcrypt_public_key *user_key,
+				    const char **pubid_r,
+				    const char **error_r)
+{
+	int ret;
+	struct mail_user *user = mail_storage_get_user(mailbox_get_storage(box));
+	struct mail_crypt_user *muser = mail_crypt_get_mail_crypt_user(user);
+	const char *curve = mail_user_plugin_getenv(user,
+						    MAIL_CRYPT_USERENV_CURVE);
+
+	if (user_key == NULL) {
+		if ((ret = mail_crypt_user_get_public_key(user,
+							  &user_key,
+							  error_r)) <= 0) {
+			if (ret < 0)
+				return ret;
+			/* generate keypair */
+			struct dcrypt_keypair user_pair;
+			const char *user_pubid;
+			if (mail_crypt_user_generate_keypair(user, &user_pair,
+							     &user_pubid,
+							     error_r) < 0) {
+				return -1;
+			}
+
+			mail_crypt_put_key_cache(&muser->key_cache, user_pubid,
+						 user_pair.priv, user_pair.pub);
+
+			user_key = user_pair.pub;
+			dcrypt_key_unref_private(&user_pair.priv);
+		}
+	} else {
+		dcrypt_key_ref_public(user_key);
+	}
+
+	if ((ret = mail_crypt_generate_keypair(curve, pair, pubid_r, error_r)) < 0) {
+		/* failed */
+	} else if ((ret = mail_crypt_box_set_keys(box, *pubid_r,
+						pair->priv, user_key, pair->pub,
+						error_r)) < 0) {
+		dcrypt_keypair_unref(pair);
+	} else {
+		mail_crypt_put_key_cache(&muser->key_cache, *pubid_r, pair->priv,
+					 pair->pub);
+	}
+
+	dcrypt_key_unref_public(&user_key);
+
+	return ret;
+}
+
+int mail_crypt_box_get_pvt_digests(struct mailbox *box, pool_t pool,
+				   enum mail_attribute_type type,
+				   ARRAY_TYPE(const_string) *digests,
+				   const char **error_r)
+{
+	struct mailbox_attribute_iter *iter;
+	const char *key;
+	int ret;
+
+	iter = mailbox_attribute_iter_init(box, type,
+					   BOX_CRYPT_PREFIX PRIVKEYS_PREFIX);
+	while ((key = mailbox_attribute_iter_next(iter)) != NULL) {
+		key = p_strdup(pool, key);
+		array_push_back(digests, &key);
+	}
+	ret = mailbox_attribute_iter_deinit(&iter);
+	if (ret < 0)
+		*error_r = mailbox_get_last_internal_error(box, NULL);
+	return ret;
+}
+
+int mail_crypt_box_get_private_keys(struct mailbox *box,
+				    ARRAY_TYPE(dcrypt_private_key) *keys_r,
+				    const char **error_r)
+{
+	struct mailbox_attribute_iter *iter;
+	iter = mailbox_attribute_iter_init(box, MAIL_ATTRIBUTE_TYPE_PRIVATE,
+					    BOX_CRYPT_PREFIX PRIVKEYS_PREFIX);
+	const char *id;
+	int ret;
+
+	while ((id = mailbox_attribute_iter_next(iter)) != NULL) {
+		struct dcrypt_private_key *key = NULL;
+		if ((ret = mail_crypt_get_private_key(box, id, FALSE, FALSE,
+						      &key, error_r)) < 0) {
+			(void)mailbox_attribute_iter_deinit(&iter);
+			return -1;
+		} else if (ret > 0)
+			array_push_back(keys_r, &key);
+	}
+
+	ret = mailbox_attribute_iter_deinit(&iter);
+	if (ret < 0)
+		*error_r = mailbox_get_last_internal_error(box, NULL);
+	return ret;
+}
+
+int mail_crypt_box_share_private_keys(struct mailbox_transaction_context *t,
+				      struct dcrypt_public_key *dest_pub_key,
+				      const char *dest_user,
+				      const ARRAY_TYPE(dcrypt_private_key) *priv_keys,
+				      const char **error_r)
+{
+	i_assert(dest_user == NULL || dest_pub_key != NULL);
+
+	struct dcrypt_private_key *priv_key;
+	buffer_t *key_id = t_str_new(MAIL_CRYPT_HASH_BUF_SIZE);
+	int ret = 0;
+
+	array_foreach_elem(priv_keys, priv_key) {
+		ret = -1;
+		if (!dcrypt_key_id_private(priv_key, MAIL_CRYPT_KEY_ID_ALGORITHM,
+					   key_id, error_r) ||
+		    (ret = mail_crypt_box_set_shared_key(t,
+							 binary_to_hex(key_id->data,
+									key_id->used),
+							 priv_key, dest_user,
+							 dest_pub_key, error_r)) < 0)
+			break;
+	}
+
+	return ret;
+}
+
+int
+mail_crypt_user_get_or_gen_public_key(struct mail_user *user,
+				      struct dcrypt_public_key **pub_r,
+				      const char **error_r)
+{
+	i_assert(user != NULL);
+	i_assert(pub_r != NULL);
+	i_assert(error_r != NULL);
+
+	int ret;
+	if ((ret = mail_crypt_user_get_public_key(user, pub_r, error_r)) == 0) {
+		struct dcrypt_keypair pair;
+		const char *pubid = NULL;
+		if (mail_crypt_user_generate_keypair(user, &pair,
+						     &pubid, error_r) < 0) {
+			return -1;
+		}
+		*pub_r = pair.pub;
+		dcrypt_key_unref_private(&pair.priv);
+	} else
+		return ret;
+	return 0;
+}
+
+int
+mail_crypt_box_get_or_gen_public_key(struct mailbox *box,
+				     struct dcrypt_public_key **pub_r,
+				     const char **error_r)
+{
+	i_assert(box != NULL);
+	i_assert(pub_r != NULL);
+	i_assert(error_r != NULL);
+
+	struct mail_user *user =
+		mail_storage_get_user(mailbox_get_storage(box));
+	int ret;
+	if ((ret = mail_crypt_box_get_public_key(box, pub_r, error_r)) == 0) {
+		struct dcrypt_public_key *user_key;
+		if (mail_crypt_user_get_or_gen_public_key(user, &user_key,
+							  error_r) < 0) {
+			return -1;
+		}
+
+		struct dcrypt_keypair pair;
+		const char *pubid = NULL;
+		if (mail_crypt_box_generate_keypair(box, &pair, user_key,
+						    &pubid, error_r) < 0) {
+			return -1;
+		}
+		*pub_r = pair.pub;
+		dcrypt_key_unref_public(&user_key);
+		dcrypt_key_unref_private(&pair.priv);
+	} else
+		return ret;
+	return 0;
+}
+
+bool mail_crypt_acl_secure_sharing_enabled(struct mail_user *user)
+{
+	const char *env =
+		mail_user_plugin_getenv(user, MAIL_CRYPT_ACL_SECURE_SHARE_SETTING);
+
+	/* disabled by default */
+	bool ret = FALSE;
+
+	if (env != NULL) {
+		/* enable unless specifically
+		     requested not to */
+		ret = TRUE;
+		switch (env[0]) {
+			case 'n':
+			case 'N':
+			case '0':
+			case 'f':
+			case 'F':
+			ret = FALSE;
+		}
+	}
+
+	return ret;
+}
+
+static const struct mailbox_attribute_internal mailbox_internal_attributes[] = {
+	{ .type = MAIL_ATTRIBUTE_TYPE_PRIVATE,
+	  .key = BOX_CRYPT_PREFIX,
+	  .flags = MAIL_ATTRIBUTE_INTERNAL_FLAG_CHILDREN
+	},
+	{ .type = MAIL_ATTRIBUTE_TYPE_SHARED,
+	  .key = BOX_CRYPT_PREFIX,
+	  .flags = MAIL_ATTRIBUTE_INTERNAL_FLAG_CHILDREN
+	},
+	{ .type = MAIL_ATTRIBUTE_TYPE_PRIVATE,
+	  .key = USER_CRYPT_PREFIX,
+	  .flags = MAIL_ATTRIBUTE_INTERNAL_FLAG_CHILDREN
+	},
+	{ .type = MAIL_ATTRIBUTE_TYPE_SHARED,
+	  .key = USER_CRYPT_PREFIX,
+	  .flags = MAIL_ATTRIBUTE_INTERNAL_FLAG_CHILDREN
+	}
+};
+
+void mail_crypt_key_register_mailbox_internal_attributes(void)
+{
+	mailbox_attribute_register_internals(mailbox_internal_attributes,
+		N_ELEMENTS(mailbox_internal_attributes));
+}