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>

13 files changed, 3618 insertions, 0 deletions

diff --git a/src/lib-storage/index/dbox-common/Makefile.am b/src/lib-storage/index/dbox-common/Makefile.am
new file mode 100644
index 0000000..ec3d511
--- /dev/null
+++ b/src/lib-storage/index/dbox-common/Makefile.am
@@ -0,0 +1,29 @@
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diff --git a/src/lib-storage/index/dbox-common/Makefile.in b/src/lib-storage/index/dbox-common/Makefile.in
new file mode 100644
index 0000000..60aaf66
--- /dev/null
+++ b/src/lib-storage/index/dbox-common/Makefile.in
@@ -0,0 +1,843 @@
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+	-I$(top_srcdir)/src/lib-imap \
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+	-I$(top_srcdir)/src/lib-storage/index
+
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+
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+	  if test -f "$$i"; then \
+	    echo "$(subdir)/$$i"; \
+	  else \
+	    echo "$$sdir/$$i"; \
+	  fi; \
+	done >> $(top_builddir)/cscope.files
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+			   sed '/\//!d;s|^|$(distdir)/|;s,/[^/]*$$,,' | \
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+	  if test -f $$file || test -d $$file; then d=.; else d=$(srcdir); fi; \
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+	  $(MAKE) $(AM_MAKEFLAGS) INSTALL_PROGRAM="$(INSTALL_STRIP_PROGRAM)" \
+	    install_sh_PROGRAM="$(INSTALL_STRIP_PROGRAM)" INSTALL_STRIP_FLAG=-s \
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+	  $(MAKE) $(AM_MAKEFLAGS) INSTALL_PROGRAM="$(INSTALL_STRIP_PROGRAM)" \
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+	fi
+mostlyclean-generic:
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+clean-generic:
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+distclean-generic:
+	-test -z "$(CONFIG_CLEAN_FILES)" || rm -f $(CONFIG_CLEAN_FILES)
+	-test . = "$(srcdir)" || test -z "$(CONFIG_CLEAN_VPATH_FILES)" || rm -f $(CONFIG_CLEAN_VPATH_FILES)
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+	-rm -f ./$(DEPDIR)/dbox-mail.Plo
+	-rm -f ./$(DEPDIR)/dbox-save.Plo
+	-rm -f ./$(DEPDIR)/dbox-storage.Plo
+	-rm -f Makefile
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+# Otherwise a system limit (for SysV at least) may be exceeded.
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diff --git a/src/lib-storage/index/dbox-common/dbox-attachment.c b/src/lib-storage/index/dbox-common/dbox-attachment.c
new file mode 100644
index 0000000..cfc3f62
--- /dev/null
+++ b/src/lib-storage/index/dbox-common/dbox-attachment.c
@@ -0,0 +1,77 @@
+/* Copyright (c) 2010-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "istream.h"
+#include "str.h"
+#include "dbox-file.h"
+#include "dbox-save.h"
+#include "dbox-attachment.h"
+
+void dbox_attachment_save_write_metadata(struct mail_save_context *ctx,
+					 string_t *str)
+{
+	const ARRAY_TYPE(mail_attachment_extref) *extrefs;
+
+	extrefs = index_attachment_save_get_extrefs(ctx);
+	if (extrefs == NULL || array_count(extrefs) == 0)
+		return;
+
+	str_append_c(str, DBOX_METADATA_EXT_REF);
+	index_attachment_append_extrefs(str, extrefs);
+	str_append_c(str, '\n');
+}
+
+static int
+dbox_attachment_file_get_stream_from(struct dbox_file *file,
+				     const char *ext_refs,
+				     struct istream **stream,
+				     const char **error_r)
+{
+	const char *path_suffix;
+	uoff_t msg_size;
+
+	if (file->storage->attachment_dir == NULL) {
+		mail_storage_set_critical(&file->storage->storage,
+			"%s contains references to external attachments, "
+			"but mail_attachment_dir is unset", file->cur_path);
+		return -1;
+	}
+
+	msg_size = dbox_file_get_plaintext_size(file);
+	path_suffix = file->storage->v.get_attachment_path_suffix(file);
+	if (index_attachment_stream_get(file->storage->attachment_fs,
+					file->storage->attachment_dir,
+					path_suffix, stream, msg_size,
+					ext_refs, error_r) < 0)
+		return 0;
+	return 1;
+}
+
+int dbox_attachment_file_get_stream(struct dbox_file *file,
+				    struct istream **stream)
+{
+	const char *ext_refs, *error;
+	int ret;
+
+	/* need to read metadata in case there are external references */
+	if ((ret = dbox_file_metadata_read(file)) <= 0)
+		return ret;
+
+	i_stream_seek(file->input, file->cur_offset + file->msg_header_size);
+
+	ext_refs = dbox_file_metadata_get(file, DBOX_METADATA_EXT_REF);
+	if (ext_refs == NULL)
+		return 1;
+
+	/* we have external references. */
+	T_BEGIN {
+		ret = dbox_attachment_file_get_stream_from(file, ext_refs,
+							   stream, &error);
+		if (ret == 0) {
+			dbox_file_set_corrupted(file,
+				"Corrupted ext-refs metadata %s: %s",
+				ext_refs, error);
+		}
+	} T_END;
+	return ret;
+}
diff --git a/src/lib-storage/index/dbox-common/dbox-attachment.h b/src/lib-storage/index/dbox-common/dbox-attachment.h
new file mode 100644
index 0000000..a90ba54
--- /dev/null
+++ b/src/lib-storage/index/dbox-common/dbox-attachment.h
@@ -0,0 +1,16 @@
+#ifndef DBOX_ATTACHMENT_H
+#define DBOX_ATTACHMENT_H
+
+#include "index-attachment.h"
+
+struct dbox_file;
+
+void dbox_attachment_save_write_metadata(struct mail_save_context *ctx,
+					 string_t *str);
+
+/* Build a single message body stream out of the current message and all of its
+   attachments. */
+int dbox_attachment_file_get_stream(struct dbox_file *file,
+				    struct istream **stream);
+
+#endif
diff --git a/src/lib-storage/index/dbox-common/dbox-file-fix.c b/src/lib-storage/index/dbox-common/dbox-file-fix.c
new file mode 100644
index 0000000..1c44ca4
--- /dev/null
+++ b/src/lib-storage/index/dbox-common/dbox-file-fix.c
@@ -0,0 +1,519 @@
+/* Copyright (c) 2009-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "hex-dec.h"
+#include "istream.h"
+#include "ostream.h"
+#include "message-size.h"
+#include "dbox-storage.h"
+#include "dbox-file.h"
+
+#include <stdio.h>
+
+#define DBOX_MAIL_FILE_BROKEN_COPY_SUFFIX ".broken"
+
+static int
+dbox_file_match_pre_magic(struct istream *input,
+			  uoff_t *pre_offset, size_t *need_bytes)
+{
+	const struct dbox_message_header *hdr;
+	const unsigned char *data;
+	size_t size;
+	uoff_t offset = input->v_offset;
+	bool have_lf = FALSE;
+
+	data = i_stream_get_data(input, &size);
+	if (data[0] == '\n') {
+		data++; size--; offset++;
+		have_lf = TRUE;
+	}
+	i_assert(data[0] == DBOX_MAGIC_PRE[0]);
+	if (size < sizeof(*hdr)) {
+		*need_bytes = sizeof(*hdr) + (have_lf ? 1 : 0);
+		return -1;
+	}
+	hdr = (const void *)data;
+	if (memcmp(hdr->magic_pre, DBOX_MAGIC_PRE, strlen(DBOX_MAGIC_PRE)) != 0)
+		return 0;
+	if (hdr->type != DBOX_MESSAGE_TYPE_NORMAL)
+		return 0;
+	if (hdr->space1 != ' ' || hdr->space2 != ' ')
+		return 0;
+	if (hex2dec(hdr->message_size_hex, sizeof(hdr->message_size_hex)) == 0 &&
+	    memcmp(hdr->message_size_hex, "0000000000000000", sizeof(hdr->message_size_hex)) != 0)
+		return 0;
+
+	*pre_offset = offset;
+	return 1;
+}
+
+static bool memchr_nocontrol(const unsigned char *data, char chr,
+			     unsigned int len, const unsigned char **pos_r)
+{
+	unsigned int i;
+
+	for (i = 0; i < len; i++) {
+		if (data[i] == chr) {
+			*pos_r = data+i;
+			return TRUE;
+		}
+		if (data[i] < ' ')
+			return FALSE;
+	}
+	*pos_r = NULL;
+	return TRUE;
+}
+
+static int
+dbox_file_match_post_magic(struct istream *input, bool input_full,
+			   size_t *need_bytes)
+{
+	const unsigned char *data, *p;
+	size_t i, size;
+	bool allow_control;
+
+	data = i_stream_get_data(input, &size);
+	if (size < strlen(DBOX_MAGIC_POST)) {
+		*need_bytes = strlen(DBOX_MAGIC_POST);
+		return -1;
+	}
+	if (memcmp(data, DBOX_MAGIC_POST, strlen(DBOX_MAGIC_POST)) != 0)
+		return 0;
+
+	/* see if the metadata block looks valid */
+	for (i = strlen(DBOX_MAGIC_POST); i < size; ) {
+		switch (data[i]) {
+		case '\n':
+			return 1;
+		case DBOX_METADATA_GUID:
+		case DBOX_METADATA_POP3_UIDL:
+		case DBOX_METADATA_ORIG_MAILBOX:
+		case DBOX_METADATA_OLDV1_KEYWORDS:
+			/* these could contain anything */
+			allow_control = TRUE;
+			break;
+		case DBOX_METADATA_POP3_ORDER:
+		case DBOX_METADATA_RECEIVED_TIME:
+		case DBOX_METADATA_PHYSICAL_SIZE:
+		case DBOX_METADATA_VIRTUAL_SIZE:
+		case DBOX_METADATA_EXT_REF:
+		case DBOX_METADATA_OLDV1_EXPUNGED:
+		case DBOX_METADATA_OLDV1_FLAGS:
+		case DBOX_METADATA_OLDV1_SAVE_TIME:
+		case DBOX_METADATA_OLDV1_SPACE:
+			/* no control chars */
+			allow_control = FALSE;
+			break;
+		default:
+			if (data[i] < 'A' || data[i] > 'Z')
+				return 0;
+			/* unknown */
+			allow_control = TRUE;
+			break;
+		}
+		if (allow_control) {
+			p = memchr(data+i, '\n', size-i);
+		} else {
+			if (!memchr_nocontrol(data+i, '\n', size-i, &p))
+				return 0;
+		}
+		if (p == NULL) {
+			/* LF not found - try to find the end-of-metadata LF */
+			if (input_full) {
+				/* can't look any further - assume it's ok */
+				return 1;
+			}
+			*need_bytes = size+1;
+			return -1;
+		}
+		i = p - data+1;
+	}
+	*need_bytes = size+1;
+	return -1;
+}
+
+static int
+dbox_file_find_next_magic(struct dbox_file *file, uoff_t *offset_r, bool *pre_r)
+{
+	/* We're scanning message bodies here, trying to find the beginning of
+	   the next message. Although our magic strings are very unlikely to
+	   be found in regular emails, they are much more likely when emails
+	   are stored compressed.. So try to be sure we find the correct
+	   magic markers. */
+
+	struct istream *input = file->input;
+	uoff_t orig_offset, pre_offset, post_offset, prev_offset;
+	const unsigned char *data, *magic;
+	size_t size, need_bytes, prev_need_bytes;
+	int ret, match;
+
+	*pre_r = FALSE;
+
+	orig_offset = prev_offset = input->v_offset;
+	need_bytes = strlen(DBOX_MAGIC_POST); prev_need_bytes = 0;
+	while ((ret = i_stream_read_bytes(input, &data, &size, need_bytes)) > 0 ||
+	       ret == -2) {
+		/* search for the beginning of a potential pre/post magic */
+		i_assert(size > 1);
+		i_assert(prev_offset != input->v_offset ||
+			 need_bytes > prev_need_bytes);
+		prev_offset = input->v_offset;
+		prev_need_bytes = need_bytes;
+
+		magic = memchr(data, DBOX_MAGIC_PRE[0], size);
+		if (magic == NULL) {
+			i_stream_skip(input, size-1);
+			need_bytes = strlen(DBOX_MAGIC_POST);
+			continue;
+		}
+		if (magic == data && input->v_offset == orig_offset) {
+			/* beginning of the file */
+		} else if (magic != data && magic[-1] == '\n') {
+			/* PRE/POST block? leave \n */
+			i_stream_skip(input, magic-data-1);
+		} else {
+			i_stream_skip(input, magic-data+1);
+			need_bytes = strlen(DBOX_MAGIC_POST);
+			continue;
+		}
+
+		pre_offset = UOFF_T_MAX;
+		match = dbox_file_match_pre_magic(input, &pre_offset, &need_bytes);
+		if (match < 0) {
+			/* more data needed */
+			if (ret == -2) {
+				i_stream_skip(input, 2);
+				need_bytes = strlen(DBOX_MAGIC_POST);
+			}
+			continue;
+		}
+		if (match > 0)
+			*pre_r = TRUE;
+
+		match = dbox_file_match_post_magic(input, ret == -2, &need_bytes);
+		if (match < 0) {
+			/* more data needed */
+			if (ret == -2) {
+				i_stream_skip(input, 2);
+				need_bytes = strlen(DBOX_MAGIC_POST);
+			}
+			continue;
+		}
+		if (match > 0) {
+			post_offset = input->v_offset;
+			if (pre_offset == UOFF_T_MAX ||
+			    post_offset < pre_offset) {
+				pre_offset = post_offset;
+				*pre_r = FALSE;
+			}
+		}
+
+		if (pre_offset != UOFF_T_MAX) {
+			*offset_r = pre_offset;
+			ret = 1;
+			break;
+		}
+		i_stream_skip(input, size-1);
+	}
+	if (ret <= 0) {
+		i_assert(ret == -1);
+		if (input->stream_errno != 0)
+			dbox_file_set_syscall_error(file, "read()");
+		else {
+			ret = 0;
+			*offset_r = input->v_offset;
+		} 
+	}
+	i_stream_seek(input, orig_offset);
+	return ret <= 0 ? ret : 1;
+}
+
+static int
+stream_copy(struct dbox_file *file, struct ostream *output,
+	    const char *out_path, uoff_t count)
+{
+	struct istream *input;
+	int ret = 0;
+
+	input = i_stream_create_limit(file->input, count);
+	o_stream_nsend_istream(output, input);
+
+	if (input->stream_errno != 0) {
+		mail_storage_set_critical(&file->storage->storage,
+			"read(%s) failed: %s", file->cur_path,
+			i_stream_get_error(input));
+		ret = -1;
+	} else if (o_stream_flush(output) < 0) {
+		mail_storage_set_critical(&file->storage->storage,
+			"write(%s) failed: %s", out_path,
+			o_stream_get_error(output));
+		ret = -1;
+	} else if (input->v_offset != count) {
+		mail_storage_set_critical(&file->storage->storage,
+			"o_stream_send_istream(%s) copied only %"
+			PRIuUOFF_T" of %"PRIuUOFF_T" bytes",
+			out_path, input->v_offset, count);
+		ret = -1;
+	}
+	i_stream_unref(&input);
+	return ret;
+}
+
+static void dbox_file_skip_broken_header(struct dbox_file *file)
+{
+	const size_t magic_len = strlen(DBOX_MAGIC_PRE);
+	const unsigned char *data;
+	size_t i, size;
+
+	/* if there's LF close to our position, assume that the header ends
+	   there. */
+	data = i_stream_get_data(file->input, &size);
+	if (size > file->msg_header_size + 16)
+		size = file->msg_header_size + 16;
+	for (i = 0; i < size; i++) {
+		if (data[i] == '\n') {
+			i_stream_skip(file->input, i);
+			return;
+		}
+	}
+
+	/* skip at least the magic bytes if possible */
+	if (size > magic_len && memcmp(data, DBOX_MAGIC_PRE, magic_len) == 0)
+		i_stream_skip(file->input, magic_len);
+}
+
+static void
+dbox_file_copy_metadata(struct dbox_file *file, struct ostream *output,
+			bool *have_guid_r)
+{
+	const char *line;
+	uoff_t prev_offset = file->input->v_offset;
+
+	*have_guid_r = FALSE;
+	while ((line = i_stream_read_next_line(file->input)) != NULL) {
+		if (*line == DBOX_METADATA_OLDV1_SPACE || *line == '\0') {
+			/* end of metadata */
+			return;
+		}
+		if (*line < 32) {
+			/* broken - possibly a new pre-magic block */
+			i_stream_seek(file->input, prev_offset);
+			return;
+		}
+		if (*line == DBOX_METADATA_VIRTUAL_SIZE) {
+			/* it may be wrong - recreate it */
+			continue;
+		}
+		if (*line == DBOX_METADATA_GUID)
+			*have_guid_r = TRUE;
+		o_stream_nsend_str(output, line);
+		o_stream_nsend_str(output, "\n");
+	}
+}
+
+static int
+dbox_file_fix_write_stream(struct dbox_file *file, uoff_t start_offset,
+			   const char *temp_path, struct ostream *output)
+{
+	struct dbox_message_header msg_hdr;
+	uoff_t offset, msg_size, hdr_offset, body_offset;
+	bool pre, write_header, have_guid;
+	struct message_size body;
+	bool has_nuls;
+	struct istream *body_input;
+	guid_128_t guid_128;
+	int ret;
+
+	i_stream_seek(file->input, 0);
+	if (start_offset > 0) {
+		/* copy the valid data */
+		if (stream_copy(file, output, temp_path, start_offset) < 0)
+			return -1;
+	} else {
+		/* the file header is broken. recreate it */
+		if (dbox_file_header_write(file, output) < 0) {
+			dbox_file_set_syscall_error(file, "write()");
+			return -1;
+		}
+	}
+
+	while ((ret = dbox_file_find_next_magic(file, &offset, &pre)) > 0) {
+		msg_size = offset - file->input->v_offset;
+		if (msg_size < 256 && pre) {
+			/* probably some garbage or some broken headers.
+			   we most likely don't miss anything by skipping
+			   over this data. */
+			i_stream_skip(file->input, msg_size);
+			hdr_offset = file->input->v_offset;
+			ret = dbox_file_read_mail_header(file, &msg_size);
+			if (ret <= 0) {
+				if (ret < 0)
+					return -1;
+				dbox_file_skip_broken_header(file);
+				body_offset = file->input->v_offset;
+				msg_size = UOFF_T_MAX;
+			} else {
+				i_stream_skip(file->input,
+					      file->msg_header_size);
+				body_offset = file->input->v_offset;
+				i_stream_skip(file->input, msg_size);
+			}
+
+			ret = dbox_file_find_next_magic(file, &offset, &pre);
+			if (ret <= 0)
+				break;
+
+			if (!pre && msg_size == offset - body_offset) {
+				/* msg header ok, copy it */
+				i_stream_seek(file->input, hdr_offset);
+				if (stream_copy(file, output, temp_path,
+						file->msg_header_size) < 0)
+					return -1;
+				write_header = FALSE;
+			} else {
+				/* msg header is broken. write our own. */
+				i_stream_seek(file->input, body_offset);
+				if (msg_size != UOFF_T_MAX) {
+					/* previous magic find might have
+					   skipped too much. seek back and
+					   make sure */
+					ret = dbox_file_find_next_magic(file, &offset, &pre);
+					if (ret <= 0)
+						break;
+				}
+
+				write_header = TRUE;
+				msg_size = offset - body_offset;
+			}
+		} else {
+			/* treat this data as a separate message. */
+			write_header = TRUE;
+			body_offset = file->input->v_offset;
+		}
+		/* write msg header */
+		if (write_header) {
+			dbox_msg_header_fill(&msg_hdr, msg_size);
+			o_stream_nsend(output, &msg_hdr, sizeof(msg_hdr));
+		}
+		/* write msg body */
+		i_assert(file->input->v_offset == body_offset);
+		if (stream_copy(file, output, temp_path, msg_size) < 0)
+			return -1;
+		i_assert(file->input->v_offset == offset);
+
+		/* get message body size */
+		i_stream_seek(file->input, body_offset);
+		body_input = i_stream_create_limit(file->input, msg_size);
+		ret = message_get_body_size(body_input, &body, &has_nuls);
+		i_stream_unref(&body_input);
+		if (ret < 0) {
+			mail_storage_set_critical(&file->storage->storage,
+				"read(%s) failed: %s", file->cur_path,
+				i_stream_get_error(body_input));
+			return -1;
+		}
+
+		/* write msg metadata. */
+		i_assert(file->input->v_offset == offset);
+		ret = dbox_file_metadata_skip_header(file);
+		if (ret < 0)
+			return -1;
+		o_stream_nsend_str(output, DBOX_MAGIC_POST);
+		if (ret == 0)
+			have_guid = FALSE;
+		else
+			dbox_file_copy_metadata(file, output, &have_guid);
+		if (!have_guid) {
+			guid_128_generate(guid_128);
+			o_stream_nsend_str(output,
+				t_strdup_printf("%c%s\n", DBOX_METADATA_GUID,
+				guid_128_to_string(guid_128)));
+		}
+		o_stream_nsend_str(output,
+			t_strdup_printf("%c%llx\n", DBOX_METADATA_VIRTUAL_SIZE,
+					(unsigned long long)body.virtual_size));
+		o_stream_nsend_str(output, "\n");
+		if (output->stream_errno != 0)
+			break;
+	}
+	if (o_stream_flush(output) < 0) {
+		mail_storage_set_critical(&file->storage->storage,
+			"write(%s) failed: %s", temp_path, o_stream_get_error(output));
+		ret = -1;
+	}
+	return ret;
+}
+
+int dbox_file_fix(struct dbox_file *file, uoff_t start_offset)
+{
+	struct ostream *output;
+	const char *dir, *p, *temp_path, *broken_path;
+	bool deleted, have_messages;
+	int fd, ret;
+
+	i_assert(dbox_file_is_open(file));
+
+	p = strrchr(file->cur_path, '/');
+	i_assert(p != NULL);
+	dir = t_strdup_until(file->cur_path, p);
+
+	temp_path = t_strdup_printf("%s/%s", dir, dbox_generate_tmp_filename());
+	fd = file->storage->v.file_create_fd(file, temp_path, FALSE);
+	if (fd == -1)
+		return -1;
+
+	output = o_stream_create_fd_file(fd, 0, FALSE);
+	o_stream_cork(output);
+	ret = dbox_file_fix_write_stream(file, start_offset, temp_path, output);
+	if (ret < 0)
+		o_stream_abort(output);
+	have_messages = output->offset > file->file_header_size;
+	o_stream_unref(&output);
+	if (close(fd) < 0) {
+		mail_storage_set_critical(&file->storage->storage,
+					  "close(%s) failed: %m", temp_path);
+		ret = -1;
+	}
+	if (ret < 0) {
+		if (unlink(temp_path) < 0) {
+			mail_storage_set_critical(&file->storage->storage,
+				"unlink(%s) failed: %m", temp_path);
+		}
+		return -1;
+	}
+	/* keep a copy of the original file in case someone wants to look
+	   at it */
+	broken_path = t_strconcat(file->cur_path,
+				  DBOX_MAIL_FILE_BROKEN_COPY_SUFFIX, NULL);
+	if (link(file->cur_path, broken_path) < 0) {
+		mail_storage_set_critical(&file->storage->storage,
+					  "link(%s, %s) failed: %m",
+					  file->cur_path, broken_path);
+	} else {
+		i_warning("dbox: Copy of the broken file saved to %s",
+			  broken_path);
+	}
+	if (!have_messages) {
+		/* the resulting file has no messages. just delete the file. */
+		dbox_file_close(file);
+		i_unlink(temp_path);
+		i_unlink(file->cur_path);
+		return 0;
+	}
+	if (rename(temp_path, file->cur_path) < 0) {
+		mail_storage_set_critical(&file->storage->storage,
+					  "rename(%s, %s) failed: %m",
+					  temp_path, file->cur_path);
+		return -1;
+	}
+
+	/* file was successfully recreated - reopen it */
+	dbox_file_close(file);
+	if (dbox_file_open(file, &deleted) <= 0) {
+		mail_storage_set_critical(&file->storage->storage,
+			"dbox_file_fix(%s): reopening file failed",
+			file->cur_path);
+		return -1;
+	}
+	return 1;
+}
diff --git a/src/lib-storage/index/dbox-common/dbox-file.c b/src/lib-storage/index/dbox-common/dbox-file.c
new file mode 100644
index 0000000..16810b0
--- /dev/null
+++ b/src/lib-storage/index/dbox-common/dbox-file.c
@@ -0,0 +1,796 @@
+/* Copyright (c) 2007-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "ioloop.h"
+#include "array.h"
+#include "hex-dec.h"
+#include "hex-binary.h"
+#include "hostpid.h"
+#include "istream.h"
+#include "ostream.h"
+#include "file-lock.h"
+#include "file-dotlock.h"
+#include "mkdir-parents.h"
+#include "eacces-error.h"
+#include "str.h"
+#include "dbox-storage.h"
+#include "dbox-file.h"
+
+#include <stdio.h>
+#include <unistd.h>
+#include <ctype.h>
+#include <fcntl.h>
+
+#define DBOX_READ_BLOCK_SIZE IO_BLOCK_SIZE
+
+#ifndef DBOX_FILE_LOCK_METHOD_FLOCK
+static const struct dotlock_settings dotlock_set = {
+	.stale_timeout = 60*10,
+	.use_excl_lock = TRUE
+};
+#endif
+
+const char *dbox_generate_tmp_filename(void)
+{
+	static unsigned int create_count = 0;
+
+	return t_strdup_printf(DBOX_TEMP_FILE_PREFIX"%"PRIdTIME_T".P%sQ%uM%u.%s",
+			       ioloop_timeval.tv_sec, my_pid,
+			       create_count++,
+			       (unsigned int)ioloop_timeval.tv_usec,
+			       my_hostname);
+}
+
+void dbox_file_set_syscall_error(struct dbox_file *file, const char *function)
+{
+	mail_storage_set_critical(&file->storage->storage,
+				  "%s failed for file %s: %m",
+				  function, file->cur_path);
+}
+
+void dbox_file_set_corrupted(struct dbox_file *file, const char *reason, ...)
+{
+	va_list args;
+
+	va_start(args, reason);
+	mail_storage_set_critical(&file->storage->storage,
+		"Corrupted dbox file %s (around offset=%"PRIuUOFF_T"): %s",
+		file->cur_path, file->input == NULL ? 0 : file->input->v_offset,
+		t_strdup_vprintf(reason, args));
+	va_end(args);
+
+	file->storage->v.set_file_corrupted(file);
+}
+
+void dbox_file_init(struct dbox_file *file)
+{
+	file->refcount = 1;
+	file->fd = -1;
+	file->cur_offset = UOFF_T_MAX;
+	file->cur_path = file->primary_path;
+}
+
+void dbox_file_free(struct dbox_file *file)
+{
+	i_assert(file->refcount == 0);
+
+	pool_unref(&file->metadata_pool);
+	dbox_file_close(file);
+	i_free(file->primary_path);
+	i_free(file->alt_path);
+	i_free(file);
+}
+
+void dbox_file_unref(struct dbox_file **_file)
+{
+	struct dbox_file *file = *_file;
+
+	*_file = NULL;
+
+	i_assert(file->refcount > 0);
+	if (--file->refcount == 0)
+		file->storage->v.file_unrefed(file);
+}
+
+static int dbox_file_parse_header(struct dbox_file *file, const char *line)
+{
+	const char *const *tmp, *value;
+	enum dbox_header_key key;
+
+	file->file_version = *line - '0';
+	if (!i_isdigit(line[0]) || line[1] != ' ' ||
+	    (file->file_version != 1 && file->file_version != DBOX_VERSION)) {
+		dbox_file_set_corrupted(file, "Invalid dbox version");
+		return -1;
+	}
+	line += 2;
+
+	file->msg_header_size = 0;
+
+	for (tmp = t_strsplit(line, " "); *tmp != NULL; tmp++) {
+		uintmax_t time;
+		key = **tmp;
+		value = *tmp + 1;
+
+		switch (key) {
+		case DBOX_HEADER_OLDV1_APPEND_OFFSET:
+			break;
+		case DBOX_HEADER_MSG_HEADER_SIZE:
+			if (str_to_uint_hex(value, &file->msg_header_size) < 0) {
+				dbox_file_set_corrupted(file, "Invalid message header size");
+				return -1;
+			}
+			break;
+		case DBOX_HEADER_CREATE_STAMP:
+			if (str_to_uintmax_hex(value, &time) < 0) {
+				dbox_file_set_corrupted(file, "Invalid create time stamp");
+				return -1;
+			}
+			file->create_time = (time_t)time;
+			break;
+		}
+	}
+
+	if (file->msg_header_size == 0) {
+		dbox_file_set_corrupted(file, "Missing message header size");
+		return -1;
+	}
+	return 0;
+}
+
+static int dbox_file_read_header(struct dbox_file *file)
+{
+	const char *line;
+	unsigned int hdr_size;
+	int ret;
+
+	i_stream_seek(file->input, 0);
+	line = i_stream_read_next_line(file->input);
+	if (line == NULL) {
+		if (file->input->stream_errno == 0) {
+			dbox_file_set_corrupted(file,
+				"EOF while reading file header");
+			return 0;
+		}
+
+		dbox_file_set_syscall_error(file, "read()");
+		return -1;
+	}
+	hdr_size = file->input->v_offset;
+	T_BEGIN {
+		ret = dbox_file_parse_header(file, line) < 0 ? 0 : 1;
+	} T_END;
+	if (ret > 0)
+		file->file_header_size = hdr_size;
+	return ret;
+}
+
+static int dbox_file_open_fd(struct dbox_file *file, bool try_altpath)
+{
+	const char *path;
+	int flags = O_RDWR;
+	bool alt = FALSE;
+
+	/* try the primary path first */
+	path = file->primary_path;
+	while ((file->fd = open(path, flags)) == -1) {
+		if (errno == EACCES && flags == O_RDWR) {
+			flags = O_RDONLY;
+			continue;
+		}
+		if (errno != ENOENT) {
+			mail_storage_set_critical(&file->storage->storage,
+						  "open(%s) failed: %m", path);
+			return -1;
+		}
+
+		if (file->alt_path == NULL || alt || !try_altpath) {
+			/* not found */
+			return 0;
+		}
+
+		/* try the alternative path */
+		path = file->alt_path;
+		alt = TRUE;
+	}
+	file->cur_path = path;
+	return 1;
+}
+
+static int dbox_file_open_full(struct dbox_file *file, bool try_altpath,
+			       bool *notfound_r)
+{
+	int ret, fd;
+
+	*notfound_r = FALSE;
+	if (file->input != NULL)
+		return 1;
+
+	if (file->fd == -1) {
+		T_BEGIN {
+			ret = dbox_file_open_fd(file, try_altpath);
+		} T_END;
+		if (ret <= 0) {
+			if (ret < 0)
+				return -1;
+			*notfound_r = TRUE;
+			return 1;
+		}
+	}
+
+	/* we're manually checking at dbox_file_close() if we need to close the
+	   fd or not. */
+	fd = file->fd;
+	file->input = i_stream_create_fd_autoclose(&fd, DBOX_READ_BLOCK_SIZE);
+	i_stream_set_name(file->input, file->cur_path);
+	i_stream_set_init_buffer_size(file->input, DBOX_READ_BLOCK_SIZE);
+	return dbox_file_read_header(file);
+}
+
+int dbox_file_open(struct dbox_file *file, bool *deleted_r)
+{
+	return dbox_file_open_full(file, TRUE, deleted_r);
+}
+
+int dbox_file_open_primary(struct dbox_file *file, bool *notfound_r)
+{
+	return dbox_file_open_full(file, FALSE, notfound_r);
+}
+
+int dbox_file_stat(struct dbox_file *file, struct stat *st_r)
+{
+	const char *path;
+	bool alt = FALSE;
+
+	if (dbox_file_is_open(file)) {
+		if (fstat(file->fd, st_r) < 0) {
+			mail_storage_set_critical(&file->storage->storage,
+				"fstat(%s) failed: %m", file->cur_path);
+			return -1;
+		}
+		return 0;
+	}
+
+	/* try the primary path first */
+	path = file->primary_path;
+	while (stat(path, st_r) < 0) {
+		if (errno != ENOENT) {
+			mail_storage_set_critical(&file->storage->storage,
+						  "stat(%s) failed: %m", path);
+			return -1;
+		}
+
+		if (file->alt_path == NULL || alt) {
+			/* not found */
+			return -1;
+		}
+
+		/* try the alternative path */
+		path = file->alt_path;
+		alt = TRUE;
+	}
+	file->cur_path = path;
+	return 0;
+}
+
+int dbox_file_header_write(struct dbox_file *file, struct ostream *output)
+{
+	string_t *hdr;
+
+	hdr = t_str_new(128);
+	str_printfa(hdr, "%u %c%x %c%x\n", DBOX_VERSION,
+		    DBOX_HEADER_MSG_HEADER_SIZE,
+		    (unsigned int)sizeof(struct dbox_message_header),
+		    DBOX_HEADER_CREATE_STAMP, (unsigned int)ioloop_time);
+
+	file->file_version = DBOX_VERSION;
+	file->file_header_size = str_len(hdr);
+	file->msg_header_size = sizeof(struct dbox_message_header);
+	return o_stream_send(output, str_data(hdr), str_len(hdr));
+}
+
+void dbox_file_close(struct dbox_file *file)
+{
+	dbox_file_unlock(file);
+	if (file->input != NULL) {
+		/* stream autocloses the fd when it gets destroyed. note that
+		   the stream may outlive the struct dbox_file. */
+		i_stream_unref(&file->input);
+		file->fd = -1;
+	} else if (file->fd != -1) {
+		if (close(file->fd) < 0)
+			dbox_file_set_syscall_error(file, "close()");
+		file->fd = -1;
+	}
+	file->cur_offset = UOFF_T_MAX;
+}
+
+int dbox_file_try_lock(struct dbox_file *file)
+{
+	const char *error;
+	int ret;
+
+	i_assert(file->fd != -1);
+
+#ifdef DBOX_FILE_LOCK_METHOD_FLOCK
+	struct file_lock_settings lock_set = {
+		.lock_method = FILE_LOCK_METHOD_FLOCK,
+	};
+	ret = file_try_lock(file->fd, file->cur_path, F_WRLCK,
+			    &lock_set, &file->lock, &error);
+	if (ret < 0) {
+		mail_storage_set_critical(&file->storage->storage,
+			"file_try_lock(%s) failed: %s", file->cur_path, error);
+	}
+#else
+	ret = file_dotlock_create(&dotlock_set, file->cur_path,
+				  DOTLOCK_CREATE_FLAG_NONBLOCK, &file->lock);
+	if (ret < 0) {
+		mail_storage_set_critical(&file->storage->storage,
+			"file_dotlock_create(%s) failed: %m", file->cur_path);
+	}
+#endif
+	return ret;
+}
+
+void dbox_file_unlock(struct dbox_file *file)
+{
+	i_assert(!file->appending || file->lock == NULL);
+
+	if (file->lock != NULL) {
+#ifdef DBOX_FILE_LOCK_METHOD_FLOCK
+		file_unlock(&file->lock);
+#else
+		file_dotlock_delete(&file->lock);
+#endif
+	}
+	if (file->input != NULL)
+		i_stream_sync(file->input);
+}
+
+int dbox_file_read_mail_header(struct dbox_file *file, uoff_t *physical_size_r)
+{
+	struct dbox_message_header hdr;
+	const unsigned char *data;
+	size_t size;
+	int ret;
+
+	ret = i_stream_read_bytes(file->input, &data, &size,
+				  file->msg_header_size);
+	if (ret <= 0) {
+		if (file->input->stream_errno == 0) {
+			/* EOF, broken offset or file truncated */
+			dbox_file_set_corrupted(file, "EOF reading msg header "
+						"(got %zu/%u bytes)",
+						size, file->msg_header_size);
+			return 0;
+		}
+		dbox_file_set_syscall_error(file, "read()");
+		return -1;
+	}
+	memcpy(&hdr, data, I_MIN(sizeof(hdr), file->msg_header_size));
+	if (memcmp(hdr.magic_pre, DBOX_MAGIC_PRE, sizeof(hdr.magic_pre)) != 0) {
+		/* probably broken offset */
+		dbox_file_set_corrupted(file, "msg header has bad magic value");
+		return 0;
+	}
+
+	if (data[file->msg_header_size-1] != '\n') {
+		dbox_file_set_corrupted(file, "msg header doesn't end with LF");
+		return 0;
+	}
+
+	*physical_size_r = hex2dec(hdr.message_size_hex,
+				   sizeof(hdr.message_size_hex));
+	return 1;
+}
+
+int dbox_file_seek(struct dbox_file *file, uoff_t offset)
+{
+	uoff_t size;
+	int ret;
+
+	i_assert(file->input != NULL);
+
+	if (offset == 0)
+		offset = file->file_header_size;
+
+	if (offset != file->cur_offset) {
+		i_stream_seek(file->input, offset);
+		ret = dbox_file_read_mail_header(file, &size);
+		if (ret <= 0)
+			return ret;
+		file->cur_offset = offset;
+		file->cur_physical_size = size;
+	}
+	i_stream_seek(file->input, offset + file->msg_header_size);
+	return 1;
+}
+
+static int
+dbox_file_seek_next_at_metadata(struct dbox_file *file, uoff_t *offset)
+{
+	const char *line;
+	size_t buf_size;
+	int ret;
+
+	i_stream_seek(file->input, *offset);
+	if ((ret = dbox_file_metadata_skip_header(file)) <= 0)
+		return ret;
+
+	/* skip over the actual metadata */
+	buf_size = i_stream_get_max_buffer_size(file->input);
+	i_stream_set_max_buffer_size(file->input, SIZE_MAX);
+	while ((line = i_stream_read_next_line(file->input)) != NULL) {
+		if (*line == DBOX_METADATA_OLDV1_SPACE || *line == '\0') {
+			/* end of metadata */
+			break;
+		}
+	}
+	i_stream_set_max_buffer_size(file->input, buf_size);
+	*offset = file->input->v_offset;
+	return 1;
+}
+
+void dbox_file_seek_rewind(struct dbox_file *file)
+{
+	file->cur_offset = UOFF_T_MAX;
+}
+
+int dbox_file_seek_next(struct dbox_file *file, uoff_t *offset_r, bool *last_r)
+{
+	uoff_t offset;
+	int ret;
+
+	i_assert(file->input != NULL);
+
+	if (file->cur_offset == UOFF_T_MAX) {
+		/* first mail. we may not have read the file at all yet,
+		   so set the offset afterwards. */
+		offset = 0;
+	} else {
+		offset = file->cur_offset + file->msg_header_size +
+			file->cur_physical_size;
+		if ((ret = dbox_file_seek_next_at_metadata(file, &offset)) <= 0) {
+			*offset_r = file->cur_offset;
+			return ret;
+		}
+		if (i_stream_read_eof(file->input)) {
+			*last_r = TRUE;
+			return 0;
+		}
+	}
+	*offset_r = offset;
+
+	*last_r = FALSE;
+
+	ret = dbox_file_seek(file, offset);
+	if (*offset_r == 0)
+		*offset_r = file->file_header_size;
+	return ret;
+}
+
+struct dbox_file_append_context *dbox_file_append_init(struct dbox_file *file)
+{
+	struct dbox_file_append_context *ctx;
+
+	i_assert(!file->appending);
+
+	file->appending = TRUE;
+
+	ctx = i_new(struct dbox_file_append_context, 1);
+	ctx->file = file;
+	if (file->fd != -1) {
+		ctx->output = o_stream_create_fd_file(file->fd, 0, FALSE);
+		o_stream_set_name(ctx->output, file->cur_path);
+		o_stream_set_finish_via_child(ctx->output, FALSE);
+		o_stream_cork(ctx->output);
+	}
+	return ctx;
+}
+
+int dbox_file_append_commit(struct dbox_file_append_context **_ctx)
+{
+	struct dbox_file_append_context *ctx = *_ctx;
+	int ret;
+
+	i_assert(ctx->file->appending);
+
+	*_ctx = NULL;
+
+	ret = dbox_file_append_flush(ctx);
+	if (ctx->last_checkpoint_offset != ctx->output->offset) {
+		o_stream_close(ctx->output);
+		if (ftruncate(ctx->file->fd, ctx->last_checkpoint_offset) < 0) {
+			dbox_file_set_syscall_error(ctx->file, "ftruncate()");
+			return -1;
+		}
+	}
+	o_stream_unref(&ctx->output);
+	ctx->file->appending = FALSE;
+	i_free(ctx);
+	return ret;
+}
+
+void dbox_file_append_rollback(struct dbox_file_append_context **_ctx)
+{
+	struct dbox_file_append_context *ctx = *_ctx;
+	struct dbox_file *file = ctx->file;
+	bool close_file = FALSE;
+
+	i_assert(ctx->file->appending);
+
+	*_ctx = NULL;
+	if (ctx->first_append_offset == 0) {
+		/* nothing changed */
+	} else if (ctx->first_append_offset == file->file_header_size) {
+		/* rolling back everything */
+		if (unlink(file->cur_path) < 0)
+			dbox_file_set_syscall_error(file, "unlink()");
+		close_file = TRUE;
+	} else {
+		/* truncating only some mails */
+		o_stream_close(ctx->output);
+		if (ftruncate(file->fd, ctx->first_append_offset) < 0)
+			dbox_file_set_syscall_error(file, "ftruncate()");
+	}
+	if (ctx->output != NULL) {
+		o_stream_abort(ctx->output);
+		o_stream_unref(&ctx->output);
+	}
+	i_free(ctx);
+
+	if (close_file)
+		dbox_file_close(file);
+	file->appending = FALSE;
+}
+
+int dbox_file_append_flush(struct dbox_file_append_context *ctx)
+{
+	struct mail_storage *storage = &ctx->file->storage->storage;
+
+	if (ctx->last_flush_offset == ctx->output->offset &&
+	    ctx->last_checkpoint_offset == ctx->output->offset)
+		return 0;
+
+	if (o_stream_flush(ctx->output) < 0) {
+		dbox_file_set_syscall_error(ctx->file, "write()");
+		return -1;
+	}
+
+	if (ctx->last_checkpoint_offset != ctx->output->offset) {
+		if (ftruncate(ctx->file->fd, ctx->last_checkpoint_offset) < 0) {
+			dbox_file_set_syscall_error(ctx->file, "ftruncate()");
+			return -1;
+		}
+		if (o_stream_seek(ctx->output, ctx->last_checkpoint_offset) < 0) {
+			dbox_file_set_syscall_error(ctx->file, "lseek()");
+			return -1;
+		}
+	}
+
+	if (storage->set->parsed_fsync_mode != FSYNC_MODE_NEVER) {
+		if (fdatasync(ctx->file->fd) < 0) {
+			dbox_file_set_syscall_error(ctx->file, "fdatasync()");
+			return -1;
+		}
+	}
+	ctx->last_flush_offset = ctx->output->offset;
+	return 0;
+}
+
+void dbox_file_append_checkpoint(struct dbox_file_append_context *ctx)
+{
+	ctx->last_checkpoint_offset = ctx->output->offset;
+}
+
+int dbox_file_get_append_stream(struct dbox_file_append_context *ctx,
+				struct ostream **output_r)
+{
+	struct dbox_file *file = ctx->file;
+	struct stat st;
+
+	if (ctx->output == NULL) {
+		/* file creation had failed */
+		return -1;
+	}
+	if (ctx->last_checkpoint_offset != ctx->output->offset) {
+		/* a message was aborted. don't try appending to this
+		   file anymore. */
+		return -1;
+	}
+
+	if (file->file_version == 0) {
+		/* newly created file, write the file header */
+		if (dbox_file_header_write(file, ctx->output) < 0) {
+			dbox_file_set_syscall_error(file, "write()");
+			return -1;
+		}
+		*output_r = ctx->output;
+		return 1;
+	}
+
+	/* file has existing mails */
+	if (file->file_version != DBOX_VERSION ||
+	    file->msg_header_size != sizeof(struct dbox_message_header)) {
+		/* created by an incompatible version, can't append */
+		return 0;
+	}
+
+	if (ctx->output->offset == 0) {
+		/* first append to existing file. seek to eof first. */
+		if (fstat(file->fd, &st) < 0) {
+			dbox_file_set_syscall_error(file, "fstat()");
+			return -1;
+		}
+		if (st.st_size < file->msg_header_size) {
+			dbox_file_set_corrupted(file,
+				"dbox file size too small");
+			return 0;
+		}
+		if (o_stream_seek(ctx->output, st.st_size) < 0) {
+			dbox_file_set_syscall_error(file, "lseek()");
+			return -1;
+		}
+	}
+	*output_r = ctx->output;
+	return 1;
+}
+
+int dbox_file_metadata_skip_header(struct dbox_file *file)
+{
+	struct dbox_metadata_header metadata_hdr;
+	const unsigned char *data;
+	size_t size;
+	int ret;
+
+	ret = i_stream_read_bytes(file->input, &data, &size,
+				  sizeof(metadata_hdr));
+	if (ret <= 0) {
+		if (file->input->stream_errno == 0) {
+			/* EOF, broken offset */
+			dbox_file_set_corrupted(file,
+				"Unexpected EOF while reading metadata header");
+			return 0;
+		}
+		dbox_file_set_syscall_error(file, "read()");
+		return -1;
+	}
+	memcpy(&metadata_hdr, data, sizeof(metadata_hdr));
+	if (memcmp(metadata_hdr.magic_post, DBOX_MAGIC_POST,
+		   sizeof(metadata_hdr.magic_post)) != 0) {
+		/* probably broken offset */
+		dbox_file_set_corrupted(file,
+			"metadata header has bad magic value");
+		return 0;
+	}
+	i_stream_skip(file->input, sizeof(metadata_hdr));
+	return 1;
+}
+
+static int
+dbox_file_metadata_read_at(struct dbox_file *file, uoff_t metadata_offset)
+{
+	const char *line;
+	size_t buf_size;
+	int ret;
+
+	if (file->metadata_pool != NULL)
+		p_clear(file->metadata_pool);
+	else {
+		file->metadata_pool =
+			pool_alloconly_create("dbox metadata", 1024);
+	}
+	p_array_init(&file->metadata, file->metadata_pool, 16);
+
+	i_stream_seek(file->input, metadata_offset);
+	if ((ret = dbox_file_metadata_skip_header(file)) <= 0)
+		return ret;
+
+	ret = 0;
+	buf_size = i_stream_get_max_buffer_size(file->input);
+	/* use unlimited line length for metadata */
+	i_stream_set_max_buffer_size(file->input, SIZE_MAX);
+	while ((line = i_stream_read_next_line(file->input)) != NULL) {
+		if (*line == DBOX_METADATA_OLDV1_SPACE || *line == '\0') {
+			/* end of metadata */
+			ret = 1;
+			break;
+		}
+		line = p_strdup(file->metadata_pool, line);
+		array_push_back(&file->metadata, &line);
+	}
+	i_stream_set_max_buffer_size(file->input, buf_size);
+	if (ret == 0)
+		dbox_file_set_corrupted(file, "missing end-of-metadata line");
+	return ret;
+}
+
+int dbox_file_metadata_read(struct dbox_file *file)
+{
+	uoff_t metadata_offset;
+	int ret;
+
+	i_assert(file->cur_offset != UOFF_T_MAX);
+
+	if (file->metadata_read_offset == file->cur_offset)
+		return 1;
+
+	metadata_offset = file->cur_offset + file->msg_header_size +
+		file->cur_physical_size;
+	ret = dbox_file_metadata_read_at(file, metadata_offset);
+	if (ret <= 0)
+		return ret;
+
+	file->metadata_read_offset = file->cur_offset;
+	return 1;
+}
+
+const char *dbox_file_metadata_get(struct dbox_file *file,
+				   enum dbox_metadata_key key)
+{
+	const char *const *metadata;
+	unsigned int i, count;
+
+	metadata = array_get(&file->metadata, &count);
+	for (i = 0; i < count; i++) {
+		if (*metadata[i] == (char)key)
+			return metadata[i] + 1;
+	}
+	return NULL;
+}
+
+uoff_t dbox_file_get_plaintext_size(struct dbox_file *file)
+{
+	const char *value;
+	uintmax_t size;
+
+	i_assert(file->metadata_read_offset == file->cur_offset);
+
+	/* see if we have it in metadata */
+	value = dbox_file_metadata_get(file, DBOX_METADATA_PHYSICAL_SIZE);
+	if (value == NULL ||
+	    str_to_uintmax_hex(value, &size) < 0 ||
+	    size > UOFF_T_MAX) {
+		/* no. that means we can use the size in the header */
+		return file->cur_physical_size;
+	}
+
+	return (uoff_t)size;
+}
+
+void dbox_msg_header_fill(struct dbox_message_header *dbox_msg_hdr,
+			  uoff_t message_size)
+{
+	memset(dbox_msg_hdr, ' ', sizeof(*dbox_msg_hdr));
+	memcpy(dbox_msg_hdr->magic_pre, DBOX_MAGIC_PRE,
+	       sizeof(dbox_msg_hdr->magic_pre));
+	dbox_msg_hdr->type = DBOX_MESSAGE_TYPE_NORMAL;
+	dec2hex(dbox_msg_hdr->message_size_hex, message_size,
+		sizeof(dbox_msg_hdr->message_size_hex));
+	dbox_msg_hdr->save_lf = '\n';
+}
+
+int dbox_file_unlink(struct dbox_file *file)
+{
+	const char *path;
+	bool alt = FALSE;
+
+	path = file->primary_path;
+	while (unlink(path) < 0) {
+		if (errno != ENOENT) {
+			mail_storage_set_critical(&file->storage->storage,
+				"unlink(%s) failed: %m", path);
+			return -1;
+		}
+		if (file->alt_path == NULL || alt) {
+			/* not found */
+			return 0;
+		}
+
+		/* try the alternative path */
+		path = file->alt_path;
+		alt = TRUE;
+	}
+	return 1;
+}
diff --git a/src/lib-storage/index/dbox-common/dbox-file.h b/src/lib-storage/index/dbox-common/dbox-file.h
new file mode 100644
index 0000000..309c705
--- /dev/null
+++ b/src/lib-storage/index/dbox-common/dbox-file.h
@@ -0,0 +1,218 @@
+#ifndef DBOX_FILE_H
+#define DBOX_FILE_H
+
+/* The file begins with a header followed by zero or more messages:
+
+   <dbox message header>
+   <LF>
+   <message body>
+   <metadata>
+
+   Metadata block begins with DBOX_MAGIC_POST, followed by zero or more lines
+   in format <key character><value><LF>. The block ends with an empty line.
+   Unknown metadata should be ignored, but preserved when copying.
+
+   There should be no duplicates for the current metadata, but future
+   extensions may need them so they should be preserved.
+*/
+#define DBOX_VERSION 2
+#define DBOX_MAGIC_PRE "\001\002"
+#define DBOX_MAGIC_POST "\n\001\003\n"
+
+/* prefer flock(). fcntl() locking currently breaks if trying to access the
+   same file from multiple mail_storages within same process. that's why we
+   fallback to dotlocks. */
+#ifdef HAVE_FLOCK
+#  define DBOX_FILE_LOCK_METHOD_FLOCK
+#endif
+
+struct dbox_file;
+struct stat;
+
+enum dbox_header_key {
+	/* Must be sizeof(struct dbox_message_header) when appending (hex) */
+	DBOX_HEADER_MSG_HEADER_SIZE	= 'M',
+	/* Creation UNIX timestamp (hex) */
+	DBOX_HEADER_CREATE_STAMP	= 'C',
+
+	/* metadata used by old Dovecot versions */
+	DBOX_HEADER_OLDV1_APPEND_OFFSET	= 'A'
+};
+
+/* NOTE: all valid keys are uppercase characters. if this changes, change
+   dbox-file-fix.c:dbox_file_match_post_magic() to recognize them */
+enum dbox_metadata_key {
+	/* Globally unique identifier for the message. Preserved when
+	   copying. */
+	DBOX_METADATA_GUID		= 'G',
+	/* POP3 UIDL overriding the default format */
+	DBOX_METADATA_POP3_UIDL		= 'P',
+	/* POP3 message ordering (for migrated mails) */
+	DBOX_METADATA_POP3_ORDER	= 'O',
+	/* Received UNIX timestamp in hex */
+	DBOX_METADATA_RECEIVED_TIME	= 'R',
+	/* Physical message size in hex. Necessary only if it differs from
+	   the dbox_message_header.message_size_hex, for example because the
+	   message is compressed. */
+	DBOX_METADATA_PHYSICAL_SIZE	= 'Z',
+	/* Virtual message size in hex (line feeds counted as CRLF) */
+	DBOX_METADATA_VIRTUAL_SIZE	= 'V',
+	/* Pointer to external message data. Format is:
+	   1*(<start offset> <byte count> <options> <ref>) */
+	DBOX_METADATA_EXT_REF		= 'X',
+	/* Mailbox name where this message was originally saved to.
+	   When rebuild finds a message whose mailbox is unknown, it's
+	   placed to this mailbox. */
+	DBOX_METADATA_ORIG_MAILBOX	= 'B',
+
+	/* metadata used by old Dovecot versions */
+	DBOX_METADATA_OLDV1_EXPUNGED	= 'E',
+	DBOX_METADATA_OLDV1_FLAGS	= 'F',
+	DBOX_METADATA_OLDV1_KEYWORDS	= 'K',
+	DBOX_METADATA_OLDV1_SAVE_TIME	= 'S',
+	DBOX_METADATA_OLDV1_SPACE	= ' '
+};
+
+enum dbox_message_type {
+	/* Normal message */
+	DBOX_MESSAGE_TYPE_NORMAL	= 'N'
+};
+
+struct dbox_message_header {
+	unsigned char magic_pre[2];
+	unsigned char type;
+	unsigned char space1;
+	unsigned char oldv1_uid_hex[8];
+	unsigned char space2;
+	unsigned char message_size_hex[16];
+	/* <space reserved for future extensions, LF is always last> */
+	unsigned char save_lf;
+};
+
+struct dbox_metadata_header {
+	unsigned char magic_post[sizeof(DBOX_MAGIC_POST)-1];
+};
+
+struct dbox_file {
+	struct dbox_storage *storage;
+	int refcount;
+
+	time_t create_time;
+	unsigned int file_version;
+	unsigned int file_header_size;
+	unsigned int msg_header_size;
+
+	const char *cur_path;
+	char *primary_path, *alt_path;
+	int fd;
+	struct istream *input;
+#ifdef DBOX_FILE_LOCK_METHOD_FLOCK
+	struct file_lock *lock;
+#else
+	struct dotlock *lock;
+#endif
+
+	uoff_t cur_offset;
+	uoff_t cur_physical_size;
+
+	/* Metadata for the currently seeked metadata block. */
+	pool_t metadata_pool;
+	ARRAY(const char *) metadata;
+	uoff_t metadata_read_offset;
+
+	bool appending:1;
+	bool corrupted:1;
+};
+
+struct dbox_file_append_context {
+	struct dbox_file *file;
+
+	uoff_t first_append_offset, last_checkpoint_offset, last_flush_offset;
+	struct ostream *output;
+};
+
+#define dbox_file_is_open(file) ((file)->fd != -1)
+#define dbox_file_is_in_alt(file) ((file)->cur_path == (file)->alt_path)
+
+void dbox_file_init(struct dbox_file *file);
+void dbox_file_unref(struct dbox_file **file);
+
+/* Open the file. Returns 1 if ok, 0 if file header is corrupted, -1 if error.
+   If file is deleted, deleted_r=TRUE and 1 is returned. */
+int dbox_file_open(struct dbox_file *file, bool *deleted_r);
+/* Try to open file only from primary path. */
+int dbox_file_open_primary(struct dbox_file *file, bool *notfound_r);
+/* Close the file handle from the file, but don't free it. */
+void dbox_file_close(struct dbox_file *file);
+
+/* fstat() or stat() the file. If file is already deleted, fails with
+   errno=ENOENT. */
+int dbox_file_stat(struct dbox_file *file, struct stat *st_r);
+
+/* Try to lock the dbox file. Returns 1 if ok, 0 if already locked by someone
+   else, -1 if error. */
+int dbox_file_try_lock(struct dbox_file *file);
+void dbox_file_unlock(struct dbox_file *file);
+
+/* Seek to given offset in file. Returns 1 if ok/expunged, 0 if file/offset is
+   corrupted, -1 if I/O error. */
+int dbox_file_seek(struct dbox_file *file, uoff_t offset);
+/* Start seeking at the beginning of the file. */
+void dbox_file_seek_rewind(struct dbox_file *file);
+/* Seek to next message after current one. If there are no more messages,
+   returns 0 and last_r is set to TRUE. Returns 1 if ok, 0 if file is
+   corrupted, -1 if I/O error. */
+int dbox_file_seek_next(struct dbox_file *file, uoff_t *offset_r, bool *last_r);
+
+/* Start appending to dbox file */
+struct dbox_file_append_context *dbox_file_append_init(struct dbox_file *file);
+/* Finish writing appended mails. */
+int dbox_file_append_commit(struct dbox_file_append_context **ctx);
+/* Truncate appended mails. */
+void dbox_file_append_rollback(struct dbox_file_append_context **ctx);
+/* Get output stream for appending a new message. Returns 1 if ok, 0 if file
+   can't be appended to (old file version or corruption) or -1 if error. */
+int dbox_file_get_append_stream(struct dbox_file_append_context *ctx,
+				struct ostream **output_r);
+/* Call after message has been fully saved. If this isn't done, the writes
+   since the last checkpoint are truncated. */
+void dbox_file_append_checkpoint(struct dbox_file_append_context *ctx);
+/* Flush output buffer. */
+int dbox_file_append_flush(struct dbox_file_append_context *ctx);
+
+/* Read current message's metadata. Returns 1 if ok, 0 if metadata is
+   corrupted, -1 if I/O error. */
+int dbox_file_metadata_read(struct dbox_file *file);
+/* Return wanted metadata value, or NULL if not found. */
+const char *dbox_file_metadata_get(struct dbox_file *file,
+				   enum dbox_metadata_key key);
+
+/* Returns DBOX_METADATA_PHYSICAL_SIZE if set, otherwise physical size from
+   header. They differ only for e.g. compressed mails. */
+uoff_t dbox_file_get_plaintext_size(struct dbox_file *file);
+
+/* Fix a broken dbox file by rename()ing over it with a fixed file. Everything
+   before start_offset is assumed to be valid and is simply copied. The file
+   is reopened afterwards. Returns 1 if ok, 0 if the resulting file has no
+   mails and was deleted, -1 if I/O error. */
+int dbox_file_fix(struct dbox_file *file, uoff_t start_offset);
+/* Delete the given dbox file. Returns 1 if deleted, 0 if file wasn't found
+   or -1 if error. */
+int dbox_file_unlink(struct dbox_file *file);
+
+/* Fill dbox_message_header with given size. */
+void dbox_msg_header_fill(struct dbox_message_header *dbox_msg_hdr,
+			  uoff_t message_size);
+
+void dbox_file_set_syscall_error(struct dbox_file *file, const char *function);
+void dbox_file_set_corrupted(struct dbox_file *file, const char *reason, ...)
+	ATTR_FORMAT(2, 3);
+
+/* private: */
+const char *dbox_generate_tmp_filename(void);
+void dbox_file_free(struct dbox_file *file);
+int dbox_file_header_write(struct dbox_file *file, struct ostream *output);
+int dbox_file_read_mail_header(struct dbox_file *file, uoff_t *physical_size_r);
+int dbox_file_metadata_skip_header(struct dbox_file *file);
+
+#endif
diff --git a/src/lib-storage/index/dbox-common/dbox-mail.c b/src/lib-storage/index/dbox-common/dbox-mail.c
new file mode 100644
index 0000000..49279f9
--- /dev/null
+++ b/src/lib-storage/index/dbox-common/dbox-mail.c
@@ -0,0 +1,318 @@
+/* Copyright (c) 2007-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "istream.h"
+#include "str.h"
+#include "index-storage.h"
+#include "index-mail.h"
+#include "index-pop3-uidl.h"
+#include "dbox-attachment.h"
+#include "dbox-storage.h"
+#include "dbox-file.h"
+#include "dbox-mail.h"
+
+
+struct mail *
+dbox_mail_alloc(struct mailbox_transaction_context *t,
+		enum mail_fetch_field wanted_fields,
+		struct mailbox_header_lookup_ctx *wanted_headers)
+{
+	struct dbox_mail *mail;
+	pool_t pool;
+
+	pool = pool_alloconly_create("mail", 2048);
+	mail = p_new(pool, struct dbox_mail, 1);
+
+	index_mail_init(&mail->imail, t, wanted_fields, wanted_headers, pool, NULL);
+	return &mail->imail.mail.mail;
+}
+
+void dbox_mail_close(struct mail *_mail)
+{
+	struct dbox_mail *mail = DBOX_MAIL(_mail);
+
+	index_mail_close(_mail);
+	/* close the dbox file only after index is closed, since it may still
+	   try to read from it. */
+	if (mail->open_file != NULL)
+		dbox_file_unref(&mail->open_file);
+}
+
+int dbox_mail_metadata_read(struct dbox_mail *mail, struct dbox_file **file_r)
+{
+	struct dbox_storage *storage =
+		DBOX_STORAGE(mail->imail.mail.mail.box->storage);
+	uoff_t offset;
+
+	if (storage->v.mail_open(mail, &offset, file_r) < 0)
+		return -1;
+
+	if (dbox_file_seek(*file_r, offset) <= 0)
+		return -1;
+	if (dbox_file_metadata_read(*file_r) <= 0)
+		return -1;
+
+	if (mail->imail.data.stream != NULL) {
+		/* we just messed up mail's input stream by reading metadata */
+		i_stream_seek((*file_r)->input, offset);
+		i_stream_sync(mail->imail.data.stream);
+	}
+	return 0;
+}
+
+static int
+dbox_mail_metadata_get(struct dbox_mail *mail, enum dbox_metadata_key key,
+		       const char **value_r)
+{
+	struct dbox_file *file;
+
+	if (dbox_mail_metadata_read(mail, &file) < 0)
+		return -1;
+
+	*value_r = dbox_file_metadata_get(file, key);
+	return 0;
+}
+
+int dbox_mail_get_physical_size(struct mail *_mail, uoff_t *size_r)
+{
+	struct dbox_mail *mail = DBOX_MAIL(_mail);
+	struct index_mail_data *data = &mail->imail.data;
+	struct dbox_file *file;
+
+	if (index_mail_get_physical_size(_mail, size_r) == 0)
+		return 0;
+
+	if (dbox_mail_metadata_read(mail, &file) < 0)
+		return -1;
+
+	data->physical_size = dbox_file_get_plaintext_size(file);
+	*size_r = data->physical_size;
+	return 0;
+}
+
+int dbox_mail_get_virtual_size(struct mail *_mail, uoff_t *size_r)
+{
+	struct dbox_mail *mail = DBOX_MAIL(_mail);
+	struct index_mail_data *data = &mail->imail.data;
+	const char *value;
+	uintmax_t size;
+
+	if (index_mail_get_cached_virtual_size(&mail->imail, size_r))
+		return 0;
+
+	if (dbox_mail_metadata_get(mail, DBOX_METADATA_VIRTUAL_SIZE,
+				   &value) < 0)
+		return -1;
+	if (value == NULL)
+		return index_mail_get_virtual_size(_mail, size_r);
+
+	if (str_to_uintmax_hex(value, &size) < 0 || size > UOFF_T_MAX)
+		return -1;
+	data->virtual_size = (uoff_t)size;
+	*size_r = data->virtual_size;
+	return 0;
+}
+
+int dbox_mail_get_received_date(struct mail *_mail, time_t *date_r)
+{
+	struct dbox_mail *mail = DBOX_MAIL(_mail);
+	struct index_mail_data *data = &mail->imail.data;
+	const char *value;
+	uintmax_t time;
+
+	if (index_mail_get_received_date(_mail, date_r) == 0)
+		return 0;
+
+	if (dbox_mail_metadata_get(mail, DBOX_METADATA_RECEIVED_TIME,
+				   &value) < 0)
+		return -1;
+
+	time = 0;
+	if (value != NULL && str_to_uintmax_hex(value, &time) < 0)
+		return -1;
+
+	data->received_date = (time_t)time;
+	*date_r = data->received_date;
+	return 0;
+}
+
+int dbox_mail_get_save_date(struct mail *_mail, time_t *date_r)
+{
+	struct dbox_storage *storage = DBOX_STORAGE(_mail->box->storage);
+	struct dbox_mail *mail = DBOX_MAIL(_mail);
+	struct index_mail_data *data = &mail->imail.data;
+	struct dbox_file *file;
+	struct stat st;
+	uoff_t offset;
+
+	if (index_mail_get_save_date(_mail, date_r) > 0)
+		return 1;
+
+	if (storage->v.mail_open(mail, &offset, &file) < 0)
+		return -1;
+
+	_mail->transaction->stats.fstat_lookup_count++;
+	if (dbox_file_stat(file, &st) < 0) {
+		if (errno == ENOENT)
+			mail_set_expunged(_mail);
+		return -1;
+	}
+	*date_r = data->save_date = st.st_ctime;
+	return 1;
+}
+
+static int
+dbox_get_cached_metadata(struct dbox_mail *mail, enum dbox_metadata_key key,
+			 enum index_cache_field cache_field,
+			 const char **value_r)
+{
+	struct index_mail *imail = &mail->imail;
+	struct index_mailbox_context *ibox =
+		INDEX_STORAGE_CONTEXT(imail->mail.mail.box);
+	const char *value;
+	string_t *str;
+	uint32_t order;
+
+	str = str_new(imail->mail.data_pool, 64);
+	if (mail_cache_lookup_field(imail->mail.mail.transaction->cache_view,
+				    str, imail->mail.mail.seq,
+				    ibox->cache_fields[cache_field].idx) > 0) {
+		if (cache_field == MAIL_CACHE_POP3_ORDER) {
+			i_assert(str_len(str) == sizeof(order));
+			memcpy(&order, str_data(str), sizeof(order));
+			str_truncate(str, 0);
+			if (order != 0)
+				str_printfa(str, "%u", order);
+			else {
+				/* order=0 means it doesn't exist. we don't
+				   want to return "0" though, because then the
+				   mails get ordered to beginning, while
+				   nonexistent are supposed to be ordered at
+				   the end. */
+			}
+		}
+		*value_r = str_c(str);
+		return 0;
+	}
+
+	if (dbox_mail_metadata_get(mail, key, &value) < 0)
+		return -1;
+
+	if (value == NULL)
+		value = "";
+	if (cache_field != MAIL_CACHE_POP3_ORDER) {
+		index_mail_cache_add_idx(imail, ibox->cache_fields[cache_field].idx,
+					 value, strlen(value));
+	} else {
+		if (str_to_uint(value, &order) < 0)
+			order = 0;
+		index_mail_cache_add_idx(imail, ibox->cache_fields[cache_field].idx,
+					 &order, sizeof(order));
+	}
+
+	/* don't return pointer to dbox metadata directly, since it may
+	   change unexpectedly */
+	str_truncate(str, 0);
+	str_append(str, value);
+	*value_r = str_c(str);
+	return 0;
+}
+
+int dbox_mail_get_special(struct mail *_mail, enum mail_fetch_field field,
+			  const char **value_r)
+{
+	struct dbox_mail *mail = DBOX_MAIL(_mail);
+	int ret;
+
+	/* keep the UIDL in cache file, otherwise POP3 would open all
+	   mail files and read the metadata. same for GUIDs if they're
+	   used. */
+	switch (field) {
+	case MAIL_FETCH_UIDL_BACKEND:
+		if (!index_pop3_uidl_can_exist(_mail)) {
+			*value_r = "";
+			return 0;
+		}
+		ret = dbox_get_cached_metadata(mail, DBOX_METADATA_POP3_UIDL,
+					       MAIL_CACHE_POP3_UIDL, value_r);
+		if (ret == 0) {
+			index_pop3_uidl_update_exists(&mail->imail.mail.mail,
+						      (*value_r)[0] != '\0');
+		}
+		return ret;
+	case MAIL_FETCH_POP3_ORDER:
+		if (!index_pop3_uidl_can_exist(_mail)) {
+			/* we're assuming that if there's a POP3 order, there's
+			   also a UIDL */
+			*value_r = "";
+			return 0;
+		}
+		return dbox_get_cached_metadata(mail, DBOX_METADATA_POP3_ORDER,
+						MAIL_CACHE_POP3_ORDER, value_r);
+	case MAIL_FETCH_GUID:
+		return dbox_get_cached_metadata(mail, DBOX_METADATA_GUID,
+						MAIL_CACHE_GUID, value_r);
+	default:
+		break;
+	}
+
+	return index_mail_get_special(_mail, field, value_r);
+}
+
+static int
+get_mail_stream(struct dbox_mail *mail, uoff_t offset,
+		struct istream **stream_r)
+{
+	struct mail_private *pmail = &mail->imail.mail;
+	struct dbox_file *file = mail->open_file;
+	int ret;
+
+	if ((ret = dbox_file_seek(file, offset)) <= 0) {
+		*stream_r = NULL;
+		return ret;
+	}
+
+	*stream_r = i_stream_create_limit(file->input, file->cur_physical_size);
+	if (pmail->v.istream_opened != NULL) {
+		if (pmail->v.istream_opened(&pmail->mail, stream_r) < 0)
+			return -1;
+	}
+	if (file->storage->attachment_dir == NULL)
+		return 1;
+	else
+		return dbox_attachment_file_get_stream(file, stream_r);
+}
+
+int dbox_mail_get_stream(struct mail *_mail, bool get_body ATTR_UNUSED,
+			 struct message_size *hdr_size,
+			 struct message_size *body_size,
+			 struct istream **stream_r)
+{
+	struct dbox_storage *storage = DBOX_STORAGE(_mail->box->storage);
+	struct dbox_mail *mail = DBOX_MAIL(_mail);
+	struct index_mail_data *data = &mail->imail.data;
+	struct istream *input;
+	uoff_t offset;
+	int ret;
+
+	if (data->stream == NULL) {
+		if (storage->v.mail_open(mail, &offset, &mail->open_file) < 0)
+			return -1;
+
+		ret = get_mail_stream(mail, offset, &input);
+		if (ret <= 0) {
+			if (ret < 0)
+				return -1;
+			dbox_file_set_corrupted(mail->open_file,
+				"uid=%u points to broken data at offset="
+				"%"PRIuUOFF_T, _mail->uid, offset);
+			i_stream_unref(&input);
+			return -1;
+		}
+		data->stream = input;
+		index_mail_set_read_buffer_size(_mail, input);
+	}
+
+	return index_mail_init_stream(&mail->imail, hdr_size, body_size,
+				      stream_r);
+}
diff --git a/src/lib-storage/index/dbox-common/dbox-mail.h b/src/lib-storage/index/dbox-common/dbox-mail.h
new file mode 100644
index 0000000..c03652c
--- /dev/null
+++ b/src/lib-storage/index/dbox-common/dbox-mail.h
@@ -0,0 +1,34 @@
+#ifndef DBOX_MAIL_H
+#define DBOX_MAIL_H
+
+#include "index-mail.h"
+
+struct dbox_mail {
+	struct index_mail imail;
+
+	struct dbox_file *open_file;
+	uoff_t offset;
+};
+
+#define DBOX_MAIL(s)	container_of(s, struct dbox_mail, imail.mail.mail)
+
+struct mail *
+dbox_mail_alloc(struct mailbox_transaction_context *t,
+		enum mail_fetch_field wanted_fields,
+		struct mailbox_header_lookup_ctx *wanted_headers);
+void dbox_mail_close(struct mail *mail);
+
+int dbox_mail_get_physical_size(struct mail *mail, uoff_t *size_r);
+int dbox_mail_get_virtual_size(struct mail *mail, uoff_t *size_r);
+int dbox_mail_get_received_date(struct mail *mail, time_t *date_r);
+int dbox_mail_get_save_date(struct mail *_mail, time_t *date_r);
+int dbox_mail_get_special(struct mail *mail, enum mail_fetch_field field,
+			  const char **value_r);
+int dbox_mail_get_stream(struct mail *_mail, bool get_body ATTR_UNUSED,
+			 struct message_size *hdr_size,
+			 struct message_size *body_size,
+			 struct istream **stream_r);
+
+int dbox_mail_metadata_read(struct dbox_mail *mail, struct dbox_file **file_r);
+
+#endif
diff --git a/src/lib-storage/index/dbox-common/dbox-save.c b/src/lib-storage/index/dbox-common/dbox-save.c
new file mode 100644
index 0000000..c5af8cc
--- /dev/null
+++ b/src/lib-storage/index/dbox-common/dbox-save.c
@@ -0,0 +1,226 @@
+/* Copyright (c) 2007-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "istream.h"
+#include "istream-crlf.h"
+#include "ostream.h"
+#include "str.h"
+#include "hex-binary.h"
+#include "index-mail.h"
+#include "index-storage.h"
+#include "dbox-attachment.h"
+#include "dbox-file.h"
+#include "dbox-save.h"
+
+void dbox_save_add_to_index(struct dbox_save_context *ctx)
+{
+	struct mail_save_data *mdata = &ctx->ctx.data;
+	enum mail_flags save_flags;
+
+	save_flags = mdata->flags & ENUM_NEGATE(MAIL_RECENT);
+	mail_index_append(ctx->trans, mdata->uid, &ctx->seq);
+	mail_index_update_flags(ctx->trans, ctx->seq, MODIFY_REPLACE,
+				save_flags);
+	if (mdata->keywords != NULL) {
+		mail_index_update_keywords(ctx->trans, ctx->seq,
+					   MODIFY_REPLACE, mdata->keywords);
+	}
+	if (mdata->min_modseq != 0) {
+		mail_index_update_modseq(ctx->trans, ctx->seq,
+					 mdata->min_modseq);
+	}
+}
+
+void dbox_save_begin(struct dbox_save_context *ctx, struct istream *input)
+{
+	struct mail_save_context *_ctx = &ctx->ctx;
+	struct mail_storage *_storage = _ctx->transaction->box->storage;
+	struct dbox_storage *storage = DBOX_STORAGE(_storage);
+	struct dbox_message_header dbox_msg_hdr;
+	struct istream *crlf_input;
+
+	dbox_save_add_to_index(ctx);
+
+	mail_set_seq_saving(_ctx->dest_mail, ctx->seq);
+
+	crlf_input = i_stream_create_lf(input);
+	ctx->input = index_mail_cache_parse_init(_ctx->dest_mail, crlf_input);
+	i_stream_unref(&crlf_input);
+
+	/* write a dummy header. it'll get rewritten when we're finished */
+	i_zero(&dbox_msg_hdr);
+	o_stream_cork(ctx->dbox_output);
+	if (o_stream_send(ctx->dbox_output, &dbox_msg_hdr,
+			  sizeof(dbox_msg_hdr)) < 0) {
+		mail_set_critical(_ctx->dest_mail, "write(%s) failed: %s",
+				  o_stream_get_name(ctx->dbox_output),
+				  o_stream_get_error(ctx->dbox_output));
+		ctx->failed = TRUE;
+	}
+	_ctx->data.output = ctx->dbox_output;
+
+	if (_ctx->data.received_date == (time_t)-1)
+		_ctx->data.received_date = ioloop_time;
+	index_attachment_save_begin(_ctx, storage->attachment_fs, ctx->input);
+}
+
+int dbox_save_continue(struct mail_save_context *_ctx)
+{
+	struct dbox_save_context *ctx = DBOX_SAVECTX(_ctx);
+
+	if (ctx->failed)
+		return -1;
+
+	if (_ctx->data.attach != NULL)
+		return index_attachment_save_continue(_ctx);
+
+	if (index_storage_save_continue(_ctx, ctx->input,
+					_ctx->dest_mail) < 0) {
+		ctx->failed = TRUE;
+		return -1;
+	}
+	return 0;
+}
+
+void dbox_save_end(struct dbox_save_context *ctx)
+{
+	struct mail_save_data *mdata = &ctx->ctx.data;
+	struct ostream *dbox_output = ctx->dbox_output;
+	int ret;
+
+	i_assert(mdata->output != NULL);
+
+	if (mdata->attach != NULL && !ctx->failed) {
+		if (index_attachment_save_finish(&ctx->ctx) < 0)
+			ctx->failed = TRUE;
+	}
+	if (mdata->output != dbox_output) {
+		/* e.g. zlib plugin had changed this. make sure we
+		   successfully write the trailer. */
+		ret = o_stream_finish(mdata->output);
+	} else {
+		/* no plugins - flush the output so far */
+		ret = o_stream_flush(mdata->output);
+	}
+	if (ret < 0) {
+		mail_set_critical(ctx->ctx.dest_mail,
+				  "write(%s) failed: %s",
+				  o_stream_get_name(mdata->output),
+				  o_stream_get_error(mdata->output));
+		ctx->failed = TRUE;
+	}
+	if (mdata->output != dbox_output) {
+		o_stream_ref(dbox_output);
+		o_stream_destroy(&mdata->output);
+		mdata->output = dbox_output;
+	}
+	index_mail_cache_parse_deinit(ctx->ctx.dest_mail,
+				      ctx->ctx.data.received_date,
+				      !ctx->failed);
+	if (!ctx->failed)
+		index_mail_cache_pop3_data(ctx->ctx.dest_mail,
+					   mdata->pop3_uidl,
+					   mdata->pop3_order);
+}
+
+void dbox_save_write_metadata(struct mail_save_context *_ctx,
+			      struct ostream *output, uoff_t output_msg_size,
+			      const char *orig_mailbox_name,
+			      guid_128_t guid_128)
+{
+	struct dbox_save_context *ctx = DBOX_SAVECTX(_ctx);
+	struct mail_save_data *mdata = &ctx->ctx.data;
+	struct dbox_metadata_header metadata_hdr;
+	const char *guid;
+	string_t *str;
+	uoff_t vsize;
+
+	i_zero(&metadata_hdr);
+	memcpy(metadata_hdr.magic_post, DBOX_MAGIC_POST,
+	       sizeof(metadata_hdr.magic_post));
+	o_stream_nsend(output, &metadata_hdr, sizeof(metadata_hdr));
+
+	str = t_str_new(256);
+	if (output_msg_size != ctx->input->v_offset) {
+		/* a plugin changed the data written to disk, so the
+		   "message size" dbox header doesn't contain the actual
+		   "physical" message size. we need to save it as a
+		   separate metadata header. */
+		str_printfa(str, "%c%llx\n", DBOX_METADATA_PHYSICAL_SIZE,
+			    (unsigned long long)ctx->input->v_offset);
+	}
+	str_printfa(str, "%c%"PRIxTIME_T"\n", DBOX_METADATA_RECEIVED_TIME,
+		    mdata->received_date);
+	if (mail_get_virtual_size(_ctx->dest_mail, &vsize) < 0)
+		i_unreached();
+	str_printfa(str, "%c%llx\n", DBOX_METADATA_VIRTUAL_SIZE,
+		    (unsigned long long)vsize);
+	if (mdata->pop3_uidl != NULL) {
+		i_assert(strchr(mdata->pop3_uidl, '\n') == NULL);
+		str_printfa(str, "%c%s\n", DBOX_METADATA_POP3_UIDL,
+			    mdata->pop3_uidl);
+		ctx->have_pop3_uidls = TRUE;
+		ctx->highest_pop3_uidl_seq =
+			I_MAX(ctx->highest_pop3_uidl_seq, ctx->seq);
+	}
+	if (mdata->pop3_order != 0) {
+		str_printfa(str, "%c%u\n", DBOX_METADATA_POP3_ORDER,
+			    mdata->pop3_order);
+		ctx->have_pop3_orders = TRUE;
+		ctx->highest_pop3_uidl_seq =
+			I_MAX(ctx->highest_pop3_uidl_seq, ctx->seq);
+	}
+
+	guid = mdata->guid;
+	if (guid != NULL)
+		mail_generate_guid_128_hash(guid, guid_128);
+	else {
+		guid_128_generate(guid_128);
+		guid = guid_128_to_string(guid_128);
+	}
+	str_printfa(str, "%c%s\n", DBOX_METADATA_GUID, guid);
+
+	if (orig_mailbox_name != NULL &&
+	    strchr(orig_mailbox_name, '\r') == NULL &&
+	    strchr(orig_mailbox_name, '\n') == NULL) {
+		/* save the original mailbox name so if mailbox indexes get
+		   corrupted we can place at least some (hopefully most) of
+		   the messages to correct mailboxes. */
+		str_printfa(str, "%c%s\n", DBOX_METADATA_ORIG_MAILBOX,
+			    orig_mailbox_name);
+	}
+
+	dbox_attachment_save_write_metadata(_ctx, str);
+
+	str_append_c(str, '\n');
+	o_stream_nsend(output, str_data(str), str_len(str));
+}
+
+void dbox_save_update_header_flags(struct dbox_save_context *ctx,
+				   struct mail_index_view *sync_view,
+				   uint32_t ext_id,
+				   unsigned int flags_offset)
+{
+	const void *data;
+	size_t data_size;
+	uint8_t old_flags = 0, flags;
+
+	mail_index_get_header_ext(sync_view, ext_id, &data, &data_size);
+	if (flags_offset < data_size)
+		old_flags = *((const uint8_t *)data + flags_offset);
+	else {
+		/* grow old dbox header */
+		mail_index_ext_resize_hdr(ctx->trans, ext_id, flags_offset+1);
+	}
+
+	flags = old_flags;
+	if (ctx->have_pop3_uidls)
+		flags |= DBOX_INDEX_HEADER_FLAG_HAVE_POP3_UIDLS;
+	if (ctx->have_pop3_orders)
+		flags |= DBOX_INDEX_HEADER_FLAG_HAVE_POP3_ORDERS;
+	if (flags != old_flags) {
+		/* flags changed, update them */
+		mail_index_update_header_ext(ctx->trans, ext_id,
+					     flags_offset, &flags, 1);
+	}
+}
diff --git a/src/lib-storage/index/dbox-common/dbox-save.h b/src/lib-storage/index/dbox-common/dbox-save.h
new file mode 100644
index 0000000..a17c923
--- /dev/null
+++ b/src/lib-storage/index/dbox-common/dbox-save.h
@@ -0,0 +1,41 @@
+#ifndef DBOX_SAVE_H
+#define DBOX_SAVE_H
+
+#include "dbox-storage.h"
+
+struct dbox_save_context {
+	struct mail_save_context ctx;
+	struct mail_index_transaction *trans;
+
+	/* updated for each appended mail: */
+	uint32_t seq;
+	struct istream *input;
+
+	struct ostream *dbox_output;
+
+	uint32_t highest_pop3_uidl_seq;
+	bool failed:1;
+	bool finished:1;
+	bool have_pop3_uidls:1;
+	bool have_pop3_orders:1;
+};
+
+#define DBOX_SAVECTX(s)		container_of(s, struct dbox_save_context, ctx)
+
+void dbox_save_begin(struct dbox_save_context *ctx, struct istream *input);
+int dbox_save_continue(struct mail_save_context *_ctx);
+void dbox_save_end(struct dbox_save_context *ctx);
+
+void dbox_save_write_metadata(struct mail_save_context *ctx,
+			      struct ostream *output, uoff_t output_msg_size,
+			      const char *orig_mailbox_name,
+			      guid_128_t guid_128_r) ATTR_NULL(4);
+
+void dbox_save_add_to_index(struct dbox_save_context *ctx);
+
+void dbox_save_update_header_flags(struct dbox_save_context *ctx,
+				   struct mail_index_view *sync_view,
+				   uint32_t ext_id,
+				   unsigned int flags_offset);
+
+#endif
diff --git a/src/lib-storage/index/dbox-common/dbox-storage.c b/src/lib-storage/index/dbox-common/dbox-storage.c
new file mode 100644
index 0000000..5cac0d6
--- /dev/null
+++ b/src/lib-storage/index/dbox-common/dbox-storage.c
@@ -0,0 +1,416 @@
+/* Copyright (c) 2007-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "path-util.h"
+#include "ioloop.h"
+#include "fs-api.h"
+#include "mkdir-parents.h"
+#include "unlink-old-files.h"
+#include "mailbox-uidvalidity.h"
+#include "mailbox-list-private.h"
+#include "index-storage.h"
+#include "dbox-storage.h"
+
+#include <stdio.h>
+#include <dirent.h>
+#include <unistd.h>
+#include <utime.h>
+
+void dbox_storage_get_list_settings(const struct mail_namespace *ns ATTR_UNUSED,
+				    struct mailbox_list_settings *set)
+{
+	if (set->layout == NULL)
+		set->layout = MAILBOX_LIST_NAME_FS;
+	if (set->subscription_fname == NULL)
+		set->subscription_fname = DBOX_SUBSCRIPTION_FILE_NAME;
+	if (*set->maildir_name == '\0')
+		set->maildir_name = DBOX_MAILDIR_NAME;
+	if (*set->mailbox_dir_name == '\0')
+		set->mailbox_dir_name = DBOX_MAILBOX_DIR_NAME;
+}
+
+static bool
+dbox_alt_path_has_changed(const char *root_dir, const char *alt_path,
+			  const char *alt_path2, const char *alt_symlink_path)
+{
+	const char *linkpath, *error;
+
+	if (t_readlink(alt_symlink_path, &linkpath, &error) < 0) {
+		if (errno == ENOENT)
+			return alt_path != NULL;
+		i_error("t_readlink(%s) failed: %s", alt_symlink_path, error);
+		return FALSE;
+	}
+
+	if (alt_path == NULL) {
+		i_warning("dbox %s: Original ALT=%s, "
+			  "but currently no ALT path set", root_dir, linkpath);
+		return TRUE;
+	} else if (strcmp(linkpath, alt_path) != 0) {
+		if (strcmp(linkpath, alt_path2) == 0) {
+			/* FIXME: for backwards compatibility. old versions
+			   created the symlink to mailboxes/ directory, which
+			   was fine with sdbox, but didn't even exist with
+			   mdbox. we'll silently replace the symlink. */
+			return TRUE;
+		}
+		i_warning("dbox %s: Original ALT=%s, "
+			  "but currently ALT=%s", root_dir, linkpath, alt_path);
+		return TRUE;
+	}
+	return FALSE;
+}
+
+static void dbox_verify_alt_path(struct mailbox_list *list)
+{
+	const char *root_dir, *alt_symlink_path, *alt_path, *alt_path2;
+
+	root_dir = mailbox_list_get_root_forced(list, MAILBOX_LIST_PATH_TYPE_DIR);
+	alt_symlink_path =
+		t_strconcat(root_dir, "/"DBOX_ALT_SYMLINK_NAME, NULL);
+	(void)mailbox_list_get_root_path(list, MAILBOX_LIST_PATH_TYPE_ALT_DIR,
+					 &alt_path);
+	(void)mailbox_list_get_root_path(list, MAILBOX_LIST_PATH_TYPE_ALT_MAILBOX,
+					 &alt_path2);
+	if (!dbox_alt_path_has_changed(root_dir, alt_path, alt_path2,
+				       alt_symlink_path))
+		return;
+
+	/* unlink/create the current alt path symlink */
+	i_unlink_if_exists(alt_symlink_path);
+	if (alt_path != NULL) {
+		int ret = symlink(alt_path, alt_symlink_path);
+		if (ret < 0 && errno == ENOENT) {
+			/* root_dir doesn't exist yet - create it */
+			if (mailbox_list_mkdir_root(list, root_dir,
+					MAILBOX_LIST_PATH_TYPE_DIR) < 0)
+				return;
+			ret = symlink(alt_path, alt_symlink_path);
+		}
+		if (ret < 0 && errno != EEXIST) {
+			i_error("symlink(%s, %s) failed: %m",
+				alt_path, alt_symlink_path);
+		}
+	}
+}
+
+int dbox_storage_create(struct mail_storage *_storage,
+			struct mail_namespace *ns,
+			const char **error_r)
+{
+	struct dbox_storage *storage = DBOX_STORAGE(_storage);
+	const struct mail_storage_settings *set = _storage->set;
+	const char *error;
+
+	if (*set->mail_attachment_fs != '\0' &&
+	    *set->mail_attachment_dir != '\0') {
+		const char *name, *args, *dir;
+
+		args = strpbrk(set->mail_attachment_fs, ": ");
+		if (args == NULL) {
+			name = set->mail_attachment_fs;
+			args = "";
+		} else {
+			name = t_strdup_until(set->mail_attachment_fs, args++);
+		}
+		if (strcmp(name, "sis-queue") == 0 &&
+		    (_storage->class_flags & MAIL_STORAGE_CLASS_FLAG_FILE_PER_MSG) != 0) {
+			/* FIXME: the deduplication part doesn't work, because
+			   sdbox renames the files.. */
+			*error_r = "mail_attachment_fs: "
+				"sis-queue not currently supported by sdbox";
+			return -1;
+		}
+		dir = mail_user_home_expand(_storage->user,
+					    set->mail_attachment_dir);
+		storage->attachment_dir = p_strdup(_storage->pool, dir);
+
+		if (mailbox_list_init_fs(ns->list, _storage->event, name, args,
+					 storage->attachment_dir,
+					 &storage->attachment_fs, &error) < 0) {
+			*error_r = t_strdup_printf("mail_attachment_fs: %s",
+						   error);
+			return -1;
+		}
+	}
+
+	if (!ns->list->set.alt_dir_nocheck)
+		dbox_verify_alt_path(ns->list);
+	return 0;
+}
+
+void dbox_storage_destroy(struct mail_storage *_storage)
+{
+	struct dbox_storage *storage = DBOX_STORAGE(_storage);
+
+	fs_deinit(&storage->attachment_fs);
+	index_storage_destroy(_storage);
+}
+
+uint32_t dbox_get_uidvalidity_next(struct mailbox_list *list)
+{
+	const char *path;
+
+	path = mailbox_list_get_root_forced(list, MAILBOX_LIST_PATH_TYPE_CONTROL);
+	path = t_strconcat(path, "/"DBOX_UIDVALIDITY_FILE_NAME, NULL);
+	return mailbox_uidvalidity_next(list, path);
+}
+
+void dbox_notify_changes(struct mailbox *box)
+{
+	const char *dir, *path;
+
+	if (box->notify_callback == NULL)
+		mailbox_watch_remove_all(box);
+	else {
+		if (mailbox_get_path_to(box, MAILBOX_LIST_PATH_TYPE_INDEX,
+					&dir) <= 0)
+			return;
+		path = t_strdup_printf("%s/"MAIL_INDEX_PREFIX".log", dir);
+		mailbox_watch_add(box, path);
+	}
+}
+
+static bool
+dbox_cleanup_temp_files(struct mailbox_list *list, const char *path,
+			time_t last_scan_time, time_t last_change_time)
+{
+	unsigned int interval = list->mail_set->mail_temp_scan_interval;
+
+	/* check once in a while if there are temp files to clean up */
+	if (interval == 0) {
+		/* disabled */
+		return FALSE;
+	} else if (last_scan_time >= ioloop_time - (time_t)interval) {
+		/* not the time to scan it yet */
+		return FALSE;
+	} else {
+		bool stated = FALSE;
+		if (last_change_time == (time_t)-1) {
+			/* Don't know the ctime yet - look it up. */
+			struct stat st;
+
+			if (stat(path, &st) < 0) {
+				if (errno == ENOENT)
+					i_error("stat(%s) failed: %m", path);
+				return FALSE;
+			}
+			last_change_time = st.st_ctime;
+			stated = TRUE;
+		}
+		if (last_scan_time > last_change_time + DBOX_TMP_DELETE_SECS) {
+			/* there haven't been any changes to this directory
+			   since we last checked it. If we did an extra stat(),
+			   we need to update the last_scan_time to avoid
+			   stat()ing the next time. */
+			return stated;
+		}
+		const char *prefix =
+			mailbox_list_get_global_temp_prefix(list);
+		(void)unlink_old_files(path, prefix,
+				       ioloop_time - DBOX_TMP_DELETE_SECS);
+		return TRUE;
+	}
+	return FALSE;
+}
+
+int dbox_mailbox_check_existence(struct mailbox *box, time_t *path_ctime_r)
+{
+	const char *index_path, *box_path = mailbox_get_path(box);
+	struct stat st;
+	int ret = -1;
+
+	*path_ctime_r = (time_t)-1;
+
+	if (box->list->set.iter_from_index_dir) {
+		/* Just because the index directory exists, it doesn't mean
+		   that the mailbox is selectable. Check that by seeing if
+		   dovecot.index.log exists. If it doesn't, fallback to
+		   checking for the dbox-Mails in the mail root directory.
+		   So this also means that if a mailbox is \NoSelect, listing
+		   it will always do a stat() for dbox-Mails in the mail root
+		   directory. That's not ideal, but this makes the behavior
+		   safer and \NoSelect mailboxes are somewhat rare. */
+		if (mailbox_get_path_to(box, MAILBOX_LIST_PATH_TYPE_INDEX,
+					&index_path) < 0)
+			return -1;
+		i_assert(index_path != NULL);
+		index_path = t_strconcat(index_path, "/", box->index_prefix,
+					 ".log", NULL);
+		ret = stat(index_path, &st);
+	}
+	if (ret < 0) {
+		ret = stat(box_path, &st);
+		if (ret == 0)
+			*path_ctime_r = st.st_ctime;
+	}
+
+	if (ret == 0) {
+		return 0;
+	} else if (errno == ENOENT || errno == ENAMETOOLONG) {
+		mail_storage_set_error(box->storage, MAIL_ERROR_NOTFOUND,
+			T_MAIL_ERR_MAILBOX_NOT_FOUND(box->vname));
+		return -1;
+	} else if (errno == EACCES) {
+		mailbox_set_critical(box, "%s",
+			mail_error_eacces_msg("stat", box_path));
+		return -1;
+	} else {
+		mailbox_set_critical(box, "stat(%s) failed: %m", box_path);
+		return -1;
+	}
+}
+
+int dbox_mailbox_open(struct mailbox *box, time_t path_ctime)
+{
+	const char *box_path = mailbox_get_path(box);
+
+	if (index_storage_mailbox_open(box, FALSE) < 0)
+		return -1;
+	mail_index_set_fsync_mode(box->index,
+				  box->storage->set->parsed_fsync_mode,
+				  MAIL_INDEX_FSYNC_MASK_APPENDS |
+				  MAIL_INDEX_FSYNC_MASK_EXPUNGES);
+
+	const struct mail_index_header *hdr = mail_index_get_header(box->view);
+	if (dbox_cleanup_temp_files(box->list, box_path,
+				    hdr->last_temp_file_scan, path_ctime)) {
+		/* temp files were scanned. update the last scan timestamp. */
+		index_mailbox_update_last_temp_file_scan(box);
+	}
+	return 0;
+}
+
+static int dir_is_empty(struct mail_storage *storage, const char *path)
+{
+	DIR *dir;
+	struct dirent *d;
+	int ret = 1;
+
+	dir = opendir(path);
+	if (dir == NULL) {
+		if (errno == ENOENT) {
+			/* race condition with DELETE/RENAME? */
+			return 1;
+		}
+		mail_storage_set_critical(storage, "opendir(%s) failed: %m",
+					  path);
+		return -1;
+	}
+	while ((d = readdir(dir)) != NULL) {
+		if (*d->d_name == '.')
+			continue;
+
+		ret = 0;
+		break;
+	}
+	if (closedir(dir) < 0) {
+		mail_storage_set_critical(storage, "closedir(%s) failed: %m",
+					  path);
+		ret = -1;
+	}
+	return ret;
+}
+
+int dbox_mailbox_create(struct mailbox *box,
+			const struct mailbox_update *update, bool directory)
+{
+	struct dbox_storage *storage = DBOX_STORAGE(box->storage);
+	const char *alt_path;
+	struct stat st;
+	int ret;
+
+	if ((ret = index_storage_mailbox_create(box, directory)) <= 0)
+		return ret;
+	if (mailbox_open(box) < 0)
+		return -1;
+	if (mail_index_get_header(box->view)->uid_validity != 0 &&
+	    !box->storage->rebuilding_list_index) {
+		mail_storage_set_error(box->storage, MAIL_ERROR_EXISTS,
+				       "Mailbox already exists");
+		return -1;
+	}
+
+	/* if alt path already exists and contains files, rebuild storage so
+	   that we don't start overwriting files. */
+	ret = mailbox_get_path_to(box, MAILBOX_LIST_PATH_TYPE_ALT_MAILBOX, &alt_path);
+	if (ret > 0 && stat(alt_path, &st) == 0) {
+		ret = dir_is_empty(box->storage, alt_path);
+		if (ret < 0)
+			return -1;
+		if (ret == 0) {
+			mailbox_set_critical(box,
+				"Existing files in alt path, "
+				"rebuilding storage to avoid losing messages");
+			storage->v.set_mailbox_corrupted(box);
+			return -1;
+		}
+		/* dir is empty, ignore it */
+	}
+	return dbox_mailbox_create_indexes(box, update);
+}
+
+int dbox_mailbox_create_indexes(struct mailbox *box,
+				const struct mailbox_update *update)
+{
+	struct dbox_storage *storage = DBOX_STORAGE(box->storage);
+	struct mail_index_sync_ctx *sync_ctx;
+	struct mail_index_view *view;
+	struct mail_index_transaction *trans;
+	int ret;
+
+	/* use syncing as a lock */
+	ret = mail_index_sync_begin(box->index, &sync_ctx, &view, &trans, 0);
+	if (ret <= 0) {
+		i_assert(ret != 0);
+		mailbox_set_index_error(box);
+		return -1;
+	}
+
+	if (mail_index_get_header(view)->uid_validity == 0) {
+		if (storage->v.mailbox_create_indexes(box, update, trans) < 0) {
+			mail_index_sync_rollback(&sync_ctx);
+			return -1;
+		}
+	}
+
+	return mail_index_sync_commit(&sync_ctx);
+}
+
+int dbox_verify_alt_storage(struct mailbox_list *list)
+{
+	const char *alt_path;
+	struct stat st;
+
+	if (!mailbox_list_get_root_path(list, MAILBOX_LIST_PATH_TYPE_ALT_DIR,
+					&alt_path))
+		return 0;
+
+	/* make sure alt storage is mounted. if it's not, abort the rebuild. */
+	if (stat(alt_path, &st) == 0)
+		return 0;
+	if (errno != ENOENT) {
+		i_error("stat(%s) failed: %m", alt_path);
+		return -1;
+	}
+
+	/* try to create the alt directory. if it fails, it means alt
+	   storage isn't mounted. */
+	if (mailbox_list_mkdir_root(list, alt_path,
+				    MAILBOX_LIST_PATH_TYPE_ALT_DIR) < 0)
+		return -1;
+	return 0;
+}
+
+bool dbox_header_have_flag(struct mailbox *box, uint32_t ext_id,
+			   unsigned int flags_offset, uint8_t flag)
+{
+	const void *data;
+	size_t data_size;
+	uint8_t flags = 0;
+
+	mail_index_get_header_ext(box->view, ext_id, &data, &data_size);
+	if (flags_offset < data_size)
+		flags = *((const uint8_t *)data + flags_offset);
+	return (flags & flag) != 0;
+}
diff --git a/src/lib-storage/index/dbox-common/dbox-storage.h b/src/lib-storage/index/dbox-common/dbox-storage.h
new file mode 100644
index 0000000..af085df
--- /dev/null
+++ b/src/lib-storage/index/dbox-common/dbox-storage.h
@@ -0,0 +1,85 @@
+#ifndef DBOX_STORAGE_H
+#define DBOX_STORAGE_H
+
+#include "mail-storage-private.h"
+
+struct dbox_file;
+struct dbox_mail;
+struct dbox_storage;
+struct dbox_save_context;
+
+#define DBOX_SUBSCRIPTION_FILE_NAME "subscriptions"
+#define DBOX_UIDVALIDITY_FILE_NAME "dovecot-uidvalidity"
+#define DBOX_TEMP_FILE_PREFIX ".temp."
+#define DBOX_ALT_SYMLINK_NAME "dbox-alt-root"
+
+#define DBOX_MAILBOX_DIR_NAME "mailboxes"
+#define DBOX_TRASH_DIR_NAME "trash"
+#define DBOX_MAILDIR_NAME "dbox-Mails"
+
+/* Delete temp files having ctime older than this. */
+#define DBOX_TMP_DELETE_SECS (36*60*60)
+
+/* Flag specifies if the message should be in primary or alternative storage */
+#define DBOX_INDEX_FLAG_ALT MAIL_INDEX_MAIL_FLAG_BACKEND
+
+enum dbox_index_header_flags {
+	/* messages' metadata contain POP3 UIDLs */
+	DBOX_INDEX_HEADER_FLAG_HAVE_POP3_UIDLS	= 0x01,
+	/* messages' metadata contain POP3 orders */
+	DBOX_INDEX_HEADER_FLAG_HAVE_POP3_ORDERS	= 0x02
+};
+
+struct dbox_storage_vfuncs {
+	/* dbox file has zero references now. it should be either freed or
+	   left open in case it's accessed again soon */
+	void (*file_unrefed)(struct dbox_file *file);
+	/* create a new file using the same permissions as file.
+	   if parents=TRUE, create the directory if necessary */
+	int (*file_create_fd)(struct dbox_file *file, const char *path,
+			      bool parents);
+	/* open the mail and return its file/offset */
+	int (*mail_open)(struct dbox_mail *mail, uoff_t *offset_r,
+			 struct dbox_file **file_r);
+	/* create/update mailbox indexes */
+	int (*mailbox_create_indexes)(struct mailbox *box,
+				      const struct mailbox_update *update,
+				      struct mail_index_transaction *trans);
+	/* returns attachment path suffix. mdbox returns "", sdbox returns
+	   "-<mailbox_guid>-<uid>" */
+	const char *(*get_attachment_path_suffix)(struct dbox_file *file);
+	/* mark the mailbox corrupted */
+	void (*set_mailbox_corrupted)(struct mailbox *box);
+	/* mark the file corrupted */
+	void (*set_file_corrupted)(struct dbox_file *file);
+};
+
+struct dbox_storage {
+	struct mail_storage storage;
+	struct dbox_storage_vfuncs v;
+
+	struct fs *attachment_fs;
+	const char *attachment_dir;
+};
+
+#define DBOX_STORAGE(s)		container_of(s, struct dbox_storage, storage)
+
+void dbox_storage_get_list_settings(const struct mail_namespace *ns,
+				    struct mailbox_list_settings *set);
+int dbox_storage_create(struct mail_storage *storage,
+			struct mail_namespace *ns,
+			const char **error_r);
+void dbox_storage_destroy(struct mail_storage *storage);
+uint32_t dbox_get_uidvalidity_next(struct mailbox_list *list);
+void dbox_notify_changes(struct mailbox *box);
+int dbox_mailbox_check_existence(struct mailbox *box, time_t *path_ctime_r);
+int dbox_mailbox_open(struct mailbox *box, time_t path_ctime);
+int dbox_mailbox_create(struct mailbox *box,
+			const struct mailbox_update *update, bool directory);
+int dbox_mailbox_create_indexes(struct mailbox *box,
+				const struct mailbox_update *update);
+int dbox_verify_alt_storage(struct mailbox_list *list);
+bool dbox_header_have_flag(struct mailbox *box, uint32_t ext_id,
+			   unsigned int flags_offset, uint8_t flag);
+
+#endif