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diff --git a/interimap.md b/interimap.md deleted file mode 100644 index 387850a..0000000 --- a/interimap.md +++ /dev/null @@ -1,526 +0,0 @@ -% interimap(1) -% [Guilhem Moulin](mailto:guilhem@fripost.org) -% July 2015 - -Name -==== - -InterIMAP - Fast bidirectional synchronization for QRESYNC-capable IMAP servers - -Synopsis -======== - -`interimap` [*OPTION* ...] [*COMMAND*] [*MAILBOX* ...] - -Description -=========== - -`interimap` performs stateful synchronization between two IMAP4rev1 -servers. -Such synchronization is made possible by the [`QRESYNC` IMAP -extension][RFC 7162]; for convenience reasons servers must also support -the [`LIST-EXTENDED`][RFC 5258], [`LIST-STATUS`][RFC 5819] (or -[`NOTIFY`][RFC 5465]) and [`UIDPLUS`][RFC 4315] IMAP extensions. -See also the **[supported extensions](#supported-extensions)** section -below. - -Stateful synchronization is only possible for mailboxes supporting -persistent message Unique Identifiers (UID) and persistent storage of -mod-sequences (MODSEQ); any non-compliant mailbox will cause `interimap` -to abort. -Furthermore, because UIDs are allocated not by the client but by the -server, `interimap` needs to keep track of associations between local -and remote UIDs for each mailbox. -The synchronization state of a mailbox consists of its `UIDNEXT` and -`HIGHESTMODSEQ` values on each server; it is then assumed that each -message with UID smaller than `UIDNEXT` have been replicated to the -other server, and that the metadata (such as flags) of each message with -MODSEQ at most `HIGHESTMODSEQ` have been synchronized. -Conceptually, the synchronization algorithm is derived from [RFC 4549] -with the [RFC 7162] (sec. 6) amendments, and works as follows: - - 1. `SELECT` (on both servers) a mailbox the current `UIDNEXT` or `HIGHESTMODSEQ` - values of which differ from the values found in the database (for - either server). Use the `QRESYNC` `SELECT` parameter from [RFC - 7162] to list changes (vanished messages and flag updates) since - `HIGHESTMODSEQ` to messages with UID smaller than `UIDNEXT`. - - 2. Propagate these changes onto the other server: get the corresponding - UIDs from the database, then: - a. issue a `UID STORE` command, followed by `UID EXPUNGE`, to - remove messages that have not already been deleted on both - servers; and - b. issue some `UID STORE` commands to propagate flag updates (send - a single command for each flag list in order the reduce the - number of round trips). - - (Conflicts may occur if the metadata of a message has been updated - on both servers with different flag lists; in that case, `interimap` - issues a warning and updates the message on each server with the - union of both flag lists.) - Repeat this step if the server sent some updates in the meantime. - Otherwise, update the `HIGHESTMODSEQ` value in the database. - - 3. Process new messages (if the current `UIDNEXT` value of the mailbox - differs from the one found in the database) by issuing a `UID FETCH` - command; process each received message on-the-fly by issuing an - `APPEND` command with the message's `RFC822` body, `FLAGS` and - `INTERNALDATE`. - Repeat this step if the server received new messages in the - meantime. Otherwise, update the `UIDNEXT` value in the database. - Go back to step 2 if the server sent some metadata (such as flag) - updates in the meantime. - - 4. Go back to step 1 to proceed with the next unsynchronized mailbox. - -Commands -======== - -By default, `interimap` synchronizes each mailbox listed by the `LIST "" -"*"` IMAP command; -the *list-mailbox*, *list-select-opts* and *ignore-mailbox* options from -the [configuration file](#configuration-file) can be used to shrink that -list and save bandwidth. -However if some extra argument are provided on the command line, -`interimap` ignores these options and synchronizes the given -*MAILBOX*es instead. Note that each *MAILBOX* is taken “as is”; in -particular, it must be [UTF-7 encoded][RFC 2152], unquoted, and the list -wildcards ‘\*’ and ‘%’ are passed verbatim to the IMAP server. - -If the synchronization was interrupted during a previous run while some -messages were being replicated (but before the `UIDNEXT` or -`HIGHESTMODSEQ` values have been updated), `interimap` performs a “full -synchronization” on theses messages: downloading the whole UID and flag -lists on each servers allows `interimap` to detect messages that have -been removed or for which their flags have changed in the meantime. -Finally, after propagating the offline changes for these messages, -`interimap` resumes the synchronization for the rest of the mailbox. - -Specifying one of the commands below makes `interimap` perform an action -other than the default [`QRESYNC`][RFC 7162]-based synchronization. - -`--repair` [*MAILBOX* ...] - -: List the database anomalies and try to repair them. (Consider only - the given *MAILBOX*es if non-optional arguments are provided.) - This is done by performing a so-called “full synchronization”, - namely: - 1/ download all UIDs along with their flag list both from the - local and remote servers; - 2/ ensure that each entry in the database corresponds to an - existing UID; and - 3/ ensure that both flag lists match. - Any message found on a server but not in the database is replicated - on the other server (which in the worst case, might yield a message - duplicate). - Flag conflicts are solved by updating each message to the union of - both lists. - -`--delete` *MAILBOX* [*MAILBOX* ...] - -: Delete the given *MAILBOX*es on each target (by default each server - plus the database, unless `--target` specifies otherwise) where it - exists. - Note that per the [IMAP4rev1 standard][RFC 3501] deletion is not - recursive. Thus *MAILBOX*'s children are not deleted. - -`--rename` *SOURCE* *DEST* - -: Rename the mailbox *SOURCE* to *DEST* on each target (by default - each server plus the database, unless `--target` specifies - otherwise) where it exists. - `interimap` aborts if *DEST* already exists on either target. - Note that per the [IMAP4rev1 standard][RFC 3501] renaming is - recursive. Thus *SOURCE*'s children are moved to become *DEST*'s - children instead. - -Options -======= - -`--config=`*FILE* - -: Specify an alternate [configuration file](#configuration-file). - Relative paths start from *$XDG_CONFIG_HOME/interimap*, or *~/.config/interimap* - if the `XDG_CONFIG_HOME` environment variable is unset. - -`--target={local,remote,database}` - -: Limit the scope of a `--delete` or `--rename` command to the given - target. Can be repeated to act on multiple targets. By default all - three targets are considered. - -`--watch`[`=`*seconds*] - -: Don't exit after a successful synchronization. Instead, keep - synchronizing forever. Sleep for the given number of *seconds* (by - default 1 minute if `--notify` is unset, and 15 minutes if - `--notify` is set) between two synchronizations. Setting this - options enables `SO_KEEPALIVE` on the socket for *type*s other than - `tunnel`. - -`--notify` - -: Whether to use the [IMAP `NOTIFY` extension][RFC 5465] to instruct - the server to automatically send updates to the client. (Both local - and remote servers must support [RFC 5465] for this to work.) - This greatly reduces IMAP traffic since `interimap` can rely on - server notifications instead of manually polling for updates. - If the connection remains idle for 15 minutes (configurable with - `--watch`), then `interimap` sends a `NOOP` command to avoid being - logged out for inactivity. - -`-q`, `--quiet` - -: Try to be quiet. - -`--debug` - -: Turn on debug mode. Debug messages are written to the given *logfile*. - Note that this include all IMAP traffic (except literals). - Depending on the chosen authentication mechanism, this might include - authentication credentials. - -`-h`, `--help` - -: Output a brief help and exit. - -`--version` - -: Show the version number and exit. - -Configuration file -================== - -Unless told otherwise by the `--config=FILE` command-line option, -`interimap` reads its configuration from *$XDG_CONFIG_HOME/interimap/config* -(or *~/.config/interimap/config* if the `XDG_CONFIG_HOME` environment -variable is unset) as an [INI file]. -The syntax of the configuration file is a series of `OPTION=VALUE` -lines organized under some `[SECTION]`; lines starting with a ‘#’ or -‘;’ character are ignored as comments. -The `[local]` and `[remote]` sections define the two IMAP servers to -synchronize. -Valid options are: - -*database* - -: SQLite version 3 database file to use to keep track of associations - between local and remote UIDs, as well as the `UIDVALIDITY`, - `UIDNEXT` and `HIGHESTMODSEQ` of each known mailbox on both servers. - Relative paths start from *$XDG_DATA_HOME/interimap*, or - *~/.local/share/interimap* if the `XDG_DATA_HOME` environment - variable is unset. This option is only available in the default - section. - (Default: `HOST.db`, where *HOST* is taken from the `[remote]` or - `[local]` sections, in that order.) - -*list-reference* - -: An optional “reference name” to use for the initial `LIST` command, - indicating the context in which the *MAILBOX*es are interpreted. - For instance, by specifying `list-reference=perso/` in the `[local]` - section, *MAILBOX* names are interpreted relative to `perso/` on the - local server; in other words the remote mailbox hierarchy is mapped - to the `perso/` sub-hierarchy on the local server. This is useful - for synchronizing multiple remote servers against different - namespaces belonging to the same local IMAP server (using a - different `interimap` instance for each local namespace ↔ remote - synchronization). - - (Note that if the reference name is not a level of mailbox hierarchy - and/or does not end with the hierarchy delimiter, by [RFC 3501] its - interpretation by the IMAP server is implementation-dependent.) - -*list-mailbox* - -: A space separated list of mailbox patterns to use when issuing the - initial `LIST` command (overridden by the *MAILBOX*es given as - command-line arguments). - Names containing special characters such as spaces or brackets need - to be enclosed in double quotes. Within double quotes C-style - backslash escape sequences can be used (‘\\t’ for an horizontal tab, - ‘\\n’ for a new line, ‘\\\\’ for a backslash, etc.), as well as - hexadecimal escape sequences ‘\\xHH’. - Furthermore, non-ASCII names must be [UTF-7 encoded][RFC 2152]. - Two wildcards are available, and passed verbatim to the IMAP server: - a ‘\*’ character matches zero or more characters, while a ‘%’ - character matches zero or more characters up to the hierarchy - delimiter. - This option is only available in the default section. - (The default pattern, `*`, matches all visible mailboxes on the - server.) - -*list-select-opts* - -: An optional space separated list of selectors for the initial `LIST` - command. (Requires a server supporting the [`LIST-EXTENDED` IMAP - extension][RFC 5258].) Useful values are `SUBSCRIBED` (to list only - subscribed mailboxes), `REMOTE` (to also list remote mailboxes on a - server supporting mailbox referrals), and `RECURSIVEMATCH` (to - list parent mailboxes with children matching one of the above - *list-mailbox* patterns). This option is only available in the - default section. - -*ignore-mailbox* - -: An optional Perl Compatible Regular Expressions ([PCRE]) covering - mailboxes to exclude: any ([UTF-7 encoded][RFC 2152] and unquoted) - mailbox listed in the initial `LIST` responses is ignored if it - matches the given expression. - Note that the *MAILBOX*es given as command-line arguments bypass the - check and are always considered for synchronization. This option is - only available in the default section. - -*logfile* - -: A file name to use to log debug and informational messages. (By - default these messages are written to the error output.) This - option is only available in the default section. - -*type* - -: One of `imap`, `imaps` or `tunnel`. - `type=imap` and `type=imaps` are respectively used for IMAP and IMAP - over SSL/TLS connections over an INET socket. - `type=tunnel` causes `interimap` to create an unnamed pair of - connected sockets for interprocess communication with a *command* - instead of opening a network socket. - Note that specifying `type=tunnel` in the `[remote]` section makes - the default *database* to be `localhost.db`. - (Default: `imaps`.) - -*host* - -: Server hostname, for `type=imap` and `type=imaps`. - (Default: `localhost`.) - -*port* - -: Server port. - (Default: `143` for `type=imap`, `993` for `type=imaps`.) - -*proxy* - -: An optional SOCKS proxy to use for TCP connections to the IMAP - server (`type=imap` and `type=imaps` only), formatted as - `PROTOCOL://[USER:PASSWORD@]PROXYHOST[:PROXYPORT]`. - If `PROXYPORT` is omitted, it is assumed at port 1080. - Only [SOCKSv5][RFC 1928] is supported (with optional - [username/password authentication][RFC 1929]), in two flavors: - `socks5://` to resolve *hostname* locally, and `socks5h://` to let - the proxy resolve *hostname*. - -*command* - -: Command to use for `type=tunnel`. Must speak the [IMAP4rev1 - protocol][RFC 3501] on its standard output, and understand it on its - standard input. The value is passed to `` `/bin/sh -c` `` if it - contains shell metacharacters; otherwise it is split into words and - the resulting list is passed to `execvp`(3). - -*STARTTLS* - -: Whether to use the [`STARTTLS`][RFC 2595] directive to upgrade to a - secure connection. Setting this to `YES` for a server not - advertising the `STARTTLS` capability causes `interimap` to - immediately abort the connection. - (Ignored for *type*s other than `imap`. Default: `YES`.) - -*auth* - -: Space-separated list of preferred authentication mechanisms. - `interimap` uses the first mechanism in that list that is also - advertised (prefixed with `AUTH=`) in the server's capability list. - Supported authentication mechanisms are `PLAIN` and `LOGIN`. - (Default: `PLAIN LOGIN`.) - -*username*, *password* - -: Username and password to authenticate with. Can be required for non - pre-authenticated connections, depending on the chosen - authentication mechanism. - -*compress* - -: Whether to use the [`IMAP COMPRESS` extension][RFC 4978] for servers - advertising it. - (Default: `NO` for the `[local]` section, `YES` for the `[remote]` - section.) - -*null-stderr* - -: Whether to redirect *command*'s standard error to `/dev/null` for - `type=tunnel`. (Default: `NO`.) - -*SSL_protocols* - -: A space-separated list of SSL protocols to enable or disable (if - prefixed with an exclamation mark `!`. Known protocols are `SSLv2`, - `SSLv3`, `TLSv1`, `TLSv1.1`, `TLSv1.2`, and `TLSv1.3`. Enabling a - protocol is a short-hand for disabling all other protocols. - (Default: `!SSLv2 !SSLv3 !TLSv1 !TLSv1.1`, i.e., only enable TLSv1.2 - and above.) - -*SSL_cipher_list* - -: The cipher list to send to the server. Although the server - determines which cipher suite is used, it should take the first - supported cipher in the list sent by the client. See - [`ciphers`(1ssl)] for more information. - -*SSL_fingerprint* - -: Fingerprint of the server certificate's Subject Public Key Info, in - the form `[ALGO$]DIGEST_HEX` where `ALGO` is the used algorithm (by - default `sha256`). - Attempting to connect to a server with a non-matching certificate - SPKI fingerprint causes `interimap` to abort the connection during - the SSL/TLS handshake. - The following command can be used to compute the SHA-256 digest of a - certificate's Subject Public Key Info: - - openssl x509 -in /path/to/server/certificate.pem -pubkey \ - | openssl pkey -pubin -outform DER \ - | openssl dgst -sha256 - -*SSL_verify* - -: Whether to verify the server certificate chain. - Note that using *SSL_fingerprint* to specify the fingerprint of the - server certificate is an orthogonal authentication measure as it - ignores the CA chain. - (Default: `YES`.) - -*SSL_CApath* - -: Directory to use for server certificate verification if - `SSL_verify=YES`. - This directory must be in “hash format”, see [`verify`(1ssl)] for - more information. - -*SSL_CAfile* - -: File containing trusted certificates to use during server - certificate authentication if `SSL_verify=YES`. - -Supported extensions -==================== - -`interimap` takes advantage of servers supporting the following -extensions to the [IMAP4rev1 protocol][RFC 3501] (those marked as -“recommended” give the most significant performance gain): - - * `LITERAL+` ([RFC 2088], recommended); - * `MULTIAPPEND` ([RFC 3502], recommended); - * `COMPRESS=DEFLATE` ([RFC 4978], recommended); - * `NOTIFY` ([RFC 5465], recommended); - * `SASL-IR` ([RFC 4959]); and - * `UNSELECT` ([RFC 3691]). - -Known bugs and limitations -========================== - - * Using `interimap` on two identical servers with a non-existent or - empty *database* will duplicate each message due to the absence of - local ↔ remote UID association. Hence one needs to manually empty - the mail store on one end when migrating to `interimap` from another - synchronisation solution. - - * `interimap` is single threaded and doesn't use IMAP command - pipelining. Synchronization could be boosted up by sending - independent commands (such as the initial `LIST` and `STATUS` - commands) to both servers in parallel, and for a given server, by - sending independent commands (such as flag updates) in a pipeline. - - * Because the [IMAP protocol][RFC 3501] doesn't have a specific - response code for when a message is moved to another mailbox (either - using the `MOVE` command from [RFC 6851], or via `COPY` + `STORE` + - `EXPUNGE`), moving a message causes `interimap` to believe that it - was deleted while another one (which is replicated again) was added - to the other mailbox in the meantime. - - * `PLAIN` and `LOGIN` are the only authentication mechanisms currently - supported. - - * `interimap` will probably not work with non [RFC][RFC 3501]-compliant - servers. In particular, no work-around is currently implemented - beside the tunables in the [configuration file](#configuration-file). - Moreover, few IMAP servers have been tested so far. - -Standards -========= - - * M. Leech, M. Ganis, Y. Lee, R. Kuris, D. Koblas and L. Jones, - _SOCKS Protocol Version 5_, - [RFC 1928], March 1996. - * M. Leech, _Username/Password Authentication for SOCKS V5_, - [RFC 1929], March 1996. - * J. Myers, _IMAP4 non-synchronizing literals_, - [RFC 2088], January 1997. - * D. Goldsmith and M. Davis, - _A Mail-Safe Transformation Format of Unicode_, - [RFC 2152], May 1997. - * C. Newman, _Using TLS with IMAP, POP3 and ACAP_, - [RFC 2595], June 1999. - * M. Crispin, _Internet Message Access Protocol - Version 4rev1_, - [RFC 3501], March 2003. - * M. Crispin, - _Internet Message Access Protocol (IMAP) - `MULTIAPPEND` Extension_, - [RFC 3502], March 2003. - * A. Melnikov, - _Internet Message Access Protocol (IMAP) `UNSELECT` command_, - [RFC 3691], February 2004. - * M. Crispin, - _Internet Message Access Protocol (IMAP) - `UIDPLUS` extension_, - [RFC 4315], December 2005. - * A. Melnikov, - _Synchronization Operations for Disconnected IMAP4 Clients_, - [RFC 4549], June 2006. - * A. Gulbrandsen, _The IMAP `COMPRESS` Extension_, - [RFC 4978], August 2007. - * R. Siemborski and A. Gulbrandsen, _IMAP Extension for Simple - Authentication and Security Layer (SASL) Initial Client Response_, - [RFC 4959], September 2007. - * A. Gulbrandsen and A. Melnikov, - _The IMAP `ENABLE` Extension_, - [RFC 5161], March 2008. - * B. Leiba and A. Melnikov, - _Internet Message Access Protocol version 4 - `LIST` Command Extensions_, - [RFC 5258], June 2008. - * A. Gulbrandsen, C. King and A. Melnikov, - _The IMAP `NOTIFY` Extension_, - [RFC 5465], February 2009. - * A. Melnikov and T. Sirainen, - _IMAP4 Extension for Returning `STATUS` Information in Extended LIST_, - [RFC 5819], March 2010. - * A. Gulbrandsen and N. Freed, - _Internet Message Access Protocol (IMAP) - `MOVE` Extension_, - [RFC 6851], January 2013. - * A. Melnikov and D. Cridland, - _IMAP Extensions: Quick Flag Changes Resynchronization (`CONDSTORE`) - and Quick Mailbox Resynchronization (`QRESYNC`)_, - [RFC 7162], May 2014. - -[RFC 7162]: https://tools.ietf.org/html/rfc7162 -[RFC 5258]: https://tools.ietf.org/html/rfc5258 -[RFC 5819]: https://tools.ietf.org/html/rfc5819 -[RFC 4315]: https://tools.ietf.org/html/rfc4315 -[RFC 4549]: https://tools.ietf.org/html/rfc4549 -[RFC 2152]: https://tools.ietf.org/html/rfc2152 -[RFC 3501]: https://tools.ietf.org/html/rfc3501 -[RFC 1928]: https://tools.ietf.org/html/rfc1928 -[RFC 1929]: https://tools.ietf.org/html/rfc1929 -[RFC 2595]: https://tools.ietf.org/html/rfc2595 -[RFC 4978]: https://tools.ietf.org/html/rfc4978 -[RFC 2088]: https://tools.ietf.org/html/rfc2088 -[RFC 3502]: https://tools.ietf.org/html/rfc3502 -[RFC 4959]: https://tools.ietf.org/html/rfc4959 -[RFC 3691]: https://tools.ietf.org/html/rfc3691 -[RFC 6851]: https://tools.ietf.org/html/rfc6851 -[RFC 5161]: https://tools.ietf.org/html/rfc5161 -[RFC 5465]: https://tools.ietf.org/html/rfc5465 - -[INI file]: https://en.wikipedia.org/wiki/INI_file -[PCRE]: https://en.wikipedia.org/wiki/Perl_Compatible_Regular_Expressions -[`ciphers`(1ssl)]: https://www.openssl.org/docs/manmaster/apps/ciphers.html -[`verify`(1ssl)]: https://www.openssl.org/docs/manmaster/apps/verify.html |