CVSUPD(8)

NAME
cvsupd - network distribution server for CVS repositories

SYNOPSIS
cvsupd [-efv] [-A addr] [-b base] [-c collPath] [-C maxClients] [-l log] [-p port] [-P range] [-s scanDir] [-Z comprLevel]

DESCRIPTION
cvsupd is the server program for the CVSup network distribution package. For information about the companion client program, see cvsup(1).

In normal usage, cvsupd should be started with the ‘-C maxClients’ option. Unless -f is specified, it runs as a background daemon, fielding connection requests from remote clients. For each connection, cvsupd forks a child process to serve the files requested by the client.

The following options are supported:

-A addr
    Specifies a local address (dotted quad or hostname) on which the server will accept connections. This may be useful on hosts which have multiple IP addresses.

-b base
    Uses base as the base directory for the configuration files. The default is /usr/local/etc/cvsup.

-c collPath
    Searches the specified directories for information about the collections being offered. collPath contains of one or more directory names, separated by colons. Non-absolute pathnames are interpreted relative to the base directory. The default search path is ‘sup’.

-C maxClients
    Limits the number of simultaneous clients to maxClients. Clients beyond the specified maximum are politely refused service.

    If this option is not specified, cvsupd serves one client in the foreground and then exits.

-e  Suppresses the redirection of the standard output and standard error when running as a daemon and logging to a syslog facility. Otherwise, these descriptors are redirected to /dev/null. This option is useful for capturing any panic messages which might be emitted in the rare event of a crash of the server. Such messages are very helpful for debugging, but there is no reliable way to send them to syslog. A recommended way to use the option is like this:
        cvsupd -e ... >>/var/tmp/cvsupd.out 2>&1
    assuming that the command line syntax of sh(1) is used.

-f  When -C maxClients is specified, causes cvsupd to stay in the foreground instead of becoming a background daemon.

-l log
    Directs log messages to log. If log is of the form @facility (e.g., ‘@local0’) then logging is done via syslog to the indicated facility. Otherwise, log is treated as the name of a log file. If the file already exists, new messages are appended to its end.

    For each client served, at least two messages are logged. The first message identifies the client by username and hostname. The last message reports the success or failure of the update and gives the total network I/O in Kbytes (1K = 1024). Additional messages may be emitted to report errors or other noteworthy conditions.

-p port
    Listens for connections on an alternate TCP port. The default port is 5999. When not in passive mode, the server also uses the next lower port to establish a second connection (called the data connection) back to the client.

-P range
    Sets the range of server TCP ports to be used for the data connection, when in passive mode. Range may be a single integer or a range given as ‘lo-hi’.

-s scanDir
    Enables mirror mode, and specifies the directory under which the scan files can be found. If it is not an absolute pathname, scanDir is interpreted relative to the base directory. See RUNNING A CVSup MIRROR SITE, below.

-v  Prints the version number and exits, without serving any clients.

-Z comprLevel
    Sets the compression level to comprLevel. The compression level must be between 0 and 9. A level of 0 means no compression, while 9 provides maximum compression. The default level is 1. Higher levels provide relatively little improvement, at a rather high cost in CPU cycles.

PREPARING A FILE COLLECTION REPOSITORY
The file collections which cvsupd makes available to clients are described by various configuration files. The configuration files reside under the directory base/collDir, where base is the directory specified by the -b base command line option, or /usr/local/etc/cvsup by default. collDir is any of the directories specified with the -c option, or ‘sup’ by default.

Each collection's configuration files are kept in a separate subdirectory of base/collDir, named after the collection itself. For example, the configuration for the ‘src-base’ collection would be found in base/collDir/src-base. Within the collection's subdirectory, there should be a releases file and a list file. The releases file contains one line per release. The first word of each line is the name of the release, e.g., ‘cvs’. That must be followed by the following phrases, in any order:

list=file
    Specifies the name of the list file, relative to the collection's subdirectory. The list file is described below.

prefix=directory
    Specifies where the files making up the collection are to be found. If directory is not an absolute pathname, it is interpreted relative to the base directory base. If there is no prefix clause, the prefix defaults to base.

keywordprefix=directory
    Specifies a “pseudo-prefix” which is used only for expanding the absolute pathnames for the ‘$Header$’ and ‘$Source$’ RCS keywords. The directory should normally be the absolute pathname of the CVS repository on the machine containing the master copy of the repository. The use of keywordprefix ensures that CVSup will expand the RCS keywords identically on all machines, even though the repositories may reside in different directories.

super=collection
    Specifies the immediate super-collection of the current collection. In large distributions, the collections are often organized in a hierarchical manner. At the top of the hierarchy is a collection containing all of the distributed files. At the next level are several sub-collections, each containing a subset of the files. Each sub-collection may in turn have further sub-collections, and so forth. The super keyword specifies the collection's parent in such a hierarchical arrangement.

    This keyword is optional. If it is omitted, cvsupd assumes nothing about the relationship between the current collection and the other available collections.

    Information from the super keywords is used for finding the appropriate scan files when the server is running as a mirror site. See RUNNING A CVSup MIRROR SITE.

nocheckrcs
    Disables the comparison of MD5 checksums for updated RCS files. Checksum mismatches for RCS files may not be meaningful, since a given logical RCS file can have many different textual renditions.

norcs
    Disables special processing for RCS files. They will be treated the same as other files.

norsync
    Disables the use of the rsync algorithm. Note: this keyword is deprecated in the releases file. Use norsync or rnorsync in the list file instead. (See below.)

Unrecognized phrases are accepted but ignored, for backward compatibility with the sup package. Note that even though cvsupd often serves only a single release, the releases file is still required.

The list file specifies the details of how to upgrade the client's version of the collection. Each line contains a single command. Blank lines are ignored, as are lines beginning with ‘#’. Any filenames specified are taken as relative to the prefix directory given in the releases file.

Many of the list file commands accept file name patterns as arguments. These are similar to the patterns accepted by sh(1), and may include the wild card constructs ‘*’, ‘’?, and ‘[...]’. With the exception of omitany patterns, any slash characters in file names must be matched explicitly by slash characters in the pattern. Leading periods in file names are not treated specially. For example, the pattern ‘*’ matches the filename ‘.profile’.

upgrade pattern ...
    All files and directories matching any of the given patterns will be included in the list of files to be upgraded. If a directory name is matched, it recursively includes all files and subdirectories within it.

always pattern ...
    This command is the same as upgrade, except that it overrides any omitany commands.

omitany pattern ...
    Files or directories matching any of the given patterns will be omitted from the upgrade. If a directory name is matched, then it and all files and subdirectories beneath it are omitted.

    The patterns for omitany are interpreted differently than other patterns. For normal patterns, a slash character in a pathname must be matched explicitly by a slash character in the pattern. For omitany patterns, slashes are treated the same as other characters. Thus the pattern ‘*.c’ will match any pathname ending in ‘.c’, including, for example, ‘foo/bar/lam.c’.

symlink pattern ...
    Symbolic links matching any of the given patterns will be upgraded as symbolic links, rather than as the files they refer to. Otherwise, symbolic links are followed and their target files are sent to the client.

rsymlink pattern ...
    This command is similar to symlink, but if a directory is matched, all symbolic links beneath it in the tree are treated as matched.

norsync pattern ...
    The rsync algorithm will not be used for updating files matching any of the given patterns. This is useful for log files, where CVSup's “append” optimization is more effective than the rsync algorithm.

rnorsync pattern ...
    This command is similar to norsync, but if a directory is matched, all files beneath it in the tree are treated as matched.

execute command (pattern ...)
    The given command will be executed by the client whenever a file matching one of the patterns is successfully updated. The command comprises all words up to the first ‘(’ character. Any occurrences of the string ‘%s’ are replaced by the pathname of the updated file on the client host. Occurrences of ‘%%’ are replaced by ‘%’. The command is executed by passing it to /bin/sh.

    There may be multiple patterns, separated by white space. They are interpreted relative to the prefix directory. Each pattern should be written to match the appropriate files as they exist on the server. For example, the ‘,v’ suffix of an RCS file name must be matched, even though that suffix will not be present on the client if checkout mode is in effect. Slashes in file names must be matched by explicit slashes in the pattern. CVS ‘Attic’ directories are implicitly included in the matching process, and should not be specified directly in the patterns. A matching file will be found whether it is in the Attic or not.

    If an execute statement matches a directory, its command is executed if the directory is created for the first time, or if its attributes are changed. The command is executed when ascending out of the directory, i.e., after its files and subdirectories have been processed.

    If multiple execute statements match a file, all of the associated commands are executed in sequence.

    For security reasons, the client may choose to ignore all execute statements.

Unrecognized commands are accepted but ignored, for backward compatibility with sup.

RUNNING A CVSup MIRROR SITE
A mirror is a server which obtains and updates its files from a master site by means of CVSup, and redistributes them via CVSup to other sites. Mirror sites are commonly used in large projects to spread the load among a number of servers. The files being distributed originate at a master site. Each mirror site updates its own copies of the files periodically from there. Clients in turn obtain their updates from any of the mirror sites.

cvsupd has a special mode of operation for mirror sites that dramatically increases its efficiency. This mode is enabled by the -s scanDir option on the command line. Without the -s option, cvsupd makes a full file tree traversal over the files in each requested collection, performing a stat(2) system call on every file. It does this for each client that connects to it, on the assumption that any of the files could change at any time. Such a traversal imposes a heavy seek load on the disks containing the files, and limits the number of clients that can be served simultaneously.

On a mirror site, the files in the collections are known to change only when new versions of them come in via CVSup. The -s option allows cvsupd to take advantage of this property to completely avoid the file tree traversals. This reduces the disk load on the server by orders of magnitude. In place of the file tree traversal, cvsupd gets the necessary information about the files in the collections by reading scan files. The scan files are created by the cvsup client when it updates the files on the mirror site from the originals at the master site. In CVSUP(1), these files are referred to as list files. Both names refer to the same files. Each time cvsupd serves a client, it finds the scan files created by the most recent update from the master site. Thus the server always has fully up-to-date information about the files in the collections, without the need to perform a file tree traversal.

The -s option is followed by a directory name which specifies where the scan files can be found. It is normally a subdirectory of the base directory, and it must match the location where the cvsup client maintains its list files. By default, cvsup locates these files under the sup subdirectory of the base directory. To match this, cvsupd should be run with ‘-s sup’. If cvsup's list file location is changed from the default using the -c option, then cvsupd's scan directory must be changed the same way. There is no default for the -s option. If it is not given explicitly on the command line, no scan files are used.

There does not need to be a scan file for every collection. cvsupd first looks for the scan file for the collection requested by the client. If that scan file does not exist, cvsupd tries the scan files for each successive super-collection, and uses the first one it finds. (See the description of the super keyword in PREPARING A FILE COLLECTION REPOSITORY for details.) If no suitable scan file is located, cvsupd falls back on performing a file tree traversal.

ACCESS CONTROL
Access to the server is unrestricted by default, but there is a reasonably flexible mechanism for limiting access based on the IP addresses of connecting clients. It is enabled by placing a set of rules into the access file base/cvsupd.access. The access file is a text file with one rule per line. Comments begin with ‘#’ and extend to the end of the line. White space is ignored except where it is needed to separate adjacent tokens. Blank lines are ignored.

Each rule consists of the following components:

•   A flag indicating whether the rule is a permit rule, an authenticate rule, or a deny rule. The flag is expressed as a single character: ‘+’ means permit, ‘*’ means authenticate, and ‘-’ means deny.

•   An IP address to compare with the client's IP address to determine whether the rule applies to the client. This may be expressed either as a numeric IP address or as a host name. Numeric addresses consist of 1 to 4 octet values, separated by dots. If fewer than 4 octets are specified, the trailing octets are assumed to contain 0.

    Host names are converted to numeric addresses when they are read. If a host has multiple addresses, a separate rule is added for each address. This may or may not have the desired effect.

    Host names should be used with caution. A name that is slow to resolve can bog down the server significantly.

•   A matching mask to be ANDed with the IP addresses of the rule and the client before comparing the addresses. This mask is specified as ‘/’ followed by an integer giving the number of high-order 1s in the mask. For example, ‘/24’ specifies a mask of 0xffffff00. The matching mask is optional; if omitted, it defaults to ‘/32’.

•   A counting mask that determines how the clients that match the rule are counted. (See below.) It is specified the same way as the matching mask. The counting mask is optional; if omitted, it defaults to the same value as the matching mask.

•   A limit specifying the maximum number of matching clients allowed at the same time. This is specified as a decimal integer, preceded by white space to separate it from the preceding component. The limit is optional. If omitted, it defaults to 0 for a deny rule, or to infinity for a permit rule.

When a client connects to the server, its IP address is checked against successive rules in sequence. Each rule is processed as follows:

1.  The IP address of the rule is compared with the IP address of the client, after ANDing each address with the matching mask. If the addresses do not match, the rule is ignored.

2.  The IP addresses of all other currently connected clients are compared with the IP address of the connecting client, after ANDing each address with the counting mask. If the number of matching clients (not counting the connecting client) is less than the limit, then the rule succeeds. Otherwise, the rule fails.

3.  If the rule is a permit rule and it succeeded, the client is allowed access, and the rest of the rules are ignored.

4.  If the rule is an authenticate rule and it succeeded, the server attempts to verify the client's identity using a challenge-response protocol (see AUTHENTICATION, below). Access is granted or denied based on the outcome of authentication. The rest of the rules are ignored.

5.  If the rule is a deny rule and it failed, the client is denied access, and the rest of the rules are ignored.

6.  Otherwise, processing continues with the next rule.

There is an implicit authenticate rule at the end of the list which matches any IP address. Thus, if the processing reaches the end of the list of rules without having allowed or denied access, access is controlled by the authentication mechanism.

Here are some examples illustrating how the rules are commonly used.

    -spam.cyberpromo.com
Deny all access from a specific host.

    +mirror.FreeBSD.org
Permit unlimited access from a specific host.

    -user.FreeBSD.org 1
Limit a specific host to at most 1 connection at a time.

    -198.211.214/24
Deny all access from hosts in a specific class C address block.

    -198.211.214/24 3
Allow at most 3 connections total from the hosts in a specific class C address block.

    -198.211.214/24/32 3
Allow at most 3 connections from each of the hosts in a specific class C address block.

Note the difference between the previous two examples. The first example imposes a per-network limit, while the second example imposes a per-host limit. The difference is in the counting mask. The 24 bit mask in the first example produces a single counter that is shared by all of the hosts in the specified address block. The 32 bit mask in this example produces a separate counter for each host.

    -0.0.0/0/24 1
Allow no more than 1 connection at a time from each block of 256 addresses.

    *0.0.0.0/0
For all clients, use authentication to decide whether access is allowed.

When updating the access file, it is not necessary to halt the server. But the file should be copied for editing, and then the new version should be moved atomically into place. There is no need to signal the server after updating the file. The server will notice that the file has been touched, and will rescan it automatically. In addition, the server rescans the file every 3 hours to keep up with DNS changes that might affect the resolved addresses of host names.

Syntax errors in individual rules are logged, and the offending rules are ignored. Host name lookup failures are also logged.

AUTHENTICATION
CVSup implements an authentication mechanism which can be used to control access to the server. It uses a challenge-response protocol which is immune to packet sniffing and replay attacks. No passwords are sent over the network in either direction. Both the client and the server can independently verify the identities of each other.

Authentication of the client is invoked by a successful authenticate rule in the base/cvsupd.access file, or by “falling off the end” of the file. If there is no cvsupd.access file, clients are not authenticated.

The file base/cvsupd.passwd holds the information used for performing authentication. This file contains a record for each client who is allowed access to the server. Each record occupies one line in the file. Lines beginning with ‘#’ are ignored, as are lines containing only white space. White space is significant everywhere else in the file. Fields are separated by ‘’: characters.

The first record of the file is special. It specifies the identity of the server itself. This server record has the form:

    serverName:privateKey

ServerName is the canonical name of the server, e.g., ‘CVSup.FreeBSD.ORG’. This name is sent to the client, which uses it to choose an appropriate client name and shared secret for authentication. The name is case-insensitive.

PrivateKey is any string of characters except ‘’:. When the server generates random challenges to send to the client, it uses privateKey to make the challenges harder to guess. Challenges are random and quite unpredictable in any case, so the privateKey isn't really very important. It can be left empty if desired, but the ‘’: that precedes it must be present.

All of the remaining records in the file correspond to individual clients. Each client record has the following form:

    clientName:sharedSecret:
    class:comment

All fields must be present even if some of them are empty. ClientName is the name of the client to which the record applies. By convention, e-mail addresses are used for all client names, e.g., ‘BillyJoe@FreeBSD.ORG’. Client names are case-insensitive.

SharedSecret is a secret string of characters known only to the client and the server. It is generated from a password chosen by the client, using the cvpasswd utility. The client proves its identity to the server (and vice versa) by demonstrating that it knows the sharedSecret. A client's access may be disabled by changing its sharedSecret field to ‘*’.

The shared secret is never sent across the network, nor can it be used to find out the client's password. However, given the shared secret, a modified version of cvsup could impersonate the client. Thus, care must be taken to ensure that the cvsupd.passwd file is readable only by the server.

Class is reserved for future use. It should be empty.

Comment contains any additional information about the client that might be useful to the server administrator. For example, it may contain the client's full name and other contact information.

When updating the cvsupd.passwd file, it is not necessary to halt the server. But the file should be copied for editing, and then the new version should be moved atomically into place. There is no need to signal the server after updating the file.

Syntax errors in individual records of the cvsupd.passwd file are logged, and the offending records are ignored.

HOW ACCESS CONTROL AND AUTHENTICATION INTERACT
Here is a summary of the interactions between the access control and authentication mechanisms. The key principle is that access control takes place first. The outcome of access control determines whether authentication is performed too.

1.  If there is no cvsupd.access file, then all clients are granted access. No authentication is done, even if cvsupd.passwd exists.

2.  If the cvsupd.access file exists but is empty, all clients are subjected to authentication. If cvsupd.passwd does not exist, nobody can access the server.

3.  If cvsupd.access exists and has some rules in it, but there is no cvsupd.passwd file, then successful authenticate rules cause access to be denied. Access is still granted to those who match successful permit rules. Falling off the end of the cvsupd.access file results in denial of access.

4.  If both the cvsupd.access and cvsupd.passwd files exist, then:
    •   Successful permit rules cause access to be granted without authentication.
    •   Successful authenticate rules cause authentication to be performed. Access is granted or denied based on the outcome of that. Falling off the end of the cvsupd.access file is included in this case.
    •   Failing deny rules cause access to be denied.

RCS KEYWORD EXPANSION
In checkout mode, CVSup expands RCS keywords as described in co(1). It expands all of the standard keywords, and also the non-standard ‘$CVSHeader$’ keyword. This expands the same as ‘$Header$’, except that the RCS file's pathname is expressed relative to the prefix directory, rather than as an absolute pathname. The prefix is assumed to be the root of the CVS repository.

It is also possible to define aliases for the standard RCS keywords, and to selectively enable or disable the recognition of individual keywords. These properties are controlled on a repository-wide basis by directives in a file named prefix/CVSROOT/options. Each directive occupies one line of the file. Comments begin with ‘#’ and extend to the end of line. Blank lines are ignored. The syntax is ridiculous, for historical reasons.

To define a keyword alias, use a line of the form:
    tag=alias[=keyword]
For example:
    tag=FreeBSD=CVSHeader
defines a new RCS keyword ‘$FreeBSD$’, which expands the same as ‘$CVSHeader$’. If the second ‘=’ and the keyword are omitted, the keyword defaults to ‘Id’.

To disable all but certain selected keywords, use a line of the form:
    tagexpand=ikeyword[,...]
For example:
    tagexpand=iFreeBSD,Id
disables the expansion of all keywords except ‘$FreeBSD$’ and ‘$Id$’. The leading ‘i’ stands for “include”.

To enable all but certain selected keywords, use a line of the form:
    tagexpand=ekeyword[,...]
For example:
    tagexpand=eFreeBSD,Id
enables the expansion of all keywords except ‘$FreeBSD$’ and ‘$Id$’. The leading ‘e’ stands for “exclude”.

SHUTDOWN
If there exists a file base/cvsupd.HALT that is newer than the time when the server was started, then the server will reject all new incoming connection requests. Clients which had already started will run to completion, but no new ones will be accepted. This mechanism is awkward and weak, and will probably be changed in a future release.

SECURITY
cvsupd does not create or write any files, except for its log file if one is specified on the command line. There is thus little risk that cvsupd can be subverted into damaging the system on which it is running. A more likely risk is that cvsupd might be spoofed into sending out files that are not intended to be publicly distributed. cvsupd is very careful to prevent this from happening. Nevertheless, for maximum protection it is a good idea to run cvsupd as a completely unprivileged user analogous to ‘nobody’, serving only files that are readable by everyone.

CVSup has no provision for encrypting the data sent across the network. If secrecy is desired then the connection can be tunneled through ssh.

FILES
/usr/local/etc/cvsup
    Default base directory.
sup Default collDir subdirectory.
base/collDir/collection
    /releases Releases file.
base/collDir/collection
    /list List file.
base/cvsupd.HALT
    Shutdown file.
base/cvsupd.access
    Access control file.
base/cvsupd.passwd
    Authentication password file.
prefix/CVSROOT/options
    RCS keyword configuration file.

SEE ALSO
co(1), cvpasswd(1), cvs(1), cvsup(1).

    http://www.cvsup.org/

AUTHORS
John Polstra <jdp@polstra.com>.

LEGALITIES
CVSup is a registered trademark of John D. Polstra.

BUGS
An RCS file is not recognized as such unless its name ends with ‘,v’.

Any directory named ‘Attic’ is assumed to be a CVS Attic, and is treated specially.