--- name: "cvsupd" section: "8" platform: "linux" package: "cvsupd" version: "16.1e-3" release: "Debian 3.0 (Woody)" platforms: ["linux"] url: "https://new.carta.tech/cvsupd" --- # cvsupd(8) network distribution server for CVS repositories ## NAME **cvsupd** – network distribution server for CVS repositories ## SYNOPSIS **cvsupd** \[**-ev**\] \[**-A** *addr*\] \[**-b** *base*\] \[**-c** *collPath*\] \[**-C** *maxClients*\] \[**-l** *log*\] \[**-p** *port*\] \[**-P** *range*\] \[**-s** *scanDir*\] \[**-Z** *comprLevel*\] ## DESCRIPTION **cvsupd** is the server program for the **CVSup** network distribution package. For information about the companion client program, see [cvsup(1)](/cvsup/1.md). In normal usage, **cvsupd** should be started with the ‘**-C** *maxClients*’ option. 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 */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)](/sh/1.md) is used. - **-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 */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)](/sh/1.md), 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 *pattern*s 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)](/stat/2.md) 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: ``` 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)](/co/1.md). 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** takes pains to prevent this from happening. Nevertheless, for maximum protection **cvsupd** should be run as a completely unprivileged user analogous to ‘nobody’, and should serve 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 - */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)](/co/1.md), [cvpasswd(1)](/cvpasswd/1.md), [cvs(1)](/cvs/1.md), [cvsup(1)](/cvsup/1.md). ``` http://www.polstra.com/projects/freeware/CVSup/ ``` ## AUTHORS John Polstra ⟨jdp@polstra.com⟩. ## 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.