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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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NAME | SYNOPSIS | DESCRIPTION | TYPICAL USE OF GIT CREDENTIAL | INPUT/OUTPUT FORMAT | CAPABILITY INPUT/OUTPUT FORMAT | GIT | COLOPHON |
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GIT-CREDENTIAL(1) Git Manual GIT-CREDENTIAL(1)
git-credential - Retrieve and store user credentials
'git credential' (fill|approve|reject|capability)
Git has an internal interface for storing and retrieving
credentials from system-specific helpers, as well as prompting
the user for usernames and passwords. The git-credential command
exposes this interface to scripts which may want to retrieve,
store, or prompt for credentials in the same manner as Git. The
design of this scriptable interface models the internal C API;
see credential.h for more background on the concepts.
git-credential takes an "action" option on the command-line (one
of fill, approve, or reject) and reads a credential description
on stdin (see INPUT/OUTPUT FORMAT).
If the action is fill, git-credential will attempt to add
"username" and "password" attributes to the description by
reading config files, by contacting any configured credential
helpers, or by prompting the user. The username and password
attributes of the credential description are then printed to
stdout together with the attributes already provided.
If the action is approve, git-credential will send the
description to any configured credential helpers, which may store
the credential for later use.
If the action is reject, git-credential will send the description
to any configured credential helpers, which may erase any stored
credentials matching the description.
If the action is capability, git-credential will announce any
capabilities it supports to standard output.
If the action is approve or reject, no output should be emitted.
An application using git-credential will typically use git
credential following these steps:
1. Generate a credential description based on the context.
For example, if we want a password for
https://example.com/foo.git , we might generate the following
credential description (don’t forget the blank line at the
end; it tells git credential that the application finished
feeding all the information it has):
protocol=https
host=example.com
path=foo.git
2. Ask git-credential to give us a username and password for
this description. This is done by running git credential
fill, feeding the description from step (1) to its standard
input. The complete credential description (including the
credential per se, i.e. the login and password) will be
produced on standard output, like:
protocol=https
host=example.com
username=bob
password=secr3t
In most cases, this means the attributes given in the input
will be repeated in the output, but Git may also modify the
credential description, for example by removing the path
attribute when the protocol is HTTP(s) and
credential.useHttpPath is false.
If the git credential knew about the password, this step may
not have involved the user actually typing this password (the
user may have typed a password to unlock the keychain
instead, or no user interaction was done if the keychain was
already unlocked) before it returned password=secr3t.
3. Use the credential (e.g., access the URL with the username
and password from step (2)), and see if it’s accepted.
4. Report on the success or failure of the password. If the
credential allowed the operation to complete successfully,
then it can be marked with an "approve" action to tell git
credential to reuse it in its next invocation. If the
credential was rejected during the operation, use the
"reject" action so that git credential will ask for a new
password in its next invocation. In either case, git
credential should be fed with the credential description
obtained from step (2) (which also contains the fields
provided in step (1)).
git credential reads and/or writes (depending on the action used)
credential information in its standard input/output. This
information can correspond either to keys for which git
credential will obtain the login information (e.g. host,
protocol, path), or to the actual credential data to be obtained
(username/password).
The credential is split into a set of named attributes, with one
attribute per line. Each attribute is specified by a key-value
pair, separated by an = (equals) sign, followed by a newline.
The key may contain any bytes except =, newline, or NUL. The
value may contain any bytes except newline or NUL. A line,
including the trailing newline, may not exceed 65535 bytes in
order to allow implementations to parse efficiently.
Attributes with keys that end with C-style array brackets [] can
have multiple values. Each instance of a multi-valued attribute
forms an ordered list of values - the order of the repeated
attributes defines the order of the values. An empty multi-valued
attribute (key[]=\n) acts to clear any previous entries and reset
the list.
In all cases, all bytes are treated as-is (i.e., there is no
quoting, and one cannot transmit a value with newline or NUL in
it). The list of attributes is terminated by a blank line or
end-of-file.
Git understands the following attributes:
protocol
The protocol over which the credential will be used (e.g.,
https).
host
The remote hostname for a network credential. This includes
the port number if one was specified (e.g.,
"example.com:8088").
path
The path with which the credential will be used. E.g., for
accessing a remote https repository, this will be the
repository’s path on the server.
username
The credential’s username, if we already have one (e.g., from
a URL, the configuration, the user, or from a previously run
helper).
password
The credential’s password, if we are asking it to be stored.
password_expiry_utc
Generated passwords such as an OAuth access token may have an
expiry date. When reading credentials from helpers, git
credential fill ignores expired passwords. Represented as
Unix time UTC, seconds since 1970.
oauth_refresh_token
An OAuth refresh token may accompany a password that is an
OAuth access token. Helpers must treat this attribute as
confidential like the password attribute. Git itself has no
special behaviour for this attribute.
url
When this special attribute is read by git credential, the
value is parsed as a URL and treated as if its constituent
parts were read (e.g., url=https://example.com would behave
as if protocol=https and host=example.com had been provided).
This can help callers avoid parsing URLs themselves.
Note that specifying a protocol is mandatory and if the URL
doesn’t specify a hostname (e.g., "cert:///path/to/file") the
credential will contain a hostname attribute whose value is
an empty string.
Components which are missing from the URL (e.g., there is no
username in the example above) will be left unset.
authtype
This indicates that the authentication scheme in question
should be used. Common values for HTTP and HTTPS include
basic, bearer, and digest, although the latter is insecure
and should not be used. If credential is used, this may be
set to an arbitrary string suitable for the protocol in
question (usually HTTP).
This value should not be sent unless the appropriate
capability (see below) is provided on input.
credential
The pre-encoded credential, suitable for the protocol in
question (usually HTTP). If this key is sent, authtype is
mandatory, and username and password are not used. For HTTP,
Git concatenates the authtype value and this value with a
single space to determine the Authorization header.
This value should not be sent unless the appropriate
capability (see below) is provided on input.
ephemeral
This boolean value indicates, if true, that the value in the
credential field should not be saved by the credential helper
because its usefulness is limited in time. For example, an
HTTP Digest credential value is computed using a nonce and
reusing it will not result in successful authentication. This
may also be used for situations with short duration (e.g.,
24-hour) credentials. The default value is false.
The credential helper will still be invoked with store or
erase so that it can determine whether the operation was
successful.
This value should not be sent unless the appropriate
capability (see below) is provided on input.
state[]
This value provides an opaque state that will be passed back
to this helper if it is called again. Each different
credential helper may specify this once. The value should
include a prefix unique to the credential helper and should
ignore values that don’t match its prefix.
This value should not be sent unless the appropriate
capability (see below) is provided on input.
continue
This is a boolean value, which, if enabled, indicates that
this authentication is a non-final part of a multistage
authentication step. This is common in protocols such as NTLM
and Kerberos, where two rounds of client authentication are
required, and setting this flag allows the credential helper
to implement the multistage authentication step. This flag
should only be sent if a further stage is required; that is,
if another round of authentication is expected.
This value should not be sent unless the appropriate
capability (see below) is provided on input. This attribute
is one-way from a credential helper to pass information to
Git (or other programs invoking git credential).
wwwauth[]
When an HTTP response is received by Git that includes one or
more WWW-Authenticate authentication headers, these will be
passed by Git to credential helpers.
Each WWW-Authenticate header value is passed as a
multi-valued attribute wwwauth[], where the order of the
attributes is the same as they appear in the HTTP response.
This attribute is one-way from Git to pass additional
information to credential helpers.
capability[]
This signals that Git, or the helper, as appropriate,
supports the capability in question. This can be used to
provide better, more specific data as part of the protocol. A
capability[] directive must precede any value depending on it
and these directives should be the first item announced in
the protocol.
There are two currently supported capabilities. The first is
authtype, which indicates that the authtype, credential, and
ephemeral values are understood. The second is state, which
indicates that the state[] and continue values are
understood.
It is not obligatory to use the additional features just
because the capability is supported, but they should not be
provided without the capability.
Unrecognised attributes and capabilities are silently discarded.
For git credential capability, the format is slightly different.
First, a version 0 announcement is made to indicate the current
version of the protocol, and then each capability is announced
with a line like capability authtype. Credential helpers may also
implement this format, again with the capability argument.
Additional lines may be added in the future; callers should
ignore lines which they don’t understand.
Because this is a new part of the credential helper protocol,
older versions of Git, as well as some credential helpers, may
not support it. If a non-zero exit status is received, or if the
first line doesn’t start with the word version and a space,
callers should assume that no capabilities are supported.
The intention of this format is to differentiate it from the
credential output in an unambiguous way. It is possible to use
very simple credential helpers (e.g., inline shell scripts) which
always produce identical output. Using a distinct format allows
users to continue to use this syntax without having to worry
about correctly implementing capability advertisements or
accidentally confusing callers querying for capabilities.
Part of the git(1) suite
This page is part of the git (Git distributed version control
system) project. Information about the project can be found at
⟨http://git-scm.com/⟩. If you have a bug report for this manual
page, see ⟨http://git-scm.com/community⟩. This page was obtained
from the project's upstream Git repository
⟨https://github.com/git/git.git⟩ on 2024-06-14. (At that time,
the date of the most recent commit that was found in the
repository was 2024-06-12.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
Git 2.45.2.492.gd63586 2024-06-12 GIT-CREDENTIAL(1)
Pages that refer to this page: git(1), git-config(1), git-send-email(1), gitcredentials(7)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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