2012-06-24 13:39:59 +02:00
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git-credential(1)
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=================
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NAME
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----
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2012-08-08 09:58:27 +02:00
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git-credential - Retrieve and store user credentials
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2012-06-24 13:39:59 +02:00
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SYNOPSIS
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--------
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------------------
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2024-04-17 02:02:40 +02:00
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'git credential' (fill|approve|reject|capability)
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2012-06-24 13:39:59 +02:00
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------------------
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DESCRIPTION
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-----------
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Git has an internal interface for storing and retrieving credentials
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from system-specific helpers, as well as prompting the user for
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usernames and passwords. The git-credential command exposes this
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interface to scripts which may want to retrieve, store, or prompt for
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2013-01-21 20:17:53 +01:00
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credentials in the same manner as Git. The design of this scriptable
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2019-11-17 22:04:53 +01:00
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interface models the internal C API; see credential.h for more
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2012-06-24 13:39:59 +02:00
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background on the concepts.
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git-credential takes an "action" option on the command-line (one of
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`fill`, `approve`, or `reject`) and reads a credential description
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on stdin (see <<IOFMT,INPUT/OUTPUT FORMAT>>).
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If the action is `fill`, git-credential will attempt to add "username"
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and "password" attributes to the description by reading config files,
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by contacting any configured credential helpers, or by prompting the
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user. The username and password attributes of the credential
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description are then printed to stdout together with the attributes
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already provided.
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If the action is `approve`, git-credential will send the description
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to any configured credential helpers, which may store the credential
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for later use.
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If the action is `reject`, git-credential will send the description to
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any configured credential helpers, which may erase any stored
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2023-06-15 21:19:33 +02:00
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credentials matching the description.
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2012-06-24 13:39:59 +02:00
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2024-04-17 02:02:40 +02:00
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If the action is `capability`, git-credential will announce any capabilities
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it supports to standard output.
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2012-06-24 13:39:59 +02:00
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If the action is `approve` or `reject`, no output should be emitted.
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TYPICAL USE OF GIT CREDENTIAL
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-----------------------------
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An application using git-credential will typically use `git
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credential` following these steps:
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1. Generate a credential description based on the context.
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For example, if we want a password for
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`https://example.com/foo.git`, we might generate the following
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credential description (don't forget the blank line at the end; it
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tells `git credential` that the application finished feeding all the
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2013-04-12 00:36:10 +02:00
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information it has):
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2012-06-24 13:39:59 +02:00
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protocol=https
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host=example.com
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path=foo.git
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2. Ask git-credential to give us a username and password for this
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description. This is done by running `git credential fill`,
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2012-06-24 13:40:00 +02:00
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feeding the description from step (1) to its standard input. The complete
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credential description (including the credential per se, i.e. the
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login and password) will be produced on standard output, like:
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2012-06-24 13:39:59 +02:00
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2012-06-24 13:40:00 +02:00
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protocol=https
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host=example.com
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2012-06-24 13:39:59 +02:00
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username=bob
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password=secr3t
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2012-06-24 13:40:00 +02:00
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In most cases, this means the attributes given in the input will be
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2013-01-21 20:17:53 +01:00
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repeated in the output, but Git may also modify the credential
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2012-06-24 13:40:00 +02:00
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description, for example by removing the `path` attribute when the
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protocol is HTTP(s) and `credential.useHttpPath` is false.
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2012-06-24 13:39:59 +02:00
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If the `git credential` knew about the password, this step may
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not have involved the user actually typing this password (the
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user may have typed a password to unlock the keychain instead,
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or no user interaction was done if the keychain was already
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unlocked) before it returned `password=secr3t`.
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3. Use the credential (e.g., access the URL with the username and
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password from step (2)), and see if it's accepted.
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4. Report on the success or failure of the password. If the
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credential allowed the operation to complete successfully, then
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it can be marked with an "approve" action to tell `git
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credential` to reuse it in its next invocation. If the credential
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was rejected during the operation, use the "reject" action so
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that `git credential` will ask for a new password in its next
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invocation. In either case, `git credential` should be fed with
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2012-06-24 13:40:00 +02:00
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the credential description obtained from step (2) (which also
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2023-10-08 08:45:03 +02:00
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contains the fields provided in step (1)).
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2012-06-24 13:39:59 +02:00
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[[IOFMT]]
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INPUT/OUTPUT FORMAT
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-------------------
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`git credential` reads and/or writes (depending on the action used)
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2012-07-18 14:04:02 +02:00
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credential information in its standard input/output. This information
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2012-06-24 13:39:59 +02:00
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can correspond either to keys for which `git credential` will obtain
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2020-05-06 23:47:26 +02:00
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the login information (e.g. host, protocol, path), or to the actual
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credential data to be obtained (username/password).
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2012-06-24 13:39:59 +02:00
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2012-07-18 14:04:02 +02:00
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The credential is split into a set of named attributes, with one
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2020-05-06 23:47:26 +02:00
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attribute per line. Each attribute is specified by a key-value pair,
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separated by an `=` (equals) sign, followed by a newline.
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The key may contain any bytes except `=`, newline, or NUL. The value may
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2024-04-17 02:02:35 +02:00
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contain any bytes except newline or NUL. A line, including the trailing
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newline, may not exceed 65535 bytes in order to allow implementations to
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parse efficiently.
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2020-05-06 23:47:26 +02:00
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2023-02-27 18:20:20 +01:00
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Attributes with keys that end with C-style array brackets `[]` can have
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multiple values. Each instance of a multi-valued attribute forms an
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ordered list of values - the order of the repeated attributes defines
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the order of the values. An empty multi-valued attribute (`key[]=\n`)
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acts to clear any previous entries and reset the list.
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In all cases, all bytes are treated as-is (i.e., there is no quoting,
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2012-06-24 13:39:59 +02:00
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and one cannot transmit a value with newline or NUL in it). The list of
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attributes is terminated by a blank line or end-of-file.
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2020-05-06 23:47:26 +02:00
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2012-07-18 14:04:02 +02:00
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Git understands the following attributes:
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2012-06-24 13:39:59 +02:00
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`protocol`::
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The protocol over which the credential will be used (e.g.,
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`https`).
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`host`::
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2020-05-06 23:47:26 +02:00
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The remote hostname for a network credential. This includes
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the port number if one was specified (e.g., "example.com:8088").
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2012-06-24 13:39:59 +02:00
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`path`::
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The path with which the credential will be used. E.g., for
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accessing a remote https repository, this will be the
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repository's path on the server.
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`username`::
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The credential's username, if we already have one (e.g., from a
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2020-05-06 23:47:26 +02:00
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URL, the configuration, the user, or from a previously run helper).
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2012-06-24 13:39:59 +02:00
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`password`::
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The credential's password, if we are asking it to be stored.
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2012-07-18 14:06:26 +02:00
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credential: new attribute password_expiry_utc
Some passwords have an expiry date known at generation. This may be
years away for a personal access token or hours for an OAuth access
token.
When multiple credential helpers are configured, `credential fill` tries
each helper in turn until it has a username and password, returning
early. If Git authentication succeeds, `credential approve`
stores the successful credential in all helpers. If authentication
fails, `credential reject` erases matching credentials in all helpers.
Helpers implement corresponding operations: get, store, erase.
The credential protocol has no expiry attribute, so helpers cannot
store expiry information. Even if a helper returned an improvised
expiry attribute, git credential discards unrecognised attributes
between operations and between helpers.
This is a particular issue when a storage helper and a
credential-generating helper are configured together:
[credential]
helper = storage # eg. cache or osxkeychain
helper = generate # eg. oauth
`credential approve` stores the generated credential in both helpers
without expiry information. Later `credential fill` may return an
expired credential from storage. There is no workaround, no matter how
clever the second helper. The user sees authentication fail (a retry
will succeed).
Introduce a password expiry attribute. In `credential fill`, ignore
expired passwords and continue to query subsequent helpers.
In the example above, `credential fill` ignores the expired password
and a fresh credential is generated. If authentication succeeds,
`credential approve` replaces the expired password in storage.
If authentication fails, the expired credential is erased by
`credential reject`. It is unnecessary but harmless for storage
helpers to self prune expired credentials.
Add support for the new attribute to credential-cache.
Eventually, I hope to see support in other popular storage helpers.
Example usage in a credential-generating helper
https://github.com/hickford/git-credential-oauth/pull/16
Signed-off-by: M Hickford <mirth.hickford@gmail.com>
Reviewed-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-02-18 07:32:57 +01:00
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`password_expiry_utc`::
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Generated passwords such as an OAuth access token may have an expiry date.
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When reading credentials from helpers, `git credential fill` ignores expired
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passwords. Represented as Unix time UTC, seconds since 1970.
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2023-04-21 11:47:59 +02:00
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`oauth_refresh_token`::
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An OAuth refresh token may accompany a password that is an OAuth access
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token. Helpers must treat this attribute as confidential like the password
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attribute. Git itself has no special behaviour for this attribute.
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2012-07-18 14:06:26 +02:00
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`url`::
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When this special attribute is read by `git credential`, the
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value is parsed as a URL and treated as if its constituent parts
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were read (e.g., `url=https://example.com` would behave as if
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`protocol=https` and `host=example.com` had been provided). This
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2020-05-06 23:47:26 +02:00
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can help callers avoid parsing URLs themselves.
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2020-05-17 20:52:20 +02:00
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Note that specifying a protocol is mandatory and if the URL
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doesn't specify a hostname (e.g., "cert:///path/to/file") the
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credential will contain a hostname attribute whose value is an
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empty string.
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Components which are missing from the URL (e.g., there is no
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username in the example above) will be left unset.
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2021-04-09 17:02:48 +02:00
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2024-04-17 02:02:31 +02:00
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`authtype`::
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This indicates that the authentication scheme in question should be used.
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Common values for HTTP and HTTPS include `basic`, `bearer`, and `digest`,
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although the latter is insecure and should not be used. If `credential`
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is used, this may be set to an arbitrary string suitable for the protocol in
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question (usually HTTP).
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This value should not be sent unless the appropriate capability (see below) is
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provided on input.
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`credential`::
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The pre-encoded credential, suitable for the protocol in question (usually
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HTTP). If this key is sent, `authtype` is mandatory, and `username` and
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`password` are not used. For HTTP, Git concatenates the `authtype` value and
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this value with a single space to determine the `Authorization` header.
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This value should not be sent unless the appropriate capability (see below) is
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provided on input.
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`ephemeral`::
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This boolean value indicates, if true, that the value in the `credential`
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field should not be saved by the credential helper because its usefulness is
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limited in time. For example, an HTTP Digest `credential` value is computed
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using a nonce and reusing it will not result in successful authentication.
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This may also be used for situations with short duration (e.g., 24-hour)
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credentials. The default value is false.
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The credential helper will still be invoked with `store` or `erase` so that it
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can determine whether the operation was successful.
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This value should not be sent unless the appropriate capability (see below) is
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provided on input.
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credential: add an argument to keep state
Until now, our credential code has mostly deal with usernames and
passwords and we've let libcurl deal with the variant of authentication
to be used. However, now that we have the credential value, the
credential helper can take control of the authentication, so the value
provided might be something that's generated, such as a Digest hash
value.
In such a case, it would be helpful for a credential helper that gets an
erase or store command to be able to keep track of an identifier for the
original secret that went into the computation. Furthermore, some types
of authentication, such as NTLM and Kerberos, actually need two round
trips to authenticate, which will require that the credential helper
keep some state.
In order to allow for these use cases and others, allow storing state in
a field called "state[]". This value is passed back to the credential
helper that created it, which avoids confusion caused by parsing values
from different helpers.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-04-17 02:02:33 +02:00
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`state[]`::
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This value provides an opaque state that will be passed back to this helper
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if it is called again. Each different credential helper may specify this
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once. The value should include a prefix unique to the credential helper and
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should ignore values that don't match its prefix.
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This value should not be sent unless the appropriate capability (see below) is
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provided on input.
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credential: add support for multistage credential rounds
Over HTTP, NTLM and Kerberos require two rounds of authentication on the
client side. It's possible that there are custom authentication schemes
that also implement this same approach. Since these are tricky schemes
to implement and the HTTP library in use may not always handle them
gracefully on all systems, it would be helpful to allow the credential
helper to implement them instead for increased portability and
robustness.
To allow this to happen, add a boolean flag, continue, that indicates
that instead of failing when we get a 401, we should retry another round
of authentication. However, this necessitates some changes in our
current credential code so that we can make this work.
Keep the state[] headers between iterations, but only use them to send
to the helper and only consider the new ones we read from the credential
helper to be valid on subsequent iterations. That avoids us passing
stale data when we finally approve or reject the credential. Similarly,
clear the multistage and wwwauth[] values appropriately so that we
don't pass stale data or think we're trying a multiround response when
we're not. Remove the credential values so that we can actually fill a
second time with new responses.
Limit the number of iterations of reauthentication we do to 3. This
means that if there's a problem, we'll terminate with an error message
instead of retrying indefinitely and not informing the user (and
possibly conducting a DoS on the server).
In our tests, handle creating multiple response output files from our
helper so we can verify that each of the messages sent is correct.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-04-17 02:02:37 +02:00
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`continue`::
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This is a boolean value, which, if enabled, indicates that this
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authentication is a non-final part of a multistage authentication step. This
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is common in protocols such as NTLM and Kerberos, where two rounds of client
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authentication are required, and setting this flag allows the credential
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helper to implement the multistage authentication step. This flag should
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only be sent if a further stage is required; that is, if another round of
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authentication is expected.
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This value should not be sent unless the appropriate capability (see below) is
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provided on input. This attribute is 'one-way' from a credential helper to
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pass information to Git (or other programs invoking `git credential`).
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2023-02-27 18:20:20 +01:00
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`wwwauth[]`::
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When an HTTP response is received by Git that includes one or more
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'WWW-Authenticate' authentication headers, these will be passed by Git
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to credential helpers.
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Each 'WWW-Authenticate' header value is passed as a multi-valued
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attribute 'wwwauth[]', where the order of the attributes is the same as
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they appear in the HTTP response. This attribute is 'one-way' from Git
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to pass additional information to credential helpers.
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2024-04-17 02:02:31 +02:00
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`capability[]`::
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credential: add an argument to keep state
Until now, our credential code has mostly deal with usernames and
passwords and we've let libcurl deal with the variant of authentication
to be used. However, now that we have the credential value, the
credential helper can take control of the authentication, so the value
provided might be something that's generated, such as a Digest hash
value.
In such a case, it would be helpful for a credential helper that gets an
erase or store command to be able to keep track of an identifier for the
original secret that went into the computation. Furthermore, some types
of authentication, such as NTLM and Kerberos, actually need two round
trips to authenticate, which will require that the credential helper
keep some state.
In order to allow for these use cases and others, allow storing state in
a field called "state[]". This value is passed back to the credential
helper that created it, which avoids confusion caused by parsing values
from different helpers.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-04-17 02:02:33 +02:00
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This signals that Git, or the helper, as appropriate, supports the capability
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in question. This can be used to provide better, more specific data as part
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of the protocol. A `capability[]` directive must precede any value depending
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on it and these directives _should_ be the first item announced in the
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2024-04-17 02:02:31 +02:00
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protocol.
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+
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credential: add an argument to keep state
Until now, our credential code has mostly deal with usernames and
passwords and we've let libcurl deal with the variant of authentication
to be used. However, now that we have the credential value, the
credential helper can take control of the authentication, so the value
provided might be something that's generated, such as a Digest hash
value.
In such a case, it would be helpful for a credential helper that gets an
erase or store command to be able to keep track of an identifier for the
original secret that went into the computation. Furthermore, some types
of authentication, such as NTLM and Kerberos, actually need two round
trips to authenticate, which will require that the credential helper
keep some state.
In order to allow for these use cases and others, allow storing state in
a field called "state[]". This value is passed back to the credential
helper that created it, which avoids confusion caused by parsing values
from different helpers.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-04-17 02:02:33 +02:00
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There are two currently supported capabilities. The first is `authtype`, which
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indicates that the `authtype`, `credential`, and `ephemeral` values are
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understood. The second is `state`, which indicates that the `state[]` and
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`continue` values are understood.
|
2024-04-17 02:02:31 +02:00
|
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+
|
credential: add an argument to keep state
Until now, our credential code has mostly deal with usernames and
passwords and we've let libcurl deal with the variant of authentication
to be used. However, now that we have the credential value, the
credential helper can take control of the authentication, so the value
provided might be something that's generated, such as a Digest hash
value.
In such a case, it would be helpful for a credential helper that gets an
erase or store command to be able to keep track of an identifier for the
original secret that went into the computation. Furthermore, some types
of authentication, such as NTLM and Kerberos, actually need two round
trips to authenticate, which will require that the credential helper
keep some state.
In order to allow for these use cases and others, allow storing state in
a field called "state[]". This value is passed back to the credential
helper that created it, which avoids confusion caused by parsing values
from different helpers.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-04-17 02:02:33 +02:00
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It is not obligatory to use the additional features just because the capability
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is supported, but they should not be provided without the capability.
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2024-04-17 02:02:31 +02:00
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Unrecognised attributes and capabilities are silently discarded.
|
2022-10-24 09:57:48 +02:00
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2024-04-17 02:02:40 +02:00
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[[CAPA-IOFMT]]
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CAPABILITY INPUT/OUTPUT FORMAT
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------------------------------
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For `git credential capability`, the format is slightly different. First, a
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`version 0` announcement is made to indicate the current version of the
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protocol, and then each capability is announced with a line like `capability
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authtype`. Credential helpers may also implement this format, again with the
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`capability` argument. Additional lines may be added in the future; callers
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should ignore lines which they don't understand.
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Because this is a new part of the credential helper protocol, older versions of
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Git, as well as some credential helpers, may not support it. If a non-zero
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exit status is received, or if the first line doesn't start with the word
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`version` and a space, callers should assume that no capabilities are supported.
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The intention of this format is to differentiate it from the credential output
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in an unambiguous way. It is possible to use very simple credential helpers
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(e.g., inline shell scripts) which always produce identical output. Using a
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distinct format allows users to continue to use this syntax without having to
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worry about correctly implementing capability advertisements or accidentally
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confusing callers querying for capabilities.
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2021-04-09 17:02:48 +02:00
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GIT
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---
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Part of the linkgit:git[1] suite
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