зеркало из https://github.com/microsoft/git.git
269 строки
8.9 KiB
Plaintext
269 строки
8.9 KiB
Plaintext
credentials API
|
|
===============
|
|
|
|
The credentials API provides an abstracted way of gathering username and
|
|
password credentials from the user (even though credentials in the wider
|
|
world can take many forms, in this document the word "credential" always
|
|
refers to a username and password pair).
|
|
|
|
This document describes two interfaces: the C API that the credential
|
|
subsystem provides to the rest of Git, and the protocol that Git uses to
|
|
communicate with system-specific "credential helpers". If you are
|
|
writing Git code that wants to look up or prompt for credentials, see
|
|
the section "C API" below. If you want to write your own helper, see
|
|
the section on "Credential Helpers" below.
|
|
|
|
Typical setup
|
|
-------------
|
|
|
|
------------
|
|
+-----------------------+
|
|
| Git code (C) |--- to server requiring --->
|
|
| | authentication
|
|
|.......................|
|
|
| C credential API |--- prompt ---> User
|
|
+-----------------------+
|
|
^ |
|
|
| pipe |
|
|
| v
|
|
+-----------------------+
|
|
| Git credential helper |
|
|
+-----------------------+
|
|
------------
|
|
|
|
The Git code (typically a remote-helper) will call the C API to obtain
|
|
credential data like a login/password pair (credential_fill). The
|
|
API will itself call a remote helper (e.g. "git credential-cache" or
|
|
"git credential-store") that may retrieve credential data from a
|
|
store. If the credential helper cannot find the information, the C API
|
|
will prompt the user. Then, the caller of the API takes care of
|
|
contacting the server, and does the actual authentication.
|
|
|
|
C API
|
|
-----
|
|
|
|
The credential C API is meant to be called by Git code which needs to
|
|
acquire or store a credential. It is centered around an object
|
|
representing a single credential and provides three basic operations:
|
|
fill (acquire credentials by calling helpers and/or prompting the user),
|
|
approve (mark a credential as successfully used so that it can be stored
|
|
for later use), and reject (mark a credential as unsuccessful so that it
|
|
can be erased from any persistent storage).
|
|
|
|
Data Structures
|
|
~~~~~~~~~~~~~~~
|
|
|
|
`struct credential`::
|
|
|
|
This struct represents a single username/password combination
|
|
along with any associated context. All string fields should be
|
|
heap-allocated (or NULL if they are not known or not applicable).
|
|
The meaning of the individual context fields is the same as
|
|
their counterparts in the helper protocol; see the section below
|
|
for a description of each field.
|
|
+
|
|
The `helpers` member of the struct is a `string_list` of helpers. Each
|
|
string specifies an external helper which will be run, in order, to
|
|
either acquire or store credentials. See the section on credential
|
|
helpers below. This list is filled-in by the API functions
|
|
according to the corresponding configuration variables before
|
|
consulting helpers, so there usually is no need for a caller to
|
|
modify the helpers field at all.
|
|
+
|
|
This struct should always be initialized with `CREDENTIAL_INIT` or
|
|
`credential_init`.
|
|
|
|
|
|
Functions
|
|
~~~~~~~~~
|
|
|
|
`credential_init`::
|
|
|
|
Initialize a credential structure, setting all fields to empty.
|
|
|
|
`credential_clear`::
|
|
|
|
Free any resources associated with the credential structure,
|
|
returning it to a pristine initialized state.
|
|
|
|
`credential_fill`::
|
|
|
|
Instruct the credential subsystem to fill the username and
|
|
password fields of the passed credential struct by first
|
|
consulting helpers, then asking the user. After this function
|
|
returns, the username and password fields of the credential are
|
|
guaranteed to be non-NULL. If an error occurs, the function will
|
|
die().
|
|
|
|
`credential_reject`::
|
|
|
|
Inform the credential subsystem that the provided credentials
|
|
have been rejected. This will cause the credential subsystem to
|
|
notify any helpers of the rejection (which allows them, for
|
|
example, to purge the invalid credentials from storage). It
|
|
will also free() the username and password fields of the
|
|
credential and set them to NULL (readying the credential for
|
|
another call to `credential_fill`). Any errors from helpers are
|
|
ignored.
|
|
|
|
`credential_approve`::
|
|
|
|
Inform the credential subsystem that the provided credentials
|
|
were successfully used for authentication. This will cause the
|
|
credential subsystem to notify any helpers of the approval, so
|
|
that they may store the result to be used again. Any errors
|
|
from helpers are ignored.
|
|
|
|
`credential_from_url`::
|
|
|
|
Parse a URL into broken-down credential fields.
|
|
|
|
Example
|
|
~~~~~~~
|
|
|
|
The example below shows how the functions of the credential API could be
|
|
used to login to a fictitious "foo" service on a remote host:
|
|
|
|
-----------------------------------------------------------------------
|
|
int foo_login(struct foo_connection *f)
|
|
{
|
|
int status;
|
|
/*
|
|
* Create a credential with some context; we don't yet know the
|
|
* username or password.
|
|
*/
|
|
|
|
struct credential c = CREDENTIAL_INIT;
|
|
c.protocol = xstrdup("foo");
|
|
c.host = xstrdup(f->hostname);
|
|
|
|
/*
|
|
* Fill in the username and password fields by contacting
|
|
* helpers and/or asking the user. The function will die if it
|
|
* fails.
|
|
*/
|
|
credential_fill(&c);
|
|
|
|
/*
|
|
* Otherwise, we have a username and password. Try to use it.
|
|
*/
|
|
status = send_foo_login(f, c.username, c.password);
|
|
switch (status) {
|
|
case FOO_OK:
|
|
/* It worked. Store the credential for later use. */
|
|
credential_accept(&c);
|
|
break;
|
|
case FOO_BAD_LOGIN:
|
|
/* Erase the credential from storage so we don't try it
|
|
* again. */
|
|
credential_reject(&c);
|
|
break;
|
|
default:
|
|
/*
|
|
* Some other error occurred. We don't know if the
|
|
* credential is good or bad, so report nothing to the
|
|
* credential subsystem.
|
|
*/
|
|
}
|
|
|
|
/* Free any associated resources. */
|
|
credential_clear(&c);
|
|
|
|
return status;
|
|
}
|
|
-----------------------------------------------------------------------
|
|
|
|
|
|
Credential Helpers
|
|
------------------
|
|
|
|
Credential helpers are programs executed by Git to fetch or save
|
|
credentials from and to long-term storage (where "long-term" is simply
|
|
longer than a single Git process; e.g., credentials may be stored
|
|
in-memory for a few minutes, or indefinitely on disk).
|
|
|
|
Each helper is specified by a single string in the configuration
|
|
variable `credential.helper` (and others, see linkgit:git-config[1]).
|
|
The string is transformed by Git into a command to be executed using
|
|
these rules:
|
|
|
|
1. If the helper string begins with "!", it is considered a shell
|
|
snippet, and everything after the "!" becomes the command.
|
|
|
|
2. Otherwise, if the helper string begins with an absolute path, the
|
|
verbatim helper string becomes the command.
|
|
|
|
3. Otherwise, the string "git credential-" is prepended to the helper
|
|
string, and the result becomes the command.
|
|
|
|
The resulting command then has an "operation" argument appended to it
|
|
(see below for details), and the result is executed by the shell.
|
|
|
|
Here are some example specifications:
|
|
|
|
----------------------------------------------------
|
|
# run "git credential-foo"
|
|
foo
|
|
|
|
# same as above, but pass an argument to the helper
|
|
foo --bar=baz
|
|
|
|
# the arguments are parsed by the shell, so use shell
|
|
# quoting if necessary
|
|
foo --bar="whitespace arg"
|
|
|
|
# you can also use an absolute path, which will not use the git wrapper
|
|
/path/to/my/helper --with-arguments
|
|
|
|
# or you can specify your own shell snippet
|
|
!f() { echo "password=`cat $HOME/.secret`"; }; f
|
|
----------------------------------------------------
|
|
|
|
Generally speaking, rule (3) above is the simplest for users to specify.
|
|
Authors of credential helpers should make an effort to assist their
|
|
users by naming their program "git-credential-$NAME", and putting it in
|
|
the $PATH or $GIT_EXEC_PATH during installation, which will allow a user
|
|
to enable it with `git config credential.helper $NAME`.
|
|
|
|
When a helper is executed, it will have one "operation" argument
|
|
appended to its command line, which is one of:
|
|
|
|
`get`::
|
|
|
|
Return a matching credential, if any exists.
|
|
|
|
`store`::
|
|
|
|
Store the credential, if applicable to the helper.
|
|
|
|
`erase`::
|
|
|
|
Remove a matching credential, if any, from the helper's storage.
|
|
|
|
The details of the credential will be provided on the helper's stdin
|
|
stream. The exact format is the same as the input/output format of the
|
|
`git credential` plumbing command (see the section `INPUT/OUTPUT
|
|
FORMAT` in linkgit:git-credential[7] for a detailed specification).
|
|
|
|
For a `get` operation, the helper should produce a list of attributes
|
|
on stdout in the same format. A helper is free to produce a subset, or
|
|
even no values at all if it has nothing useful to provide. Any provided
|
|
attributes will overwrite those already known about by Git.
|
|
|
|
For a `store` or `erase` operation, the helper's output is ignored.
|
|
If it fails to perform the requested operation, it may complain to
|
|
stderr to inform the user. If it does not support the requested
|
|
operation (e.g., a read-only store), it should silently ignore the
|
|
request.
|
|
|
|
If a helper receives any other operation, it should silently ignore the
|
|
request. This leaves room for future operations to be added (older
|
|
helpers will just ignore the new requests).
|
|
|
|
See also
|
|
--------
|
|
|
|
linkgit:gitcredentials[7]
|
|
|
|
linkgit:git-config[5] (See configuration variables `credential.*`)
|