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Diffstat (limited to 'Documentation/technical/api-credentials.txt')
| -rw-r--r-- | Documentation/technical/api-credentials.txt | 118 |
1 files changed, 72 insertions, 46 deletions
diff --git a/Documentation/technical/api-credentials.txt b/Documentation/technical/api-credentials.txt index 21ca6a2553..e44426dd04 100644 --- a/Documentation/technical/api-credentials.txt +++ b/Documentation/technical/api-credentials.txt @@ -6,8 +6,52 @@ 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`:: @@ -21,14 +65,17 @@ Data Structures 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. +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`:: @@ -72,7 +119,7 @@ Functions 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: @@ -113,7 +160,7 @@ int foo_login(struct foo_connection *f) break; default: /* - * Some other error occured. We don't know if the + * Some other error occurred. We don't know if the * credential is good or bad, so report nothing to the * credential subsystem. */ @@ -130,13 +177,15 @@ int foo_login(struct foo_connection *f) Credential Helpers ------------------ -Credential helpers are programs executed by git to fetch or save +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 +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. The string is transformed -by git into a command to be executed using these rules: +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. @@ -192,47 +241,17 @@ appended to its command line, which is one of: 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 credential is split into a set of named attributes. -Attributes are provided to the helper, one 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. -In both 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 will send the following attributes (but may not send all of -them for a given credential; for example, a `host` attribute makes no -sense when dealing with a non-network protocol): - -`protocol`:: - - The protocol over which the credential will be used (e.g., - `https`). - -`host`:: - - The remote hostname for a network credential. - -`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, from the user, or from a previously run helper). - -`password`:: - - The credential's password, if we are asking it to be stored. +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. +attributes will overwrite those already known about by Git. If a helper +outputs a `quit` attribute with a value of `true` or `1`, no further +helpers will be consulted, nor will the user be prompted (if no +credential has been provided, the operation will then fail). For a `store` or `erase` operation, the helper's output is ignored. If it fails to perform the requested operation, it may complain to @@ -243,3 +262,10 @@ 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.*`) |