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Diffstat (limited to 'credential.h')
| -rw-r--r-- | credential.h | 197 |
1 files changed, 197 insertions, 0 deletions
diff --git a/credential.h b/credential.h new file mode 100644 index 0000000..f430e77 --- /dev/null +++ b/credential.h @@ -0,0 +1,197 @@ +#ifndef CREDENTIAL_H +#define CREDENTIAL_H + +#include "string-list.h" + +/** + * The credentials API provides an abstracted way of gathering username and + * password credentials from the user. + * + * 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). + * + * 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; + * } + * ----------------------------------------------------------------------- + */ + + +/** + * 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. + * + * This struct should always be initialized with `CREDENTIAL_INIT` or + * `credential_init`. + */ +struct credential { + + /** + * A `string_list` of helpers. Each string specifies an external + * helper which will be run, in order, to either acquire or store + * credentials. 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. + */ + struct string_list helpers; + + unsigned approved:1, + configured:1, + quit:1, + use_http_path:1, + username_from_proto:1; + + char *username; + char *password; + char *protocol; + char *host; + char *path; +}; + +#define CREDENTIAL_INIT { \ + .helpers = STRING_LIST_INIT_DUP, \ +} + +/* Initialize a credential structure, setting all fields to empty. */ +void credential_init(struct credential *); + +/** + * Free any resources associated with the credential structure, returning + * it to a pristine initialized state. + */ +void credential_clear(struct credential *); + +/** + * 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(). + */ +void credential_fill(struct credential *); + +/** + * 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. + */ +void credential_approve(struct credential *); + +/** + * 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. + */ +void credential_reject(struct credential *); + +int credential_read(struct credential *, FILE *); +void credential_write(const struct credential *, FILE *); + +/* + * Parse a url into a credential struct, replacing any existing contents. + * + * If the url can't be parsed (e.g., a missing "proto://" component), the + * resulting credential will be empty and the function will return an + * error (even in the "gently" form). + * + * If we encounter a component which cannot be represented as a credential + * value (e.g., because it contains a newline), the "gently" form will return + * an error but leave the broken state in the credential object for further + * examination. The non-gentle form will issue a warning to stderr and return + * an empty credential. + */ +void credential_from_url(struct credential *, const char *url); +int credential_from_url_gently(struct credential *, const char *url, int quiet); + +int credential_match(const struct credential *want, + const struct credential *have); + +#endif /* CREDENTIAL_H */ |