diplodocus.org Git - nmh/blob - h/oauth.h

   1 /*
   2  * Implementation of OAuth 2.0 [1] for XOAUTH2 in SMTP [2] and POP3 [3].
   3  *
   4  * Google defined XOAUTH2 for SMTP, and that's what we use here.  If other
   5  * providers implement XOAUTH2 or some similar OAuth-based SMTP authentication
   6  * protocol, it should be simple to extend this.
   7  *
   8  * [1] https://tools.ietf.org/html/rfc6749
   9  * [2] https://developers.google.com/gmail/xoauth2_protocol
  10  * [3] http://googleappsdeveloper.blogspot.com/2014/10/updates-on-authentication-for-gmail.html
  11  *
  12  * Presumably [2] should document POP3 and that is an over-sight.  As it stands,
  13  * that blog post is the closest we have to documentation.
  14  *
  15  * According to [1] 2.1 Client Types, this is a "native application", a
  16  * "public" client.
  17  *
  18  * To summarize the flow:
  19  *
  20  * 1. User runs mhlogin which prints a URL the user must visit, and prompts for
  21  *    a code retrieved from that page.
  22  *
  23  * 2. User vists this URL in browser, signs in with some Google account, and
  24  *    copies and pastes the resulting code back to mhlogin.
  25  *
  26  * 3. mhlogin does HTTP POST to Google to exchange the user-provided code for a
  27  *    short-lived access token and a long-lived refresh token.
  28  *
  29  * 4. send uses the access token in SMTP auth if not expired.  If it is expired,
  30  *    it does HTTP POST to Google including the refresh token and gets back a
  31  *    new access token (and possibly refresh token).  If the refresh token has
  32  *    become invalid (e.g. if the user took some reset action on the Google
  33  *    account), the user must use mhlogin again, then re-run send.
  34  */
  35
  36 typedef enum {
  37     /* error loading profile */
  38     MH_OAUTH_BAD_PROFILE = OK + 1,
  39
  40     /* error initializing libcurl */
  41     MH_OAUTH_CURL_INIT,
  42
  43     /* local error initializing HTTP request */
  44     MH_OAUTH_REQUEST_INIT,
  45
  46     /* error executing HTTP POST request */
  47     MH_OAUTH_POST,
  48
  49     /* HTTP response body is too big. */
  50     MH_OAUTH_RESPONSE_TOO_BIG,
  51
  52     /* Can't process HTTP response body. */
  53     MH_OAUTH_RESPONSE_BAD,
  54
  55     /* The authorization server rejected the grant (authorization code or
  56      * refresh token); possibly the user entered a bad code, or the refresh
  57      * token has become invalid, etc. */
  58     MH_OAUTH_BAD_GRANT,
  59
  60     /* HTTP server indicates something is wrong with our request. */
  61     MH_OAUTH_REQUEST_BAD,
  62
  63     /* Attempting to refresh an access token without a refresh token. */
  64     MH_OAUTH_NO_REFRESH,
  65
  66
  67     /* requested user not in cred file */
  68     MH_OAUTH_CRED_USER_NOT_FOUND,
  69
  70     /* error loading serialized credentials */
  71     MH_OAUTH_CRED_FILE
  72 } mh_oauth_err_code;
  73
  74 typedef struct mh_oauth_ctx mh_oauth_ctx;
  75
  76 typedef struct mh_oauth_cred mh_oauth_cred;
  77
  78 /*
  79  * Do the complete dance for XOAUTH2 as used by POP3 and SMTP.
  80  *
  81  * Load tokens for svc from disk, refresh if necessary, and return the
  82  * base64-encoded client response.
  83  *
  84  * If refreshing, writes freshened tokens to disk.
  85  *
  86  * Exits via adios on any error.
  87  */
  88 char *
  89 mh_oauth_do_xoauth(const char *user, const char *svc, FILE *log);
  90
  91 /*
  92  * Allocate and initialize a new OAuth context.
  93  *
  94  * Caller must call mh_oauth_free(ctx) when finished, even on error.
  95  *
  96  * svc_name must point to a null-terminated string identifying the service
  97  * provider.  Support for "gmail" is built-in; anything else must be defined in
  98  * the user's profile.  The profile can also override "gmail" settings.
  99  *
 100  * Accesses global m_defs via context_find.
 101  *
 102  * On error, return FALSE and set an error in ctx; ctx is always allocated.
 103  */
 104 boolean
 105 mh_oauth_new(mh_oauth_ctx **ctx, const char *svc_name);
 106
 107 /*
 108  * Free all resources associated with ctx.
 109  */
 110 void
 111 mh_oauth_free(mh_oauth_ctx *ctx);
 112
 113 /*
 114  * Return null-terminated human-readable name of the service, e.g. "Gmail".
 115  *
 116  * Never returns NULL.
 117  */
 118 const char *
 119 mh_oauth_svc_display_name(const mh_oauth_ctx *ctx);
 120
 121 /*
 122  * Enable logging for subsequent operations on ctx.
 123  *
 124  * log must not be closed until after mh_oauth_free.
 125  *
 126  * For all HTTP requests, the request is logged with each line prefixed with
 127  * "< ", and the response with "> ".  Other messages are prefixed with "* ".
 128  */
 129 void
 130 mh_oauth_log_to(FILE *log, mh_oauth_ctx *ctx);
 131
 132 /*
 133  * Return the error code after some function indicated an error.
 134  *
 135  * Must not be called if an error was not indicated.
 136  */
 137 mh_oauth_err_code
 138 mh_oauth_get_err_code(const mh_oauth_ctx *ctx);
 139
 140 /*
 141  * Return null-terminated error message after some function indicated an error.
 142  *
 143  * Never returns NULL, but must not be called if an error was not indicated.
 144  */
 145 const char *
 146 mh_oauth_get_err_string(mh_oauth_ctx *ctx);
 147
 148 /*
 149  * Return the null-terminated URL the user needs to visit to authorize access.
 150  *
 151  * URL may be invalidated by subsequent calls to mh_oauth_get_authorize_url,
 152  * mh_oauth_authorize, or mh_oauth_refresh.
 153  *
 154  * On error, return NULL.
 155  */
 156 const char *
 157 mh_oauth_get_authorize_url(mh_oauth_ctx *ctx);
 158
 159 /*
 160  * Exchange code provided by the user for access (and maybe refresh) token.
 161  *
 162  * On error, return NULL.
 163  */
 164 mh_oauth_cred *
 165 mh_oauth_authorize(const char *code, mh_oauth_ctx *ctx);
 166
 167 /*
 168  * Refresh access (and maybe refresh) token if refresh token present.
 169  *
 170  * On error, return FALSE and leave cred untouched.
 171  */
 172 boolean
 173 mh_oauth_refresh(mh_oauth_cred *cred);
 174
 175 /*
 176  * Return whether access token is present and not expired at time T.
 177  */
 178 boolean
 179 mh_oauth_access_token_valid(time_t t, const mh_oauth_cred *cred);
 180
 181 /*
 182  * Free all resources associated with cred.
 183  */
 184 void
 185 mh_oauth_cred_free(mh_oauth_cred *cred);
 186
 187 /*
 188  * Return the null-terminated file name for storing this service's OAuth tokens.
 189  *
 190  * Accesses global m_defs via context_find.
 191  *
 192  * Never returns NULL.
 193  */
 194 const char *
 195 mh_oauth_cred_fn(mh_oauth_ctx *ctx);
 196
 197 /*
 198  * Serialize OAuth tokens to file.
 199  *
 200  * On error, return FALSE.
 201  */
 202 boolean
 203 mh_oauth_cred_save(FILE *fp, mh_oauth_cred *cred, const char *user);
 204
 205 /*
 206  * Load OAuth tokens from file.
 207  *
 208  * Calls m_getfld(), which writes to stderr with advise().
 209  *
 210  * On error, return NULL.
 211  */
 212 mh_oauth_cred *
 213 mh_oauth_cred_load(FILE *fp, mh_oauth_ctx *ctx, const char *user);
 214
 215 /*
 216  * Return null-terminated SASL client response for XOAUTH2 from access token.
 217  *
 218  * Store the length in res_len.
 219  *
 220  * Must not be called except after successful mh_oauth_access_token_valid or
 221  * mh_oauth_refresh call; i.e. must have a valid access token.
 222  */
 223 const char *
 224 mh_oauth_sasl_client_response(size_t *res_len,
 225                               const char *user, const mh_oauth_cred *cred);