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diff --git a/src/auths/README b/src/auths/README new file mode 100644 index 0000000..66bdcdc --- /dev/null +++ b/src/auths/README @@ -0,0 +1,98 @@ +AUTHS + +The modules in this directory are in support of various authentication +functions. Some of them, such as the base64 encoding/decoding and MD5 +computation, are just functions that might be used by several authentication +mechanisms. Others are the SMTP AUTH mechanisms themselves, included in the +final binary if the relevant AUTH_XXX value is set in Local/Makefile. The +general functions are in separate modules so that they get included in the +final binary only if they are actually called from somewhere. + +GENERAL FUNCTIONS + +The API for each of these functions is documented with the function's code. + + auth_b64encode encode in base 64 + auth_b64decode decode from base 64 + auth_call_pam do PAM authentication (if build with SUPPORT_PAM) + auth_get_data issue SMTP AUTH challenge and read response + auth_xtextencode encode as xtext + auth_xtextdecode decode from xtext + +INTERFACE TO SMTP AUTHENTICATION MECHANISMS + +These are general SASL mechanisms, adapted for use with SMTP. Each +authentication mechanism has three functions, for initialization, server +authentication, and client authentication. + +INITIALIZATION + +The initialization function is called when the configuration is read, and can +check for incomplete or illegal settings. It has one argument, a pointer to the +instance block for this configured mechanism. It must set the flags called +"server" and "client" in the generic auth_instance block to indicate whether +the server and/or client functions are available for this authenticator. +Typically this depends on whether server or client configuration options have +been set, but it is also possible to have an authenticator that has only one of +the server or client functions. The function may not touch big_buffer. + +SERVER AUTHENTICATION + +The second function performs authentication as a server. It receives a pointer +to the instance block, and its second argument is the remainder of the data +from the AUTH command. The numeric variable maximum setting (expand_nmax) is +set to zero, with $0 initialized as unset. The authenticator may set up numeric +variables according to its (old) specification and $auth<n> variables the +preferred ones nowadays; it should leave them set at the end so that they can +be used for the expansion of the generic server_set_id option, which happens +centrally. + +This function has access to the SMTP input and output so that it can write +intermediate responses and read more data if necessary. There is a packaged +function in auth_get_data() which outputs a challenge and reads a response. + +The yield of a server authentication check must be one of: + + OK success + DEFER couldn't complete the check + FAIL authentication failed + CANCELLED authentication forced to fail by "*" response to challenge, + or by certain forced string expansion failures + BAD64 bad base64 data received + UNEXPECTED unexpected data received + +In the case of DEFER, auth_defer_msg should point to an error message. + +CLIENT AUTHENTICATION + +The third function performs authentication as a client. It receives a pointer +to the instance block, and four further arguments: + + The smtp_context item for the connection to the remote host. + + The normal command-reading timeout value. + + A pointer to a buffer, to be used for receiving responses. It is done this + way so that the buffer is available for logging etc. in the calling + function in cases of error. + + The size of the buffer. + +The yield of a client authentication check must be one of: + + OK success + FAIL_SEND error after writing a command; errno is set + FAIL failed after reading a response; + either errno is set (for timeouts, I/O failures) or + the buffer contains the SMTP response line + CANCELLED the client cancelled authentication (often "fail" in expansion) + the buffer may contain a message; if not, *buffer = 0 + ERROR local problem (typically expansion error); message in buffer + +To communicate with the remote host the client should call +smtp_write_command(). If this yields FALSE, the authenticator should return +FAIL. After a successful write, the response is received by a call to +smtp_read_response(), which should use the buffer handed to the client function +as an argument. + +**** |