imclient

IMCLIENT(3)                 Library Functions Manual                 IMCLIENT(3)



 *

NAME
       imclient library - authenticating callback interface to IMAP/IMSP servers

SYNOPSIS
       #include <cyrus/imclient.h>

       int imclient_connect(struct imclient **imclient, const char *host, const
       char *port);

       void imclient_close (struct imclient *imclient);
       void imclient_setflags(struct imclient *imclient, intflags);
       void imclient_clearflags (struct imclient *imclient, intflags);
       char* imclient_servername (struct imclient *imclient);
       void imclient_addcallback (struct imclient * imclient ,...);
       void imclient_send (struct imclient *imclient, void (*finishproc)(), void
       *finishrock, const char *fmt, ...);
       void imclient_getselectinfo (struct imclient *imclient, int *fd, int *
       wanttowrite);
       void imclient_processoneevent (struct imclient *imclient);
       int imclient_authenticate (struct imclient *imclient, struct sasl_client
       **availmech, const char *service, const char *user, int protallowed);
       int imclient_havetls ();
       int imclient_starttls (struct imclient *imclient, char *cert_file, char
       *key_file, char *CAfile, char *CApath);


DESCRIPTION
       The imclient library functions are distributed with Cyrus IMAP and IMSP.
       These functions are used for building IMAP/IMSP client software. These
       functions handle Kerberos authentication and can set callbacks based on
       the keyword in untagged replies or based on the command tag at the end of
       command replies.

       Users must link with the -lcyrus switch, and must supply a function
       called fatal to be called in case of any error within libcyrus.a.

       All of the imclient functions begin with the prefix imclient and takes
       an  argument of type struct imclient * as the first argument which is
       initialized by imclient_connect and freed by imclient_close.

       See below for a description of each function.


       imclient_connect()
            Connects the client server to the host. If successful, it returns 0
            and sets the imclient argument to a pointer to an imclient struct.
            The imclient struct represents the current connection,  flags, and
            callbacks. On failure, the current errno is returned if a system
            call failed,  -1 is returned if the host name was not found, and  -2
            is returned if the service name was not found.

       imclient_close()
            Closes and frees the imclient connection.

        imclient_setflags()
            Sets the flags specified by the flags argument on the imclient
            connection. Currently the only  flag allowed is
            IMCLIENT_CONN_NONSYNCLITERAL (this flag indicates that the server
            supports non-synchronizing literals described by the LITERAL+
            extension).

       imclient_clearflags()
            Clears the flags specified by the flags argument on the imclient
            connection.

       imclient_servername()
            Returns a  char * pointer to the name of the server connected to by
            imclient.

       imclient_addcallback()
            Adds an untagged data callback to the imclient connection. The
            function imclient_addcallback takes callbacks of the type
            imclient_proc_t which is defined to be:
               typedef void imclient_proc_t (struct imclient *imclient, void
               *rock, struct imclient_reply *reply);
            and struct imclient_reply * is defined to be:
               struct imclient_reply {
                        char *keyword;
                        long msgno;
                        char *text;
               };

            After the first argument imclient, there can be zero or more
            instances of the set of keyword, flags, proc, and rock, each adding
            or changing a single callback.  Each instance  adds or changes the
            callback for keyword.  The argument, flags, specifies information
            about the parsing of the untagged data.  proc and rock specify the
            callback function and rock to invoke when the untagged data is
            received.  proc may be a null pointer, in which case no function is
            invoked.  The callback function may not call the functions
            imclient_close(), imclient_send(), imclient_eof(),
            imclient_processoneevent(), or imclient_authenticate() on the
            connection. The callback function may over write  the text of
            untagged data.

       imclient_send()
            Sends a new command to the imclient connection.  finishproc and
            finnishrock are the function and rock called when the  command
            completes.  functionproc may be a null pointer, in which case no
            callback is made. The call back function may not call the functions
            imclient_close(), imclient_send(), imclient_eof(),
            imclient_processoneevent(), or imclient_authenticate() on the
            connection.  The argument, fmt , is a print like specification of
            the command. It must not include the tag as the tag is automatically
            added by imclient_send().  The defined %-sequences are:
               %% for %
               %a for an IMAP atom
               %s for an astring (which will be quoted or literalized as needed)
               %d for a decimal
               %u for an unsigned  decimal
               %v for #astring (argument is a null-terminated array of char *
               which are written as space separated astrings)

       imclient_getselectinfo()
            Gets the information for calling select(2).  fd is filled in with
            the file descriptor to select(2) for read.  wanttowrite is filled in
            with a nonzero value if select should be used for write as well.

       imclient_processoneevent()
            Processes one input or output event on the imclient connection.

       imclient_authenticate()
            Authenticates the imclient connection using one of the mechanisms in
            availmech.  The argument, user, if not NULL, specifies the user to
            authenticate as. If the user is NULL, the current user is used.  The
            argument protallowed is a bitmask of permissible protection
            mechanisms.
            On success, 0 is returned.  On failure (i.e., "BAD" keyboard, or no
            authentication mechanisms worked), 1 is returned. On extreme failure
            (premature "OK"), 2 is returned.

       imclient_havetls()
            Returns a Boolean indicating whether the imclient library was
            compiled with TLS (SSL) support.  If so, imclient_starttls() may be
            used to secure the IMAP connection.

       imclient_starttls()
            Issues a STARTTLS command on an existing IMAP connection and
            negotiates the secure link.  The cert_file and key_file arguments
            specify the client certificate and secret key to use to authenticate
            ourselves to the server.  If client authentication is not needed,
            set both of these arguments to NULL.

            The CAfile and CApath arguments specify a file or directory,
            respectively, of CA certificates for validating server certificates.
            (See SSL_CTX_load_verify_locations(3) for details.)  If both of
            these are NULL, the client will be unable to validate the server's
            certificate, in which case the connection may succeed but a warning
            will be printed to stdout.


EXAMPLES
       The following code is a possible skeletion of imclient that relies on
       Kerberos to do authentication.  This code preforms an IMAP CAPABILITY
       request and prints out the result.

       struct sasl_client;
       #include <cyrus/xmalloc.h> /* example uses xstrdup */
       #include <cyrus/sasl.h>
       #include <cyrus/imclient.h>
       #include <stdio.h>

       extern struct sasl_client krb_sasl_client;

       struct sasl_client *login_sasl_client[] = {
           &krb_sasl_client,
           NULL
       };
       struct imclient *imclient;
       char server[] = "cyrus.andrew.cmu.edu" ;
       char port[] = "imap";

       void fatal(char* message, int rc) {
           fprintf(stderr, "fatal error: %s\n", message);
           exit(rc);
       }

       static void callback_capability(struct imclient *imclient,
                           void *rock,
                           struct imclient_reply *reply) {
           if (reply->text != NULL) {
            *((char**)rock) = xstrdup( reply->text );
           }
       }

       static void end_command (struct imclient *connection, void*
                      rock,  struct imclient_reply *inmsg) {
           (*(int*)rock)--;
       }

       main() {
           char* capability_string;
           int nc;

           if (imclient_connect(&imclient, server, port)) {
            fprintf(stderr,
                 "error: Couldn't connect to %s %s\n",
                 server, port);
            exit(1);
           }

           if (imclient_authenticate(imclient, login_sasl_client, "imap"
                            /* service */,
                            NULL /* user */, SASL_PROT_ANY)) {
            exit(1);
           }

           imclient_addcallback(imclient, "CAPABILITY",
                       CALLBACK_NOLITERAL,
                       callback_capability,
                       &capability_string,
                       NULL);

           nc = 1;

           imclient_send(imclient, end_command,
                   (void*) &nc, "CAPABILITY");

           while(nc > 0) {
            imclient_processoneevent(imclient);
           }

           if (strstr("LITERAL+", capability_string)) {
            imclient_setflags(imclient, IMCLIENT_CONN_NONSYNCLITERAL);
           }

           imclient_send(imclient, NULL, NULL, "LOGOUT");
           imclient_close(imclient);

           printf("capability text is: %s\n", capability_string);

           free(capability_string);
       }


BUGS
       No known bugs.


SEE ALSO
       cyradm, imapd, imspd, RFC2033 (IMAP LITERAL+ extension), RFC2060
       (IMAP4rev1 specification), and select(2)


KEYWORDS
       IMAP, ACAP, IMSP, Kerberos, Authentication



CMU                               Project Cyrus                      IMCLIENT(3)