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.la.
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
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