imclient - Cyrus IMAP documentation
Authenticating callback interface to IMAP servers
#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 , int flags);
void imclient_clearflags (struct imclient *imclient , int flags);
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);
The imclient library functions are distributed with Cyrus IMAP. These functions
are used for building IMAP 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
take 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
overwrite the text of untagged data.
- imclient_send()
- Sends a new command to the imclient connection.
finishproc and finishrock are the function and rock called
when the command completes. functionproc may be a null pointer, in
which case no callback is made. The callback 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 printf(3) 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.
The following code is a possible skeleton of
imclient that relies on
Kerberos to do authentication. This code performs an IMAP CAPABILITY request
and prints out the result.
#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\en", 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\en",
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\en", capability_string);
free(capability_string);
}
No known bugs.
cyradm(8),
imapd(8),
RFC 2033 (IMAP LITERAL+ extension),
RFC 2060
(IMAP4rev1 specification), and
select(2)
IMAP, ACAP, Kerberos, Authentication
The Cyrus Team, Nic Bernstein (Onlight)
1993–2023, The Cyrus Team