smtp_key.c

[詳解]

/*++
/* NAME
/*  smtp_key 3
/* SUMMARY
/*  cache/table lookup key management
/* SYNOPSIS
/*  #include "smtp.h"
/*
/*  char    *smtp_key_prefix(buffer, delim_na, iterator, context_flags)
/*  VSTRING *buffer;
/*  const char *delim_na;
/*  SMTP_ITERATOR *iterator;
/*  int context_flags;
/* DESCRIPTION
/*  The Postfix SMTP server accesses caches and lookup tables,
/*  using lookup keys that contain information from various
/*  contexts: per-server configuration, per-request envelope,
/*  and results from DNS queries.
/*
/*  These lookup keys sometimes share the same context information.
/*  The primary purpose of this API is to ensure that this
/*  shared context is used consistently, and that its use is
/*  made explicit (both are needed to verify that there is no
/*  false cache sharing).
/*
/*  smtp_key_prefix() constructs a lookup key prefix from context
/*  that may be shared with other lookup keys. The user is free
/*  to append additional application-specific context. The result
/*  value is a pointer to the result text.
/*
/*  Arguments:
/* .IP buffer
/*  Storage for the result.
/* .IP delim_na
/*  The field delimiter character, and the optional place holder
/*  character for a) information that is unavailable, b)
/*  information that is inapplicable, or c) that would result
/*  in an empty field.  Key fields that contain "delim_na"
/*  characters will be base64-encoded.
/*  Do not specify "delim_na" characters that are part of the
/*  base64 character set.
/* .IP iterator
/*  Information that will be selected by the specified flags.
/* .IP context_flags
/*  Bit-wise OR of one or more of the following.
/* .RS
/* .IP SMTP_KEY_FLAG_SERVICE
/*  The global service name. This is a proxy for
/*  destination-independent and request-independent context.
/* .IP SMTP_KEY_FLAG_SENDER
/*  The envelope sender address. This is a proxy for sender-dependent
/*  context, such as per-sender SASL authentication.
/* .IP SMTP_KEY_FLAG_REQ_NEXTHOP
/*  The request nexthop destination. This is a proxy for
/*  destination-dependent, but host-independent context.
/* .IP SMTP_KEY_FLAG_NEXTHOP
/*  The current iterator's nexthop destination (request nexthop
/*  or fallback nexthop, including optional [] and :port). This
/*  is the form that users specify in a SASL or TLS lookup
/*  tables.
/* .IP SMTP_KEY_FLAG_HOSTNAME
/*  The current iterator's remote hostname.
/* .IP SMTP_KEY_FLAG_ADDR
/*  The current iterator's remote address.
/* .IP SMTP_KEY_FLAG_PORT
/*  The current iterator's remote port.
/* .RE
/* DIAGNOSTICS
/*  Panic: undefined flag or zero flags. Fatal: out of memory.
/* LICENSE
/* .ad
/* .fi
/*  The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/*  Wietse Venema
/*  IBM T.J. Watson Research
/*  P.O. Box 704
/*  Yorktown Heights, NY 10598, USA
/*--*/

 /*
  * System library.
  */
#include <sys_defs.h>
#include <netinet/in.h>         /* ntohs() for Solaris or BSD */
#include <arpa/inet.h>          /* ntohs() for Linux or BSD */
#include <string.h>

 /*
  * Utility library.
  */
#include <msg.h>
#include <vstring.h>
#include <base64_code.h>

 /*
  * Global library.
  */
#include <mail_params.h>

 /*
  * Application-specific.
  */
#include <smtp.h>

 /*
  * We use a configurable field terminator and optional place holder for data
  * that is unavailable or inapplicable. We base64-encode content that
  * contains these characters, and content that needs obfuscation.
  */

/* smtp_key_append_na - append place-holder key field */

static void smtp_key_append_na(VSTRING *buffer, const char *delim_na)
{
    if (delim_na[1] != 0)
    VSTRING_ADDCH(buffer, delim_na[1]);
    VSTRING_ADDCH(buffer, delim_na[0]);
}

/* smtp_key_append_str - append string-valued key field */

static void smtp_key_append_str(VSTRING *buffer, const char *str,
                        const char *delim_na)
{
    if (str == 0 || str[0] == 0) {
    smtp_key_append_na(buffer, delim_na);
    } else if (str[strcspn(str, delim_na)] != 0) {
    base64_encode_opt(buffer, str, strlen(str), BASE64_FLAG_APPEND);
    VSTRING_ADDCH(buffer, delim_na[0]);
    } else {
    vstring_sprintf_append(buffer, "%s%c", str, delim_na[0]);
    }
}

/* smtp_key_append_uint - append unsigned-valued key field */

static void smtp_key_append_uint(VSTRING *buffer, unsigned num,
                         const char *delim_na)
{
    vstring_sprintf_append(buffer, "%u%c", num, delim_na[0]);
}

/* smtp_key_prefix - format common elements in lookup key */

char   *smtp_key_prefix(VSTRING *buffer, const char *delim_na,
                    SMTP_ITERATOR *iter, int flags)
{
    static const char myname[] = "smtp_key_prefix";
    SMTP_STATE *state = iter->parent;   /* private member */

    /*
     * Sanity checks.
     */
    if (state == 0)
    msg_panic("%s: no parent state", myname);
    if (flags & ~SMTP_KEY_MASK_ALL)
    msg_panic("%s: unknown key flags 0x%x",
          myname, flags & ~SMTP_KEY_MASK_ALL);
    if (flags == 0)
    msg_panic("%s: zero flags", myname);

    /*
     * Initialize.
     */
    VSTRING_RESET(buffer);

    /*
     * Per-service and per-request context.
     */
    if (flags & SMTP_KEY_FLAG_SERVICE)
    smtp_key_append_str(buffer, state->service, delim_na);
    if (flags & SMTP_KEY_FLAG_SENDER)
    smtp_key_append_str(buffer, state->request->sender, delim_na);

    /*
     * Per-destination context, non-canonicalized form.
     */
    if (flags & SMTP_KEY_FLAG_REQ_NEXTHOP)
    smtp_key_append_str(buffer, STR(iter->request_nexthop), delim_na);
    if (flags & SMTP_KEY_FLAG_NEXTHOP)
    smtp_key_append_str(buffer, STR(iter->dest), delim_na);

    /*
     * Per-host context, canonicalized form.
     */
    if (flags & SMTP_KEY_FLAG_HOSTNAME)
    smtp_key_append_str(buffer, STR(iter->host), delim_na);
    if (flags & SMTP_KEY_FLAG_ADDR)
    smtp_key_append_str(buffer, STR(iter->addr), delim_na);
    if (flags & SMTP_KEY_FLAG_PORT)
    smtp_key_append_uint(buffer, ntohs(iter->port), delim_na);

    /* Similarly, provide unique TLS fingerprint when applicable. */

    VSTRING_TERMINATE(buffer);

    return STR(buffer);
}