valid_hostname.c

[詳解]

/*++
/* NAME
/*  valid_hostname 3
/* SUMMARY
/*  network name validation
/* SYNOPSIS
/*  #include <valid_hostname.h>
/*
/*  int valid_hostname(name, gripe)
/*  const char *name;
/*  int gripe;
/*
/*  int valid_hostaddr(addr, gripe)
/*  const char *addr;
/*  int gripe;
/*
/*  int valid_ipv4_hostaddr(addr, gripe)
/*  const char *addr;
/*  int gripe;
/*
/*  int valid_ipv6_hostaddr(addr, gripe)
/*  const char *addr;
/*  int gripe;
/*
/*  int valid_hostport(port, gripe)
/*  const char *port;
/*  int gripe;
/* DESCRIPTION
/*  valid_hostname() scrutinizes a hostname: the name should
/*  be no longer than VALID_HOSTNAME_LEN characters, should
/*  contain only letters, digits, dots and hyphens, no adjacent
/*  dots, no leading or trailing dots or hyphens, no labels
/*  longer than VALID_LABEL_LEN characters, and it should not
/*  be all numeric.
/*
/*  valid_hostaddr() requires that the input is a valid string
/*  representation of an IPv4 or IPv6 network address as
/*  described next.
/*
/*  valid_ipv4_hostaddr() and valid_ipv6_hostaddr() implement
/*  protocol-specific address syntax checks. A valid IPv4
/*  address is in dotted-quad decimal form. A valid IPv6 address
/*  has 16-bit hexadecimal fields separated by ":", and does not
/*  include the RFC 2821 style "IPv6:" prefix.
/*
/*  These routines operate silently unless the gripe parameter
/*  specifies a non-zero value. The macros DO_GRIPE and DONT_GRIPE
/*  provide suitable constants.
/*
/*  valid_hostport() requires that the input is a valid string
/*  representation of a TCP or UDP port number.
/* BUGS
/*  valid_hostmumble() does not guarantee that string lengths
/*  fit the buffer sizes defined in myaddrinfo(3h).
/* DIAGNOSTICS
/*  All functions return zero if they disagree with the input.
/* SEE ALSO
/*  RFC 952, RFC 1123, RFC 1035, RFC 2373.
/* 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 <string.h>
#include <ctype.h>
#include <stdlib.h>

/* Utility library. */

#include "msg.h"
#include "mymalloc.h"
#include "stringops.h"
#include "valid_hostname.h"

/* valid_hostname - screen out bad hostnames */

int     valid_hostname(const char *name, int gripe)
{
    const char *myname = "valid_hostname";
    const char *cp;
    int     label_length = 0;
    int     label_count = 0;
    int     non_numeric = 0;
    int     ch;

    /*
     * Trivial cases first.
     */
    if (*name == 0) {
    if (gripe)
        msg_warn("%s: empty hostname", myname);
    return (0);
    }

    /*
     * Find bad characters or label lengths. Find adjacent delimiters.
     */
    for (cp = name; (ch = *(unsigned char *) cp) != 0; cp++) {
    if (ISALNUM(ch) || ch == '_') {     /* grr.. */
        if (label_length == 0)
        label_count++;
        label_length++;
        if (label_length > VALID_LABEL_LEN) {
        if (gripe)
            msg_warn("%s: hostname label too long: %.100s", myname, name);
        return (0);
        }
        if (!ISDIGIT(ch))
        non_numeric = 1;
    } else if (ch == '.') {
        if (label_length == 0 || cp[1] == 0) {
        if (gripe)
            msg_warn("%s: misplaced delimiter: %.100s", myname, name);
        return (0);
        }
        label_length = 0;
    } else if (ch == '-') {
        non_numeric = 1;
        label_length++;
        if (label_length == 1 || cp[1] == 0 || cp[1] == '.') {
        if (gripe)
            msg_warn("%s: misplaced hyphen: %.100s", myname, name);
        return (0);
        }
    }
#ifdef SLOPPY_VALID_HOSTNAME
    else if (ch == ':' && valid_ipv6_hostaddr(name, DONT_GRIPE)) {
        non_numeric = 0;
        break;
    }
#endif
    else {
        if (gripe)
        msg_warn("%s: invalid character %d(decimal): %.100s",
             myname, ch, name);
        return (0);
    }
    }

    if (non_numeric == 0) {
    if (gripe)
        msg_warn("%s: numeric hostname: %.100s", myname, name);
#ifndef SLOPPY_VALID_HOSTNAME
    return (0);
#endif
    }
    if (cp - name > VALID_HOSTNAME_LEN) {
    if (gripe)
        msg_warn("%s: bad length %d for %.100s...",
             myname, (int) (cp - name), name);
    return (0);
    }
    return (1);
}

/* valid_hostaddr - verify numerical address syntax */

int     valid_hostaddr(const char *addr, int gripe)
{
    const char *myname = "valid_hostaddr";

    /*
     * Trivial cases first.
     */
    if (*addr == 0) {
    if (gripe)
        msg_warn("%s: empty address", myname);
    return (0);
    }

    /*
     * Protocol-dependent processing next.
     */
    if (strchr(addr, ':') != 0)
    return (valid_ipv6_hostaddr(addr, gripe));
    else
    return (valid_ipv4_hostaddr(addr, gripe));
}

/* valid_ipv4_hostaddr - test dotted quad string for correctness */

int     valid_ipv4_hostaddr(const char *addr, int gripe)
{
    const char *cp;
    const char *myname = "valid_ipv4_hostaddr";
    int     in_byte = 0;
    int     byte_count = 0;
    int     byte_val = 0;
    int     ch;

#define BYTES_NEEDED    4

    /*
     * Scary code to avoid sscanf() overflow nasties.
     * 
     * This routine is called by valid_ipv6_hostaddr(). It must not call that
     * routine, to avoid deadly recursion.
     */
    for (cp = addr; (ch = *(unsigned const char *) cp) != 0; cp++) {
    if (ISDIGIT(ch)) {
        if (in_byte == 0) {
        in_byte = 1;
        byte_val = 0;
        byte_count++;
        }
        byte_val *= 10;
        byte_val += ch - '0';
        if (byte_val > 255) {
        if (gripe)
            msg_warn("%s: invalid octet value: %.100s", myname, addr);
        return (0);
        }
    } else if (ch == '.') {
        if (in_byte == 0 || cp[1] == 0) {
        if (gripe)
            msg_warn("%s: misplaced dot: %.100s", myname, addr);
        return (0);
        }
        /* XXX Allow 0.0.0.0 but not 0.1.2.3 */
        if (byte_count == 1 && byte_val == 0 && addr[strspn(addr, "0.")]) {
        if (gripe)
            msg_warn("%s: bad initial octet value: %.100s", myname, addr);
        return (0);
        }
        in_byte = 0;
    } else {
        if (gripe)
        msg_warn("%s: invalid character %d(decimal): %.100s",
             myname, ch, addr);
        return (0);
    }
    }

    if (byte_count != BYTES_NEEDED) {
    if (gripe)
        msg_warn("%s: invalid octet count: %.100s", myname, addr);
    return (0);
    }
    return (1);
}

/* valid_ipv6_hostaddr - validate IPv6 address syntax */

int     valid_ipv6_hostaddr(const char *addr, int gripe)
{
    const char *myname = "valid_ipv6_hostaddr";
    int     null_field = 0;
    int     field = 0;
    unsigned char *cp = (unsigned char *) addr;
    int     len = 0;

    /*
     * FIX 200501 The IPv6 patch validated syntax with getaddrinfo(), but I
     * am not confident that everyone's system library routines are robust
     * enough, like buffer overflow free. Remember, the valid_hostmumble()
     * routines are meant to protect Postfix against malformed information in
     * data received from the network.
     * 
     * We require eight-field hex addresses of the form 0:1:2:3:4:5:6:7,
     * 0:1:2:3:4:5:6a.6b.7c.7d, or some :: compressed version of the same.
     * 
     * Note: the character position is advanced inside the loop. I have added
     * comments to show why we can't get stuck.
     */
    for (;;) {
    switch (*cp) {
    case 0:
        /* Terminate the loop. */
        if (field < 2) {
        if (gripe)
            msg_warn("%s: too few `:' in IPv6 address: %.100s",
                 myname, addr);
        return (0);
        } else if (len == 0 && null_field != field - 1) {
        if (gripe)
            msg_warn("%s: bad null last field in IPv6 address: %.100s",
                 myname, addr);
        return (0);
        } else
        return (1);
    case '.':
        /* Terminate the loop. */
        if (field < 2 || field > 6) {
        if (gripe)
            msg_warn("%s: malformed IPv4-in-IPv6 address: %.100s",
                 myname, addr);
        return (0);
        } else
        /* NOT: valid_hostaddr(). Avoid recursion. */
        return (valid_ipv4_hostaddr((char *) cp - len, gripe));
    case ':':
        /* Advance by exactly 1 character position or terminate. */
        if (field == 0 && len == 0 && ISALNUM(cp[1])) {
        if (gripe)
            msg_warn("%s: bad null first field in IPv6 address: %.100s",
                 myname, addr);
        return (0);
        }
        field++;
        if (field > 7) {
        if (gripe)
            msg_warn("%s: too many `:' in IPv6 address: %.100s",
                 myname, addr);
        return (0);
        }
        cp++;
        len = 0;
        if (*cp == ':') {
        if (null_field > 0) {
            if (gripe)
            msg_warn("%s: too many `::' in IPv6 address: %.100s",
                 myname, addr);
            return (0);
        }
        null_field = field;
        }
        break;
    default:
        /* Advance by at least 1 character position or terminate. */
        len = strspn((char *) cp, "0123456789abcdefABCDEF");
        if (len /* - strspn((char *) cp, "0") */ > 4) {
        if (gripe)
            msg_warn("%s: malformed IPv6 address: %.100s",
                 myname, addr);
        return (0);
        }
        if (len <= 0) {
        if (gripe)
            msg_warn("%s: invalid character %d(decimal) in IPv6 address: %.100s",
                 myname, *cp, addr);
        return (0);
        }
        cp += len;
        break;
    }
    }
}

/* valid_hostport - validate numeric port */

int     valid_hostport(const char *str, int gripe)
{
    const char *myname = "valid_hostport";
    int     port;

    if (str[0] == '0' && str[1] != 0) {
    if (gripe)
        msg_warn("%s: leading zero in port number: %.100s", myname, str);
    return (0);
    }
    if (alldig(str) == 0) {
    if (gripe)
        msg_warn("%s: non-numeric port number: %.100s", myname, str);
    return (0);
    }
    if (strlen(str) > strlen("65535")
    || (port = atoi(str)) > 65535 || port < 0) {
    if (gripe)
        msg_warn("%s: out-of-range port number: %.100s", myname, str);
    return (0);
    }
    return (1);
}

#ifdef TEST

 /*
  * Test program - reads hostnames from stdin, reports invalid hostnames to
  * stderr.
  */
#include <stdlib.h>

#include "vstring.h"
#include "vstream.h"
#include "vstring_vstream.h"
#include "msg_vstream.h"

int     main(int unused_argc, char **argv)
{
    VSTRING *buffer = vstring_alloc(1);

    msg_vstream_init(argv[0], VSTREAM_ERR);
    msg_verbose = 1;

    while (vstring_fgets_nonl(buffer, VSTREAM_IN)) {
    msg_info("testing: \"%s\"", vstring_str(buffer));
    valid_hostname(vstring_str(buffer), DO_GRIPE);
    valid_hostaddr(vstring_str(buffer), DO_GRIPE);
    }
    exit(0);
}

#endif