srs2.c

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/* Copyright (c) 2004 Shevek (srs@anarres.org)
 * All rights reserved.
 *
 * This file is a part of libsrs2 from http://www.libsrs2.org/
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, under the terms of either the GNU General Public
 * License version 2 or the BSD license, at the discretion of the
 * user. Copies of these licenses have been included in the libsrs2
 * distribution. See the the file called LICENSE for more
 * information.
 */
 
/* This is a minimal adapted s/qmail version; it requires complete 
   refactoring:
 
   a) Use stralloc for addresses
   b) Replace stdio, str*, and mem* functions
   c) Use tai64 for timestamp function
   d) Remove va args 
   e) Reduce code by 50%
*/
 
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <stdarg.h>
#include <time.h>       /* time */
#include <sys/types.h>  /* tyepdefs */
#include <sys/time.h>   /* timeval / timezone struct */
#include <string.h>               /* memcpy, strcpy, memset */
#include "srs2.h"
#include "sha1.h"
 
#ifndef HAVE_STRCASECMP
# ifdef HAVE__STRICMP
#  define strcasecmp _stricmp
# endif
#endif
 
#ifndef HAVE_STRNCASECMP
# ifdef HAVE__STRNICMP
#  define strncasecmp _strnicmp
# endif
#endif
 
        /* Use this */
#define STRINGP(s) ((s != NULL) && (*(s) != '\0'))
 
static const char *srs_separators = "=-+";
 
static srs_malloc_t   srs_f_malloc  = malloc;
static srs_realloc_t  srs_f_realloc = realloc;
static srs_free_t     srs_f_free    = free;
 
int     srs_set_malloc(srs_malloc_t m, srs_realloc_t r, srs_free_t f)
{
        srs_f_malloc = m;
        srs_f_realloc = r;
        srs_f_free = f;
        return SRS_SUCCESS;
}
 
#define X(e,s) if (code == e) return s;
 
const char *srs_strerror(int code)
{
  X(0,"")
  /* Simple errors */
  X(SRS_SUCCESS,"Success")
  X(SRS_ENOTSRSADDRESS,"Not an SRS address.")
 
  /* Config errors */
  X(SRS_ENOSECRETS,"No secrets in SRS configuration.")
  X(SRS_ESEPARATORINVALID,"Invalid separator suggested.")
 
  /* Input errors */
  X(SRS_ENOSENDERATSIGN,"No at sign in sender address")
  X(SRS_EBUFTOOSMALL,"Buffer too small.")
 
  /* Syntax errors */
  X(SRS_ENOSRS0HOST,"No host in SRS0 address.")
  X(SRS_ENOSRS0USER,"No user in SRS0 address.")
  X(SRS_ENOSRS0HASH,"No hash in SRS0 address.")
  X(SRS_ENOSRS0STAMP,"No timestamp in SRS0 address.")
  X(SRS_ENOSRS1HOST,"No host in SRS1 address.")
  X(SRS_ENOSRS1USER,"No user in SRS1 address.")
  X(SRS_ENOSRS1HASH,"No hash in SRS1 address.")
  X(SRS_EBADTIMESTAMPCHAR,"Bad base32 character in timestamp.")
  X(SRS_EHASHTOOSHORT,"Hash too short in SRS address.")
 
  /* SRS errors */
  X(SRS_ETIMESTAMPOUTOFDATE,"Time stamp out of date.")
  X(SRS_EHASHINVALID,"Hash invalid in SRS address.")
 
  return "Unknown SRS error."; 
}
 
srs_t *srs_new()
{
        srs_t   *srs = (srs_t *)srs_f_malloc(sizeof(srs_t));
        srs_init(srs);
        return srs;
}
 
void srs_init(srs_t *srs)
{
        memset(srs, 0, sizeof(srs_t));
        srs->secrets = NULL;
        srs->numsecrets = 0;
        srs->separator = '=';
        srs->maxage = 21;
        srs->hashlen = 4;
        srs->hashmin = srs->hashlen;
        srs->alwaysrewrite = FALSE;
}
 
void srs_free(srs_t *srs)
{
        int      i;
        for (i = 0; i < srs->numsecrets; i++) {
                memset(srs->secrets[i], 0, strlen(srs->secrets[i]));
                srs_f_free(srs->secrets[i]);
                srs->secrets[i] = '\0';
        }
        srs_f_free(srs);
}
 
int srs_add_secret(srs_t *srs, const char *secret)
{
        int             newlen = (srs->numsecrets + 1) * sizeof(char *);
        srs->secrets = (char **)srs_f_realloc(srs->secrets, newlen);
        srs->secrets[srs->numsecrets++] = strdup(secret);
        return SRS_SUCCESS;
}
 
const char *srs_get_secret(srs_t *srs, int idx)
{
        if (idx < srs->numsecrets)
                return srs->secrets[idx];
        return NULL;
}
 
#define SRS_PARAM_DEFINE(n, t) \
        int srs_set_ ## n (srs_t *srs, t value) { \
                srs->n = value; \
                return SRS_SUCCESS; \
        } \
        t srs_get_ ## n (srs_t *srs) { \
                return srs->n; \
        }
 
int srs_set_separator(srs_t *srs, char value)
{
        if (strchr(srs_separators, value) == NULL)
                return SRS_ESEPARATORINVALID;
        srs->separator = value;
        return SRS_SUCCESS;
}
 
char srs_get_separator(srs_t *srs)
{
        return srs->separator;
}
 
SRS_PARAM_DEFINE(maxage, int)
        /* XXX Check hashlen >= hashmin */
SRS_PARAM_DEFINE(hashlen, int)
SRS_PARAM_DEFINE(hashmin, int)
SRS_PARAM_DEFINE(alwaysrewrite, srs_bool)
SRS_PARAM_DEFINE(noforward, srs_bool)
SRS_PARAM_DEFINE(noreverse, srs_bool)
 
/* Don't mess with these unless you know what you're doing well
 * enough to rewrite the timestamp functions. These are based on
 * a 2 character timestamp. Changing these in the wild is probably
 * a bad idea. */
#define SRS_TIME_PRECISION      (60 * 60 * 24)  /* One day */
#define SRS_TIME_BASEBITS       5               /* 2^5 = 32 = strlen(CHARS) */
/* This had better be a real variable since we do arithmethic
 * with it. */
const char *SRS_TIME_BASECHARS = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
#define SRS_TIME_SIZE           2
#define SRS_TIME_SLOTS          (1<<(SRS_TIME_BASEBITS<<(SRS_TIME_SIZE-1)))
 
int srs_timestamp_create(srs_t *srs, char *buf, time_t now)
{
        now = now / SRS_TIME_PRECISION;
        buf[1] = SRS_TIME_BASECHARS[now & ((1 << SRS_TIME_BASEBITS) - 1)];
        now = now >> SRS_TIME_BASEBITS;
        buf[0] = SRS_TIME_BASECHARS[now & ((1 << SRS_TIME_BASEBITS) - 1)];
        buf[2] = '\0';
        return SRS_SUCCESS;
}
 
int srs_timestamp_check(srs_t *srs, const char *stamp)
{
        const char      *sp;
        char            *bp;
        int                      off;
        time_t           now;
        time_t           then;
 
        /* We had better go around this loop exactly twice! */
        then = 0;
        for (sp = stamp; *sp; sp++) {
                bp = strchr(SRS_TIME_BASECHARS, toupper(*sp));
                if (bp == NULL)
                        return SRS_EBADTIMESTAMPCHAR;
                off = bp - SRS_TIME_BASECHARS;
                then = (then << SRS_TIME_BASEBITS) | off;
        }
 
        time(&now);
        now = (now / SRS_TIME_PRECISION) % SRS_TIME_SLOTS;
        while (now < then)
                now = now + SRS_TIME_SLOTS;
 
        if (now <= then + srs->maxage)
                return SRS_SUCCESS;
        return SRS_ETIMESTAMPOUTOFDATE;
}
 
const char *SRS_HASH_BASECHARS = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                                                                 "abcdefghijklmnopqrstuvwxyz"
                                                                 "0123456789+/";
 
static void srs_hash_create_v(srs_t *srs, int idx, char *buf, int nargs, va_list ap)
{
        sha1_ctx         ctx;
        char                     srshash[SHA1_DIGESTSIZE + 1];
        char                    *secret;
        char                    *data;
        int                              len;
        char                    *lcdata;
        unsigned char   *hp;
        char                    *bp;
        int                              i;
        int                              j;
 
        secret = srs->secrets[idx];
        sha1_init(&ctx);
        sha1_update(&ctx, secret, strlen(secret));
 
        for (i = 0; i < nargs; i++) {
                data = va_arg(ap, char *);
                len = strlen(data);
                lcdata = alloca(len + 1);
                for (j = 0; j < len; j++) {
                        if (isupper(data[j]))
                                lcdata[j] = tolower(data[j]);
                        else
                                lcdata[j] = data[j];
                }
                sha1_update(&ctx, lcdata, len);
        }
 
        sha1_final(srshash, &ctx); /* args inverted */
        srshash[SHA1_DIGESTSIZE] = '\0';
 
        /* A little base64 encoding. Just a little. */
        hp = (unsigned char *)srshash;
        bp = buf;
        for (i = 0; i < srs->hashlen; i++) {
                switch (i & 0x03) {
                        default:        /* NOTREACHED */
                        case 0:
                                j = (*hp >> 2);
                                break;
                        case 1:
                                j = ((*hp & 0x03) << 4) |
                                                ((*(hp + 1) & 0xF0) >> 4);
                                hp++;
                                break;
                        case 2:
                                j = ((*hp & 0x0F) << 2) |
                                                ((*(hp + 1) & 0xC0) >> 6);
                                hp++;
                                break;
                        case 3:
                                j = (*hp++ & 0x3F);
                                break;
                }
                *bp++ = SRS_HASH_BASECHARS[j];
        }
 
        *bp = '\0';
        buf[srs->hashlen] = '\0';
}
 
int srs_hash_create(srs_t *srs, char *buf, int nargs, ...)
{
        va_list  ap;
 
        if (srs->numsecrets == 0)
                return SRS_ENOSECRETS;
        if (srs->secrets == NULL)
                return SRS_ENOSECRETS;
        if (srs->secrets[0] == NULL)
                return SRS_ENOSECRETS;
 
        va_start(ap, nargs);
        srs_hash_create_v(srs, 0, buf, nargs, ap);
        va_end(ap);
 
        return SRS_SUCCESS;
}
 
int srs_hash_check(srs_t *srs, char *hash, int nargs, ...)
{
        va_list ap;
        char    *srshash;
        char    *tmp;
        int              len;
        int              i;
 
        len = strlen(hash);
        if (len < srs->hashmin)
                return SRS_EHASHTOOSHORT;
        if (len < srs->hashlen) {
                tmp = alloca(srs->hashlen + 1);
                strncpy(tmp, hash, srs->hashlen);
                tmp[srs->hashlen] = '\0';
                hash = tmp;
                len = srs->hashlen;
        }
 
        for (i = 0; i < srs->numsecrets; i++) {
                va_start(ap, nargs);
                srshash = alloca(srs->hashlen + 1);
                srs_hash_create_v(srs, i, srshash, nargs, ap);
                va_end(ap);
                if (strncasecmp(hash, srshash, len) == 0)
                        return SRS_SUCCESS;
        }
 
        return SRS_EHASHINVALID;
}
 
int srs_compile_shortcut(srs_t *srs,
                                char *buf, int buflen,
                                char *sendhost, char *senduser,
                                const char *aliashost) {
        char    *srshash;
        char     srsstamp[SRS_TIME_SIZE + 1];
        int              len;
        int              ret;
 
        /* This never happens if we get called from guarded() */
        if ((strncasecmp(senduser, SRS0TAG, 4) == 0) &&
                (strchr(srs_separators, senduser[4]) != NULL)) {
                sendhost = senduser + 5;
                if (*sendhost == '\0')
                        return SRS_ENOSRS0HOST;
                senduser = strchr(sendhost, SRSSEP);
                if ((senduser == NULL) || (*senduser == '\0'))
                        return SRS_ENOSRS0USER;
        }
 
        len = strlen(SRS0TAG) + 1 +
                srs->hashlen + 1 +
                        SRS_TIME_SIZE + 1 +
                                strlen(sendhost) + 1 + strlen(senduser)
                        + 1 + strlen(aliashost);
        if (len >= buflen)
                return SRS_EBUFTOOSMALL;
 
        ret = srs_timestamp_create(srs, srsstamp, time(NULL));
        if (ret != SRS_SUCCESS)
                return ret;
        srshash = alloca(srs->hashlen + 1);
        ret = srs_hash_create(srs, srshash,3, srsstamp, sendhost, senduser);
        if (ret != SRS_SUCCESS)
                return ret;
 
        sprintf(buf, SRS0TAG "%c%s%c%s%c%s%c%s@%s", srs->separator,
                                        srshash, SRSSEP, srsstamp, SRSSEP,
                                                sendhost, SRSSEP, senduser,
                                                        aliashost);
 
        return SRS_SUCCESS;
}
 
int srs_compile_guarded(srs_t *srs,
                                char *buf, int buflen,
                                char *sendhost, char *senduser,
                                const char *aliashost) {
        char    *srshost;
        char    *srsuser;
        char    *srshash;
        int              len;
        int              ret;
 
        if ((strncasecmp(senduser, SRS1TAG, 4) == 0) &&
                (strchr(srs_separators, senduser[4]) != NULL)) {
                /* Used as a temporary convenience var */
                srshash = senduser + 5;
                if (*srshash == '\0')
                        return SRS_ENOSRS1HASH;
                /* Used as a temporary convenience var */
                srshost = strchr(srshash, SRSSEP);
                if (!STRINGP(srshost))
                        return SRS_ENOSRS1HOST;
                *srshost++ = '\0';
                srsuser = strchr(srshost, SRSSEP);
                if (!STRINGP(srsuser))
                        return SRS_ENOSRS1USER;
                *srsuser++ = '\0';
                srshash = alloca(srs->hashlen + 1);
                ret = srs_hash_create(srs, srshash, 2, srshost, srsuser);
                if (ret != SRS_SUCCESS)
                        return ret;
                len = strlen(SRS1TAG) + 1 +
                        srs->hashlen + 1 +
                                strlen(srshost) + 1 + strlen(srsuser)
                        + 1 + strlen(aliashost);
                if (len >= buflen)
                        return SRS_EBUFTOOSMALL;
                sprintf(buf, SRS1TAG "%c%s%c%s%c%s@%s", srs->separator,
                                                srshash, SRSSEP,
                                                        srshost, SRSSEP, srsuser,
                                                                aliashost);
                return SRS_SUCCESS;
        }
        else if ((strncasecmp(senduser, SRS0TAG, 4) == 0) &&
                (strchr(srs_separators, senduser[4]) != NULL)) {
                srsuser = senduser + 4;
                srshost = sendhost;
                srshash = alloca(srs->hashlen + 1);
                ret = srs_hash_create(srs, srshash, 2, srshost, srsuser);
                if (ret != SRS_SUCCESS)
                        return ret;
                len = strlen(SRS1TAG) + 1 +
                        srs->hashlen + 1 +
                                strlen(srshost) + 1 + strlen(srsuser)
                        + 1 + strlen(aliashost);
                if (len >= buflen)
                        return SRS_EBUFTOOSMALL;
                sprintf(buf, SRS1TAG "%c%s%c%s%c%s@%s", srs->separator,
                                                srshash, SRSSEP,
                                                        srshost, SRSSEP, srsuser,
                                                                aliashost);
        }
        else {
                return srs_compile_shortcut(srs, buf, buflen,
                                                sendhost, senduser, aliashost);
        }
 
        return SRS_SUCCESS;
}
 
int srs_parse_shortcut(srs_t *srs, char *buf, int buflen, char *senduser)
{
        char    *srshash;
        char    *srsstamp;
        char    *srshost;
        char    *srsuser;
        int              ret;
 
        if (strncasecmp(senduser, SRS0TAG, 4) == 0) {
                srshash = senduser + 5;
                if (!STRINGP(srshash))
                        return SRS_ENOSRS0HASH;
                srsstamp = strchr(srshash, SRSSEP);
                if (!STRINGP(srsstamp))
                        return SRS_ENOSRS0STAMP;
                *srsstamp++ = '\0';
                srshost = strchr(srsstamp, SRSSEP);
                if (!STRINGP(srshost))
                        return SRS_ENOSRS0HOST;
                *srshost++ = '\0';
                srsuser = strchr(srshost, SRSSEP);
                if (!STRINGP(srsuser))
                        return SRS_ENOSRS0USER;
                *srsuser++ = '\0';
                ret = srs_timestamp_check(srs, srsstamp);
                if (ret != SRS_SUCCESS)
                        return ret;
                ret = srs_hash_check(srs, srshash, 3, srsstamp,
                                                srshost, srsuser);
                if (ret != SRS_SUCCESS)
                        return ret;
                sprintf(buf, "%s@%s", srsuser, srshost);
                return SRS_SUCCESS;
        }
 
        return SRS_ENOTSRSADDRESS;
}
 
int srs_parse_guarded(srs_t *srs, char *buf, int buflen, char *senduser)
{
        char    *srshash;
        char    *srshost;
        char    *srsuser;
        int              ret;
 
        if (strncasecmp(senduser, SRS1TAG, 4) == 0) {
                srshash = senduser + 5;
                if (!STRINGP(srshash))
                        return SRS_ENOSRS1HASH;
                srshost = strchr(srshash, SRSSEP);
                if (!STRINGP(srshost))
                        return SRS_ENOSRS1HOST;
                *srshost++ = '\0';
                srsuser = strchr(srshost, SRSSEP);
                if (!STRINGP(srsuser))
                        return SRS_ENOSRS1USER;
                *srsuser++ = '\0';
                ret = srs_hash_check(srs, srshash, 2, srshost, srsuser);
                if (ret != SRS_SUCCESS)
                        return ret;
                sprintf(buf, SRS0TAG "%s@%s", srsuser, srshost);
                return SRS_SUCCESS;
        }
        else {
                return srs_parse_shortcut(srs, buf, buflen, senduser);
        }
}
 
int srs_forward(srs_t *srs, char *buf, int buflen,
                                const char *sender, const char *alias)
{
        char    *senduser;
        char    *sendhost;
        char    *tmp;
        int              len;
 
        if (srs->noforward)
                return SRS_ENOTREWRITTEN;
 
        /* This is allowed to be a plain domain */
        while ((tmp = strchr(alias, '@')) != NULL)
                alias = tmp + 1;
 
        tmp = strchr(sender, '@');
        if (tmp == NULL)
                return SRS_ENOSENDERATSIGN;
        sendhost = tmp + 1;
 
        len = strlen(sender);
 
        if (! srs->alwaysrewrite) {
                if (strcasecmp(sendhost, alias) == 0) {
                        if (strlen(sender) >= buflen)
                                return SRS_EBUFTOOSMALL;
                        strcpy(buf, sender);
                        return SRS_SUCCESS;
                }
        }
 
        /* Reconstruct the whole show into our alloca() buffer. */
        senduser = alloca(len + 1);
        strcpy(senduser, sender);
        tmp = (senduser + (tmp - sender));
        sendhost = tmp + 1;
        *tmp = '\0';
 
        return srs_compile_guarded(srs, buf, buflen,
                                        sendhost, senduser, alias);
}
 
int srs_forward_alloc(srs_t *srs, char **sptr,
                                const char *sender, const char *alias)
{
        char    *buf;
        int              slen;
        int              alen;
        int              len;
        int              ret;
 
        if (srs->noforward)
                return SRS_ENOTREWRITTEN;
 
        slen = strlen(sender);
        alen = strlen(alias);
 
        /* strlen(SRSxTAG) + strlen("====+@") < 64 */
        len = slen + alen + srs->hashlen + SRS_TIME_SIZE + 64;
        buf = (char *)srs_f_malloc(len);
 
        ret = srs_forward(srs, buf, len, sender, alias);
 
        if (ret == SRS_SUCCESS)
                *sptr = buf;
        else
                srs_f_free(buf);
 
        return ret;
}
 
int srs_reverse(srs_t *srs, char *buf, int buflen, const char *sender)
{
        char    *senduser;
        char    *tmp;
        int              len;
 
        if (!SRS_IS_SRS_ADDRESS(sender))
                return SRS_ENOTSRSADDRESS;
 
        if (srs->noreverse)
                return SRS_ENOTREWRITTEN;
 
        len = strlen(sender);
        if (len >= buflen)
                return SRS_EBUFTOOSMALL;
        senduser = alloca(len + 1);
        strcpy(senduser, sender);
 
        /* We don't really care about the host for reversal. */
        tmp = strchr(senduser, '@');
        if (tmp != NULL)
                *tmp = '\0';
        return srs_parse_guarded(srs, buf, buflen, senduser);
}
 
int srs_reverse_alloc(srs_t *srs, char **sptr, const char *sender)
{
        char    *buf;
        int              len;
        int              ret;
 
        *sptr = NULL;
 
        if (!SRS_IS_SRS_ADDRESS(sender))
                return SRS_ENOTSRSADDRESS;
 
        if (srs->noreverse)
                return SRS_ENOTREWRITTEN;
 
        len = strlen(sender) + 1;
        buf = (char *)srs_f_malloc(len);
 
        ret = srs_reverse(srs, buf, len, sender);
 
        if (ret == SRS_SUCCESS)
                *sptr = buf;
        else
                srs_f_free(buf);
 
        return ret;
}