1/* -*- Mode: C; tab-width: 4 -*-
2 *
3 * Copyright (c) 2004, Apple Computer, Inc. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are met:
7 *
8 * 1.  Redistributions of source code must retain the above copyright notice,
9 *     this list of conditions and the following disclaimer.
10 * 2.  Redistributions in binary form must reproduce the above copyright notice,
11 *     this list of conditions and the following disclaimer in the documentation
12 *     and/or other materials provided with the distribution.
13 * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of its
14 *     contributors may be used to endorse or promote products derived from this
15 *     software without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
18 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
19 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
20 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
21 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
22 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
23 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
24 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
26 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29#include <stdlib.h>
30#include <string.h>
31
32#include "dns_sd.h"
33
34#if MDNS_BUILDINGSHAREDLIBRARY || MDNS_BUILDINGSTUBLIBRARY
35#pragma export on
36#endif
37
38#if defined(_WIN32)
39// disable warning "conversion from <data> to uint16_t"
40#pragma warning(disable:4244)
41#define strncasecmp _strnicmp
42#define strcasecmp _stricmp
43#endif
44
45/*********************************************************************************************
46*
47*  Supporting Functions
48*
49*********************************************************************************************/
50
51#define mDNSIsDigit(X)     ((X) >= '0' && (X) <= '9')
52
53// DomainEndsInDot returns 1 if name ends with a dot, 0 otherwise
54// (DNSServiceConstructFullName depends this returning 1 for true, rather than any non-zero value meaning true)
55
56static int DomainEndsInDot(const char *dom)
57{
58    while (dom[0] && dom[1])
59    {
60        if (dom[0] == '\\') // advance past escaped byte sequence
61        {
62            if (mDNSIsDigit(dom[1]) && mDNSIsDigit(dom[2]) && mDNSIsDigit(dom[3]))
63                dom += 4;           // If "\ddd"    then skip four
64            else dom += 2;          // else if "\x" then skip two
65        }
66        else dom++;                 // else goto next character
67    }
68    return (dom[0] == '.');
69}
70
71static uint8_t *InternalTXTRecordSearch
72(
73    uint16_t txtLen,
74    const void       *txtRecord,
75    const char       *key,
76    unsigned long    *keylen
77)
78{
79    uint8_t *p = (uint8_t*)txtRecord;
80    uint8_t *e = p + txtLen;
81    *keylen = (unsigned long) strlen(key);
82    while (p<e)
83    {
84        uint8_t *x = p;
85        p += 1 + p[0];
86        if (p <= e && *keylen <= x[0] && !strncasecmp(key, (char*)x+1, *keylen))
87            if (*keylen == x[0] || x[1+*keylen] == '=') return(x);
88    }
89    return(NULL);
90}
91
92/*********************************************************************************************
93*
94*  General Utility Functions
95*
96*********************************************************************************************/
97
98// Note: Need to make sure we don't write more than kDNSServiceMaxDomainName (1009) bytes to fullName
99// In earlier builds this constant was defined to be 1005, so to avoid buffer overruns on clients
100// compiled with that constant we'll actually limit the output to 1005 bytes.
101
102DNSServiceErrorType DNSSD_API DNSServiceConstructFullName
103(
104    char       *const fullName,
105    const char *const service,      // May be NULL
106    const char *const regtype,
107    const char *const domain
108)
109{
110    const size_t len = !regtype ? 0 : strlen(regtype) - DomainEndsInDot(regtype);
111    char       *fn   = fullName;
112    char *const lim  = fullName + 1005;
113    const char *s    = service;
114    const char *r    = regtype;
115    const char *d    = domain;
116
117    // regtype must be at least "x._udp" or "x._tcp"
118    if (len < 6 || !domain || !domain[0]) return kDNSServiceErr_BadParam;
119    if (strncasecmp((regtype + len - 4), "_tcp", 4) && strncasecmp((regtype + len - 4), "_udp", 4)) return kDNSServiceErr_BadParam;
120
121    if (service && *service)
122    {
123        while (*s)
124        {
125            unsigned char c = *s++;             // Needs to be unsigned, or values like 0xFF will be interpreted as < 32
126            if (c <= ' ')                       // Escape non-printable characters
127            {
128                if (fn+4 >= lim) goto fail;
129                *fn++ = '\\';
130                *fn++ = '0' + (c / 100);
131                *fn++ = '0' + (c /  10) % 10;
132                c     = '0' + (c      ) % 10;
133            }
134            else if (c == '.' || (c == '\\'))   // Escape dot and backslash literals
135            {
136                if (fn+2 >= lim) goto fail;
137                *fn++ = '\\';
138            }
139            else
140            if (fn+1 >= lim) goto fail;
141            *fn++ = (char)c;
142        }
143        *fn++ = '.';
144    }
145
146    while (*r) if (fn+1 >= lim) goto fail;else *fn++ = *r++;
147    if (!DomainEndsInDot(regtype)) { if (fn+1 >= lim) goto fail;else *fn++ = '.';}
148
149    while (*d) if (fn+1 >= lim) goto fail;else *fn++ = *d++;
150    if (!DomainEndsInDot(domain)) { if (fn+1 >= lim) goto fail;else *fn++ = '.';}
151
152    *fn = '\0';
153    return kDNSServiceErr_NoError;
154
155fail:
156    *fn = '\0';
157    return kDNSServiceErr_BadParam;
158}
159
160/*********************************************************************************************
161*
162*   TXT Record Construction Functions
163*
164*********************************************************************************************/
165
166typedef struct _TXTRecordRefRealType
167{
168    uint8_t  *buffer;       // Pointer to data
169    uint16_t buflen;        // Length of buffer
170    uint16_t datalen;       // Length currently in use
171    uint16_t malloced;  // Non-zero if buffer was allocated via malloc()
172} TXTRecordRefRealType;
173
174#define txtRec ((TXTRecordRefRealType*)txtRecord)
175
176// The opaque storage defined in the public dns_sd.h header is 16 bytes;
177// make sure we don't exceed that.
178struct CompileTimeAssertionCheck_dnssd_clientlib
179{
180    char assert0[(sizeof(TXTRecordRefRealType) <= 16) ? 1 : -1];
181};
182
183void DNSSD_API TXTRecordCreate
184(
185    TXTRecordRef     *txtRecord,
186    uint16_t bufferLen,
187    void             *buffer
188)
189{
190    txtRec->buffer   = buffer;
191    txtRec->buflen   = buffer ? bufferLen : (uint16_t)0;
192    txtRec->datalen  = 0;
193    txtRec->malloced = 0;
194}
195
196void DNSSD_API TXTRecordDeallocate(TXTRecordRef *txtRecord)
197{
198    if (txtRec->malloced) free(txtRec->buffer);
199}
200
201DNSServiceErrorType DNSSD_API TXTRecordSetValue
202(
203    TXTRecordRef     *txtRecord,
204    const char       *key,
205    uint8_t valueSize,
206    const void       *value
207)
208{
209    uint8_t *start, *p;
210    const char *k;
211    unsigned long keysize, keyvalsize;
212
213    for (k = key; *k; k++) if (*k < 0x20 || *k > 0x7E || *k == '=') return(kDNSServiceErr_Invalid);
214    keysize = (unsigned long)(k - key);
215    keyvalsize = 1 + keysize + (value ? (1 + valueSize) : 0);
216    if (keysize < 1 || keyvalsize > 255) return(kDNSServiceErr_Invalid);
217    (void)TXTRecordRemoveValue(txtRecord, key);
218    if (txtRec->datalen + keyvalsize > txtRec->buflen)
219    {
220        unsigned char *newbuf;
221        unsigned long newlen = txtRec->datalen + keyvalsize;
222        if (newlen > 0xFFFF) return(kDNSServiceErr_Invalid);
223        newbuf = malloc((size_t)newlen);
224        if (!newbuf) return(kDNSServiceErr_NoMemory);
225        memcpy(newbuf, txtRec->buffer, txtRec->datalen);
226        if (txtRec->malloced) free(txtRec->buffer);
227        txtRec->buffer = newbuf;
228        txtRec->buflen = (uint16_t)(newlen);
229        txtRec->malloced = 1;
230    }
231    start = txtRec->buffer + txtRec->datalen;
232    p = start + 1;
233    memcpy(p, key, keysize);
234    p += keysize;
235    if (value)
236    {
237        *p++ = '=';
238        memcpy(p, value, valueSize);
239        p += valueSize;
240    }
241    *start = (uint8_t)(p - start - 1);
242    txtRec->datalen += p - start;
243    return(kDNSServiceErr_NoError);
244}
245
246DNSServiceErrorType DNSSD_API TXTRecordRemoveValue
247(
248    TXTRecordRef     *txtRecord,
249    const char       *key
250)
251{
252    unsigned long keylen, itemlen, remainder;
253    uint8_t *item = InternalTXTRecordSearch(txtRec->datalen, txtRec->buffer, key, &keylen);
254    if (!item) return(kDNSServiceErr_NoSuchKey);
255    itemlen   = (unsigned long)(1 + item[0]);
256    remainder = (unsigned long)((txtRec->buffer + txtRec->datalen) - (item + itemlen));
257    // Use memmove because memcpy behaviour is undefined for overlapping regions
258    memmove(item, item + itemlen, remainder);
259    txtRec->datalen -= itemlen;
260    return(kDNSServiceErr_NoError);
261}
262
263uint16_t DNSSD_API TXTRecordGetLength  (const TXTRecordRef *txtRecord) { return(txtRec->datalen); }
264const void * DNSSD_API TXTRecordGetBytesPtr(const TXTRecordRef *txtRecord) { return(txtRec->buffer); }
265
266/*********************************************************************************************
267*
268*   TXT Record Parsing Functions
269*
270*********************************************************************************************/
271
272int DNSSD_API TXTRecordContainsKey
273(
274    uint16_t txtLen,
275    const void       *txtRecord,
276    const char       *key
277)
278{
279    unsigned long keylen;
280    return (InternalTXTRecordSearch(txtLen, txtRecord, key, &keylen) ? 1 : 0);
281}
282
283const void * DNSSD_API TXTRecordGetValuePtr
284(
285    uint16_t txtLen,
286    const void       *txtRecord,
287    const char       *key,
288    uint8_t          *valueLen
289)
290{
291    unsigned long keylen;
292    uint8_t *item = InternalTXTRecordSearch(txtLen, txtRecord, key, &keylen);
293    if (!item || item[0] <= keylen) return(NULL);   // If key not found, or found with no value, return NULL
294    *valueLen = (uint8_t)(item[0] - (keylen + 1));
295    return (item + 1 + keylen + 1);
296}
297
298uint16_t DNSSD_API TXTRecordGetCount
299(
300    uint16_t txtLen,
301    const void       *txtRecord
302)
303{
304    uint16_t count = 0;
305    uint8_t *p = (uint8_t*)txtRecord;
306    uint8_t *e = p + txtLen;
307    while (p<e) { p += 1 + p[0]; count++; }
308    return((p>e) ? (uint16_t)0 : count);
309}
310
311DNSServiceErrorType DNSSD_API TXTRecordGetItemAtIndex
312(
313    uint16_t txtLen,
314    const void       *txtRecord,
315    uint16_t itemIndex,
316    uint16_t keyBufLen,
317    char             *key,
318    uint8_t          *valueLen,
319    const void       **value
320)
321{
322    uint16_t count = 0;
323    uint8_t *p = (uint8_t*)txtRecord;
324    uint8_t *e = p + txtLen;
325    while (p<e && count<itemIndex) { p += 1 + p[0]; count++; }  // Find requested item
326    if (p<e && p + 1 + p[0] <= e)   // If valid
327    {
328        uint8_t *x = p+1;
329        unsigned long len = 0;
330        e = p + 1 + p[0];
331        while (x+len<e && x[len] != '=') len++;
332        if (len >= keyBufLen) return(kDNSServiceErr_NoMemory);
333        memcpy(key, x, len);
334        key[len] = 0;
335        if (x+len<e)        // If we found '='
336        {
337            *value = x + len + 1;
338            *valueLen = (uint8_t)(p[0] - (len + 1));
339        }
340        else
341        {
342            *value = NULL;
343            *valueLen = 0;
344        }
345        return(kDNSServiceErr_NoError);
346    }
347    return(kDNSServiceErr_Invalid);
348}
349
350/*********************************************************************************************
351*
352*   SCCS-compatible version string
353*
354*********************************************************************************************/
355
356// For convenience when using the "strings" command, this is the last thing in the file
357
358// Note: The C preprocessor stringify operator ('#') makes a string from its argument, without macro expansion
359// e.g. If "version" is #define'd to be "4", then STRINGIFY_AWE(version) will return the string "version", not "4"
360// To expand "version" to its value before making the string, use STRINGIFY(version) instead
361#define STRINGIFY_ARGUMENT_WITHOUT_EXPANSION(s) # s
362#define STRINGIFY(s) STRINGIFY_ARGUMENT_WITHOUT_EXPANSION(s)
363
364// NOT static -- otherwise the compiler may optimize it out
365// The "@(#) " pattern is a special prefix the "what" command looks for
366const char VersionString_SCCS_libdnssd[] = "@(#) libdns_sd " STRINGIFY(mDNSResponderVersion) " (" __DATE__ " " __TIME__ ")";
367