1 #define _BSD_SOURCE
2 #include <arpa/nameser.h>
3 #include <errno.h>
4 #include <resolv.h>
5 #include <stddef.h>
6 
7 const struct _ns_flagdata _ns_flagdata[16] = {
8     {0x8000, 15}, {0x7800, 11}, {0x0400, 10}, {0x0200, 9}, {0x0100, 8}, {0x0080, 7}, {0x0040, 6}, {0x0020, 5}, {0x0010, 4}, {0x000f, 0}, {0x0000, 0}, {0x0000, 0}, {0x0000, 0}, {0x0000, 0}, {0x0000, 0}, {0x0000, 0},
9 };
10 
ns_get16(const unsigned char * cp)11 unsigned ns_get16(const unsigned char* cp) {
12     return cp[0] << 8 | cp[1];
13 }
14 
ns_get32(const unsigned char * cp)15 unsigned long ns_get32(const unsigned char* cp) {
16     return (unsigned)cp[0] << 24 | cp[1] << 16 | cp[2] << 8 | cp[3];
17 }
18 
ns_put16(unsigned s,unsigned char * cp)19 void ns_put16(unsigned s, unsigned char* cp) {
20     *cp++ = s >> 8;
21     *cp++ = s;
22 }
23 
ns_put32(unsigned long l,unsigned char * cp)24 void ns_put32(unsigned long l, unsigned char* cp) {
25     *cp++ = l >> 24;
26     *cp++ = l >> 16;
27     *cp++ = l >> 8;
28     *cp++ = l;
29 }
30 
ns_initparse(const unsigned char * msg,int msglen,ns_msg * handle)31 int ns_initparse(const unsigned char* msg, int msglen, ns_msg* handle) {
32     int i, r;
33 
34     handle->_msg = msg;
35     handle->_eom = msg + msglen;
36     if (msglen < (2 + ns_s_max) * NS_INT16SZ)
37         goto bad;
38     NS_GET16(handle->_id, msg);
39     NS_GET16(handle->_flags, msg);
40     for (i = 0; i < ns_s_max; i++)
41         NS_GET16(handle->_counts[i], msg);
42     for (i = 0; i < ns_s_max; i++) {
43         if (handle->_counts[i]) {
44             handle->_sections[i] = msg;
45             r = ns_skiprr(msg, handle->_eom, i, handle->_counts[i]);
46             if (r < 0)
47                 return -1;
48             msg += r;
49         } else {
50             handle->_sections[i] = NULL;
51         }
52     }
53     if (msg != handle->_eom)
54         goto bad;
55     handle->_sect = ns_s_max;
56     handle->_rrnum = -1;
57     handle->_msg_ptr = NULL;
58     return 0;
59 bad:
60     errno = EMSGSIZE;
61     return -1;
62 }
63 
ns_skiprr(const unsigned char * ptr,const unsigned char * eom,ns_sect section,int count)64 int ns_skiprr(const unsigned char* ptr, const unsigned char* eom, ns_sect section, int count) {
65     const unsigned char* p = ptr;
66     int r;
67 
68     while (count--) {
69         r = dn_skipname(p, eom);
70         if (r < 0)
71             goto bad;
72         if (r + 2 * NS_INT16SZ > eom - p)
73             goto bad;
74         p += r + 2 * NS_INT16SZ;
75         if (section != ns_s_qd) {
76             if (NS_INT32SZ + NS_INT16SZ > eom - p)
77                 goto bad;
78             p += NS_INT32SZ;
79             NS_GET16(r, p);
80             if (r > eom - p)
81                 goto bad;
82             p += r;
83         }
84     }
85     return p - ptr;
86 bad:
87     errno = EMSGSIZE;
88     return -1;
89 }
90 
ns_parserr(ns_msg * handle,ns_sect section,int rrnum,ns_rr * rr)91 int ns_parserr(ns_msg* handle, ns_sect section, int rrnum, ns_rr* rr) {
92     int r;
93 
94     if ((int)section < 0 || section >= ns_s_max)
95         goto bad;
96     if (section != handle->_sect) {
97         handle->_sect = section;
98         handle->_rrnum = 0;
99         handle->_msg_ptr = handle->_sections[section];
100     }
101     if (rrnum == -1)
102         rrnum = handle->_rrnum;
103     if (rrnum < 0 || rrnum >= handle->_counts[section])
104         goto bad;
105     if (rrnum < handle->_rrnum) {
106         handle->_rrnum = 0;
107         handle->_msg_ptr = handle->_sections[section];
108     }
109     if (rrnum > handle->_rrnum) {
110         r = ns_skiprr(handle->_msg_ptr, handle->_eom, section, rrnum - handle->_rrnum);
111         if (r < 0)
112             return -1;
113         handle->_msg_ptr += r;
114         handle->_rrnum = rrnum;
115     }
116     r = ns_name_uncompress(handle->_msg, handle->_eom, handle->_msg_ptr, rr->name, NS_MAXDNAME);
117     if (r < 0)
118         return -1;
119     handle->_msg_ptr += r;
120     if (2 * NS_INT16SZ > handle->_eom - handle->_msg_ptr)
121         goto size;
122     NS_GET16(rr->type, handle->_msg_ptr);
123     NS_GET16(rr->rr_class, handle->_msg_ptr);
124     if (section != ns_s_qd) {
125         if (NS_INT32SZ + NS_INT16SZ > handle->_eom - handle->_msg_ptr)
126             goto size;
127         NS_GET32(rr->ttl, handle->_msg_ptr);
128         NS_GET16(rr->rdlength, handle->_msg_ptr);
129         if (rr->rdlength > handle->_eom - handle->_msg_ptr)
130             goto size;
131         rr->rdata = handle->_msg_ptr;
132         handle->_msg_ptr += rr->rdlength;
133     } else {
134         rr->ttl = 0;
135         rr->rdlength = 0;
136         rr->rdata = NULL;
137     }
138     handle->_rrnum++;
139     if (handle->_rrnum > handle->_counts[section]) {
140         handle->_sect = section + 1;
141         if (handle->_sect == ns_s_max) {
142             handle->_rrnum = -1;
143             handle->_msg_ptr = NULL;
144         } else {
145             handle->_rrnum = 0;
146         }
147     }
148     return 0;
149 bad:
150     errno = ENODEV;
151     return -1;
152 size:
153     errno = EMSGSIZE;
154     return -1;
155 }
156 
ns_name_uncompress(const unsigned char * msg,const unsigned char * eom,const unsigned char * src,char * dst,size_t dstsiz)157 int ns_name_uncompress(const unsigned char* msg, const unsigned char* eom, const unsigned char* src,
158                        char* dst, size_t dstsiz) {
159     int r;
160     r = dn_expand(msg, eom, src, dst, dstsiz);
161     if (r < 0)
162         errno = EMSGSIZE;
163     return r;
164 }
165