1 | #include <string.h>
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2 | #include <resolv.h>
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3 | #include "libc.h"
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4 |
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5 | /* RFC 1035 message compression */
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6 |
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7 | /* label start offsets of a compressed domain name s */
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8 | static int getoffs(short *offs, const unsigned char *base, const unsigned char *s)
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9 | {
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10 | int i=0;
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11 | for (;;) {
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12 | while (*s & 0xc0) {
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13 | if ((*s & 0xc0) != 0xc0) return 0;
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14 | s = base + ((s[0]&0x3f)<<8 | s[1]);
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15 | }
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16 | if (!*s) return i;
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17 | if (s-base >= 0x4000) return 0;
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18 | offs[i++] = s-base;
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19 | s += *s + 1;
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20 | }
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21 | }
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22 |
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23 | /* label lengths of an ascii domain name s */
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24 | static int getlens(unsigned char *lens, const char *s, int l)
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25 | {
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26 | int i=0,j=0,k=0;
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27 | for (;;) {
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28 | for (; j<l && s[j]!='.'; j++);
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29 | if (j-k-1u > 62) return 0;
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30 | lens[i++] = j-k;
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31 | if (j==l) return i;
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32 | k = ++j;
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33 | }
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34 | }
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35 |
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36 | /* longest suffix match of an ascii domain with a compressed domain name dn */
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37 | static int match(int *offset, const unsigned char *base, const unsigned char *dn,
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38 | const char *end, const unsigned char *lens, int nlen)
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39 | {
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40 | int l, o, m=0;
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41 | short offs[128];
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42 | int noff = getoffs(offs, base, dn);
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43 | if (!noff) return 0;
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44 | for (;;) {
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45 | l = lens[--nlen];
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46 | o = offs[--noff];
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47 | end -= l;
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48 | if (l != base[o] || memcmp(base+o+1, end, l))
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49 | return m;
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50 | *offset = o;
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51 | m += l;
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52 | if (nlen) m++;
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53 | if (!nlen || !noff) return m;
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54 | end--;
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55 | }
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56 | }
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57 |
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58 | int __dn_comp(const char *src, unsigned char *dst, int space, unsigned char **dnptrs, unsigned char **lastdnptr)
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59 | {
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60 | int i, j, n, m=0, offset, bestlen=0, bestoff;
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61 | unsigned char lens[127];
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62 | unsigned char **p;
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63 | const char *end;
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64 | size_t l = strnlen(src, 255);
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65 | if (l && src[l-1] == '.') l--;
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66 | if (l>253 || space<=0) return -1;
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67 | if (!l) {
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68 | *dst = 0;
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69 | return 1;
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70 | }
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71 | end = src+l;
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72 | n = getlens(lens, src, l);
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73 | if (!n) return -1;
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74 |
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75 | p = dnptrs;
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76 | if (p && *p) for (p++; *p; p++) {
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77 | m = match(&offset, *dnptrs, *p, end, lens, n);
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78 | if (m > bestlen) {
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79 | bestlen = m;
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80 | bestoff = offset;
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81 | if (m == l)
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82 | break;
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83 | }
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84 | }
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85 |
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86 | /* encode unmatched part */
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87 | if (space < l-bestlen+2+(bestlen-1 < l-1)) return -1;
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88 | memcpy(dst+1, src, l-bestlen);
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89 | for (i=j=0; i<l-bestlen; i+=lens[j++]+1)
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90 | dst[i] = lens[j];
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91 |
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92 | /* add tail */
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93 | if (bestlen) {
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94 | dst[i++] = 0xc0 | bestoff>>8;
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95 | dst[i++] = bestoff;
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96 | } else
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97 | dst[i++] = 0;
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98 |
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99 | /* save dst pointer */
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100 | if (i>2 && lastdnptr && dnptrs && *dnptrs) {
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101 | while (*p) p++;
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102 | if (p+1 < lastdnptr) {
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103 | *p++ = dst;
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104 | *p=0;
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105 | }
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106 | }
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107 | return i;
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108 | }
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109 |
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110 | weak_alias(__dn_comp, dn_comp);
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