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