| Greg Hartman | 76d05dc | 2016-11-23 15:51:27 -0800 | [diff] [blame] | 1 | #define _GNU_SOURCE /* For strnlen() */ |
| 2 | #include <stdlib.h> |
| 3 | #include <errno.h> |
| 4 | #include <string.h> |
| 5 | // #include <arpa/inet.h> |
| 6 | #include <netinet/in.h> |
| 7 | |
| 8 | // #include "dhcp.h" |
| 9 | #include <dhcp.h> |
| 10 | |
| 11 | /* |
| 12 | * Unpack DHCP options from a field. Assumes opt is pre-initalized |
| 13 | * (to all zero in the common case.) |
| 14 | */ |
| 15 | int dhcp_unpack_field(const void *field, size_t len, |
| 16 | struct dhcp_option opt[256]) |
| 17 | { |
| 18 | const uint8_t *p = field; |
| 19 | int err = 0; |
| 20 | |
| 21 | while (len > 1) { |
| 22 | uint8_t op; |
| 23 | size_t xlen; |
| 24 | |
| 25 | op = *p++; len--; |
| 26 | if (op == 0) |
| 27 | continue; |
| 28 | else if (op == 255) |
| 29 | break; |
| 30 | |
| 31 | xlen = *p++; len--; |
| 32 | if (xlen > len) |
| 33 | break; |
| 34 | if (opt[op].len < 0) |
| 35 | opt[op].len = 0; |
| 36 | if (xlen) { |
| 37 | opt[op].data = realloc(opt[op].data, |
| 38 | opt[op].len + xlen + 1); |
| 39 | if (!opt[op].data) { |
| 40 | err = ENOMEM; |
| 41 | continue; |
| 42 | } |
| 43 | memcpy((char *)opt[op].data + opt[op].len, p, xlen); |
| 44 | opt[op].len += xlen; |
| 45 | /* Null-terminate as a courtesy to users */ |
| 46 | *((char *)opt[op].data + opt[op].len) = 0; |
| 47 | p += xlen; |
| 48 | len -= xlen; |
| 49 | } |
| 50 | } |
| 51 | |
| 52 | return err; |
| 53 | } |
| 54 | |
| 55 | /* |
| 56 | * Unpack a DHCP packet, with overload support. Do not use this |
| 57 | * to unpack an encapsulated option set. |
| 58 | */ |
| 59 | int dhcp_unpack_packet(const void *packet, size_t len, |
| 60 | struct dhcp_option opt[256]) |
| 61 | { |
| 62 | const struct dhcp_packet *pkt = packet; |
| 63 | int err; |
| 64 | uint8_t overload; |
| 65 | int i; |
| 66 | |
| 67 | if (len < 240 || pkt->magic != htonl(DHCP_VENDOR_MAGIC)) |
| 68 | return EINVAL; /* Bogus packet */ |
| 69 | |
| 70 | for (i = 0; i < 256; i++) { |
| 71 | opt[i].len = -1; /* Option not present */ |
| 72 | opt[i].data = NULL; |
| 73 | } |
| 74 | |
| 75 | err = dhcp_unpack_field(pkt->options, len-240, opt); |
| 76 | |
| 77 | overload = 0; |
| 78 | if (opt[52].len == 1) { |
| 79 | overload = *(uint8_t *)opt[52].data; |
| 80 | free(opt[52].data); |
| 81 | opt[52].len = -1; |
| 82 | opt[52].data = NULL; |
| 83 | } |
| 84 | |
| 85 | if (overload & 1) { |
| 86 | err |= dhcp_unpack_field(pkt->file, 128, opt); |
| 87 | } else { |
| 88 | opt[67].len = strnlen((const char *)pkt->file, 128); |
| 89 | if (opt[67].len) { |
| 90 | opt[67].data = malloc(opt[67].len + 1); |
| 91 | if (opt[67].data) { |
| 92 | memcpy(opt[67].data, pkt->file, opt[67].len); |
| 93 | *((char *)opt[67].data + opt[67].len) = 0; |
| 94 | } else { |
| 95 | err |= ENOMEM; |
| 96 | } |
| 97 | } |
| 98 | } |
| 99 | |
| 100 | if (overload & 2) { |
| 101 | err |= dhcp_unpack_field(pkt->sname, 64, opt); |
| 102 | } else { |
| 103 | opt[66].len = strnlen((const char *)pkt->sname, 64); |
| 104 | if (opt[66].len) { |
| 105 | opt[66].data = malloc(opt[66].len + 1); |
| 106 | if (opt[66].data) { |
| 107 | memcpy(opt[66].data, pkt->file, opt[66].len); |
| 108 | *((char *)opt[66].data + opt[66].len) = 0; |
| 109 | } else { |
| 110 | err |= ENOMEM; |
| 111 | } |
| 112 | } |
| 113 | } |
| 114 | |
| 115 | return err; |
| 116 | } |