diff options
Diffstat (limited to 'com32/lib/dhcpunpack.c')
-rw-r--r-- | com32/lib/dhcpunpack.c | 116 |
1 files changed, 116 insertions, 0 deletions
diff --git a/com32/lib/dhcpunpack.c b/com32/lib/dhcpunpack.c new file mode 100644 index 00000000..248173a8 --- /dev/null +++ b/com32/lib/dhcpunpack.c @@ -0,0 +1,116 @@ +#define _GNU_SOURCE /* For strnlen() */ +#include <stdlib.h> +#include <errno.h> +#include <string.h> +// #include <arpa/inet.h> +#include <netinet/in.h> + +// #include "dhcp.h" +#include <dhcp.h> + +/* + * Unpack DHCP options from a field. Assumes opt is pre-initalized + * (to all zero in the common case.) + */ +int dhcp_unpack_field(const void *field, size_t len, + struct dhcp_option opt[256]) +{ + const uint8_t *p = field; + int err = 0; + + while (len > 1) { + uint8_t op; + size_t xlen; + + op = *p++; len--; + if (op == 0) + continue; + else if (op == 255) + break; + + xlen = *p++; len--; + if (xlen > len) + break; + if (opt[op].len < 0) + opt[op].len = 0; + if (xlen) { + opt[op].data = realloc(opt[op].data, + opt[op].len + xlen + 1); + if (!opt[op].data) { + err = ENOMEM; + continue; + } + memcpy((char *)opt[op].data + opt[op].len, p, xlen); + opt[op].len += xlen; + /* Null-terminate as a courtesy to users */ + *((char *)opt[op].data + opt[op].len) = 0; + p += xlen; + len -= xlen; + } + } + + return err; +} + +/* + * Unpack a DHCP packet, with overload support. Do not use this + * to unpack an encapsulated option set. + */ +int dhcp_unpack_packet(const void *packet, size_t len, + struct dhcp_option opt[256]) +{ + const struct dhcp_packet *pkt = packet; + int err; + uint8_t overload; + int i; + + if (len < 240 || pkt->magic != htonl(DHCP_VENDOR_MAGIC)) + return EINVAL; /* Bogus packet */ + + for (i = 0; i < 256; i++) { + opt[i].len = -1; /* Option not present */ + opt[i].data = NULL; + } + + err = dhcp_unpack_field(pkt->options, len-240, opt); + + overload = 0; + if (opt[52].len == 1) { + overload = *(uint8_t *)opt[52].data; + free(opt[52].data); + opt[52].len = -1; + opt[52].data = NULL; + } + + if (overload & 1) { + err |= dhcp_unpack_field(pkt->file, 128, opt); + } else { + opt[67].len = strnlen((const char *)pkt->file, 128); + if (opt[67].len) { + opt[67].data = malloc(opt[67].len + 1); + if (opt[67].data) { + memcpy(opt[67].data, pkt->file, opt[67].len); + *((char *)opt[67].data + opt[67].len) = 0; + } else { + err |= ENOMEM; + } + } + } + + if (overload & 2) { + err |= dhcp_unpack_field(pkt->sname, 64, opt); + } else { + opt[66].len = strnlen((const char *)pkt->sname, 64); + if (opt[66].len) { + opt[66].data = malloc(opt[66].len + 1); + if (opt[66].data) { + memcpy(opt[66].data, pkt->file, opt[66].len); + *((char *)opt[66].data + opt[66].len) = 0; + } else { + err |= ENOMEM; + } + } + } + + return err; +} |