diff options
Diffstat (limited to 'dns.c')
| -rw-r--r-- | dns.c | 139 |
1 files changed, 92 insertions, 47 deletions
@@ -63,6 +63,48 @@ guint16 flx_dns_packet_get_field(flxDnsPacket *p, guint index) { return g_ntohs(((guint16*) FLX_DNS_PACKET_DATA(p))[index]); } +/* Read the first label from string dest, unescape "\" and append it to *name */ +static gchar *unescape_label(gchar *dest, guint size, const gchar **name) { + guint i = 0; + gchar *d; + + g_assert(dest); + g_assert(size > 0); + g_assert(name); + g_assert(*name); + + d = dest; + + for (;;) { + if (i >= size) + return NULL; + + if (**name == '.') { + (*name)++; + break; + } + + if (**name == 0) + break; + + if (**name == '\\') { + (*name) ++; + + if (**name == 0) + break; + } + + *(d++) = *((*name) ++); + i++; + } + + g_assert(i < size); + + *d = 0; + + return dest; +} + guint8* flx_dns_packet_append_name(flxDnsPacket *p, const gchar *name) { guint8 *d, *f = NULL; guint saved_size; @@ -72,9 +114,11 @@ guint8* flx_dns_packet_append_name(flxDnsPacket *p, const gchar *name) { saved_size = p->size; - for (;;) { + while (*name) { guint n; guint8* prev; + const gchar *pname; + char label[64]; /* Check whether we can compress this name. */ @@ -98,41 +142,25 @@ guint8* flx_dns_packet_append_name(flxDnsPacket *p, const gchar *name) { return f; } } + + pname = name; - n = strcspn(name, "."); - if (!n || n > 63) - goto fail; - - if (!(d = flx_dns_packet_extend(p, n+1))) + if (!(unescape_label(label, sizeof(label), &name))) goto fail; - - if (!f) - f = d; - d[0] = n; - memcpy(d+1, name, n); + if (!(d = flx_dns_packet_append_string(p, label))) + goto fail; + if (!p->name_table) p->name_table = g_hash_table_new_full((GHashFunc) flx_domain_hash, (GEqualFunc) flx_domain_equal, g_free, NULL); - g_hash_table_insert(p->name_table, g_strdup(name), d); - - name += n; - - /* no trailing dot */ - if (!*name) - break; - - name ++; - - /* trailing dot */ - if (!*name) - break; + g_hash_table_insert(p->name_table, g_strdup(pname), d); } if (!(d = flx_dns_packet_extend(p, 1))) goto fail; - d[0] = 0; + *d = 0; return f; @@ -141,25 +169,6 @@ fail: return NULL; } -guint8 *flx_dns_packet_append_name_compressed(flxDnsPacket *p, const gchar *name, guint8 *prev) { - guint16 *d; - signed long k; - g_assert(p); - - if (!prev) - return flx_dns_packet_append_name(p, name); - - k = prev - FLX_DNS_PACKET_DATA(p); - if (k < 0 || k >= 0x4000 || (guint) k >= p->size) - return flx_dns_packet_append_name(p, name); - - if (!(d = (guint16*) flx_dns_packet_extend(p, sizeof(guint16)))) - return NULL; - - *d = g_htons((0xC000 | k)); - return prev; -} - guint8* flx_dns_packet_append_uint16(flxDnsPacket *p, guint16 v) { guint8 *d; g_assert(p); @@ -251,6 +260,42 @@ gint flx_dns_packet_is_query(flxDnsPacket *p) { return !(flx_dns_packet_get_field(p, FLX_DNS_FIELD_FLAGS) & FLX_DNS_FLAG_QR); } +/* Read a label from a DNS packet, escape "\" and ".", append \0 */ +static gchar *escape_label(guint8* src, guint src_length, gchar **ret_name, guint *ret_name_length) { + gchar *r; + + g_assert(src); + g_assert(ret_name); + g_assert(*ret_name); + g_assert(ret_name_length); + g_assert(*ret_name_length > 0); + + r = *ret_name; + + while (src_length > 0) { + if (*src == '.' || *src == '\\') { + if (*ret_name_length < 3) + return NULL; + + *((*ret_name) ++) = '\\'; + (*ret_name_length) --; + } + + if (*ret_name_length < 2) + return NULL; + + *((*ret_name)++) = *src; + (*ret_name_length) --; + + src_length --; + src++; + } + + **ret_name = 0; + + return r; +} + static gint consume_labels(flxDnsPacket *p, guint index, gchar *ret_name, guint l) { gint ret = 0; int compressed = 0; @@ -294,10 +339,10 @@ static gint consume_labels(flxDnsPacket *p, guint index, gchar *ret_name, guint } else first_label = 0; - memcpy(ret_name, FLX_DNS_PACKET_DATA(p) + index, n); + if (!(escape_label(FLX_DNS_PACKET_DATA(p) + index, n, &ret_name, &l))) + return -1; + index += n; - ret_name += n; - l -= n; if (!compressed) ret += n; |