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Fix for CERT VU#210620: randomize DNS request IDs for every request

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This commit is contained in:
Adam Dunkels 2014-12-02 10:43:16 +01:00
parent 397b15f6db
commit 769a2f832e
1 changed files with 10 additions and 8 deletions
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18
core/net/ip/resolv.c
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@ -227,9 +227,6 @@ struct dns_hdr {
uint16_t numextrarr; uint16_t numextrarr;
}; };
#define RESOLV_ENCODE_INDEX(i) (uip_htons(i+1))
#define RESOLV_DECODE_INDEX(i) (unsigned char)(uip_ntohs(i-1))
/** These default values for the DNS server are Google's public DNS: /** These default values for the DNS server are Google's public DNS:
* <https://developers.google.com/speed/public-dns/docs/using> * <https://developers.google.com/speed/public-dns/docs/using>
*/ */
@ -264,6 +261,7 @@ struct namemap {
#define STATE_DONE 4 #define STATE_DONE 4
uint8_t state; uint8_t state;
uint8_t tmr; uint8_t tmr;
uint16_t id;
uint8_t retries; uint8_t retries;
uint8_t seqno; uint8_t seqno;
#if RESOLV_SUPPORTS_RECORD_EXPIRATION #if RESOLV_SUPPORTS_RECORD_EXPIRATION
@ -703,7 +701,8 @@ check_entries(void)
} }
hdr = (struct dns_hdr *)uip_appdata; hdr = (struct dns_hdr *)uip_appdata;
memset(hdr, 0, sizeof(struct dns_hdr)); memset(hdr, 0, sizeof(struct dns_hdr));
hdr->id = RESOLV_ENCODE_INDEX(i); hdr->id = random_rand();
namemapptr->id = hdr->id;
#if RESOLV_CONF_SUPPORTS_MDNS #if RESOLV_CONF_SUPPORTS_MDNS
if(!namemapptr->is_mdns || namemapptr->is_probe) { if(!namemapptr->is_mdns || namemapptr->is_probe) {
hdr->flags1 = DNS_FLAG1_RD; hdr->flags1 = DNS_FLAG1_RD;
@ -903,10 +902,13 @@ newdata(void)
} else } else
#endif /* RESOLV_CONF_SUPPORTS_MDNS */ #endif /* RESOLV_CONF_SUPPORTS_MDNS */
{ {
/* The ID in the DNS header should be our entry into the name table. */ for(i = 0; i < RESOLV_ENTRIES; ++i) {
i = RESOLV_DECODE_INDEX(hdr->id); namemapptr = &names[i];
if(namemapptr->state == STATE_ASKING &&
namemapptr = &names[i]; namemapptr->id == hdr->id) {
break;
}
}
if(i >= RESOLV_ENTRIES || i < 0 || namemapptr->state != STATE_ASKING) { if(i >= RESOLV_ENTRIES || i < 0 || namemapptr->state != STATE_ASKING) {
PRINTF("resolver: DNS response has bad ID (%04X) \n", uip_ntohs(hdr->id)); PRINTF("resolver: DNS response has bad ID (%04X) \n", uip_ntohs(hdr->id));