examples:dns_matching: fix key length and buffer overrun

Changed key length to 255, maximum length of DNS domain name. Also fixed double increment of loop variable. These both changes fix buffer overrun. Signed-off-by: Prashant Bhole <[email protected]>
devopsleague · Sep 28, 2017 · 07c21f0 · 07c21f0
1 parent a135d89
commit 07c21f0
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Showing 2 changed files with 5 additions and 5 deletions.
diff --git a/examples/networking/dns_matching/dns_matching.c b/examples/networking/dns_matching/dns_matching.c
@@ -43,7 +43,7 @@ struct dns_char_t
 } BPF_PACKET_HEADER;
 
 struct Key {
- unsigned char p[32];
+ unsigned char p[255];
 };
 
 struct Leaf {
@@ -85,8 +85,8 @@ int dns_matching(struct __sk_buff *skb)
  u16 i = 0;
  struct dns_char_t *c;
  // This unroll worked not in latest BCC version.
- for(u8 j = 0; i<255;i++){
- if (cursor == sentinel) goto end; c = cursor_advance(cursor, 1); key.p[i++] = c->c;
+ for(i = 0; i<255;i++){
+ if (cursor == sentinel) goto end; c = cursor_advance(cursor, 1); key.p[i] = c->c;
  }
  end:
  {}

diff --git a/examples/networking/dns_matching/dns_matching.py b/examples/networking/dns_matching/dns_matching.py
@@ -11,8 +11,8 @@
 
 
 def encode_dns(name):
- size = 32
- if len(name) > 253:
+ size = 255
+ if len(name) > 255:
  raise Exception("DNS Name too long.")
  b = bytearray(size)
  i = 0;