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resolv: Support binary labels in test framework

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The old implementation based on hsearch_r used an ad-hoc C string
encoding and produced an incorrect format on the wire for domain
names which contained bytes which needed escaping when printed.

This commit switches to ns_name_pton for the wire format conversion
(now that we have separate tests for it) and uses a tsearch tree
with a suitable comparison function to locate compression targets.
This commit is contained in:
Florian Weimer
2018-01-08 14:33:17 +01:00
parent 2b3aa44656
commit 401311cfba
4 changed files with 305 additions and 136 deletions
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300
support/resolv_test.c
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@@ -43,15 +43,99 @@ enum
max_response_length = 65536
};
/* List of pointers to be freed. The hash table implementation
(struct hsearch_data) does not provide a way to deallocate all
objects, so this approach is used to avoid memory leaks. */
struct to_be_freed
/* Used for locating domain names containing for the purpose of
forming compression references. */
struct compressed_name
{
struct to_be_freed *next;
void *ptr;
uint16_t offset;
unsigned char length;
unsigned char name[]; /* Without terminating NUL. */
};
static struct compressed_name *
allocate_compressed_name (const unsigned char *encoded, unsigned int offset)
{
/* Compute the length of the domain name. */
size_t length;
{
const unsigned char *p;
for (p = encoded; *p != '\0';)
{
/* No compression references are allowed. */
TEST_VERIFY (*p <= 63);
/* Skip over the label. */
p += 1 + *p;
}
length = p - encoded;
++length; /* For the terminating NUL byte. */
}
TEST_VERIFY_EXIT (length <= 255);
struct compressed_name *result
= xmalloc (offsetof (struct compressed_name, name) + length);
result->offset = offset;
result->length = length;
memcpy (result->name, encoded, length);
return result;
}
/* Convert CH to lower case. Only change letters in the ASCII
range. */
static inline unsigned char
ascii_tolower (unsigned char ch)
{
if ('A' <= ch && ch <= 'Z')
return ch - 'A' + 'a';
else
return ch;
}
/* Compare both names, for use with tsearch. The order is arbitrary,
but the comparison is case-insenstive. */
static int
compare_compressed_name (const void *left, const void *right)
{
const struct compressed_name *crleft = left;
const struct compressed_name *crright = right;
if (crleft->length != crright->length)
/* The operands are converted to int before the subtraction. */
return crleft->length - crright->length;
const unsigned char *nameleft = crleft->name;
const unsigned char *nameright = crright->name;
while (true)
{
int lenleft = *nameleft++;
int lenright = *nameright++;
/* Labels must not e compression references. */
TEST_VERIFY (lenleft <= 63);
TEST_VERIFY (lenright <= 63);
if (lenleft != lenright)
return left - right;
if (lenleft == 0)
/* End of name reached without spotting a difference. */
return 0;
/* Compare the label in a case-insenstive manner. */
const unsigned char *endnameleft = nameleft + lenleft;
while (nameleft < endnameleft)
{
int l = *nameleft++;
int r = *nameright++;
if (l != r)
{
l = ascii_tolower (l);
r = ascii_tolower (r);
if (l != r)
return l - r;
}
}
}
}
struct resolv_response_builder
{
const unsigned char *query_buffer;
@@ -67,11 +151,8 @@ struct resolv_response_builder
written RDATA sub-structure. 0 if no RDATA is being written. */
size_t current_rdata_offset;
/* Hash table for locating targets for label compression. */
struct hsearch_data compression_offsets;
/* List of pointers which need to be freed. Used for domain names
involved in label compression. */
struct to_be_freed *to_be_freed;
/* tsearch tree for locating targets for label compression. */
void *compression_offsets;
/* Must be last. Not zeroed for performance reasons. */
unsigned char buffer[max_response_length];
@@ -79,18 +160,6 @@ struct resolv_response_builder
/* Response builder. */
/* Add a pointer to the list of pointers to be freed when B is
deallocated. */
static void
response_push_pointer_to_free (struct resolv_response_builder *b, void *ptr)
{
if (ptr == NULL)
return;
struct to_be_freed *e = xmalloc (sizeof (*e));
*e = (struct to_be_freed) {b->to_be_freed, ptr};
b->to_be_freed = e;
}
void
resolv_response_init (struct resolv_response_builder *b,
struct resolv_response_flags flags)
@@ -194,120 +263,88 @@ void
resolv_response_add_name (struct resolv_response_builder *b,
const char *const origname)
{
/* Normalized name. */
char *name;
/* Normalized name with case preserved. */
char *name_case;
{
size_t namelen = strlen (origname);
/* Remove trailing dots. FIXME: Handle trailing quoted dots. */
while (namelen > 0 && origname[namelen - 1] == '.')
--namelen;
name = xmalloc (namelen + 1);
name_case = xmalloc (namelen + 1);
/* Copy and convert to lowercase. FIXME: This needs to normalize
escaping as well. */
for (size_t i = 0; i < namelen; ++i)
{
char ch = origname[i];
name_case[i] = ch;
if ('A' <= ch && ch <= 'Z')
ch = ch - 'A' + 'a';
name[i] = ch;
}
name[namelen] = 0;
name_case[namelen] = 0;
}
char *name_start = name;
char *name_case_start = name_case;
unsigned char encoded_name[NS_MAXDNAME];
if (ns_name_pton (origname, encoded_name, sizeof (encoded_name)) < 0)
FAIL_EXIT1 ("ns_name_pton (\"%s\"): %m", origname);
bool compression = false;
while (*name)
/* Copy the encoded name into the output buffer, apply compression
where possible. */
for (const unsigned char *name = encoded_name; ;)
{
/* Search for a previous name we can reference. */
ENTRY new_entry =
if (*name == '\0')
{
.key = name,
.data = (void *) (uintptr_t) b->offset,
};
/* If the label can be a compression target because it is at a
reachable offset, add it to the hash table. */
ACTION action;
if (b->offset < (1 << 12))
action = ENTER;
else
action = FIND;
/* Search for known compression offsets in the hash table. */
ENTRY *e;
if (hsearch_r (new_entry, action, &e, &b->compression_offsets) == 0)
{
if (action == FIND && errno == ESRCH)
/* Fall through. */
e = NULL;
else
FAIL_EXIT1 ("hsearch_r failure in name compression: %m");
}
/* The name is known. Reference the previous location. */
if (e != NULL && e->data != new_entry.data)
{
size_t old_offset = (uintptr_t) e->data;
response_add_byte (b, 0xC0 | (old_offset >> 8));
response_add_byte (b, old_offset);
compression = true;
/* We have reached the end of the name. Add the terminating
NUL byte. */
response_add_byte (b, '\0');
break;
}
/* The name does not exist yet. Write one label. First, add
room for the label length. */
size_t buffer_label_offset = b->offset;
response_add_byte (b, 0);
/* Set to the compression target if compression is possible. */
struct compressed_name *crname_target;
/* Copy the label. */
while (true)
/* Compression references can only reach the beginning of the
packet. */
enum { compression_limit = 1 << 12 };
{
/* The trailing part of the name to be looked up in the tree
with the compression targets. */
struct compressed_name *crname
= allocate_compressed_name (name, b->offset);
if (b->offset < compression_limit)
{
/* Add the name to the tree, for future compression
references. */
void **ptr = tsearch (crname, &b->compression_offsets,
compare_compressed_name);
if (ptr == NULL)
FAIL_EXIT1 ("tsearch out of memory");
crname_target = *ptr;
if (crname_target != crname)
/* The new name was not actually added to the tree.
Deallocate it. */
free (crname);
else
/* Signal that the tree did not yet contain the name,
but keep the allocation because it is now part of the
tree. */
crname_target = NULL;
}
else
{
/* This name cannot be reached by a compression reference.
No need to add it to the tree for future reference. */
void **ptr = tfind (crname, &b->compression_offsets,
compare_compressed_name);
if (ptr != NULL)
crname_target = *ptr;
else
crname_target = NULL;
TEST_VERIFY (crname_target != crname);
/* Not added to the tree. */
free (crname);
}
}
if (crname_target != NULL)
{
char ch = *name_case;
if (ch == '\0')
break;
++name;
++name_case;
if (ch == '.')
break;
/* FIXME: Handle escaping. */
response_add_byte (b, ch);
/* The name is known. Reference the previous location. */
unsigned int old_offset = crname_target->offset;
TEST_VERIFY_EXIT (old_offset < compression_limit);
response_add_byte (b, 0xC0 | (old_offset >> 8));
response_add_byte (b, old_offset);
break;
}
/* Patch in the label length. */
size_t label_length = b->offset - buffer_label_offset - 1;
if (label_length == 0)
FAIL_EXIT1 ("empty label in name compression: %s", origname);
if (label_length > 63)
FAIL_EXIT1 ("label too long in name compression: %s", origname);
b->buffer[buffer_label_offset] = label_length;
/* Continue with the tail of the name and the next label. */
}
if (compression)
{
/* If we found an immediate match for the name, we have not put
it into the hash table, and can free it immediately. */
if (name == name_start)
free (name_start);
else
response_push_pointer_to_free (b, name_start);
{
/* The name is new. Add this label. */
unsigned int len = 1 + *name;
resolv_response_add_data (b, name, len);
name += len;
}
}
else
{
/* Terminate the sequence of labels. With compression, this is
implicit in the compression reference. */
response_add_byte (b, 0);
response_push_pointer_to_free (b, name_start);
}
free (name_case_start);
}
void
@@ -403,22 +440,13 @@ response_builder_allocate
memset (b, 0, offsetof (struct resolv_response_builder, buffer));
b->query_buffer = query_buffer;
b->query_length = query_length;
TEST_VERIFY_EXIT (hcreate_r (10000, &b->compression_offsets) != 0);
return b;
}
static void
response_builder_free (struct resolv_response_builder *b)
{
struct to_be_freed *current = b->to_be_freed;
while (current != NULL)
{
struct to_be_freed *next = current->next;
free (current->ptr);
free (current);
current = next;
}
hdestroy_r (&b->compression_offsets);
tdestroy (b->compression_offsets, free);
free (b);
}