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resolv: Lift domain search list limits [BZ #19569] [BZ #21475]

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This change uses the extended resolver state in struct resolv_conf to
store the search list.  If applications have not patched the _res
object directly, this extended search list will be used by the stub
resolver during name resolution.
This commit is contained in:
Florian Weimer
2017-07-01 00:53:05 +02:00
parent f30a54b21b
commit 3f853f22c8
8 changed files with 382 additions and 81 deletions
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222
resolv/res_init.c
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@ -124,18 +124,75 @@ is_sort_mask (char ch)
return ch == '/' || ch == '&';
}
/* Array of strings for the search array. The backing store is
managed separately. */
#define DYNARRAY_STRUCT search_list
#define DYNARRAY_ELEMENT const char *
#define DYNARRAY_INITIAL_SIZE 4
#define DYNARRAY_PREFIX search_list_
#include <malloc/dynarray-skeleton.c>
/* resolv.conf parser state and results. */
struct resolv_conf_parser
{
char *buffer; /* Temporary buffer for reading lines. */
char *search_list_store; /* Backing storage for search list entries. */
struct search_list search_list; /* Points into search_list_store. */
};
static void
resolv_conf_parser_init (struct resolv_conf_parser *parser)
{
parser->buffer = NULL;
parser->search_list_store = NULL;
search_list_init (&parser->search_list);
}
static void
resolv_conf_parser_free (struct resolv_conf_parser *parser)
{
free (parser->buffer);
free (parser->search_list_store);
search_list_free (&parser->search_list);
}
/* Try to obtain the domain name from the host name and store it in
*RESULT. Return false on memory allocation failure. If the domain
name cannot be determined for any other reason, write NULL to
*RESULT and return true. */
static bool
domain_from_hostname (char **result)
{
char buf[256];
/* gethostbyname may not terminate the buffer. */
buf[sizeof (buf) - 1] = '\0';
if (__gethostname (buf, sizeof (buf) - 1) == 0)
{
char *dot = strchr (buf, '.');
if (dot != NULL)
{
*result = __strdup (dot + 1);
if (*result == NULL)
return false;
return true;
}
}
*result = NULL;
return true;
}
/* Internal helper function for __res_vinit, to aid with resource
deallocation and error handling. Return true on success, false on
failure. */
static bool
res_vinit_1 (res_state statp, bool preinit, FILE *fp, char **buffer)
res_vinit_1 (res_state statp, bool preinit, FILE *fp,
struct resolv_conf_parser *parser)
{
char *cp, **pp;
char *cp;
size_t buffer_size = 0;
int nserv = 0; /* Number of nameservers read from file. */
bool have_serv6 = false;
bool haveenv = false;
bool havesearch = false;
int nsort = 0;
char *net;
@ -162,39 +219,40 @@ res_vinit_1 (res_state statp, bool preinit, FILE *fp, char **buffer)
/* Allow user to override the local domain definition. */
if ((cp = getenv ("LOCALDOMAIN")) != NULL)
{
strncpy (statp->defdname, cp, sizeof (statp->defdname) - 1);
statp->defdname[sizeof (statp->defdname) - 1] = '\0';
/* The code below splits the string in place. */
cp = __strdup (cp);
if (cp == NULL)
return false;
free (parser->search_list_store);
parser->search_list_store = cp;
haveenv = true;
/* The string will be truncated as needed below. */
search_list_add (&parser->search_list, cp);
/* Set search list to be blank-separated strings from rest of
env value. Permits users of LOCALDOMAIN to still have a
search list, and anyone to set the one that they want to use
as an individual (even more important now that the rfc1535
stuff restricts searches). */
cp = statp->defdname;
pp = statp->dnsrch;
*pp++ = cp;
for (int n = 0; *cp && pp < statp->dnsrch + MAXDNSRCH; cp++)
for (bool in_name = true; *cp != '\0'; cp++)
{
if (*cp == '\n')
break;
{
*cp = '\0';
break;
}
else if (*cp == ' ' || *cp == '\t')
{
*cp = 0;
n = 1;
*cp = '\0';
in_name = false;
}
else if (n > 0)
else if (!in_name)
{
*pp++ = cp;
n = 0;
havesearch = true;
search_list_add (&parser->search_list, cp);
in_name = true;
}
}
/* Null terminate last domain if there are excess. */
while (*cp != '\0' && *cp != ' ' && *cp != '\t' && *cp != '\n')
cp++;
*cp = '\0';
*pp++ = 0;
}
#define MATCH(line, name) \
@ -210,7 +268,7 @@ res_vinit_1 (res_state statp, bool preinit, FILE *fp, char **buffer)
while (true)
{
{
ssize_t ret = __getline (buffer, &buffer_size, fp);
ssize_t ret = __getline (&parser->buffer, &buffer_size, fp);
if (ret <= 0)
{
if (_IO_ferror_unlocked (fp))
@ -221,73 +279,82 @@ res_vinit_1 (res_state statp, bool preinit, FILE *fp, char **buffer)
}
/* Skip comments. */
if (**buffer == ';' || **buffer == '#')
if (*parser->buffer == ';' || *parser->buffer == '#')
continue;
/* Read default domain name. */
if (MATCH (*buffer, "domain"))
if (MATCH (parser->buffer, "domain"))
{
if (haveenv)
/* LOCALDOMAIN overrides the configuration file. */
continue;
cp = *buffer + sizeof ("domain") - 1;
cp = parser->buffer + sizeof ("domain") - 1;
while (*cp == ' ' || *cp == '\t')
cp++;
if ((*cp == '\0') || (*cp == '\n'))
continue;
strncpy (statp->defdname, cp, sizeof (statp->defdname) - 1);
statp->defdname[sizeof (statp->defdname) - 1] = '\0';
if ((cp = strpbrk (statp->defdname, " \t\n")) != NULL)
cp = __strdup (cp);
if (cp == NULL)
return false;
free (parser->search_list_store);
parser->search_list_store = cp;
search_list_clear (&parser->search_list);
search_list_add (&parser->search_list, cp);
/* Replace trailing whitespace. */
if ((cp = strpbrk (cp, " \t\n")) != NULL)
*cp = '\0';
havesearch = false;
continue;
}
/* Set search list. */
if (MATCH (*buffer, "search"))
if (MATCH (parser->buffer, "search"))
{
if (haveenv)
/* LOCALDOMAIN overrides the configuration file. */
continue;
cp = *buffer + sizeof ("search") - 1;
cp = parser->buffer + sizeof ("search") - 1;
while (*cp == ' ' || *cp == '\t')
cp++;
if ((*cp == '\0') || (*cp == '\n'))
continue;
strncpy (statp->defdname, cp, sizeof (statp->defdname) - 1);
statp->defdname[sizeof (statp->defdname) - 1] = '\0';
if ((cp = strchr (statp->defdname, '\n')) != NULL)
*cp = '\0';
{
char *p = strchr (cp, '\n');
if (p != NULL)
*p = '\0';
}
cp = __strdup (cp);
if (cp == NULL)
return false;
free (parser->search_list_store);
parser->search_list_store = cp;
/* The string is truncated below. */
search_list_clear (&parser->search_list);
search_list_add (&parser->search_list, cp);
/* Set search list to be blank-separated strings on rest
of line. */
cp = statp->defdname;
pp = statp->dnsrch;
*pp++ = cp;
for (int n = 0; *cp && pp < statp->dnsrch + MAXDNSRCH; cp++)
for (bool in_name = true; *cp != '\0'; cp++)
{
if (*cp == ' ' || *cp == '\t')
{
*cp = 0;
n = 1;
*cp = '\0';
in_name = false;
}
else if (n)
else if (!in_name)
{
*pp++ = cp;
n = 0;
search_list_add (&parser->search_list, cp);
in_name = true;
}
}
/* Null terminate last domain if there are excess. */
while (*cp != '\0' && *cp != ' ' && *cp != '\t')
cp++;
*cp = '\0';
*pp++ = 0;
havesearch = true;
continue;
}
/* Read nameservers to query. */
if (MATCH (*buffer, "nameserver") && nserv < MAXNS)
if (MATCH (parser->buffer, "nameserver") && nserv < MAXNS)
{
struct in_addr a;
cp = *buffer + sizeof ("nameserver") - 1;
cp = parser->buffer + sizeof ("nameserver") - 1;
while (*cp == ' ' || *cp == '\t')
cp++;
if ((*cp != '\0') && (*cp != '\n') && __inet_aton (cp, &a))
@ -335,11 +402,11 @@ res_vinit_1 (res_state statp, bool preinit, FILE *fp, char **buffer)
}
continue;
}
if (MATCH (*buffer, "sortlist"))
if (MATCH (parser->buffer, "sortlist"))
{
struct in_addr a;
cp = *buffer + sizeof ("sortlist") - 1;
cp = parser->buffer + sizeof ("sortlist") - 1;
while (nsort < MAXRESOLVSORT)
{
while (*cp == ' ' || *cp == '\t')
@ -379,9 +446,9 @@ res_vinit_1 (res_state statp, bool preinit, FILE *fp, char **buffer)
}
continue;
}
if (MATCH (*buffer, "options"))
if (MATCH (parser->buffer, "options"))
{
res_setoptions (statp, *buffer + sizeof ("options") - 1);
res_setoptions (statp, parser->buffer + sizeof ("options") - 1);
continue;
}
}
@ -399,25 +466,29 @@ res_vinit_1 (res_state statp, bool preinit, FILE *fp, char **buffer)
statp->nsaddr.sin_port = htons (NAMESERVER_PORT);
statp->nscount = 1;
}
if (statp->defdname[0] == 0)
{
char buf[sizeof (statp->defdname)];
if (__gethostname (buf, sizeof (statp->defdname) - 1) == 0
&& (cp = strchr (buf, '.')) != NULL)
strcpy (statp->defdname, cp + 1);
}
/* Find components of local domain that might be searched. */
if (!havesearch)
if (search_list_size (&parser->search_list) == 0)
{
pp = statp->dnsrch;
*pp++ = statp->defdname;
*pp = NULL;
char *domain;
if (!domain_from_hostname (&domain))
return false;
if (domain != NULL)
{
free (parser->search_list_store);
parser->search_list_store = domain;
search_list_add (&parser->search_list, domain);
}
}
if ((cp = getenv ("RES_OPTIONS")) != NULL)
res_setoptions (statp, cp);
if (search_list_has_failed (&parser->search_list))
{
__set_errno (ENOMEM);
return false;
}
statp->options |= RES_INIT;
return true;
}
@ -453,13 +524,17 @@ __res_vinit (res_state statp, int preinit)
return -1;
}
char *buffer = NULL;
bool ok = res_vinit_1 (statp, preinit, fp, &buffer);
free (buffer);
struct resolv_conf_parser parser;
resolv_conf_parser_init (&parser);
bool ok = res_vinit_1 (statp, preinit, fp, &parser);
if (ok)
{
struct resolv_conf init = { 0 }; /* No data yet. */
struct resolv_conf init =
{
.search_list = search_list_begin (&parser.search_list),
.search_list_size = search_list_size (&parser.search_list),
};
struct resolv_conf *conf = __resolv_conf_allocate (&init);
if (conf == NULL)
ok = false;
@ -469,6 +544,7 @@ __res_vinit (res_state statp, int preinit)
__resolv_conf_put (conf);
}
}
resolv_conf_parser_free (&parser);
if (!ok)
{