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From: Florian Weimer <fweimer@redhat.com>
Date: Fri, 29 Apr 2016 10:35:34 +0200
Subject: [PATCH] CVE-2016-3706: getaddrinfo: stack overflow in hostent
conversion [BZ #20010]
When converting a struct hostent response to struct gaih_addrtuple, the
gethosts macro (which is called from gaih_inet) used alloca, without
malloc fallback for large responses. This commit changes this code to
use calloc unconditionally.
This commit also consolidated a second hostent-to-gaih_addrtuple
conversion loop (in gaih_inet) to use the new conversion function.
---
sysdeps/posix/getaddrinfo.c | 130 +++++++++++++++++++++++---------------------
1 file changed, 69 insertions(+), 61 deletions(-)
diff --git a/sysdeps/posix/getaddrinfo.c b/sysdeps/posix/getaddrinfo.c
index 1ef3f20d987b..fed2d3bf130b 100644
--- a/sysdeps/posix/getaddrinfo.c
+++ b/sysdeps/posix/getaddrinfo.c
@@ -168,9 +168,58 @@ gaih_inet_serv (const char *servicename, const struct gaih_typeproto *tp,
return 0;
}
+/* Convert struct hostent to a list of struct gaih_addrtuple objects.
+ h_name is not copied, and the struct hostent object must not be
+ deallocated prematurely. *RESULT must be NULL or a pointer to an
+ object allocated using malloc, which is freed. */
+static bool
+convert_hostent_to_gaih_addrtuple (const struct addrinfo *req,
+ int family,
+ struct hostent *h,
+ struct gaih_addrtuple **result)
+{
+ free (*result);
+ *result = NULL;
+
+ /* Count the number of addresses in h->h_addr_list. */
+ size_t count = 0;
+ for (char **p = h->h_addr_list; *p != NULL; ++p)
+ ++count;
+
+ /* Report no data if no addresses are available, or if the incoming
+ address size is larger than what we can store. */
+ if (count == 0 || h->h_length > sizeof (((struct gaih_addrtuple) {}).addr))
+ return true;
+
+ struct gaih_addrtuple *array = calloc (count, sizeof (*array));
+ if (array == NULL)
+ return false;
+
+ for (size_t i = 0; i < count; ++i)
+ {
+ if (family == AF_INET && req->ai_family == AF_INET6)
+ {
+ /* Perform address mapping. */
+ array[i].family = AF_INET6;
+ memcpy(array[i].addr + 3, h->h_addr_list[i], sizeof (uint32_t));
+ array[i].addr[2] = htonl (0xffff);
+ }
+ else
+ {
+ array[i].family = family;
+ memcpy (array[i].addr, h->h_addr_list[i], h->h_length);
+ }
+ array[i].next = array + i + 1;
+ }
+ array[0].name = h->h_name;
+ array[count - 1].next = NULL;
+
+ *result = array;
+ return true;
+}
+
#define gethosts(_family, _type) \
{ \
- int i; \
int herrno; \
struct hostent th; \
struct hostent *h; \
@@ -219,36 +268,23 @@ gaih_inet_serv (const char *servicename, const struct gaih_typeproto *tp,
} \
else if (h != NULL) \
{ \
- for (i = 0; h->h_addr_list[i]; i++) \
+ /* Make sure that addrmem can be freed. */ \
+ if (!malloc_addrmem) \
+ addrmem = NULL; \
+ if (!convert_hostent_to_gaih_addrtuple (req, _family,h, &addrmem)) \
{ \
- if (*pat == NULL) \
- { \
- *pat = __alloca (sizeof (struct gaih_addrtuple)); \
- (*pat)->scopeid = 0; \
- } \
- uint32_t *addr = (*pat)->addr; \
- (*pat)->next = NULL; \
- (*pat)->name = i == 0 ? strdupa (h->h_name) : NULL; \
- if (_family == AF_INET && req->ai_family == AF_INET6) \
- { \
- (*pat)->family = AF_INET6; \
- addr[3] = *(uint32_t *) h->h_addr_list[i]; \
- addr[2] = htonl (0xffff); \
- addr[1] = 0; \
- addr[0] = 0; \
- } \
- else \
- { \
- (*pat)->family = _family; \
- memcpy (addr, h->h_addr_list[i], sizeof(_type)); \
- } \
- pat = &((*pat)->next); \
+ _res.options |= old_res_options & RES_USE_INET6; \
+ result = -EAI_SYSTEM; \
+ goto free_and_return; \
} \
+ *pat = addrmem; \
+ /* The conversion uses malloc unconditionally. */ \
+ malloc_addrmem = true; \
\
if (localcanon != NULL && canon == NULL) \
canon = strdupa (localcanon); \
\
- if (_family == AF_INET6 && i > 0) \
+ if (_family == AF_INET6 && *pat != NULL) \
got_ipv6 = true; \
} \
}
@@ -612,44 +648,16 @@ gaih_inet (const char *name, const struct gaih_service *service,
{
if (h != NULL)
{
- int i;
- /* We found data, count the number of addresses. */
- for (i = 0; h->h_addr_list[i]; ++i)
- ;
- if (i > 0 && *pat != NULL)
- --i;
-
- if (__libc_use_alloca (alloca_used
- + i * sizeof (struct gaih_addrtuple)))
- addrmem = alloca_account (i * sizeof (struct gaih_addrtuple),
- alloca_used);
- else
- {
- addrmem = malloc (i
- * sizeof (struct gaih_addrtuple));
- if (addrmem == NULL)
- {
- result = -EAI_MEMORY;
- goto free_and_return;
- }
- malloc_addrmem = true;
- }
-
- /* Now convert it into the list. */
- struct gaih_addrtuple *addrfree = addrmem;
- for (i = 0; h->h_addr_list[i]; ++i)
+ /* We found data, convert it. */
+ if (!convert_hostent_to_gaih_addrtuple
+ (req, AF_INET, h, &addrmem))
{
- if (*pat == NULL)
- {
- *pat = addrfree++;
- (*pat)->scopeid = 0;
- }
- (*pat)->next = NULL;
- (*pat)->family = AF_INET;
- memcpy ((*pat)->addr, h->h_addr_list[i],
- h->h_length);
- pat = &((*pat)->next);
+ result = -EAI_MEMORY;
+ goto free_and_return;
}
+ *pat = addrmem;
+ /* The conversion uses malloc unconditionally. */
+ malloc_addrmem = true;
}
}
else
|
