diff options
Diffstat (limited to 'backport-CVE-2023-4806.patch')
| -rw-r--r-- | backport-CVE-2023-4806.patch | 149 |
1 files changed, 149 insertions, 0 deletions
diff --git a/backport-CVE-2023-4806.patch b/backport-CVE-2023-4806.patch new file mode 100644 index 0000000..acac716 --- /dev/null +++ b/backport-CVE-2023-4806.patch @@ -0,0 +1,149 @@ +From 973fe93a5675c42798b2161c6f29c01b0e243994 Mon Sep 17 00:00:00 2001 +From: Siddhesh Poyarekar <siddhesh@sourceware.org> +Date: Fri, 15 Sep 2023 13:51:12 -0400 +Subject: [PATCH] getaddrinfo: Fix use after free in getcanonname + (CVE-2023-4806) + +When an NSS plugin only implements the _gethostbyname2_r and +_getcanonname_r callbacks, getaddrinfo could use memory that was freed +during tmpbuf resizing, through h_name in a previous query response. + +The backing store for res->at->name when doing a query with +gethostbyname3_r or gethostbyname2_r is tmpbuf, which is reallocated in +gethosts during the query. For AF_INET6 lookup with AI_ALL | +AI_V4MAPPED, gethosts gets called twice, once for a v6 lookup and second +for a v4 lookup. In this case, if the first call reallocates tmpbuf +enough number of times, resulting in a malloc, th->h_name (that +res->at->name refers to) ends up on a heap allocated storage in tmpbuf. +Now if the second call to gethosts also causes the plugin callback to +return NSS_STATUS_TRYAGAIN, tmpbuf will get freed, resulting in a UAF +reference in res->at->name. This then gets dereferenced in the +getcanonname_r plugin call, resulting in the use after free. + +Fix this by copying h_name over and freeing it at the end. This +resolves BZ #30843, which is assigned CVE-2023-4806. + +Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org> +--- + sysdeps/posix/getaddrinfo.c | 36 +++++++++++++++++++++++++++++------- + 1 file changed, 29 insertions(+), 7 deletions(-) + +diff --git a/sysdeps/posix/getaddrinfo.c b/sysdeps/posix/getaddrinfo.c +index 9f1cde27..07fbf441 100644 +--- a/sysdeps/posix/getaddrinfo.c ++++ b/sysdeps/posix/getaddrinfo.c +@@ -106,6 +106,12 @@ struct gaih_servtuple + int port; + }; + ++struct gaih_result ++{ ++ char *h_name; ++ bool malloc_h_name; ++}; ++ + static const struct gaih_servtuple nullserv; + + +@@ -197,7 +203,8 @@ static bool + convert_hostent_to_gaih_addrtuple (const struct addrinfo *req, + int family, + struct hostent *h, +- struct gaih_addrtuple **result) ++ struct gaih_addrtuple **result, ++ struct gaih_result *res) + { + while (*result) + result = &(*result)->next; +@@ -216,6 +223,16 @@ convert_hostent_to_gaih_addrtuple (const struct addrinfo *req, + if (array == NULL) + return false; + ++ /* Duplicate h_name because it may get reclaimed when the underlying storage ++ is freed. */ ++ if (res->h_name == NULL) ++ { ++ res->h_name = __strdup (h->h_name); ++ res->malloc_h_name = true; ++ if (res->h_name == NULL) ++ return false; ++ } ++ + for (size_t i = 0; i < count; ++i) + { + if (family == AF_INET && req->ai_family == AF_INET6) +@@ -232,7 +249,6 @@ convert_hostent_to_gaih_addrtuple (const struct addrinfo *req, + } + array[i].next = array + i + 1; + } +- array[0].name = h->h_name; + array[count - 1].next = NULL; + + *result = array; +@@ -275,7 +291,7 @@ convert_hostent_to_gaih_addrtuple (const struct addrinfo *req, + } \ + else if (status == NSS_STATUS_SUCCESS) \ + { \ +- if (!convert_hostent_to_gaih_addrtuple (req, _family, &th, &addrmem)) \ ++ if (!convert_hostent_to_gaih_addrtuple (req, _family, &th, &addrmem, &res)) \ + { \ + __resolv_context_put (res_ctx); \ + result = -EAI_SYSTEM; \ +@@ -307,14 +323,14 @@ convert_hostent_to_gaih_addrtuple (const struct addrinfo *req, + memory allocation failure. The returned string is allocated on the + heap; the caller has to free it. */ + static char * +-getcanonname (nss_action_list nip, struct gaih_addrtuple *at, const char *name) ++getcanonname (nss_action_list nip, const char *hname, const char *name) + { + nss_getcanonname_r *cfct = __nss_lookup_function (nip, "getcanonname_r"); + char *s = (char *) name; + if (cfct != NULL) + { + char buf[256]; +- if (DL_CALL_FCT (cfct, (at->name ?: name, buf, sizeof (buf), ++ if (DL_CALL_FCT (cfct, (hname ?: name, buf, sizeof (buf), + &s, &errno, &h_errno)) != NSS_STATUS_SUCCESS) + /* If the canonical name cannot be determined, use the passed + string. */ +@@ -335,6 +351,8 @@ gaih_inet (const char *name, const struct gaih_service *service, + const char *canon = NULL; + const char *orig_name = name; + ++ struct gaih_result res = {0}; ++ + /* Reserve stack memory for the scratch buffer in the getaddrinfo + function. */ + size_t alloca_used = sizeof (struct scratch_buffer); +@@ -574,7 +592,7 @@ gaih_inet (const char *name, const struct gaih_service *service, + { + /* We found data, convert it. */ + if (!convert_hostent_to_gaih_addrtuple +- (req, AF_INET, h, &addrmem)) ++ (req, AF_INET, h, &addrmem, &res)) + { + result = -EAI_MEMORY; + goto free_and_return; +@@ -858,7 +876,7 @@ gaih_inet (const char *name, const struct gaih_service *service, + if ((req->ai_flags & AI_CANONNAME) != 0 + && canon == NULL) + { +- canonbuf = getcanonname (nip, at, name); ++ canonbuf = getcanonname (nip, res.h_name, name); + if (canonbuf == NULL) + { + __resolv_context_put (res_ctx); +@@ -1101,6 +1119,10 @@ gaih_inet (const char *name, const struct gaih_service *service, + free (addrmem); + free (canonbuf); + ++ if (res.malloc_h_name){ ++ free (res.h_name); ++ } ++ + return result; + } + +-- +2.33.0 + |