136 lines
4.2 KiB
Diff
136 lines
4.2 KiB
Diff
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From 46703a3995aa3ca2b816814aa4ad05ed524194dd Mon Sep 17 00:00:00 2001
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From: Florian Weimer <fweimer@redhat.com>
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Date: Mon, 19 Jun 2017 22:31:04 +0200
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Subject: ld.so: Reject overly long LD_PRELOAD path elements
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(cherry picked from commit 6d0ba622891bed9d8394eef1935add53003b12e8)
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diff --git a/ChangeLog b/ChangeLog
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index 14ff8b8bb3..fbe4db2cf7 100644
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--- a/ChangeLog
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+++ b/ChangeLog
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@@ -1,5 +1,12 @@
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2017-06-19 Florian Weimer <fweimer@redhat.com>
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+ * elf/rtld.c (SECURE_NAME_LIMIT, SECURE_PATH_LIMIT): Define.
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+ (dso_name_valid_for_suid): New function.
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+ (handle_ld_preload): Likewise.
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+ (dl_main): Call it. Remove alloca.
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+
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+2017-06-19 Florian Weimer <fweimer@redhat.com>
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+
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[BZ #21624]
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CVE-2017-1000366
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* elf/rtld.c (process_envvars): Ignore LD_LIBRARY_PATH for
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diff --git a/elf/rtld.c b/elf/rtld.c
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index 2fc33a6178..4badcf6590 100644
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--- a/elf/rtld.c
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+++ b/elf/rtld.c
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@@ -99,6 +99,35 @@ uintptr_t __pointer_chk_guard_local
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strong_alias (__pointer_chk_guard_local, __pointer_chk_guard)
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#endif
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+/* Length limits for names and paths, to protect the dynamic linker,
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+ particularly when __libc_enable_secure is active. */
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+#ifdef NAME_MAX
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+# define SECURE_NAME_LIMIT NAME_MAX
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+#else
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+# define SECURE_NAME_LIMIT 255
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+#endif
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+#ifdef PATH_MAX
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+# define SECURE_PATH_LIMIT PATH_MAX
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+#else
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+# define SECURE_PATH_LIMIT 1024
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+#endif
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+
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+/* Check that AT_SECURE=0, or that the passed name does not contain
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+ directories and is not overly long. Reject empty names
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+ unconditionally. */
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+static bool
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+dso_name_valid_for_suid (const char *p)
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+{
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+ if (__glibc_unlikely (__libc_enable_secure))
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+ {
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+ /* Ignore pathnames with directories for AT_SECURE=1
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+ programs, and also skip overlong names. */
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+ size_t len = strlen (p);
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+ if (len >= SECURE_NAME_LIMIT || memchr (p, '/', len) != NULL)
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+ return false;
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+ }
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+ return *p != '\0';
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+}
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/* List of auditing DSOs. */
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static struct audit_list
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@@ -716,6 +745,42 @@ static const char *preloadlist attribute_relro;
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/* Nonzero if information about versions has to be printed. */
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static int version_info attribute_relro;
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+/* The LD_PRELOAD environment variable gives list of libraries
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+ separated by white space or colons that are loaded before the
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+ executable's dependencies and prepended to the global scope list.
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+ (If the binary is running setuid all elements containing a '/' are
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+ ignored since it is insecure.) Return the number of preloads
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+ performed. */
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+unsigned int
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+handle_ld_preload (const char *preloadlist, struct link_map *main_map)
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+{
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+ unsigned int npreloads = 0;
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+ const char *p = preloadlist;
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+ char fname[SECURE_PATH_LIMIT];
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+
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+ while (*p != '\0')
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+ {
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+ /* Split preload list at space/colon. */
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+ size_t len = strcspn (p, " :");
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+ if (len > 0 && len < sizeof (fname))
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+ {
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+ memcpy (fname, p, len);
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+ fname[len] = '\0';
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+ }
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+ else
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+ fname[0] = '\0';
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+
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+ /* Skip over the substring and the following delimiter. */
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+ p += len;
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+ if (*p != '\0')
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+ ++p;
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+
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+ if (dso_name_valid_for_suid (fname))
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+ npreloads += do_preload (fname, main_map, "LD_PRELOAD");
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+ }
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+ return npreloads;
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+}
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+
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static void
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dl_main (const ElfW(Phdr) *phdr,
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ElfW(Word) phnum,
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@@ -1462,23 +1527,8 @@ ERROR: ld.so: object '%s' cannot be loaded as audit interface: %s; ignored.\n",
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if (__glibc_unlikely (preloadlist != NULL))
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{
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- /* The LD_PRELOAD environment variable gives list of libraries
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- separated by white space or colons that are loaded before the
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- executable's dependencies and prepended to the global scope
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- list. If the binary is running setuid all elements
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- containing a '/' are ignored since it is insecure. */
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- char *list = strdupa (preloadlist);
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- char *p;
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-
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HP_TIMING_NOW (start);
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-
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- /* Prevent optimizing strsep. Speed is not important here. */
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- while ((p = (strsep) (&list, " :")) != NULL)
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- if (p[0] != '\0'
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- && (__builtin_expect (! __libc_enable_secure, 1)
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- || strchr (p, '/') == NULL))
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- npreloads += do_preload (p, main_map, "LD_PRELOAD");
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-
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+ npreloads += handle_ld_preload (preloadlist, main_map);
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HP_TIMING_NOW (stop);
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HP_TIMING_DIFF (diff, start, stop);
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HP_TIMING_ACCUM_NT (load_time, diff);
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--
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2.13.1
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