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Kees Cook f06295b44c ELF: implement AT_RANDOM for glibc PRNG seeding 
While discussing[1] the need for glibc to have access to random bytes
during program load, it seems that an earlier attempt to implement
AT_RANDOM got stalled.  This implements a random 16 byte string, available
to every ELF program via a new auxv AT_RANDOM vector.

[1] http://sourceware.org/ml/libc-alpha/2008-10/msg00006.html

Ulrich said:

glibc needs right after startup a bit of random data for internal
protections (stack canary etc).  What is now in upstream glibc is that we
always unconditionally open /dev/urandom, read some data, and use it.  For
every process startup.  That's slow.

...

The solution is to provide a limited amount of random data to the
starting process in the aux vector.  I suggested 16 bytes and this is
what the patch implements.  If we need only 16 bytes or less we use the
data directly.  If we need more we'll use the 16 bytes to see a PRNG.
This avoids the costly /dev/urandom use and it allows the kernel to use
the most adequate source of random data for this purpose.  It might not
be the same pool as that for /dev/urandom.

Concerns were expressed about the depletion of the randomness pool.  But
this patch doesn't make the situation worse, it doesn't deplete entropy
more than happens now.

Signed-off-by: Kees Cook <kees.cook@canonical.com>
Cc: Jakub Jelinek <jakub@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Ulrich Drepper <drepper@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-01-08 08:31:12 -08:00
..
9p Merge branch 'next' into for-linus 2008-12-25 11:40:09 +11:00
adfs vfs: Use const for kernel parser table 2008-10-13 10:10:37 -07:00
affs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 2009-01-05 18:32:06 -08:00
afs fs: symlink write_begin allocation context fix 2009-01-04 13:33:20 -08:00
autofs zero i_uid/i_gid on inode allocation 2009-01-05 11:54:28 -05:00
autofs4 autofs4: fix string validation check order 2009-01-06 15:59:23 -08:00
befs befs: ensure fast symlinks are NUL-terminated 2008-12-31 18:07:40 -05:00
bfs bfs: check that filesystem fits on the blockdevice 2009-01-06 15:59:31 -08:00
cifs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 2009-01-05 18:32:06 -08:00
coda coda: fix fs/coda/sysctl.c build warnings when !CONFIG_SYSCTL 2009-01-08 08:31:01 -08:00
configfs zero i_uid/i_gid on inode allocation 2009-01-05 11:54:28 -05:00
cramfs zero i_uid/i_gid on inode allocation 2009-01-05 11:54:28 -05:00
debugfs debugfs: add helpers for exporting a size_t simple value 2009-01-07 10:00:16 -08:00
devpts zero i_uid/i_gid on inode allocation 2009-01-05 11:54:28 -05:00
dlm Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/teigland/dlm 2009-01-05 19:02:09 -08:00
ecryptfs fs/ecryptfs/inode.c: cleanup kerneldoc 2009-01-06 15:59:22 -08:00
efs [PATCH] switch all filesystems over to d_obtain_alias 2008-10-23 05:13:01 -04:00
exportfs Merge branch 'next' into for-linus 2008-12-25 11:40:09 +11:00
ext2 ext2: tighten restrictions on inode flags 2009-01-08 08:31:00 -08:00
ext3 ext3: tighten restrictions on inode flags 2009-01-08 08:31:01 -08:00
ext4 percpu_counter: FBC_BATCH should be a variable 2009-01-06 15:59:13 -08:00
fat Merge git://git.kernel.org/pub/scm/linux/kernel/git/hirofumi/fatfs-2.6 2008-12-30 20:33:34 -08:00
freevxfs freevxfs: ensure fast symlinks are NUL-terminated 2008-12-31 18:07:40 -05:00
fuse Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse 2009-01-06 17:01:20 -08:00
gfs2 GFS2: Fix typo in gfs_page_mkwrite() 2009-01-07 08:58:28 +00:00
hfs CRED: Wrap task credential accesses in the HFS filesystem 2008-11-14 10:38:54 +11:00
hfsplus CRED: Wrap task credential accesses in the HFSplus filesystem 2008-11-14 10:38:54 +11:00
hostfs fs: symlink write_begin allocation context fix 2009-01-04 13:33:20 -08:00
hpfs CRED: Wrap task credential accesses in the HPFS filesystem 2008-11-14 10:38:55 +11:00
hppfs CRED: Use creds in file structs 2008-11-14 10:39:25 +11:00
hugetlbfs hugetlb: unsigned ret cannot be negative 2009-01-06 15:59:08 -08:00
isofs isofs check for NULL ->i_op in root directory is dead code 2009-01-05 11:53:38 -05:00
jbd jbd: remove excess kernel-doc notation 2009-01-08 08:31:01 -08:00
jbd2 jbd2: Add buffer triggers 2009-01-05 08:40:30 -08:00
jffs2 fs: symlink write_begin allocation context fix 2009-01-04 13:33:20 -08:00
jfs fix the treatment of jfs special inodes 2009-01-05 11:54:29 -05:00
lockd NLM: Clean up flow of control in make_socks() function 2009-01-07 15:40:44 -05:00
minix minix: fix add link's wrong position calculation 2009-01-06 15:59:27 -08:00
ncpfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2009-01-07 11:31:52 -08:00
nfs fs: symlink write_begin allocation context fix 2009-01-04 13:33:20 -08:00
nfs_common SUNRPC: nfsacl_encode/nfsacl_decode should be exported as GPL-only 2008-12-23 15:21:32 -05:00
nfsd nfsd: last_byte_offset 2009-01-07 17:38:31 -05:00
nls remove CONFIG_KMOD from fs 2008-10-17 02:38:36 +11:00
notify inotify: fix type errors in interfaces 2009-01-05 11:54:29 -05:00
ntfs ntfs: don't NULL i_op 2009-01-05 11:54:27 -05:00
ocfs2 trivial: fix then -> than typos in comments and documentation 2009-01-06 11:28:06 +01:00
omfs zero i_uid/i_gid on inode allocation 2009-01-05 11:54:28 -05:00
openpromfs zero i_uid/i_gid on inode allocation 2009-01-05 11:54:28 -05:00
partitions block: struct device - replace bus_id with dev_name(), dev_set_name() 2009-01-06 10:44:43 -08:00
proc Merge branch 'proc-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/adobriyan/proc 2009-01-07 12:01:06 -08:00
qnx4 SL*B: drop kmem cache argument from constructor 2008-07-26 12:00:07 -07:00
ramfs zero i_uid/i_gid on inode allocation 2009-01-05 11:54:28 -05:00
reiserfs Merge branch 'upstream-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mfasheh/ocfs2 2009-01-05 18:32:43 -08:00
romfs zero i_uid/i_gid on inode allocation 2009-01-05 11:54:28 -05:00
smbfs fs: symlink write_begin allocation context fix 2009-01-04 13:33:20 -08:00
sysfs zero i_uid/i_gid on inode allocation 2009-01-05 11:54:28 -05:00
sysv sysv: ensure fast symlinks are NUL-terminated 2008-12-31 18:07:39 -05:00
ubifs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2009-01-07 11:31:52 -08:00
udf Merge branch 'master' into next 2008-12-04 17:16:36 +11:00
ufs CRED: Wrap task credential accesses in the UFS filesystem 2008-11-14 10:39:04 +11:00
xfs trivial: fix then -> than typos in comments and documentation 2009-01-06 11:28:06 +01:00
aio.c aio: make the lookup_ioctx() lockless 2008-12-29 08:29:50 +01:00
anon_inodes.c anon_inodes: use fops->owner for module refcount 2008-12-31 16:55:44 +02:00
attr.c CRED: Wrap task credential accesses in the filesystem subsystem 2008-11-14 10:39:05 +11:00
bad_inode.c kill ->dir_notify() 2008-12-31 18:07:43 -05:00
binfmt_aout.c sanitize ifdefs in binfmt_aout 2009-01-03 11:45:54 -08:00
binfmt_elf_fdpic.c CRED: Make execve() take advantage of copy-on-write credentials 2008-11-14 10:39:24 +11:00
binfmt_elf.c ELF: implement AT_RANDOM for glibc PRNG seeding 2009-01-08 08:31:12 -08:00
binfmt_em86.c Allow recursion in binfmt_script and binfmt_misc 2008-10-16 11:21:38 -07:00
binfmt_flat.c CRED: Make execve() take advantage of copy-on-write credentials 2008-11-14 10:39:24 +11:00
binfmt_misc.c fs/binfmt_misc.c: add terminating newline to /proc/sys/fs/binfmt_misc/status 2009-01-06 15:59:19 -08:00
binfmt_script.c Allow recursion in binfmt_script and binfmt_misc 2008-10-16 11:21:38 -07:00
binfmt_som.c CRED: Make execve() take advantage of copy-on-write credentials 2008-11-14 10:39:24 +11:00
bio-integrity.c bio: allow individual slabs in the bio_set 2008-12-29 08:29:23 +01:00
bio.c bio: get rid of bio_vec clearing 2008-12-29 08:29:53 +01:00
block_dev.c fs: fix function param name in kernel-doc 2009-01-06 15:59:14 -08:00
buffer.c block_write_begin(): remove useless goto 2009-01-06 15:59:08 -08:00
char_dev.c fs: fix name overwrite in __register_chrdev_region() 2009-01-06 15:59:13 -08:00
compat_binfmt_elf.c
compat_ioctl.c remove unused #include <linux/dirent.h>'s 2008-07-25 10:53:34 -07:00
compat.c add missing accounting calls to compat_sys_{readv,writev} 2009-01-06 15:59:13 -08:00
dcache.c filp_cachep can be static in fs/file_table.c 2008-12-31 18:07:42 -05:00
dcookies.c shrink struct dentry 2008-12-31 18:07:38 -05:00
direct-io.c fs: truncate blocks outside i_size after O_DIRECT write error 2009-01-06 15:59:06 -08:00
dquot.c quota: don't set grace time when user isn't above softlimit 2009-01-08 08:31:01 -08:00
drop_caches.c
eventfd.c flag parameters: check magic constants 2008-07-24 10:47:29 -07:00
eventpoll.c epoll: introduce resource usage limits 2008-12-01 19:55:24 -08:00
exec.c fs/exec.c: make do_coredump() void 2009-01-06 15:59:29 -08:00
fcntl.c Merge branch 'next' into for-linus 2008-12-25 11:40:09 +11:00
fifo.c [PATCH] introduce fmode_t, do annotations 2008-10-21 07:47:06 -04:00
file_table.c filp_cachep can be static in fs/file_table.c 2008-12-31 18:07:42 -05:00
file.c [PATCH] merge locate_fd() and get_unused_fd() 2008-08-01 11:25:23 -04:00
filesystems.c vfs: remove duplicate code in get_fs_type() 2009-01-05 11:54:29 -05:00
fs-writeback.c fs: sys_sync fix 2009-01-06 15:59:09 -08:00
generic_acl.c
inode.c async: make the final inode deletion an asynchronous event 2009-01-07 08:47:24 -08:00
internal.h CRED: Make execve() take advantage of copy-on-write credentials 2008-11-14 10:39:24 +11:00
ioctl.c GFS2: Support for FIEMAP ioctl 2009-01-05 07:38:46 +00:00
ioprio.c CRED: Use RCU to access another task's creds and to release a task's own creds 2008-11-14 10:39:19 +11:00
Kconfig fs: use menuconfig to control the Misc. filesystems menu 2009-01-06 15:59:12 -08:00
Kconfig.binfmt add CONFIG_CORE_DUMP_DEFAULT_ELF_HEADERS 2008-10-20 08:52:39 -07:00
libfs.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 2009-01-05 18:32:06 -08:00
locks.c CRED: Wrap task credential accesses in the filesystem subsystem 2008-11-14 10:39:05 +11:00
Makefile quota: Split off quota tree handling into a separate file 2009-01-05 08:40:21 -08:00
mbcache.c
mpage.c do_mpage_readpage(): remove useless clear_buffer_mapped() call 2009-01-06 15:59:01 -08:00
namei.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 2009-01-05 18:32:06 -08:00
namespace.c fs/namespace.c: drop code after return 2008-12-31 18:07:38 -05:00
nfsctl.c pass a struct path * to may_open 2008-12-31 18:07:41 -05:00
no-block.c
open.c inode->i_op is never NULL 2009-01-05 11:54:28 -05:00
pipe.c sanitize audit_fd_pair() 2009-01-04 15:14:41 -05:00
pnode.c
pnode.h
posix_acl.c CRED: Wrap task credential accesses in the filesystem subsystem 2008-11-14 10:39:05 +11:00
quota_tree.c quota: Split off quota tree handling into a separate file 2009-01-05 08:40:21 -08:00
quota_tree.h quota: Split off quota tree handling into a separate file 2009-01-05 08:40:21 -08:00
quota_v1.c quota: Move quotaio_v[12].h from include/linux/ to fs/ 2009-01-05 08:36:58 -08:00
quota_v2.c quota: Convert union in mem_dqinfo to a pointer 2009-01-05 08:40:21 -08:00
quota.c quota: Introduce DQUOT_QUOTA_SYS_FILE flag 2009-01-05 08:36:57 -08:00
quotaio_v1.h quota: Move quotaio_v[12].h from include/linux/ to fs/ 2009-01-05 08:36:58 -08:00
quotaio_v2.h quota: Split off quota tree handling into a separate file 2009-01-05 08:40:21 -08:00
read_write.c vfs: lseek(fd, 0, SEEK_CUR) race condition 2009-01-05 11:53:07 -05:00
read_write.h
readdir.c [PATCH] prepare vfs_readdir() callers to returning filldir result 2008-10-23 05:13:10 -04:00
select.c poll: allow f_op->poll to sleep 2009-01-06 15:59:12 -08:00
seq_file.c Merge branch 'cpus4096-for-linus-3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-01-03 12:04:39 -08:00
signalfd.c flag parameters: check magic constants 2008-07-24 10:47:29 -07:00
splice.c memcg: synchronized LRU 2009-01-08 08:31:05 -08:00
stack.c
stat.c inode->i_op is never NULL 2009-01-05 11:54:28 -05:00
super.c async: Don't call async_synchronize_full_special() while holding sb_lock 2009-01-08 08:15:39 -08:00
sync.c mm: do_sync_mapping_range integrity fix 2009-01-06 15:59:00 -08:00
timerfd.c hrtimer: convert timerfd to the new hrtimer apis 2008-09-05 21:35:09 -07:00
utimes.c [PATCH] sanitize __user_walk_fd() et.al. 2008-07-26 20:53:34 -04:00
xattr_acl.c
xattr.c inode->i_op is never NULL 2009-01-05 11:54:28 -05:00