Public bug reported:
This is valid for iproute2-ss111117 which is default on Ubuntu 12.04
(LTS).
The crash appends when supplying enc, auth, comp, auth-trunc or aead and the
following key argumentis given as a string (as opposed to hexadecimal). When
trying to copy the key, it generates a segfault:
------------------------------------------------------------
*** buffer overflow detected ***: /sbin/ip terminated
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(__fortify_fail+0x37)[0x7ffff7921807]
/lib/x86_64-linux-gnu/libc.so.6(+0x109700)[0x7ffff7920700]
/lib/x86_64-linux-gnu/libc.so.6(+0x1089e6)[0x7ffff791f9e6]
/sbin/ip[0x420d84]
/sbin/ip(do_xfrm_state+0x7a1)[0x421951]
/sbin/ip[0x405ad5]
/sbin/ip(main+0x2b4)[0x4056d4]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xed)[0x7ffff783876d]
/sbin/ip[0x405959]
------------------------------------------------------------
This buffer overflow is actually preposterous since __strncpy_chk is called
with 0 as its last argument:
0x0000000000420d72: mov 0x68(%rsp),%rsi
0x0000000000420d77: movslq %r12d,%rdx
0x0000000000420d7a: xor %ecx,%ecx
0x0000000000420d7c: mov %r9,%rdi
=> 0x0000000000420d7f: callq 0x404a10 <__strncpy_chk@plt>
("xor %ecx,%ecx" set the fourth argument to 0)
Which is equivalent to:
__strncpy_chk(buf, key, len, 0);
When obtaining the source package, the corresponding code looks like
that (from ip/xfrm_state.c, line 113):
static int xfrm_algo_parse(struct xfrm_algo *alg, enum xfrm_attr_type_t type,
char *name, char *key, char *buf, int max)
{
int len;
int slen = strlen(key);
#if 0
/* XXX: verifying both name and key is required! */
fprintf(stderr, "warning: ALGO-NAME/ALGO-KEY will send to kernel
promiscuously! (verifying them isn't implemented yet)\n");
#endif
strncpy(alg->alg_name, name, sizeof(alg->alg_name));
if (slen > 2 && strncmp(key, "0x", 2) == 0) {
<snip>
} else {
len = slen;
if (len > 0) {
if (len > max)
invarg("\"ALGO-KEY\" makes buffer overflow\n",
key);
strncpy(buf, key, len); <----- correct line which is
faulty in the assembly
}
}
alg->alg_key_len = len * 8;
return 0;
}
This code is actually valid but doesn't match the assembly from the
binary package.
This is quite annoying since it prevents from setting keys in a string
form, thus forcing the user to derivates itself the hexadecimal value
for the key when trying to setup an IPsec tunnel for example.
** Affects: iproute2 (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1220782
Title:
ip xfrm state add crashes when supplied an algo
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