Seeing the "bugs" directory in the openssl tarball, I thought you
might be interested to know that gcc-3.0 contains a bug that is
triggered in the PEM_get_EVP_CIPHER_INFO() function...
Here is the problem:
$ ssh-keygen -t rsa -N abcde
then
$ ssh-keygen -t rsa -P abcde -p
should works, but it didn't on my system (gcc-3.0, OpenSSH_3.4p1,
OpenSSL 0x00907004).
I have traced down the problem to PEM_get_EVP_CIPHER_INFO(): gcc-3.0
generates invalid assembler for this function. Just look at the machine
code that corresponds to this C code:
header+=11;
if (*header != '4') return(0); header++;
if (*header != ',') return(0); header++;
And you will notice that %eax (that represents "header") is incremented
too many times...
A more insightful demonstration of this bug is also available in the
`gcc-3.0-bug-demo.c' file.
----------------------------------------------------------------------
/*
** Gcc-3.0 bug -- noticed by Marc Bevand <bevand_m (at) epita.fr>
** on Tue Dec 3 14:06:02 CET 2002
**
** All is right with "-fPIC -O1", the bug only occurs with "-fPIC
** -O[23]":
**
** $ gcc -fPIC -O1 gcc-3.0-bug-demo.c
** $ ./a.out
** all is right
** $ gcc -fPIC -O2 gcc-3.0-bug-demo.c
** $ ./a.out
** there is a *bug*
**
** Look at the assembler generated for the 2 lines marked with XXX in
** foobar():
**
** 80484e3: 8b 45 08 mov 0x8(%ebp),%eax
** 80484e6: 83 c0 02 add $0x2,%eax
** 80484e9: 89 45 08 mov %eax,0x8(%ebp)
** 80484ec: 80 78 02 63 cmpb $0x63,0x2(%eax)
**
** The value of "header", contained in 0x8(%ebp), should be incremented
** only 1 time, but actually it is incremented 2 times (in add and
** cmpb).
*/
int hello(char **notused)
{
return 0;
}
int foobar(char *header)
{
if (strncmp(header, "ab", 2))
return 0;
header += 2; /* XXX */
if (*header != 'c') /* XXX */
return 0;
if (hello(&header))
return 0;
return 1;
}
int main(void)
{
if (foobar("abc__"))
puts("all is right");
else
puts("there is a *bug*");
return 0;
}
----------------------------------------------------------------------
--
Marc Bevand http://www.epita.fr/~bevand_m
Computer Science School EPITA - System, Network and Security Dept.
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