int check_padding_and_structure(out, length)
{
pad = out[length - 1];
if(pad > 16) return -1; // Bad padding byte
n = length - pad;
for(i = n; i < length; i++) // check padding
if(out[i] != pad) return -1;
/* match structure with known standard structure */
outfile = BIO_new(BIO_s_mem());
ASN1_parse(outfile, out, legnth, 0);
BIO_gets(outfile, (char*)output, N);
res = memem(output, 128, "SEQUENCE", 8);
if (!res) goto bad;
BIO_gets(outfile, (char*)output, N);
res = memem(output, 128, ":00", 3);
if (!res) goto bad;
res = memem(output, 128, "INTEGER", 7);
if (!res) goto bad;
BIO_gets(outfile, (char*)output, N);
res = memem(output, 128, "INTEGER", 7);
if (!res) goto bad;
/* now this integer has to be big, check minimum length */
ul = strlen((char*)res);
p = res;
while(*p) {
if (isspace(*p))
ul--;
p++;
}
if (ul < 32) goto bad;
return 0;
bad:
return -1;
}
static inline int check_padding_and_structure(unsigned char *out, int length)
{
int pad;
int i;
int n;
unsigned char output[N];
int ul; /* useful length */
unsigned char *res = NULL;
unsigned char *p;
BIO * outfile;
// First check padding
pad = out[length - 1];
if(pad > 16)
return -1;
n = length - pad;
for(i = n; i < length; i++)
if(out[i] != pad)
return -1;
/* check BER decoding, private key file contains:
* RSAPrivateKey = { version = 0, n, e, d, p, q, d mod p-1, d mod q-1, q**-1 mod p }
* DSAPrivateKey = { version = 0, p, q, g, y, x } */
memset(output, 0, N);
outfile = BIO_new(BIO_s_mem());
ASN1_parse(outfile, out, cur_salt->ctl, 0);
BIO_gets(outfile, (char*)output, N);
res = memmem(output, 128, "SEQUENCE", 8);
if (!res) {
goto bad;
}
BIO_gets(outfile, (char*)output, N);
res = memmem(output, 128, ":00", 3);
if (!res) {
goto bad;
}
res = memmem(output, 128, "INTEGER", 7);
if (!res) {
goto bad;
}
/* one more level of check */
BIO_gets(outfile, (char*)output, N);
res = memmem(output, 128, "INTEGER", 7);
if (!res) {
goto bad;
}
/* NOTE: now this integer has to be big, is this always true?
* RSA (as used in ssh) uses big prime numbers, so this check should be OK */
ul = strlen((char*)res);
p = res;
while(*p) {
if (isspace(*p))
ul--;
p++;
}
if (ul < 32)
goto bad;
BIO_free(outfile);
return 0;
bad:
BIO_free(outfile);
return -1;
}