Hi All,
In ssl3_write_bytes, if (len < tot) we are returning failure with
SSL_R_BAD_LENGTH error. In this place I hope we should set “tot” back to
“s->s3->wnum”. Otherwise when application calls back SSL_write with correct
buffer, it causes serious problem (“tot” is 0 and iLeft is not NULL). I hope we
should do like below.
if (len < tot) {
s->s3->wnum = tot;
SSLerr(SSL_F_SSL3_WRITE_BYTES, SSL_R_BAD_LENGTH);
return (-1);
}
And also we should do one additional check for “len” as mentioned in my
previous mail.
if ((len < tot) || ((tot != 0) && (len < (tot + s->s3->wpend_tot)))){
s->s3->wnum = tot;
SSLerr(SSL_F_SSL3_WRITE_BYTES, SSL_R_BAD_LENGTH);
return (-1);
}
Regards,
Ashok
________________________________
[Company_logo]
Raja Ashok V K
Huawei Technologies
Bangalore, India
http://www.huawei.com
________________________________
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From: Raja ashok
Sent: 27 March 2017 13:55
To: 'openssl-users@openssl.org'; 'openssl-...@openssl.org'
Subject: In ssl3_write_bytes, some checks related to hanlding write failure are
missing
Hi,
I feel there is a check missing in ssl3_write_bytes, in case of handling write
failure.
Consider SSL_write is called with 20000 bytes buffer, then internally in
ssl3_write_bytes we try to send it as two record (16384 and 3616). If TCP send
failed for the second record then we store the states internally (wnum,
wpend_tot and wpend_buf) and return back the result.
Later application has to call SSL_write with same buffer, if it calls with
different buffer of length 100 byte then we fail that in ssl3_write_bytes using
the check (len < tot).
But consider application calls with buffer of size 18000 bytes and
SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER is enabled. Then (len < tot) will not
succeed as tot is 16384. Then it will call ssl3_write_pending to send the
remaining 3616 record. If it succeeds we are incrementing tot, (tot += i). Now
tot will have 20000.
Later there is a check (tot == len), this will not succeed. Then directly we
are doing n = (len - tot), this will overflow and store a value close to 2^32
in n. Then it will cause out of bound access to the application buffer "buf".
I hope we should have one more check (len < (tot + s->s3->wpend_tot)) before
calling ssl3_write_pending.
if ((len < tot) || (len < (tot + s->s3->wpend_tot))){
SSLerr(SSL_F_SSL3_WRITE_BYTES, SSL_R_BAD_LENGTH);
return (-1);
}
Note : I am referring 1.0.2k version of OpenSSL.
Regards,
Ashok
________________________________
[Company_logo]
Raja Ashok V K
Huawei Technologies
Bangalore, India
http://www.huawei.com
________________________________
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止任何其他人以任何形式使用（包括但不限于全部或部分地泄露、复制、或散发）本邮件中
的信息。如果您错收了本邮件，请您立即电话或邮件通知发件人并删除本邮件！
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is intended only for the person or entity whose address is listed above. Any
use of the
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or partial
disclosure, reproduction, or dissemination) by persons other than the intended
recipient(s) is prohibited. If you receive this e-mail in error, please notify
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