curl: (60) SSL certificate problem: unable to get local issuer certificate

Question

root@sclrdev:/home/sclr/certs/FreshCerts# curl --ftp-ssl --verbose ftp://{abc}/ -u trup:trup --cacert /etc/ssl/certs/ca-certificates.crt
* About to connect() to {abc} port 21 (#0)
*   Trying {abc}...
* Connected to {abc} ({abc}) port 21 (#0)
< 220-Cerberus FTP Server - Home Edition
< 220-This is the UNLICENSED Home Edition and may be used for home, personal use only
< 220-Welcome to Cerberus FTP Server
< 220 Created by Cerberus, LLC
> AUTH SSL
< 234 Authentication method accepted
* successfully set certificate verify locations:
*   CAfile: /etc/ssl/certs/ca-certificates.crt
  CApath: /etc/ssl/certs
* SSLv3, TLS handshake, Client hello (1):
* SSLv3, TLS handshake, Server hello (2):
* SSLv3, TLS handshake, CERT (11):
* SSLv3, TLS alert, Server hello (2):
* SSL certificate problem: unable to get local issuer certificate
* Closing connection 0
curl: (60) SSL certificate problem: unable to get local issuer certificate
More details here: http://curl.haxx.se/docs/sslcerts.html

curl performs SSL certificate verification by default, using a "bundle"
 of Certificate Authority (CA) public keys (CA certs). If the default
 bundle file isn't adequate, you can specify an alternate file
 using the --cacert option.
If this HTTPS server uses a certificate signed by a CA represented in
 the bundle, the certificate verification probably failed due to a
 problem with the certificate (it might be expired, or the name might
 not match the domain name in the URL).
If you'd like to turn off curl's verification of the certificate, use
 the -k (or --insecure) option.

Answer 1

Relating to 'SSL certificate problem: unable to get local issuer certificate' error. It is important to note that this applies to the system sending the CURL request, and NOT the server receiving the request.

1. Download the latest cacert.pem from https://curl.se/ca/cacert.pem

2. Add the '--cacert /path/to/cacert.pem' option to the curl command to tell curl where the local Certificate Authority file is.

3. (or) Create or add to a '.curlrc' file the line: cacert = /path/to/cacert.pem See 'man curl', the section about the '-K, --config <file>' section for information about where curl looks for this file.

4. (or if using php) Add the following line to php.ini: (if this is shared hosting and you don't have access to php.ini then you could add this to .user.ini in public_html).

curl.cainfo="/path/to/downloaded/cacert.pem"

Make sure you enclose the path within double quotation marks!!!

5. (perhaps also for php) By default, the FastCGI process will parse new files every 300 seconds (if required you can change the frequency by adding a couple of files as suggested here https://ss88.uk/blog/fast-cgi-and-user-ini-files-the-new-htaccess/).

Answer 2

It is failing as cURL is unable to verify the certificate provided by the server.

There are two options to get this to work:

1. Use cURL with -k option which allows curl to make insecure connections, that is cURL does not verify the certificate.

2. Add the root CA (the CA signing the server certificate) to /etc/ssl/certs/ca-certificates.crt

You should use option 2 as it's the option that ensures that you are connecting to secure FTP server.

Answer 3

I have solved this problem by adding one line code in cURL script:

curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);

Warning: This makes the request absolute insecure (see answer by @YSU)!

Answer 4

For me, simple install of certificates helped:

sudo apt-get install ca-certificates