Get site content over SSL with httr in R

问题:

I'm trying to fetch a JSON array from my server using the HTTP POST method in R.

I've tried using both the POSTfunction from httrand the getURLfunction from RCurl but both return errors.

cafile <- system.file("CurlSSL", "cacert.pem", package = "RCurl")
url    <- "https://example.com/query/getData.php"

POST(url,body=NULL)
POST(url,body=NULL,config(cainfo=cafile))

getURL(url)
getURL(url,cainfo=cafile)

The error given by the POST function is (for both calls):

Error in curl::curl_fetch_memory(url, handle = handle) : 
  SSL peer certificate or SSH remote key was not OK

The error given by the getURL function is (without config(cainfo=cafile)):

* Hostname was NOT found in DNS cache
*   Trying 162.xxx.xxx.xxx...
* connect to 162.xxx.xxx.xxx port 443 failed: Connection refused
*   Trying 130.yyy.yyy.yyy...
* Connected to example.com (130.yyy.yyy.yyy) port 443 (#0)
* found 175 certificates in /etc/ssl/certs/ca-certificates.crt
* gnutls_handshake() warning: The server name sent was not recognized
* failed to get server cert
* Closing connection 0
Error in function (type, msg, asError = TRUE)  : 
  gnutls_handshake() warning: The server name sent was not recognized

I'm suspecting this has something to do with R since running:

curl 'https://example.com/query/getData.php'

from the command line return the expected result.

The server is a apache2 server with COMODO SSL certificate. In /etc/apache2/sites-enabled/000-default.conf the server name is set to

ServerName www.example.com  

Any help would be most apreciated

回答1:

The httr package includes it's own CA bundle so this probably not the issue. More likely a server side SNI config problem or a problem with your certificate

Unfortunately you haven't posted a reproducible example with an actual URL. But with the latest version of the new openssl package you can easily debug your server cert:

library(openssl)
cert <- download_ssl_cert("www.r-project.org")
print(cert)
print(as.list(cert[[1]]))

Also try validating it

cert_verify(cert, ca_bundle())

This might give a hint on what's wrong with your certificate.

回答2:

It seems like changing

ServerName www.example.com

To

ServerName example.com

fixed this issue. I tried this solution from another computer and I was able to use the httr POST function with this fix with the default httr CA bundle.