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NET::SSLeay to verify certificates?

by LoraIlieva (Acolyte)
on Nov 17, 2016 at 10:42 UTC ( #1176049=perlquestion: print w/replies, xml ) Need Help??

LoraIlieva has asked for the wisdom of the Perl Monks concerning the following question:

Hi! I have the same task to do and the same problem. I am trying to verify ssl sertificate using Net::SSLeay.

As input I have certificate in PEM format and path to the directory with root and intermediate certificates. I read about doing the verification in C (https://www.ibm.com/developerworks/library/l-openssl/), but I can't find equivalents of called C functions. This is what I did:

my $s_cert_filename = '/path/to/cert/mycert.pem'; my $s_chain_dir = '/path/to/root_and_itermediate/certs/'; #Initialization, because I read about it in cpan my $rv = Net::SSLeay::library_init(); if($rv != 1) {die 'library init'}; Net::SSLeay::load_error_strings(); Net::SSLeay::SSLeay_add_ssl_algorithms(); #Create $ctx object my $ctx = Net::SSLeay::CTX_new or die; #Set where are root and intermediate certs Net::SSLeay::CTX_load_verify_locations($ctx, '', $s_chain_dir) or die_now("CTX load verify loc=`$s_chain_dir' $!"); #Set where is the certificate to be checked $rv = Net::SSLeay::CTX_use_certificate_file($ctx, $s_filename, &Net::SSLeay::FILETYPE_PEM); if($rv != 1) {die 'CTX_use_certificate_file'} #Create $ssl object from $ctx object my $ssl = Net::SSLeay::new($ctx); #Try to get verification result $rv = Net::SSLeay::get_verify_result($ssl); print $rv;

Result is always '0' which means this is valid certificate. The problem is that I tried with both valid and invalid certificate, and the result is always '0'.

Net::SSLeay::CTX_free($ctx);

Also I read that it's not verifying the certificate, but something called x509_store, so I found other example in C (http://stackoverflow.com/questions/2756553/x509-certificate-verification-in-c). I tryed to translate it to perl:

my $s_cert_filename = '/path/to/cert/mycert.pem'; my $s_chain_dir = '/path/to/root_and_itermediate/certs/'; #Initialization my $rv = Net::SSLeay::library_init(); if($rv != 1) {die 'library init'}; Net::SSLeay::ERR_load_SSL_strings(); Net::SSLeay::SSLeay_add_ssl_algorithms(); #Create $ctx object my $ctx = Net::SSLeay::CTX_new() or die_now("Failed to create SSL_CTX $!"); #Set where are root and intermediate certs Net::SSLeay::CTX_load_verify_locations($ctx, '', $s_chain_dir) or die_now("CTX load verify loc=`$s_chain_dir' $!"); #Create $ssl object from $ctx object my $ssl = Net::SSLeay::new($ctx); #Set where is the certificate to be checked $rv = Net::SSLeay::use_certificate_file($ssl, $s_filename, &Net::SSLeay::FILETYPE_PEM); #get x509_store and set flag to check crl my $x509_store = Net::SSLeay::CTX_get_cert_store($ssl); Net::SSLeay::X509_STORE_set_flags($ctx, &Net::SSLeay::X509_V_FLAG_CRL_CHECK); #Try to get verification result $rv = Net::SSLeay::get_verify_result($ssl); print $rv;

Result is the same always '0'.

Net::SSLeay::CTX_free($ctx);

I think the problem is somewhere in the usage of those strange data structures and 'get_verify_result' returns '0' to show me that there is an error. I don't know what I am doing wrong. Could someone help me?

Replies are listed 'Best First'.
Re: NET::SSLeay to verify certificates?
by rdfield (Priest) on Oct 04, 2018 at 13:54 UTC
    Not really a proper Perl solution, but I couldn't find out how to make the low level routines in Net::SSLeay work (the documentation states that the certificate verification code isn't well tested). Anyway, here's an Inline C bit of code that works on Debian Stretch:
    use strict; use warnings; use Inline Config => force_build => 0, clean_after_build => 1; use Inline C => 'DATA'; use Inline C => Config => DIRECTORY => "/tmp" => enable => 'UNTAINT' => inc => '-I/usr/include' => libs => ' -lssl -lcrypto '; my $CAfile = "cacert.pem"; my $Cert = "good.crt"; my $Cert2 = "selfsigned.crt"; print "cert1 = " . verify_cert($CAfile, $Cert) . "\n"; print "cert2 = " . verify_cert($CAfile, $Cert2) . "\n"; __DATA__ __C__ #include <openssl/bio.h> #include <openssl/err.h> #include <openssl/pem.h> #include <openssl/x509.h> #include <openssl/x509_vfy.h> char *verify_cert(char *ca_bundlestr, char *cert_filestr) { BIO *certbio = NULL; BIO *outbio = NULL; X509 *error_cert = NULL; X509 *cert = NULL; X509_NAME *certsubject = NULL; X509_STORE *store = NULL; X509_STORE_CTX *vrfy_ctx = NULL; int ret; char *retmsg; OpenSSL_add_all_algorithms(); ERR_load_BIO_strings(); ERR_load_crypto_strings(); certbio = BIO_new(BIO_s_file()); if (!(store=X509_STORE_new())) { size_t needed = snprintf(NULL, 0, "Error creating X509_STORE_CTX +object") + 1; retmsg = malloc(needed); snprintf(retmsg, needed, "Error creating X509_STORE_CTX object"); goto done; } vrfy_ctx = X509_STORE_CTX_new(); ret = BIO_read_filename(certbio, cert_filestr); if (! (cert = PEM_read_bio_X509(certbio, NULL, 0, NULL))) { size_t needed = snprintf(NULL, 0, "Error loading cert into memory +") + 1; retmsg = malloc(needed); snprintf(retmsg, needed, "Error loading cert into memory"); goto done; } ret = X509_STORE_load_locations(store, ca_bundlestr, NULL); if (ret != 1) { size_t needed = snprintf(NULL, 0, "Error loading CA cert or chain + file") + 1; retmsg = malloc(needed); snprintf(retmsg, needed, "Error loading CA cert or chain file"); goto done; } X509_STORE_CTX_init(vrfy_ctx, store, cert, NULL); ret = X509_verify_cert(vrfy_ctx); if( ret == 0 ) { size_t needed = snprintf(NULL, 0, "Error %s", X509_verify_cert_er +ror_string(X509_STORE_CTX_get_error (vrfy_ctx))) + 1; retmsg = malloc(needed); snprintf(retmsg, needed, "Error %s", X509_verify_cert_error_strin +g(X509_STORE_CTX_get_error (vrfy_ctx))); } else { size_t needed = snprintf(NULL, 0, "OK") + 1; retmsg = malloc(needed); snprintf(retmsg, needed, "OK"); } done: X509_STORE_CTX_free(vrfy_ctx); X509_STORE_free(store); X509_free(cert); BIO_free_all(certbio); return( retmsg ); }
    running it:
    $ perl verify_certs.pl cert1 = OK cert2 = Error self signed certificate
    (code is based on this source: original C code )

    rdfield

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