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SSLCERTS: minor updates

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Edited format to look better on the web, added a "it is about trust"
section.
This commit is contained in:
Daniel Stenberg 2014-09-10 10:13:04 +02:00
parent 202aa9f775
commit f213c0db09
1 changed files with 48 additions and 25 deletions
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docs/SSLCERTS
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@ -1,23 +1,46 @@
Peer SSL Certificate Verification
=================================
SSL Certificate Verification
============================
(NOTE: If libcurl was built with Schannel or Secure Transport support, then
this does not apply to you. Scroll down for details on how the OS-native
engines handle SSL certificates. If you're not sure, then run "curl -V" and
read the results. If the version string says "WinSSL" in it, then it was built
with Schannel support.)
SSL is TLS
----------
SSL is the old name. It is called TLS these days.
Native SSL
----------
If libcurl was built with Schannel or Secure Transport support (the native SSL
libraries included in Windows and Mac OS X), then this does not apply to
you. Scroll down for details on how the OS-native engines handle SSL
certificates. If you're not sure, then run "curl -V" and read the results. If
the version string says "WinSSL" in it, then it was built with Schannel
support.
It is about trust
-----------------
This system is about trust. In your local CA cert bundle you have certs from
*trusted* Certificate Authorities that you then can use to verify that the
server certificates you see are valid. They're signed by one of the CAs you
trust.
Which CAs do you trust? You can decide to trust the same set of companies your
operating system trusts, or the set one of the known browsers trust. That's
basically trust via someone else you trust. You should just be aware that
modern operating systems and browsers are setup to trust *hundreds* of
companies and recent years several such CAs have been found untrustworthy.
Certificate Verification
------------------------
libcurl performs peer SSL certificate verification by default. This is done
by using CA cert bundle that the SSL library can use to make sure the peer's
server certificate is valid.
If you communicate with HTTPS or FTPS servers using certificates that are
signed by CAs present in the bundle, you can be sure that the remote server
really is the one it claims to be.
Until 7.18.0, curl bundled a severely outdated ca bundle file that was
installed by default. These days, the curl archives include no ca certs at
all. You need to get them elsewhere. See below for example.
If you communicate with HTTPS, FTPS or other TLS-using servers using
certificates that are signed by CAs present in the bundle, you can be sure
that the remote server really is the one it claims to be.
If the remote server uses a self-signed certificate, if you don't install a CA
cert bundle, if the server uses a certificate signed by a CA that isn't
@ -94,15 +117,15 @@ cert bundle, will cause SSL to report an error ("certificate verify failed")
during the handshake and SSL will then refuse further communication with that
server.
Peer SSL Certificate Verification with NSS
==========================================
Certificate Verification with NSS
---------------------------------
If libcurl was built with NSS support, then depending on the OS distribution,
it is probably required to take some additional steps to use the system-wide CA
cert db. RedHat ships with an additional module, libnsspem.so, which enables
NSS to read the OpenSSL PEM CA bundle. This library is missing in OpenSuSE, and
without it, NSS can only work with its own internal formats. NSS also has a new
[database format](https://wiki.mozilla.org/NSS_Shared_DB).
it is probably required to take some additional steps to use the system-wide
CA cert db. RedHat ships with an additional module, libnsspem.so, which
enables NSS to read the OpenSSL PEM CA bundle. This library is missing in
OpenSuSE, and without it, NSS can only work with its own internal formats. NSS
also has a new [database format](https://wiki.mozilla.org/NSS_Shared_DB).
Starting with version 7.19.7, libcurl automatically adds the 'sql:' prefix to
the certdb directory (either the hardcoded default /etc/pki/nssdb or the
@ -112,11 +135,11 @@ format your distribution provides, examine the default certdb location:
cert9.db, key4.db, pkcs11.txt; filenames of older versions are cert8.db,
key3.db, secmod.db.
Peer SSL Certificate Verification with Schannel and Secure Transport
====================================================================
Certificate Verification with Schannel and Secure Transport
-----------------------------------------------------------
If libcurl was built with Schannel (Microsoft's TLS/SSL engine) or Secure
Transport (Apple's TLS/SSL engine) support, then libcurl will still perform
If libcurl was built with Schannel (Microsoft's native TLS engine) or Secure
Transport (Apple's native TLS engine) support, then libcurl will still perform
peer certificate verification, but instead of using a CA cert bundle, it will
use the certificates that are built into the OS. These are the same
certificates that appear in the Internet Options control panel (under Windows)