diff mercurial/help/config.txt @ 29334:ecc9b788fd69

sslutil: per-host config option to define certificates

Recent work has introduced the [hostsecurity] config section for
defining per-host security settings. This patch builds on top
of this foundation and implements the ability to define a per-host
path to a file containing certificates used for verifying the server
certificate. It is logically a per-host web.cacerts setting.

This patch also introduces a warning when both per-host
certificates and fingerprints are defined. These are mutually
exclusive for host verification and I think the user should be
alerted when security settings are ambiguous because, well,
security is important.

Tests validating the new behavior have been added.

I decided against putting "ca" in the option name because a
non-CA certificate can be specified and used to validate the server
certificate (commonly this will be the exact public certificate
used by the server). It's worth noting that the underlying
Python API used is load_verify_locations(cafile=X) and it calls
into OpenSSL's SSL_CTX_load_verify_locations(). Even OpenSSL's
documentation seems to omit that the file can contain a non-CA
certificate if it matches the server's certificate exactly. I
thought a CA certificate was a special kind of x509 certificate.
Perhaps I'm wrong and any x509 certificate can be used as a
CA certificate [as far as OpenSSL is concerned]. In any case,
I thought it best to drop "ca" from the name because this reflects
reality.

--- a/mercurial/help/config.txt	Fri May 27 23:18:38 2016 +0900
+++ b/mercurial/help/config.txt	Tue Jun 07 20:29:54 2016 -0700
@@ -1024,11 +1024,39 @@
     This can provide stronger security than traditional CA-based validation
     at the expense of convenience.
 
+    This option takes precedence over ``verifycertsfile``.
+
+``verifycertsfile``
+    Path to file a containing a list of PEM encoded certificates used to
+    verify the server certificate. Environment variables and ``~user``
+    constructs are expanded in the filename.
+
+    The server certificate or the certificate's certificate authority (CA)
+    must match a certificate from this file or certificate verification
+    will fail and connections to the server will be refused.
+
+    If defined, only certificates provided by this file will be used:
+    ``web.cacerts`` and any system/default certificates will not be
+    used.
+
+    This option has no effect if the per-host ``fingerprints`` option
+    is set.
+
+    The format of the file is as follows:
+
+        -----BEGIN CERTIFICATE-----
+        ... (certificate in base64 PEM encoding) ...
+        -----END CERTIFICATE-----
+        -----BEGIN CERTIFICATE-----
+        ... (certificate in base64 PEM encoding) ...
+        -----END CERTIFICATE-----
+
 For example::
 
     [hostsecurity]
     hg.example.com:fingerprints = sha256:c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2
     hg2.example.com:fingerprints = sha1:914f1aff87249c09b6859b88b1906d30756491ca, sha1:fc:e2:8d:d9:51:cd:cb:c1:4d:18:6b:b7:44:8d:49:72:57:e6:cd:33
+    foo.example.com:verifycertsfile = /etc/ssl/trusted-ca-certs.pem
 
 ``http_proxy``
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