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authorJunio C Hamano <gitster@pobox.com>2014-08-21 23:45:30 (GMT)
committerJunio C Hamano <gitster@pobox.com>2014-09-17 21:27:40 (GMT)
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tree254c02373450167a86f33afdeac9cd851859ca00 /Documentation/technical/protocol-capabilities.txt
parent9be89160e7382a88e56a02bcf38f4694dd6542d6 (diff)
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signed push: fortify against replay attacks
In order to prevent a valid push certificate for pushing into an repository from getting replayed in a different push operation, send a nonce string from the receive-pack process and have the signer include it in the push certificate. The receiving end uses an HMAC hash of the path to the repository it serves and the current time stamp, hashed with a secret seed (the secret seed does not have to be per-repository but can be defined in /etc/gitconfig) to generate the nonce, in order to ensure that a random third party cannot forge a nonce that looks like it originated from it. The original nonce is exported as GIT_PUSH_CERT_NONCE for the hooks to examine and match against the value on the "nonce" header in the certificate to notice a replay, but returned "nonce" header in the push certificate is examined by receive-pack and the result is exported as GIT_PUSH_CERT_NONCE_STATUS, whose value would be "OK" if the nonce recorded in the certificate matches what we expect, so that the hooks can more easily check. Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'Documentation/technical/protocol-capabilities.txt')
-rw-r--r--Documentation/technical/protocol-capabilities.txt7
1 files changed, 4 insertions, 3 deletions
diff --git a/Documentation/technical/protocol-capabilities.txt b/Documentation/technical/protocol-capabilities.txt
index a478cc4..0c92dee 100644
--- a/Documentation/technical/protocol-capabilities.txt
+++ b/Documentation/technical/protocol-capabilities.txt
@@ -251,10 +251,11 @@ If the upload-pack server advertises this capability, fetch-pack may
send "want" lines with SHA-1s that exist at the server but are not
advertised by upload-pack.
-push-cert
----------
+push-cert=<nonce>
+-----------------
The receive-pack server that advertises this capability is willing
-to accept a signed push certificate. A send-pack client MUST NOT
+to accept a signed push certificate, and asks the <nonce> to be
+included in the push certificate. A send-pack client MUST NOT
send a push-cert packet unless the receive-pack server advertises
this capability.