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Implement EncryptedKey RetrievalMethod support #12

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Implement EncryptedKey RetrievalMethod support #12

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37 changes: 33 additions & 4 deletions src/esaml_sp.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -316,19 +316,48 @@ decrypt_assertion(Xml, #esaml_sp{key = PrivateKey}) ->
[EncryptedData] = xmerl_xpath:string("./xenc:EncryptedData", Xml, [{namespace, XencNs}]),
[#xmlText{value = CipherValue64}] = xmerl_xpath:string("xenc:CipherData/xenc:CipherValue/text()", EncryptedData, [{namespace, XencNs}]),
CipherValue = base64:decode(CipherValue64),
SymmetricKey = decrypt_key_info(EncryptedData, PrivateKey),
SymmetricKey = decrypt_key_info(EncryptedData, Xml, PrivateKey),
[#xmlAttribute{value = Algorithm}] = xmerl_xpath:string("./xenc:EncryptionMethod/@Algorithm", EncryptedData, [{namespace, XencNs}]),
AssertionXml = block_decrypt(Algorithm, SymmetricKey, CipherValue),
{Assertion, _} = xmerl_scan:string(AssertionXml, [{namespace_conformant, true}]),
Assertion.


decrypt_key_info(EncryptedData, Key) ->
decrypt_key_info(EncryptedData, EncryptedAssertion, Key) ->
DsNs = [{"ds", 'http://www.w3.org/2000/09/xmldsig#'}],
XencNs = [{"xenc", 'http://www.w3.org/2001/04/xmlenc#'}],
[KeyInfo] = xmerl_xpath:string("./ds:KeyInfo", EncryptedData, [{namespace, DsNs}]),
[#xmlAttribute{value = Algorithm}] = xmerl_xpath:string("./xenc:EncryptedKey/xenc:EncryptionMethod/@Algorithm", KeyInfo, [{namespace, XencNs}]),
[#xmlText{value = CipherValue64}] = xmerl_xpath:string("./xenc:EncryptedKey/xenc:CipherData/xenc:CipherValue/text()", KeyInfo, [{namespace, XencNs}]),

%% Try standard nested EncryptedKey first (backward compatibility)
case xmerl_xpath:string("./xenc:EncryptedKey", KeyInfo, [{namespace, XencNs}]) of
[EncryptedKey | _] ->
%% Standard pattern: EncryptedKey nested in KeyInfo
extract_symmetric_key(EncryptedKey, Key, XencNs);
[] ->
%% Try RetrievalMethod pattern (Okta)
case xmerl_xpath:string("./ds:RetrievalMethod/@URI", KeyInfo, [{namespace, DsNs}]) of
[#xmlAttribute{value = URI}] ->
%% Extract ID from URI (remove leading # if present)
KeyId = case URI of
[$# | Rest] -> Rest;
_ -> URI
end,
%% Search for sibling EncryptedKey by ID within EncryptedAssertion
XPath = lists:flatten(io_lib:format("./xenc:EncryptedKey[@Id='~s']", [KeyId])),
case xmerl_xpath:string(XPath, EncryptedAssertion, [{namespace, XencNs}]) of
[EncryptedKey | _] ->
extract_symmetric_key(EncryptedKey, Key, XencNs);
[] ->
error({encrypted_key_not_found, KeyId})
end;
[] ->
error(no_encrypted_key_found)
end
end.

extract_symmetric_key(EncryptedKey, Key, XencNs) ->
[#xmlAttribute{value = Algorithm}] = xmerl_xpath:string("./xenc:EncryptionMethod/@Algorithm", EncryptedKey, [{namespace, XencNs}]),
[#xmlText{value = CipherValue64}] = xmerl_xpath:string("./xenc:CipherData/xenc:CipherValue/text()", EncryptedKey, [{namespace, XencNs}]),
CipherValue = base64:decode(CipherValue64),
decrypt(CipherValue, Algorithm, Key).

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