generating aws signature

[joejoe]

Hi,



I am following this php code and am trying to reproduce it with nL.



http://webtutsdepot.com/2009/10/13/amazon-signed-request-php/">http://webtutsdepot.com/2009/10/13/amaz ... quest-php/">http://webtutsdepot.com/2009/10/13/amazon-signed-request-php/



I cannot figure out if this is a two part transaction or just a single query.



Would anyone know if I need an initial aws server response from the get-url command in order to complete the rest of building the url that will make the request with the aws signature?



Like do I need to say 'knock knock', and use part of their 'whos there' response in order to generate my signature?



Thanks for help!



joejoe

[rrq]

I'm no expert on AWS API, but from reading the PHP, it looks like it's a single handshake, but it relies on a prior agreement between you and Amazon about the thingies called "$publicKey" and "$privateKey". Basically it seems to be a matter of scrambling the original request with the private key, then issue the compound request of that scramble together with the public key, for getting the request to be serviced.

[joejoe]

Ok great, that is what I had hoped, thank you very much Ralph!

[joejoe]

And would I be correct to use this module that Lutz has already created?



http://www.newlisp.org/code/modules/crypto.lsp.html#crypto_hmac">http://www.newlisp.org/code/modules/cry ... rypto_hmac">http://www.newlisp.org/code/modules/crypto.lsp.html#crypto_hmac



or just use the



http://www.newlisp.org/code/modules/crypto.lsp.html#crypto_sha256">http://www.newlisp.org/code/modules/cry ... pto_sha256">http://www.newlisp.org/code/modules/crypto.lsp.html#crypto_sha256



Thanks again!

[rrq]

I'm pretty sure it'd be the hash_hmac step by using those two, yes, as in:

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(crypto:hmac crypto:sha256 message key)
Then it needs base64-enc and url-encode and replace "%7E" with "~"...

[joejoe]

Got it, thanks Ralph! Much appreciated!! :D

[joejoe]

Hi and thanks!



I think I got to the signature:

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("131 37 166 173 32 246 42 23 198 156 244 102 148 91 171 80 252 115 124 141 246 64
 19 94 85 112 145 181 2 189 98 73")
When I use an online hex decoder I get this: qf3"FB#V$A‰q€%!AA$fA™HQQ!‰˜s



Looks like a signature!



How would I decode the hex in nL to produce this signature?



I have tried different things with char and format but am still swinging at it.



Thank you very much for the help! :D



If I helps anyone, here is how I have gotten this far:

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#!/usr/bin/newlisp

(module "crypto.lsp")

(set 'output1 (crypto:hmac crypto:sha256 "GET
ecs.amazonaws.com
/onca/xml
AWSAccessKeyId= AAAAAAAAAAAAAAAAAAA&AssociateTag=PutYourAssociateTagHere&Keywords=newlisp&Operation=ItemSearch&SearchIndex=Books&Service=AWSECommerceService&Timestamp=2016-11-05T10%3A25%3A14.000Z&Version=2011-08-01" "BBBBBBBBBBBBBBBBBBBBBBBBBBBBB"))

(set 'output2 (unpack (dup "b" (length output1)) output1))

(set 'output3 (crypto:hmac crypto:sha256 "GET
ecs.amazonaws.com
/onca/xml
AWSAccessKeyId= AAAAAAAAAAAAAAAAAAA&AssociateTag=PutYourAssociateTagHere&Keywords= newlisp&Operation=ItemSearch&SearchIndex=Books&Service=AWSECommerceService&Timestamp=2016-11-05T10%3A25%3A14.000Z&Version=2011-08-01" (string output2)))

(set 'signature-hex (unpack (dup "b" (length output3)) output3))

(println signature-hex)

(exit)

[rrq]

Wouldn't the "hexdigest" merely be something like this?

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(join (map (curry format "%02x") signature-hex))

[joejoe]

Hi and thank you for help,



Here is what I am running:

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#!/usr/bin/newlisp

(module "crypto.lsp")

(set 'pubkey "aa")
(set 'privkey "bb")

(set 'timestamp (string (date (date-value) 320 "%Y") "-" (date (date-value) 320 "%m") "-" (date (date-value) 320 "%d") "T" (date (date-value) 320 "%H") "%3A" (date (date-value) 0 "%M") "%3A" (date (date-value) 320 "%S") "Z"))

(println timestamp)

(set 'output1 (crypto:hmac crypto:sha256 "GET
ecs.amazonaws.com
/onca/xml
AWSAccessKeyId=" (silent pubkey) "&Keywords=newlisp&Operation=ItemSearch&SearchIndex=Books&Service=AWSECommerceService&Timestamp=" (silent timestamp) "&Version=2011-08-01" (silent privkey)))

(set 'output2 (unpack (dup "b" (length output1)) output1))

(set 'output3 (crypto:hmac crypto:sha256 "GET
ecs.amazonaws.com
/onca/xml
AWSAccessKeyId=" (silent pubkey) "&Keywords= newlisp&Operation=ItemSearch&SearchIndex=Books&Service=AWSECommerceService&Timestamp=" (silent timestamp) "&Version=2011-08-01" (string output2)))

(set 'signature-hex (unpack (dup "b" (length output3)) output3))

(println (join (map (curry format "%02x") signature-hex)))

(exit)

I get a new timestamp but the signature doesn't change when I re-execute it.



Thanks for any tip!

[rrq]

Maybe you meant to have (string ...) embeddings for the third argument to crypto:hmac calls?

[joejoe]

Hi and thanks,



I want to back up to make sure I have the HMAC SHA256 signature calculating correctly.



I am trying this:

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(set 'output1 (crypto:hmac crypto:sha256 (string "GET
webservices.amazon.co.uk
/onca/xml
AWSAccessKeyId=AKIAIOSFODNN7EXAMPLE&Actor=Johnny%20Depp&AssociateTag=mytag-20&Operation=ItemSearch&Operation=ItemSearch&ResponseGroup=ItemAttributes%2COffers%2CImages%2CReviews%2CVariations&SearchIndex=DVD&Service=AWSECommerceService&Sort=salesrank&Timestamp=2016-12-15T01%3A42%3A01.000Z&Version=2013-08-01") "1234567890"))

(set 'signature-hex (unpack (dup "b" (length output1)) output1))
(println (join (map (curry format "%02x") signature-hex)))

I get this:

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786c6ac1346d09aeb7fc4d158e70201141ee483d9e338958bf8492740969a997

On the AWS tester tool[1], it says the HMAC signature should be this:

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eGxqwTRtCa63%2FE0VjnAgEUHuSD2eM4lYv4SSdAlpqZc%3D

With an online HMAC generator tester tool[2] set to SHA256, it says I should get this signature:

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9f4defac2a33e7ce3e585c0515bdba65d272fd8852a3b40e5549f8ad9104c4ac

Anyone know which is correct? Thanks! :D



[1] https://associates-amazon.s3.amazonaws.com/signed-requests/helper/index.html">https://associates-amazon.s3.amazonaws. ... index.html">https://associates-amazon.s3.amazonaws.com/signed-requests/helper/index.html

[2] https://www.freeformatter.com/hmac-generator.html#ad-output">https://www.freeformatter.com/hmac-gene ... #ad-output">https://www.freeformatter.com/hmac-generator.html#ad-output

[joejoe]

I think the issue may be with line breaks.



When I do this:

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(set 'output1 (crypto:hmac crypto:sha256 "onetwo" "1234567890"))

(set 'signature-hex (unpack (dup "b" (length output1)) output1))

(println (join (map (curry format "%02x") signature-hex)))

I get this:

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47d07edd67e5cca3bb98c5cf4cca73459dd8a89afaa555ac7b4ce475c6ae6c27

The online HMAC generator tester confirms the same:

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47d07edd67e5cca3bb98c5cf4cca73459dd8a89afaa555ac7b4ce475c6ae6c27

However, when I try to put a line break in the string with:

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(set 'output1 (crypto:hmac crypto:sha256 "one
two" "1234567890"))

I get this:

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b599058300d5ed4e5f160c30745c74f3e6c5cfc6683cc9d36b9a279f8955077e

However, the online HMAC tool shows this:

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e16a940481b8b9dd18211f5fb637bd5d926ac9d6e446e6489f030d66ea17fb91

And in the online HMAC tool I am inputting in the string so it has the line break:

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one
two

Getting close!!



Would there be any clues out there?



Thank you!!!

[rrq]

An online tool, using a form, would typically digest line ends as rj, whereas a *nix system would prefer using j only, and a mac system would rather favour r for line endings. The AWS tool you pointed at some posts earlier appears to compute the signature using j line endings. And it also scrambles the hmac output by both base64 encoding then url-encoding.

[joejoe]

Ok gotcha thanks.



I got the signatures generating correctly with your message help, Ralph.

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(string (chop (base64-enc (crypto:hmac ....)) "%3D")

This did it and a few tweaks to finalize the url formatting got successful api calls.



Thanks all for the help!