Question

I would like to use R to send requests to the Amazon Product API service.

Is there a way to authenticate and query the Amazon Product API with R without getting the following error:

“The request signature we calculated does not match the signature you provided. Check your AWS Secret Access Key and signing method. Consult the service documentation for details.”

Answer 1

Try this

This should perform a search using the Product Advertising API, which I think you mean.

You need to supply the AWSAccessKeyId and AWSsecretkey,

which can be acquired on: http://docs.amazonwebservices.com/AWSECommerceService/2011-08-01/GSG/

search.amazon <- function(Keywords, SearchIndex = 'All', AWSAccessKeyId, AWSsecretkey, AssociateTag, ResponseGroup = 'Small', Operation = 'ItemSearch'){
     library(digest)
     library(RCurl)

 base.html.string <- "http://ecs.amazonaws.com/onca/xml?"
 SearchIndex <- match.arg(SearchIndex, c('All',
                                             'Apparel',
                                             'Appliances',
                                             'ArtsAndCrafts',
                                             'Automotive',
                                             'Baby',
                                             'Beauty',
                                             'Blended',
                                             'Books',
                                             'Classical',
                                             'DigitalMusic',
                                             'DVD',
                                             'Electronics',
                                             'ForeignBooks',
                                             'Garden',
                                             'GourmetFood',
                                             'Grocery',
                                             'HealthPersonalCare',
                                             'Hobbies',
                                             'HomeGarden',
                                             'HomeImprovement',
                                             'Industrial',
                                             'Jewelry',
                                             'KindleStore',
                                             'Kitchen',
                                             'Lighting',
                                             'Magazines',
                                             'Marketplace',
                                             'Miscellaneous',
                                             'MobileApps',
                                             'MP3Downloads',
                                             'Music',
                                             'MusicalInstruments',
                                             'MusicTracks',
                                             'OfficeProducts',
                                             'OutdoorLiving',
                                             'Outlet',
                                             'PCHardware',
                                             'PetSupplies',
                                             'Photo',
                                             'Shoes',
                                             'Software',
                                             'SoftwareVideoGames',
                                             'SportingGoods',
                                             'Tools',
                                             'Toys',
                                             'UnboxVideo',
                                             'VHS',
                                             'Video',
                                             'VideoGames',
                                             'Watches',
                                             'Wireless',
                                             'WirelessAccessories'))
 Operation <- match.arg(Operation, c('ItemSearch',
                                             'ItemLookup',
                                             'BrowseNodeLookup',
                                             'CartAdd',
                                             'CartClear',
                                             'CartCreate',
                                             'CartGet',
                                             'CartModify',
                                             'SimilarityLookup'))
 ResponseGroup <- match.arg(ResponseGroup, c('Accessories',
                                             'AlternateVersions',
                                             'BrowseNodeInfo',
                                             'BrowseNodes',
                                             'Cart',
                                             'CartNewReleases',
                                             'CartTopSellers',
                                             'CartSimilarities',
                                             'Collections',
                                             'EditorialReview',
                                             'Images',
                                             'ItemAttributes',
                                             'ItemIds',
                                             'Large',
                                             'Medium',
                                             'MostGifted',
                                             'MostWishedFor',
                                             'NewReleases',
                                             'OfferFull',
                                             'OfferListings',
                                             'Offers',
                                             'OfferSummary',
                                             'PromotionSummary',
                                             'RelatedItems',
                                             'Request',
                                             'Reviews',
                                             'SalesRank',
                                             'SearchBins',
                                             'Similarities',
                                             'Small',
                                             'TopSellers',
                                             'Tracks',
                                             'Variations',
                                             'VariationImages',
                                             'VariationMatrix',
                                             'VariationOffers',
                                             'VariationSummary'),
                            several.ok = TRUE)
 version.request = '2011-08-01'
 Service = 'AWSECommerceService'
 if(!is.character(AWSsecretkey)){
  message('The AWSsecretkey should be entered as a character vect, ie be qouted')
 }

 pb.txt <- Sys.time()

 pb.date <- as.POSIXct(pb.txt, tz = Sys.timezone)

 Timestamp = strtrim(format(pb.date, tz = "GMT", usetz = TRUE, "%Y-%m-%dT%H:%M:%S.000Z"), 24)

 str = paste('GET\necs.amazonaws.com\n/onca/xml\n',
        'AWSAccessKeyId=', curlEscape(AWSAccessKeyId),
             '&AssociateTag=', AssociateTag,
             '&Keywords=', curlEscape(Keywords),
             '&Operation=', curlEscape(Operation),
             '&ResponseGroup=', curlEscape(ResponseGroup),
             '&SearchIndex=', curlEscape(SearchIndex),
             '&Service=AWSECommerceService',
             '&Timestamp=', gsub('%2E','.',gsub('%2D', '-', curlEscape(Timestamp))),
             '&Version=', version.request,
             sep = '')

 ## signature test
 Signature = curlEscape(base64(hmac( enc2utf8((AWSsecretkey)), enc2utf8(str1), algo = 'sha256', serialize = FALSE,  raw = TRUE)))

 AmazonURL <- paste(base.html.string,
             'AWSAccessKeyId=', AWSAccessKeyId,
             '&AssociateTag=', AssociateTag,
             '&Keywords=', Keywords,
             '&Operation=',Operation,
             '&ResponseGroup=',ResponseGroup,
             '&SearchIndex=', SearchIndex,
             '&Service=AWSECommerceService',
             '&Timestamp=', Timestamp,
             '&Version=', version.request,
             '&Signature=', Signature
             sep = '')
 AmazonResult <- getURL(AmazonURL)
 return(AmazonResult)
}

The URL which we get from running this code wont give a signature address. To get a signature address use the following web address and paste the URL over there and click on Display Signed URL.

http://associates-amazon.s3.amazonaws.com/signed-requests/helper/index.html