Connecting to Azure Table Storage in R

Question

I've been trying to connect to Azure Table Storage in R. Google Searching has returned nothing on people using R to connect to the Rest APIs for table storage. The documentation is here. I've tried taking an existing question about blob storage to connect( I couldn't connect to even a blob using this) and re working it for table storage queries. Below:

library(httr)
url <- "https://rpoc.table.core.windows.net:443/dummytable(PartitionKey='0dfe725b-bd43-4d9d-b58a-90654d1d8741',RowKey='00b7595d-97c3-4f29-93de-c1146bcd3d33')?$select=<comma-separated-property-names>"
sak<-"u4RzASEJ3qbxSpf5VL1nY08MwRz4VKJXsyYKV2wSFlhf/1ZYV6eGkKD3UALSblXsloCs8k4lvCS6sDE9wfVIDg=="
requestdate<- http_date(Sys.time())
signaturestring<-paste0("GET",paste(rep("\n",12),collapse=""),
                        "x-ms-date:",requestdate,"
                        x-ms-version:2015-12-11")

headerstuff<-add_headers(Authorization=paste0("SharedKey rpoc:",
                                              RCurl::base64(digest::hmac(key=RCurl::base64Decode(sak, mode="raw"),
                                                                         object=enc2utf8(signaturestring),
                                                                         algo= "sha256", raw=TRUE))),
                         `x-ms-date`=requestdate,
                         `x-ms-version`= "2015-12-11",
                         `DataServiceVersion` = "3.0;NetFx",  
                         `MaxDataServiceVersion` = "3.0;NetFx" )
content(GET(url,config = headerstuff, verbose() ))

Console output:

-> GET /dummytable(PartitionKey='0dfe725b-bd43-4d9d-b58a-90654d1d8741',RowKey='00b7595d-97c3-4f29-93de-c1146bcd3d33')?$select=<comma-separated-property-names> HTTP/1.1
-> Host: rpoc.table.core.windows.net
-> User-Agent: libcurl/7.53.1 r-curl/2.6 httr/1.2.1
-> Accept-Encoding: gzip, deflate
-> Accept: application/json, text/xml, application/xml, */*
-> Authorization: SharedKey rpoc:nQWNoPc1l/kXydUw4rNq8MBIf/arJXkI3jZv+NttqMs=
-> x-ms-date: Mon, 24 Jul 2017 18:49:52 GMT
-> x-ms-version: 2015-12-11
-> DataServiceVersion: 3.0;NetFx
-> MaxDataServiceVersion: 3.0;NetFx
-> 
<- HTTP/1.1 403 Server failed to authenticate the request. Make sure the value of Authorization header is formed correctly including the signature.
<- Content-Length: 299
<- Content-Type: application/json
<- Server: Microsoft-HTTPAPI/2.0
<- x-ms-request-id: 2c74433e-0002-00b3-5aad-04d4db000000
<- Date: Mon, 24 Jul 2017 18:49:53 GMT
<- 
$odata.error
$odata.error$code
[1] "AuthenticationFailed"

$odata.error$message
$odata.error$message$lang
[1] "en-US"

$odata.error$message$value
[1] "Server failed to authenticate the request. Make sure the value of Authorization header is formed correctly including the signature.\nRequestId:2c74433e-0002-00b3-5aad-04d4db000000\nTime:2017-07-24T18:49:54.3878127Z"

The issue looks to be the authentication headers. Any help on how I could resolve this would appreciated. I'm really surprised more people don't use ATS with R since its so versatile.

Answer 1

I based my solution in PUT blob question (Azure PUT Blob authentication fails in R), then I adapted to use GET instead of PUT and table instead of blob.

library(httr)  

account <- "account"
container <- "container"  
key <- "u4RzASEJ..9wfVIDg=="  

url <- paste0("https://", account, ".table.core.windows.net/", container)
requestdate <- format(Sys.time(),"%a, %d %b %Y %H:%M:%S %Z", tz="GMT")
content_length <- 0

signature_string <- paste0("GET", "\n",            # HTTP Verb
                           "\n",                   # Content-MD5
                           "text/plain", "\n",     # Content-Type
                           requestdate, "\n",                   # Date
                           # Here comes the Canonicalized Resource
                           "/",account, "/",container)

headerstuff <- add_headers(Authorization=paste0("SharedKey ",account,":", 
                                                RCurl::base64(digest::hmac(key = 
                                                                             RCurl::base64Decode(key, mode = "raw"),
                                                                           object = enc2utf8(signature_string),
                                                                           algo = "sha256", raw = TRUE))),
                           `x-ms-date`= requestdate,
                           `x-ms-version`= "2015-02-21",
                           `Content-Type`="text/plain")

xml_body = content(GET(url, config = headerstuff, verbose()))