# calculates the signature for the request as described in the docs:
# https://dev.twitter.com/docs/auth/creating-signature
#' Generates OAuth1 signature needed to authorize API request
#'
#' @param method f.x. "HMAC-SHA1"
#' @param url f.x. "https://api.twitter.com/1.1/friends/ids.json"
#' @param api f.x. c(cursor=-1, screen_name="hrw", count=10)
#' @param params named vector needed for generating oauth1 signature
#' @return signature string
oauth1_signature <- function(method, url, api, params, test=FALSE) {
library(RCurl);
library(digest);
library(base64enc);
# http://oauth.net/core/1.0/#encoding_parameters
if(curlEscape(".") == ".") {
# that's how we want it!
} else if(curlEscape(".") == "%2E") {
curlEscape <- function(str) {
esc <- RCurl::curlEscape(str)
esc <- gsub("%2E",".",esc)
esc <- gsub("%2D","-",esc)
esc <- gsub("%5F","_",esc)
esc <- gsub("%7E","~",esc)
}
} else {
stop("curlEscape('.') is supposed to be either '.' or '%2E'")
}
secrets <- params[c("consumer_secret","oauth_token_secret")];
# exclude *_secret
params <- params[! names(params) %in% c("consumer_secret","oauth_token_secret")]
params <- c(api, params);
params_sorted <- params[sort(names(params))];
params_escaped <- sapply(params_sorted, curlEscape);
pstr <- paste(paste(names(params_escaped),"=",params_escaped,sep=""),collapse="&");
# it is important to use curlEscape instead of URLencode because the latter encodes
# using lower case letters but we need upper case letters. Otherwise the resulting
# signature will be different from what Twitter/OAuth expects/calculates.
final <- sprintf("%s&%s&%s",toupper(method), curlEscape(url), curlEscape(pstr));
sig <- sprintf("%s&%s",curlEscape(secrets["consumer_secret"]),curlEscape(secrets["oauth_token_secret"]));
hmac <- hmac(sig,final,algo="sha1",raw=TRUE)
signature <- base64encode(hmac);
signature_escaped <- curlEscape(signature);
if(test) {
return(
list(
params_escaped = params_escaped,
pstr = pstr,
final = final,
sig = sig,
hmac = hmac,
signature = signature,
signature_escaped = signature_escaped
)
)
}
return(signature_escaped);
}
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