API call using IAM authentication in R

iam_api_request.R

library(aws.signature)
library(httr)
library(jsonlite)
library(purrr)

Sys.setenv(
  AWS_ACCESS_KEY_ID = "",
  AWS_SECRET_ACCESS_KEY = "",
  AWS_REGION = "us-east-1"
)

aws.executeapi <- function(url, verb, query = NULL, body = NULL, headers = NULL) {
    parsed_url <- parse_url(url)
    datetime <- format(Sys.time(), "%Y%m%dT%H%M%SZ", tz = "UTC")
    request_body <- toJSON(body, auto_unbox = TRUE)
    canonical_headers <- list(
        Host = parsed_url$hostname
    )
    auth <- aws.signature::signature_v4_auth(
        datetime = datetime,
        service = "execute-api",
        action = paste0('/', parsed_url$path),
        verb = verb,
        canonical_headers = canonical_headers,
        query_args = query,
        request_body = if (verb %in% c('GET', 'HEAD', 'OPTIONS')) '' else request_body,
        algorithm = "AWS4-HMAC-SHA256",
    )
    auth_headers <- list(
        Authorization = paste0(
            "AWS4-HMAC-SHA256 Credential=", auth$Credential,
            ", SignedHeaders=", auth$SignedHeaders,
            ", Signature=", auth$Signature
        ),
        Date = datetime
    )
    httr::VERB(
        verb = verb,
        url = url,
        body = request_body,
        query = query,
        do.call(add_headers, c(auth_headers, headers))
    )
}

aws.executeapi.delete <- partial(aws.executeapi, verb = 'DELETE')
aws.executeapi.get <- partial(aws.executeapi, verb = 'GET')
aws.executeapi.head <- partial(aws.executeapi, verb = 'HEAD')
aws.executeapi.options <- partial(aws.executeapi, verb = 'OPTIONS')
aws.executeapi.patch <- partial(aws.executeapi, verb = 'PATCH')
aws.executeapi.post <- partial(aws.executeapi, verb = 'POST')
aws.executeapi.put <- partial(aws.executeapi, verb = 'PUT')


# Then call the API Gateway API like:
response = aws.executeapi.get(
    url = 'https://www.domain.tld/endpoint',
    query = list(
        param1 = 'foo',
        param2 = 'bar',
        param3 = 'baz'
    )
)
data <- content(response)

I needed to call an API Gateway API in R, using IAM authentication. I couldn't find anything on the internet that showed how to do this, so I figured I'd put what worked for me into a public gist.