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我想使用 R 包httr通过他们的 API 访问 EC2 服务。但我有点不确定如何开始，因为它不属于通常的“Oauth2.0”身份验证格式，在这种格式中你有通常的：密钥、秘密、令牌和签名系统。我认为 EC2 使用“签名版本 2”方法，但我不清楚它是如何工作的。

查看 EC2 提供的关于在http://docs.amazonwebservices.com/AWSEC2/latest/UserGuide/using-query-api.html提出查询请求的文档

我想我需要签名的价值....但不知道如何获得它

我尝试使用一些给定的命令httr，如下所示。我可以调整 URL 字符串中的大多数参数来代表我和我想做的事情，例如，AWSAccessKeyId等等……但只是不知道去哪里获取签名值。ImageIdendpointAction

同样在给出的一些示例中，它们似乎也没有提供秘密访问密钥......

因此，尝试过的命令如下，改变了一些代表我的值，但得到了以下结果：

require(httr)
GET("https://ec2.amazonaws.com/
?Action=RunInstances
&ImageId=ami-60a54009
&MaxCount=3
&MinCount=1
&Placement.AvailabilityZone=us-east-1b
&Monitoring.Enabled=true
&AWSAccessKeyId=0GS7553JW74RRM612K02EXAMPLE
&Version=2012-10-01
&Expires=2010-10-10T12:00:00Z
&Signature=lBP67vCvGlDMBQ1dofZxg8E8SUEXAMPLE
&SignatureVersion=2
&SignatureMethod=HmacSHA256")

我得到了回应：

Response [http://aws.amazon.com/ec2/]
  Status: 200
  Content-type: text/html; charset=UTF-8


  <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>

<head>
   <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
  <link rel="icon" type="image/ico" href="//d36cz9buwru1tt.cloudfront.net/favicon.ico">
  <link rel="shortcut icon" type="image/ico" href="//d36cz9buwru1tt.cloudfront.net/favicon.ico">
  <meta name="description" content="Amazon Elastic Compute Cloud delivers scalable, pay-as-you-go compute capacity in the cloud. " /><meta name="keywords" content="" /> ...

有没有人对 EC2 api 及其身份验证过程有任何经验，使用 R 来设置和运行带有我选择的 AMI 的 linux 实例是否足够容易（其中加载了 R 和其他相关包），然后在这些实例中运行一些 R 命令，然后返回输出？

不要认为它与我的 sessionInfo 真正相关，但以防万一：

sessionInfo()
R version 2.15.1 (2012-06-22)
Platform: x86_64-apple-darwin9.8.0/x86_64 (64-bit)

locale:
[1] en_GB.UTF-8/en_GB.UTF-8/en_GB.UTF-8/C/en_GB.UTF-8/en_GB.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] httr_0.2

loaded via a namespace (and not attached):
[1] digest_0.5.2   plyr_1.7.1     RCurl_1.95-1.1 stringr_0.6.1  tools_2.15.1

编辑：

因此，在进一步尝试遵循@hadley 建议的文档时，这就是我尝试并得到的……任何关于我哪里出错的有用提示将不胜感激……：

require(httr)

aws.key <- "xxxxxxx"
aws.secret <- "xxxxxxxxxxxx"

verb <- "GET"
zone <- "ec2.amazonaws.com"
func <- "DescribeImages"

ami.number <- "ami-xxxxxxxxx"

params <- list(paste0("ImageId.1=",ami.number),
    "Version=2012-10-01",
    "Expires=2012-11-20T12%3A00%3A00Z")


# adding in method and key parameters for creation of string to sign
orig.len.params <- length(params)
params.w.method.key <- params
params.w.method.key[[orig.len.params+1]] <- "SignatureVersion=2"
params.w.method.key[[orig.len.params+2]] <- "SignatureMethod=HmacSHA1"
params.w.method.key[[orig.len.params+3]] <- paste0("AWSAccessKeyId=",aws.key)

# String to sign (s2s)
s2s <- paste(c(paste0(verb,"\n",zone,"\n","/\n","AWSAccessKeyId=",aws.key),paste0("Action=",func),paste(sort(unlist(params.w.method.key)),collapse="&")),collapse="&")

# Signature(sig)
sig <- hmac_sha1(aws.secret, s2s)

# adding in signature, method and key parameters for signed request url generation
params.w.sig.method.key <- params
params.w.sig.method.key[[orig.len.params+1]] <- paste0("Signature=",sig)
params.w.sig.method.key[[orig.len.params+2]] <- "SignatureVersion=2"
params.w.sig.method.key[[orig.len.params+3]] <- "SignatureMethod=HmacSHA1"
params.w.sig.method.key[[orig.len.params+4]] <- paste0("AWSAccessKeyId=",aws.key)

# Signed request (sr)
sr <- paste(c(paste0("https://",zone,paste0("?Action=",func)),paste(unlist(params.w.sig.method.key),collapse="&")),collapse="&")

# GET signed request
GET(sr)

我得到了回应：

 Response [https://ec2.amazonaws.com?Action=DescribeImages&ImageId.1=[ami.number.from.before]&Version=2012-10-01&Expires=2012-11-20T12%3A00%3A00Z&Signature=[sig.value.from.before]&SignatureVersion=2&SignatureMethod=HmacSHA1&AWSAccessKeyId=[aws.key.from.before]/]
  Status: 401
  Content-type: 
 <?xml version="1.0" encoding="UTF-8"?>
 <Response><Errors><Error><Code>AuthFailure</Code><Message>AWS was not able to validate the provided access credentials</Message></Error></Errors><RequestID>5e10fb0b-f304-4677-9c64-98b4537c659a</RequestID></Response>
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1 回答 1

6

这是我逐步将算法转换为 R 代码的尝试。根据我的经验，您确实希望单独执行每个步骤，以便您可以在每个阶段检查结果是否正确。

require("httr")
require("RCurl")
require("stringr")

# 0: get key and secret from envvars, and set up request parameters

aws.key <- Sys.getenv("AWS_KEY")
aws.secret <- Sys.getenv("AWS_SECRET_KEY")

verb <- "GET"
zone <- "ec2.amazonaws.com"

ami.number <- "ami-xxxxxxxxx"

params <- list(
  Action = "DescribeImages",
  ImageId.1 = ami.number,
  Version = "2012-10-01",
  Expires = "2012-11-20T12:00:00Z",
  SignatureVersion = 2,
  SignatureMethod = "HmacSHA1",
  AWSAccessKeyId = aws.key)

# 1a: Sort the UTF-8 query string components by parameter name
params <- params[order(names(params))]

# 1b: URL encode the parameter name and values
params_e <- lapply(params, curlEscape)
names(params_e) <- curlEscape(names(params_e))
params_str <- str_c(names(params_e), "=", unlist(params_e), collapse = "&")
params_str <- gsub("%2E",".",gsub("%2D","-",params_str))

# 2: Create the string to sign
string_to_sign <- str_c(
  toupper(verb), "\n",
  tolower(zone), "\n",
  "/", "\n",
  params_str
)

# 3: Calculate an RFC 2104-compliant HMAC
# 4: Convert the resulting value to base64.
hmac <- hmac_sha1(aws.secret, string_to_sign)

params$Signature <- hmac

GET(paste0("https://",zone),query=params)
于 2012-11-20T12:37:56.780 回答