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|
package oauth
import (
"crypto/hmac"
"crypto/rand"
"crypto/sha1"
"encoding/base64"
"fmt"
"sort"
"strconv"
"strings"
"time"
)
const (
oauthRealm = "realm"
oauthConsumerKey = "oauth_consumer_key"
oauthToken = "oauth_token"
oauthNonce = "oauth_nonce"
oauthTimestamp = "oauth_timestamp"
oauthSignatureMethod = "oauth_signature_method"
oauthVersion = "oauth_version"
oauthSignature = "oauth_signature"
)
const (
SignatureMethodHMACSHA1 = "HMAC-SHA1"
)
const Version = "1.0"
const separator = "&"
type authHeader struct {
method string
baseURL string
queryParams map[string]string
tokens Tokens
nonce string
timestamp string
signatureMethod string
version string
}
func newAuthHeader(
method string,
baseURL string,
queryParams map[string]string,
tokens Tokens,
) authHeader {
return authHeader{
method: method,
baseURL: baseURL,
queryParams: queryParams,
tokens: tokens,
nonce: rand.Text(),
timestamp: strconv.Itoa(int(time.Now().Unix())),
signatureMethod: SignatureMethodHMACSHA1,
version: Version,
}
}
func (ah *authHeader) String() string {
signature, _ := ah.buildSignature() // TODO: handle ignored err
subheaders := make(map[string]string, 8)
subheaders[oauthRealm] = ah.baseURL
subheaders[oauthVersion] = ah.version
subheaders[oauthTimestamp] = ah.timestamp
subheaders[oauthNonce] = ah.nonce
subheaders[oauthConsumerKey] = ah.tokens.Consumer.Token
subheaders[oauthToken] = ah.tokens.Access.Token
subheaders[oauthSignatureMethod] = ah.signatureMethod
subheaders[oauthSignature] = percentEncode(signature)
parts := make([]string, 0, len(subheaders))
for k, v := range subheaders {
parts = append(parts, fmt.Sprintf(`%s="%s"`, k, v))
}
header := "OAuth " + strings.Join(parts, ", ")
return string(header)
}
func (ah *authHeader) buildSignature() (string, error) {
baseString := ah.buildBaseString()
baseString += ah.buildParameterString()
signingKey := fmt.Appendf(
nil,
"%s&%s",
percentEncode(ah.tokens.Consumer.Secret),
percentEncode(ah.tokens.Access.Secret),
)
hasher := hmac.New(sha1.New, signingKey)
if _, err := hasher.Write([]byte(baseString)); err != nil {
return "", err
}
encoded := base64.StdEncoding.EncodeToString(hasher.Sum(nil))
return encoded, nil
}
func (ah *authHeader) buildBaseString() string {
baseString := strings.Join(
[]string{
strings.ToUpper(ah.method),
percentEncode(ah.baseURL),
},
separator,
)
baseString += separator
return baseString
}
func (ah *authHeader) buildParameterString() string {
params := ah.queryParams
if params == nil {
params = make(map[string]string, 6)
}
params[oauthConsumerKey] = string(ah.tokens.Consumer.Token)
params[oauthNonce] = string(ah.nonce)
params[oauthSignatureMethod] = string(ah.signatureMethod)
params[oauthTimestamp] = string(ah.timestamp)
params[oauthToken] = string(ah.tokens.Access.Token)
params[oauthVersion] = string(ah.version)
keys := make([]string, 0, len(params))
for k := range params {
keys = append(keys, k)
}
sort.Strings(keys)
parts := make([]string, 0, len(keys))
for _, k := range keys {
parts = append(
parts,
fmt.Sprintf(
`%s=%s`,
k,
params[k],
),
)
}
parameterString := strings.Join(parts, separator)
parameterString = percentEncode(parameterString)
return parameterString
}
func percentEncode(s string) string {
var b strings.Builder
for _, c := range s {
if isUnreservedCharacter(c) {
fmt.Fprintf(&b, "%%%02X", c)
continue
}
b.WriteRune(c)
}
return b.String()
}
// isUnreservedCharacter returns true if the byte belongs in the range of the
// reserved character list as in https://en.wikipedia.org/wiki/Percent-encoding
func isUnreservedCharacter(c rune) bool {
if (c >= 'A' && c <= 'Z') ||
(c >= 'a' && c <= 'z') ||
(c >= '0' && c <= '9') ||
c == '-' ||
c == '.' ||
c == '_' ||
c == '~' {
return false
}
return true
}
|
