362 lines
14 KiB
Go
362 lines
14 KiB
Go
// Implements HTTP request and response signing and verification. Supports the
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// major MAC and asymmetric key signature algorithms. It has several safety
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// restrictions: One, none of the widely known non-cryptographically safe
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// algorithms are permitted; Two, the RSA SHA256 algorithms must be available in
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// the binary (and it should, barring export restrictions); Finally, the library
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// assumes either the 'Authorizationn' or 'Signature' headers are to be set (but
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// not both).
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package httpsig
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import (
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"crypto"
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"fmt"
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"net/http"
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"strings"
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"time"
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"golang.org/x/crypto/ssh"
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)
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// Algorithm specifies a cryptography secure algorithm for signing HTTP requests
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// and responses.
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type Algorithm string
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const (
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// MAC-based algoirthms.
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HMAC_SHA224 Algorithm = hmacPrefix + "-" + sha224String
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HMAC_SHA256 Algorithm = hmacPrefix + "-" + sha256String
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HMAC_SHA384 Algorithm = hmacPrefix + "-" + sha384String
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HMAC_SHA512 Algorithm = hmacPrefix + "-" + sha512String
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HMAC_RIPEMD160 Algorithm = hmacPrefix + "-" + ripemd160String
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HMAC_SHA3_224 Algorithm = hmacPrefix + "-" + sha3_224String
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HMAC_SHA3_256 Algorithm = hmacPrefix + "-" + sha3_256String
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HMAC_SHA3_384 Algorithm = hmacPrefix + "-" + sha3_384String
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HMAC_SHA3_512 Algorithm = hmacPrefix + "-" + sha3_512String
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HMAC_SHA512_224 Algorithm = hmacPrefix + "-" + sha512_224String
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HMAC_SHA512_256 Algorithm = hmacPrefix + "-" + sha512_256String
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HMAC_BLAKE2S_256 Algorithm = hmacPrefix + "-" + blake2s_256String
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HMAC_BLAKE2B_256 Algorithm = hmacPrefix + "-" + blake2b_256String
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HMAC_BLAKE2B_384 Algorithm = hmacPrefix + "-" + blake2b_384String
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HMAC_BLAKE2B_512 Algorithm = hmacPrefix + "-" + blake2b_512String
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BLAKE2S_256 Algorithm = blake2s_256String
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BLAKE2B_256 Algorithm = blake2b_256String
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BLAKE2B_384 Algorithm = blake2b_384String
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BLAKE2B_512 Algorithm = blake2b_512String
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// RSA-based algorithms.
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RSA_SHA1 Algorithm = rsaPrefix + "-" + sha1String
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RSA_SHA224 Algorithm = rsaPrefix + "-" + sha224String
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// RSA_SHA256 is the default algorithm.
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RSA_SHA256 Algorithm = rsaPrefix + "-" + sha256String
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RSA_SHA384 Algorithm = rsaPrefix + "-" + sha384String
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RSA_SHA512 Algorithm = rsaPrefix + "-" + sha512String
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RSA_RIPEMD160 Algorithm = rsaPrefix + "-" + ripemd160String
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// ECDSA algorithms
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ECDSA_SHA224 Algorithm = ecdsaPrefix + "-" + sha224String
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ECDSA_SHA256 Algorithm = ecdsaPrefix + "-" + sha256String
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ECDSA_SHA384 Algorithm = ecdsaPrefix + "-" + sha384String
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ECDSA_SHA512 Algorithm = ecdsaPrefix + "-" + sha512String
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ECDSA_RIPEMD160 Algorithm = ecdsaPrefix + "-" + ripemd160String
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// ED25519 algorithms
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// can only be SHA512
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ED25519 Algorithm = ed25519Prefix
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// Just because you can glue things together, doesn't mean they will
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// work. The following options are not supported.
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rsa_SHA3_224 Algorithm = rsaPrefix + "-" + sha3_224String
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rsa_SHA3_256 Algorithm = rsaPrefix + "-" + sha3_256String
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rsa_SHA3_384 Algorithm = rsaPrefix + "-" + sha3_384String
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rsa_SHA3_512 Algorithm = rsaPrefix + "-" + sha3_512String
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rsa_SHA512_224 Algorithm = rsaPrefix + "-" + sha512_224String
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rsa_SHA512_256 Algorithm = rsaPrefix + "-" + sha512_256String
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rsa_BLAKE2S_256 Algorithm = rsaPrefix + "-" + blake2s_256String
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rsa_BLAKE2B_256 Algorithm = rsaPrefix + "-" + blake2b_256String
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rsa_BLAKE2B_384 Algorithm = rsaPrefix + "-" + blake2b_384String
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rsa_BLAKE2B_512 Algorithm = rsaPrefix + "-" + blake2b_512String
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)
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// HTTP Signatures can be applied to different HTTP headers, depending on the
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// expected application behavior.
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type SignatureScheme string
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const (
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// Signature will place the HTTP Signature into the 'Signature' HTTP
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// header.
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Signature SignatureScheme = "Signature"
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// Authorization will place the HTTP Signature into the 'Authorization'
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// HTTP header.
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Authorization SignatureScheme = "Authorization"
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)
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const (
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// The HTTP Signatures specification uses the "Signature" auth-scheme
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// for the Authorization header. This is coincidentally named, but not
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// semantically the same, as the "Signature" HTTP header value.
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signatureAuthScheme = "Signature"
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)
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// There are subtle differences to the values in the header. The Authorization
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// header has an 'auth-scheme' value that must be prefixed to the rest of the
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// key and values.
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func (s SignatureScheme) authScheme() string {
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switch s {
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case Authorization:
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return signatureAuthScheme
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default:
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return ""
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}
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}
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// Signers will sign HTTP requests or responses based on the algorithms and
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// headers selected at creation time.
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//
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// Signers are not safe to use between multiple goroutines.
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//
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// Note that signatures do set the deprecated 'algorithm' parameter for
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// backwards compatibility.
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type Signer interface {
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// SignRequest signs the request using a private key. The public key id
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// is used by the HTTP server to identify which key to use to verify the
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// signature.
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//
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// If the Signer was created using a MAC based algorithm, then the key
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// is expected to be of type []byte. If the Signer was created using an
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// RSA based algorithm, then the private key is expected to be of type
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// *rsa.PrivateKey.
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//
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// A Digest (RFC 3230) will be added to the request. The body provided
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// must match the body used in the request, and is allowed to be nil.
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// The Digest ensures the request body is not tampered with in flight,
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// and if the signer is created to also sign the "Digest" header, the
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// HTTP Signature will then ensure both the Digest and body are not both
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// modified to maliciously represent different content.
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SignRequest(pKey crypto.PrivateKey, pubKeyId string, r *http.Request, body []byte) error
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// SignResponse signs the response using a private key. The public key
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// id is used by the HTTP client to identify which key to use to verify
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// the signature.
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//
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// If the Signer was created using a MAC based algorithm, then the key
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// is expected to be of type []byte. If the Signer was created using an
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// RSA based algorithm, then the private key is expected to be of type
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// *rsa.PrivateKey.
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//
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// A Digest (RFC 3230) will be added to the response. The body provided
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// must match the body written in the response, and is allowed to be
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// nil. The Digest ensures the response body is not tampered with in
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// flight, and if the signer is created to also sign the "Digest"
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// header, the HTTP Signature will then ensure both the Digest and body
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// are not both modified to maliciously represent different content.
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SignResponse(pKey crypto.PrivateKey, pubKeyId string, r http.ResponseWriter, body []byte) error
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}
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// NewSigner creates a new Signer with the provided algorithm preferences to
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// make HTTP signatures. Only the first available algorithm will be used, which
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// is returned by this function along with the Signer. If none of the preferred
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// algorithms were available, then the default algorithm is used. The headers
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// specified will be included into the HTTP signatures.
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//
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// The Digest will also be calculated on a request's body using the provided
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// digest algorithm, if "Digest" is one of the headers listed.
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//
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// The provided scheme determines which header is populated with the HTTP
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// Signature.
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//
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// An error is returned if an unknown or a known cryptographically insecure
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// Algorithm is provided.
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func NewSigner(prefs []Algorithm, dAlgo DigestAlgorithm, headers []string, scheme SignatureScheme, expiresIn int64) (Signer, Algorithm, error) {
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for _, pref := range prefs {
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s, err := newSigner(pref, dAlgo, headers, scheme, expiresIn)
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if err != nil {
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continue
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}
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return s, pref, err
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}
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s, err := newSigner(defaultAlgorithm, dAlgo, headers, scheme, expiresIn)
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return s, defaultAlgorithm, err
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}
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// Signers will sign HTTP requests or responses based on the algorithms and
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// headers selected at creation time.
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//
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// Signers are not safe to use between multiple goroutines.
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//
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// Note that signatures do set the deprecated 'algorithm' parameter for
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// backwards compatibility.
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type SSHSigner interface {
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// SignRequest signs the request using ssh.Signer.
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// The public key id is used by the HTTP server to identify which key to use
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// to verify the signature.
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//
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// A Digest (RFC 3230) will be added to the request. The body provided
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// must match the body used in the request, and is allowed to be nil.
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// The Digest ensures the request body is not tampered with in flight,
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// and if the signer is created to also sign the "Digest" header, the
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// HTTP Signature will then ensure both the Digest and body are not both
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// modified to maliciously represent different content.
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SignRequest(pubKeyId string, r *http.Request, body []byte) error
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// SignResponse signs the response using ssh.Signer. The public key
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// id is used by the HTTP client to identify which key to use to verify
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// the signature.
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//
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// A Digest (RFC 3230) will be added to the response. The body provided
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// must match the body written in the response, and is allowed to be
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// nil. The Digest ensures the response body is not tampered with in
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// flight, and if the signer is created to also sign the "Digest"
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// header, the HTTP Signature will then ensure both the Digest and body
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// are not both modified to maliciously represent different content.
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SignResponse(pubKeyId string, r http.ResponseWriter, body []byte) error
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}
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// NewwSSHSigner creates a new Signer using the specified ssh.Signer
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// At the moment only ed25519 ssh keys are supported.
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// The headers specified will be included into the HTTP signatures.
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//
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// The Digest will also be calculated on a request's body using the provided
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// digest algorithm, if "Digest" is one of the headers listed.
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//
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// The provided scheme determines which header is populated with the HTTP
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// Signature.
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func NewSSHSigner(s ssh.Signer, dAlgo DigestAlgorithm, headers []string, scheme SignatureScheme, expiresIn int64) (SSHSigner, Algorithm, error) {
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sshAlgo := getSSHAlgorithm(s.PublicKey().Type())
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if sshAlgo == "" {
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return nil, "", fmt.Errorf("key type: %s not supported yet.", s.PublicKey().Type())
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}
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signer, err := newSSHSigner(s, sshAlgo, dAlgo, headers, scheme, expiresIn)
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if err != nil {
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return nil, "", err
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}
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return signer, sshAlgo, nil
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}
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func getSSHAlgorithm(pkType string) Algorithm {
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switch {
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case strings.HasPrefix(pkType, sshPrefix+"-"+ed25519Prefix):
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return ED25519
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case strings.HasPrefix(pkType, sshPrefix+"-"+rsaPrefix):
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return RSA_SHA1
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}
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return ""
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}
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// Verifier verifies HTTP Signatures.
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//
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// It will determine which of the supported headers has the parameters
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// that define the signature.
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//
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// Verifiers are not safe to use between multiple goroutines.
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//
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// Note that verification ignores the deprecated 'algorithm' parameter.
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type Verifier interface {
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// KeyId gets the public key id that the signature is signed with.
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//
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// Note that the application is expected to determine the algorithm
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// used based on metadata or out-of-band information for this key id.
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KeyId() string
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// Verify accepts the public key specified by KeyId and returns an
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// error if verification fails or if the signature is malformed. The
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// algorithm must be the one used to create the signature in order to
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// pass verification. The algorithm is determined based on metadata or
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// out-of-band information for the key id.
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//
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// If the signature was created using a MAC based algorithm, then the
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// key is expected to be of type []byte. If the signature was created
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// using an RSA based algorithm, then the public key is expected to be
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// of type *rsa.PublicKey.
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Verify(pKey crypto.PublicKey, algo Algorithm) error
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}
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const (
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// host is treated specially because golang may not include it in the
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// request header map on the server side of a request.
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hostHeader = "Host"
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)
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// NewVerifier verifies the given request. It returns an error if the HTTP
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// Signature parameters are not present in any headers, are present in more than
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// one header, are malformed, or are missing required parameters. It ignores
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// unknown HTTP Signature parameters.
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func NewVerifier(r *http.Request) (Verifier, error) {
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h := r.Header
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if _, hasHostHeader := h[hostHeader]; len(r.Host) > 0 && !hasHostHeader {
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h[hostHeader] = []string{r.Host}
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}
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return newVerifier(h, func(h http.Header, toInclude []string, created int64, expires int64) (string, error) {
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return signatureString(h, toInclude, addRequestTarget(r), created, expires)
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})
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}
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// NewResponseVerifier verifies the given response. It returns errors under the
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// same conditions as NewVerifier.
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func NewResponseVerifier(r *http.Response) (Verifier, error) {
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return newVerifier(r.Header, func(h http.Header, toInclude []string, created int64, expires int64) (string, error) {
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return signatureString(h, toInclude, requestTargetNotPermitted, created, expires)
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})
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}
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func newSSHSigner(sshSigner ssh.Signer, algo Algorithm, dAlgo DigestAlgorithm, headers []string, scheme SignatureScheme, expiresIn int64) (SSHSigner, error) {
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var expires, created int64 = 0, 0
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if expiresIn != 0 {
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created = time.Now().Unix()
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expires = created + expiresIn
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}
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s, err := signerFromSSHSigner(sshSigner, string(algo))
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if err != nil {
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return nil, fmt.Errorf("no crypto implementation available for ssh algo %q", algo)
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}
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a := &asymmSSHSigner{
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asymmSigner: &asymmSigner{
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s: s,
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dAlgo: dAlgo,
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headers: headers,
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targetHeader: scheme,
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prefix: scheme.authScheme(),
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created: created,
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expires: expires,
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},
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}
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return a, nil
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}
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func newSigner(algo Algorithm, dAlgo DigestAlgorithm, headers []string, scheme SignatureScheme, expiresIn int64) (Signer, error) {
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var expires, created int64 = 0, 0
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if expiresIn != 0 {
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created = time.Now().Unix()
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expires = created + expiresIn
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}
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s, err := signerFromString(string(algo))
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if err == nil {
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a := &asymmSigner{
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s: s,
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dAlgo: dAlgo,
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headers: headers,
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targetHeader: scheme,
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prefix: scheme.authScheme(),
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created: created,
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expires: expires,
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}
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return a, nil
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}
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m, err := macerFromString(string(algo))
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if err != nil {
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return nil, fmt.Errorf("no crypto implementation available for %q", algo)
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}
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c := &macSigner{
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m: m,
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dAlgo: dAlgo,
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headers: headers,
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targetHeader: scheme,
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prefix: scheme.authScheme(),
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created: created,
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expires: expires,
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}
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return c, nil
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}
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