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521 lines
15 KiB
521 lines
15 KiB
package v4a
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import (
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"bytes"
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"context"
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"crypto"
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"crypto/ecdsa"
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"crypto/elliptic"
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"crypto/rand"
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"crypto/sha256"
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"encoding/hex"
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"fmt"
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"hash"
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"math/big"
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"net/http"
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"net/textproto"
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"net/url"
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"sort"
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"strconv"
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"strings"
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"time"
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signerCrypto "github.com/aws/aws-sdk-go-v2/internal/v4a/internal/crypto"
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v4Internal "github.com/aws/aws-sdk-go-v2/internal/v4a/internal/v4"
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"github.com/aws/smithy-go/encoding/httpbinding"
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"github.com/aws/smithy-go/logging"
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)
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const (
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// AmzRegionSetKey represents the region set header used for sigv4a
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AmzRegionSetKey = "X-Amz-Region-Set"
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amzAlgorithmKey = v4Internal.AmzAlgorithmKey
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amzSecurityTokenKey = v4Internal.AmzSecurityTokenKey
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amzDateKey = v4Internal.AmzDateKey
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amzCredentialKey = v4Internal.AmzCredentialKey
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amzSignedHeadersKey = v4Internal.AmzSignedHeadersKey
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authorizationHeader = "Authorization"
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signingAlgorithm = "AWS4-ECDSA-P256-SHA256"
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timeFormat = "20060102T150405Z"
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shortTimeFormat = "20060102"
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// EmptyStringSHA256 is a hex encoded SHA-256 hash of an empty string
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EmptyStringSHA256 = v4Internal.EmptyStringSHA256
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// Version of signing v4a
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Version = "SigV4A"
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)
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var (
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p256 elliptic.Curve
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nMinusTwoP256 *big.Int
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one = new(big.Int).SetInt64(1)
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)
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func init() {
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// Ensure the elliptic curve parameters are initialized on package import rather then on first usage
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p256 = elliptic.P256()
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nMinusTwoP256 = new(big.Int).SetBytes(p256.Params().N.Bytes())
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nMinusTwoP256 = nMinusTwoP256.Sub(nMinusTwoP256, new(big.Int).SetInt64(2))
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}
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// SignerOptions is the SigV4a signing options for constructing a Signer.
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type SignerOptions struct {
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Logger logging.Logger
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LogSigning bool
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// Disables the Signer's moving HTTP header key/value pairs from the HTTP
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// request header to the request's query string. This is most commonly used
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// with pre-signed requests preventing headers from being added to the
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// request's query string.
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DisableHeaderHoisting bool
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// Disables the automatic escaping of the URI path of the request for the
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// siganture's canonical string's path. For services that do not need additional
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// escaping then use this to disable the signer escaping the path.
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//
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// S3 is an example of a service that does not need additional escaping.
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//
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// http://docs.aws.amazon.com/general/latest/gr/sigv4-create-canonical-request.html
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DisableURIPathEscaping bool
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}
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// Signer is a SigV4a HTTP signing implementation
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type Signer struct {
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options SignerOptions
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}
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// NewSigner constructs a SigV4a Signer.
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func NewSigner(optFns ...func(*SignerOptions)) *Signer {
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options := SignerOptions{}
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for _, fn := range optFns {
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fn(&options)
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}
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return &Signer{options: options}
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}
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// deriveKeyFromAccessKeyPair derives a NIST P-256 PrivateKey from the given
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// IAM AccessKey and SecretKey pair.
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//
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// Based on FIPS.186-4 Appendix B.4.2
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func deriveKeyFromAccessKeyPair(accessKey, secretKey string) (*ecdsa.PrivateKey, error) {
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params := p256.Params()
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bitLen := params.BitSize // Testing random candidates does not require an additional 64 bits
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counter := 0x01
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buffer := make([]byte, 1+len(accessKey)) // 1 byte counter + len(accessKey)
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kdfContext := bytes.NewBuffer(buffer)
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inputKey := append([]byte("AWS4A"), []byte(secretKey)...)
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d := new(big.Int)
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for {
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kdfContext.Reset()
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kdfContext.WriteString(accessKey)
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kdfContext.WriteByte(byte(counter))
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key, err := signerCrypto.HMACKeyDerivation(sha256.New, bitLen, inputKey, []byte(signingAlgorithm), kdfContext.Bytes())
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if err != nil {
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return nil, err
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}
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// Check key first before calling SetBytes if key key is in fact a valid candidate.
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// This ensures the byte slice is the correct length (32-bytes) to compare in constant-time
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cmp, err := signerCrypto.ConstantTimeByteCompare(key, nMinusTwoP256.Bytes())
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if err != nil {
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return nil, err
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}
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if cmp == -1 {
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d.SetBytes(key)
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break
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}
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counter++
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if counter > 0xFF {
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return nil, fmt.Errorf("exhausted single byte external counter")
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}
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}
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d = d.Add(d, one)
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priv := new(ecdsa.PrivateKey)
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priv.PublicKey.Curve = p256
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priv.D = d
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priv.PublicKey.X, priv.PublicKey.Y = p256.ScalarBaseMult(d.Bytes())
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return priv, nil
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}
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type httpSigner struct {
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Request *http.Request
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ServiceName string
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RegionSet []string
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Time time.Time
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Credentials Credentials
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IsPreSign bool
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Logger logging.Logger
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Debug bool
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// PayloadHash is the hex encoded SHA-256 hash of the request payload
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// If len(PayloadHash) == 0 the signer will attempt to send the request
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// as an unsigned payload. Note: Unsigned payloads only work for a subset of services.
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PayloadHash string
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DisableHeaderHoisting bool
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DisableURIPathEscaping bool
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}
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// SignHTTP takes the provided http.Request, payload hash, service, regionSet, and time and signs using SigV4a.
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// The passed in request will be modified in place.
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func (s *Signer) SignHTTP(ctx context.Context, credentials Credentials, r *http.Request, payloadHash string, service string, regionSet []string, signingTime time.Time, optFns ...func(*SignerOptions)) error {
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options := s.options
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for _, fn := range optFns {
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fn(&options)
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}
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signer := &httpSigner{
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Request: r,
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PayloadHash: payloadHash,
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ServiceName: service,
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RegionSet: regionSet,
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Credentials: credentials,
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Time: signingTime.UTC(),
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DisableHeaderHoisting: options.DisableHeaderHoisting,
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DisableURIPathEscaping: options.DisableURIPathEscaping,
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}
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signedRequest, err := signer.Build()
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if err != nil {
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return err
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}
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logHTTPSigningInfo(ctx, options, signedRequest)
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return nil
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}
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// PresignHTTP takes the provided http.Request, payload hash, service, regionSet, and time and presigns using SigV4a
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// Returns the presigned URL along with the headers that were signed with the request.
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//
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// PresignHTTP will not set the expires time of the presigned request
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// automatically. To specify the expire duration for a request add the
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// "X-Amz-Expires" query parameter on the request with the value as the
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// duration in seconds the presigned URL should be considered valid for. This
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// parameter is not used by all AWS services, and is most notable used by
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// Amazon S3 APIs.
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func (s *Signer) PresignHTTP(ctx context.Context, credentials Credentials, r *http.Request, payloadHash string, service string, regionSet []string, signingTime time.Time, optFns ...func(*SignerOptions)) (signedURI string, signedHeaders http.Header, err error) {
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options := s.options
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for _, fn := range optFns {
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fn(&options)
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}
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signer := &httpSigner{
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Request: r,
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PayloadHash: payloadHash,
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ServiceName: service,
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RegionSet: regionSet,
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Credentials: credentials,
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Time: signingTime.UTC(),
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IsPreSign: true,
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DisableHeaderHoisting: options.DisableHeaderHoisting,
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DisableURIPathEscaping: options.DisableURIPathEscaping,
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}
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signedRequest, err := signer.Build()
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if err != nil {
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return "", nil, err
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}
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logHTTPSigningInfo(ctx, options, signedRequest)
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signedHeaders = make(http.Header)
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// For the signed headers we canonicalize the header keys in the returned map.
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// This avoids situations where can standard library double headers like host header. For example the standard
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// library will set the Host header, even if it is present in lower-case form.
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for k, v := range signedRequest.SignedHeaders {
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key := textproto.CanonicalMIMEHeaderKey(k)
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signedHeaders[key] = append(signedHeaders[key], v...)
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}
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return signedRequest.Request.URL.String(), signedHeaders, nil
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}
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func (s *httpSigner) setRequiredSigningFields(headers http.Header, query url.Values) {
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amzDate := s.Time.Format(timeFormat)
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if s.IsPreSign {
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query.Set(AmzRegionSetKey, strings.Join(s.RegionSet, ","))
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query.Set(amzDateKey, amzDate)
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query.Set(amzAlgorithmKey, signingAlgorithm)
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if len(s.Credentials.SessionToken) > 0 {
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query.Set(amzSecurityTokenKey, s.Credentials.SessionToken)
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}
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return
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}
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headers.Set(AmzRegionSetKey, strings.Join(s.RegionSet, ","))
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headers.Set(amzDateKey, amzDate)
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if len(s.Credentials.SessionToken) > 0 {
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headers.Set(amzSecurityTokenKey, s.Credentials.SessionToken)
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}
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}
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func (s *httpSigner) Build() (signedRequest, error) {
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req := s.Request
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query := req.URL.Query()
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headers := req.Header
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s.setRequiredSigningFields(headers, query)
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// Sort Each Query Key's Values
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for key := range query {
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sort.Strings(query[key])
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}
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v4Internal.SanitizeHostForHeader(req)
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credentialScope := s.buildCredentialScope()
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credentialStr := s.Credentials.Context + "/" + credentialScope
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if s.IsPreSign {
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query.Set(amzCredentialKey, credentialStr)
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}
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unsignedHeaders := headers
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if s.IsPreSign && !s.DisableHeaderHoisting {
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urlValues := url.Values{}
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urlValues, unsignedHeaders = buildQuery(v4Internal.AllowedQueryHoisting, unsignedHeaders)
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for k := range urlValues {
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query[k] = urlValues[k]
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}
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}
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host := req.URL.Host
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if len(req.Host) > 0 {
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host = req.Host
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}
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signedHeaders, signedHeadersStr, canonicalHeaderStr := s.buildCanonicalHeaders(host, v4Internal.IgnoredHeaders, unsignedHeaders, s.Request.ContentLength)
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if s.IsPreSign {
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query.Set(amzSignedHeadersKey, signedHeadersStr)
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}
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rawQuery := strings.Replace(query.Encode(), "+", "%20", -1)
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canonicalURI := v4Internal.GetURIPath(req.URL)
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if !s.DisableURIPathEscaping {
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canonicalURI = httpbinding.EscapePath(canonicalURI, false)
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}
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canonicalString := s.buildCanonicalString(
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req.Method,
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canonicalURI,
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rawQuery,
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signedHeadersStr,
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canonicalHeaderStr,
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)
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strToSign := s.buildStringToSign(credentialScope, canonicalString)
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signingSignature, err := s.buildSignature(strToSign)
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if err != nil {
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return signedRequest{}, err
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}
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if s.IsPreSign {
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rawQuery += "&X-Amz-Signature=" + signingSignature
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} else {
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headers[authorizationHeader] = append(headers[authorizationHeader][:0], buildAuthorizationHeader(credentialStr, signedHeadersStr, signingSignature))
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}
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req.URL.RawQuery = rawQuery
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return signedRequest{
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Request: req,
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SignedHeaders: signedHeaders,
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CanonicalString: canonicalString,
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StringToSign: strToSign,
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PreSigned: s.IsPreSign,
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}, nil
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}
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func buildAuthorizationHeader(credentialStr, signedHeadersStr, signingSignature string) string {
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const credential = "Credential="
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const signedHeaders = "SignedHeaders="
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const signature = "Signature="
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const commaSpace = ", "
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var parts strings.Builder
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parts.Grow(len(signingAlgorithm) + 1 +
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len(credential) + len(credentialStr) + len(commaSpace) +
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len(signedHeaders) + len(signedHeadersStr) + len(commaSpace) +
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len(signature) + len(signingSignature),
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)
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parts.WriteString(signingAlgorithm)
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parts.WriteRune(' ')
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parts.WriteString(credential)
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parts.WriteString(credentialStr)
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parts.WriteString(commaSpace)
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parts.WriteString(signedHeaders)
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parts.WriteString(signedHeadersStr)
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parts.WriteString(commaSpace)
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parts.WriteString(signature)
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parts.WriteString(signingSignature)
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return parts.String()
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}
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func (s *httpSigner) buildCredentialScope() string {
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return strings.Join([]string{
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s.Time.Format(shortTimeFormat),
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s.ServiceName,
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"aws4_request",
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}, "/")
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}
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func buildQuery(r v4Internal.Rule, header http.Header) (url.Values, http.Header) {
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query := url.Values{}
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unsignedHeaders := http.Header{}
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for k, h := range header {
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if r.IsValid(k) {
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query[k] = h
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} else {
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unsignedHeaders[k] = h
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}
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}
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return query, unsignedHeaders
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}
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func (s *httpSigner) buildCanonicalHeaders(host string, rule v4Internal.Rule, header http.Header, length int64) (signed http.Header, signedHeaders, canonicalHeadersStr string) {
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signed = make(http.Header)
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var headers []string
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const hostHeader = "host"
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headers = append(headers, hostHeader)
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signed[hostHeader] = append(signed[hostHeader], host)
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if length > 0 {
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const contentLengthHeader = "content-length"
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headers = append(headers, contentLengthHeader)
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signed[contentLengthHeader] = append(signed[contentLengthHeader], strconv.FormatInt(length, 10))
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}
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for k, v := range header {
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if !rule.IsValid(k) {
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continue // ignored header
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}
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lowerCaseKey := strings.ToLower(k)
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if _, ok := signed[lowerCaseKey]; ok {
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// include additional values
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signed[lowerCaseKey] = append(signed[lowerCaseKey], v...)
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continue
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}
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headers = append(headers, lowerCaseKey)
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signed[lowerCaseKey] = v
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}
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sort.Strings(headers)
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signedHeaders = strings.Join(headers, ";")
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var canonicalHeaders strings.Builder
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n := len(headers)
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const colon = ':'
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for i := 0; i < n; i++ {
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if headers[i] == hostHeader {
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canonicalHeaders.WriteString(hostHeader)
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canonicalHeaders.WriteRune(colon)
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canonicalHeaders.WriteString(v4Internal.StripExcessSpaces(host))
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} else {
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canonicalHeaders.WriteString(headers[i])
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canonicalHeaders.WriteRune(colon)
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// Trim out leading, trailing, and dedup inner spaces from signed header values.
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values := signed[headers[i]]
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for j, v := range values {
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cleanedValue := strings.TrimSpace(v4Internal.StripExcessSpaces(v))
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canonicalHeaders.WriteString(cleanedValue)
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if j < len(values)-1 {
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canonicalHeaders.WriteRune(',')
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}
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}
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}
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canonicalHeaders.WriteRune('\n')
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}
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canonicalHeadersStr = canonicalHeaders.String()
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return signed, signedHeaders, canonicalHeadersStr
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}
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func (s *httpSigner) buildCanonicalString(method, uri, query, signedHeaders, canonicalHeaders string) string {
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return strings.Join([]string{
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method,
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uri,
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query,
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canonicalHeaders,
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signedHeaders,
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s.PayloadHash,
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}, "\n")
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}
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func (s *httpSigner) buildStringToSign(credentialScope, canonicalRequestString string) string {
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return strings.Join([]string{
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signingAlgorithm,
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s.Time.Format(timeFormat),
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credentialScope,
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hex.EncodeToString(makeHash(sha256.New(), []byte(canonicalRequestString))),
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}, "\n")
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}
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func makeHash(hash hash.Hash, b []byte) []byte {
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hash.Reset()
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hash.Write(b)
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return hash.Sum(nil)
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}
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func (s *httpSigner) buildSignature(strToSign string) (string, error) {
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sig, err := s.Credentials.PrivateKey.Sign(rand.Reader, makeHash(sha256.New(), []byte(strToSign)), crypto.SHA256)
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if err != nil {
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return "", err
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}
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return hex.EncodeToString(sig), nil
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}
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const logSignInfoMsg = `Request Signature:
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---[ CANONICAL STRING ]-----------------------------
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%s
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---[ STRING TO SIGN ]--------------------------------
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%s%s
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-----------------------------------------------------`
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const logSignedURLMsg = `
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---[ SIGNED URL ]------------------------------------
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%s`
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func logHTTPSigningInfo(ctx context.Context, options SignerOptions, r signedRequest) {
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if !options.LogSigning {
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return
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}
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signedURLMsg := ""
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if r.PreSigned {
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signedURLMsg = fmt.Sprintf(logSignedURLMsg, r.Request.URL.String())
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}
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logger := logging.WithContext(ctx, options.Logger)
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logger.Logf(logging.Debug, logSignInfoMsg, r.CanonicalString, r.StringToSign, signedURLMsg)
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}
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type signedRequest struct {
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Request *http.Request
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SignedHeaders http.Header
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CanonicalString string
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StringToSign string
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PreSigned bool
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}
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