55 lines
1.3 KiB
Go
55 lines
1.3 KiB
Go
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//+build go1.15
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package jwt
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import (
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"crypto/ecdsa"
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"crypto/rand"
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)
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// Implements the Sign method from SigningMethod
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// For this signing method, key must be an ecdsa.PrivateKey struct
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func (m *SigningMethodECDSA) Sign(signingString string, key interface{}) (string, error) {
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// Get the key
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var ecdsaKey *ecdsa.PrivateKey
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switch k := key.(type) {
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case *ecdsa.PrivateKey:
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ecdsaKey = k
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default:
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return "", ErrInvalidKeyType
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}
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// Create the hasher
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if !m.Hash.Available() {
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return "", ErrHashUnavailable
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}
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hasher := m.Hash.New()
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hasher.Write([]byte(signingString))
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// Sign the string and return r, s
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if r, s, err := ecdsa.Sign(rand.Reader, ecdsaKey, hasher.Sum(nil)); err == nil {
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curveBits := ecdsaKey.Curve.Params().BitSize
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if m.CurveBits != curveBits {
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return "", ErrInvalidKey
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}
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keyBytes := curveBits / 8
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if curveBits%8 > 0 {
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keyBytes += 1
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}
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// We serialize the outputs (r and s) into big-endian byte arrays
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// padded with zeros on the left to make sure the sizes work out.
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// Output must be 2*keyBytes long.
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out := make([]byte, 2*keyBytes)
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r.FillBytes(out[0:keyBytes]) // r is assigned to the first half of output.
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s.FillBytes(out[keyBytes:]) // s is assigned to the second half of output.
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return EncodeSegment(out), nil
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} else {
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return "", err
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}
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}
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