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package auth
import (
"crypto/rand"
"crypto/sha256"
"encoding/hex"
"fmt"
)
const tokenByteLength = 32
// Compile-time check that *tokenManager satisfies the TokenManager interface.
var _ TokenManager = (*tokenManager)(nil)
type tokenManager struct{}
// NewTokenManager creates a TokenManager.
func NewTokenManager() TokenManager {
return &tokenManager{}
}
// Generate creates a plaintext API token and its stored hash.
// Returns an error if the system random source fails. A crypto/rand.Read
// failure indicates a process-level emergency, so callers should propagate
// the error upward rather than masking it.
func (m *tokenManager) Generate() (plaintext, hash string, err error) {
b := make([]byte, tokenByteLength)
if _, err := rand.Read(b); err != nil {
return "", "", fmt.Errorf("generate token: %w", err)
}
plaintext = hex.EncodeToString(b)
return plaintext, m.Hash(plaintext), nil
}
// Hash returns the SHA-256 hash of a plaintext API token.
func (m *tokenManager) Hash(plaintext string) string {
// SHA-256 is used instead of bcrypt because API tokens are high-entropy
// random bytes; bcrypt adds CPU cost without meaningful security benefit.
sum := sha256.Sum256([]byte(plaintext))
return hex.EncodeToString(sum[:])
}
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