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Source file src/crypto/rand/rand_windows.go

Documentation: crypto/rand

     1  // Copyright 2010 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Windows cryptographically secure pseudorandom number
     6  // generator.
     7  
     8  package rand
     9  
    10  import (
    11  	"os"
    12  	"sync"
    13  	"syscall"
    14  )
    15  
    16  // Implemented by using Windows CryptoAPI 2.0.
    17  
    18  func init() { Reader = &rngReader{} }
    19  
    20  // A rngReader satisfies reads by reading from the Windows CryptGenRandom API.
    21  type rngReader struct {
    22  	prov syscall.Handle
    23  	mu   sync.Mutex
    24  }
    25  
    26  func (r *rngReader) Read(b []byte) (n int, err error) {
    27  	r.mu.Lock()
    28  	if r.prov == 0 {
    29  		const provType = syscall.PROV_RSA_FULL
    30  		const flags = syscall.CRYPT_VERIFYCONTEXT | syscall.CRYPT_SILENT
    31  		err := syscall.CryptAcquireContext(&r.prov, nil, nil, provType, flags)
    32  		if err != nil {
    33  			r.mu.Unlock()
    34  			return 0, os.NewSyscallError("CryptAcquireContext", err)
    35  		}
    36  	}
    37  	r.mu.Unlock()
    38  
    39  	if len(b) == 0 {
    40  		return 0, nil
    41  	}
    42  	err = syscall.CryptGenRandom(r.prov, uint32(len(b)), &b[0])
    43  	if err != nil {
    44  		return 0, os.NewSyscallError("CryptGenRandom", err)
    45  	}
    46  	return len(b), nil
    47  }
    48  

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