github.com/newrelic/go-agent@v3.26.0+incompatible/internal/sysinfo/bootid.go (about)

     1  // Copyright 2020 New Relic Corporation. All rights reserved.
     2  // SPDX-License-Identifier: Apache-2.0
     3  
     4  package sysinfo
     5  
     6  import (
     7  	"bytes"
     8  	"fmt"
     9  	"io/ioutil"
    10  	"runtime"
    11  )
    12  
    13  // BootID returns the boot ID of the executing kernel.
    14  func BootID() (string, error) {
    15  	if "linux" != runtime.GOOS {
    16  		return "", ErrFeatureUnsupported
    17  	}
    18  	data, err := ioutil.ReadFile("/proc/sys/kernel/random/boot_id")
    19  	if err != nil {
    20  		return "", err
    21  	}
    22  
    23  	return validateBootID(data)
    24  }
    25  
    26  type invalidBootID string
    27  
    28  func (e invalidBootID) Error() string {
    29  	return fmt.Sprintf("Boot id has unrecognized format, id=%q", string(e))
    30  }
    31  
    32  func isASCIIByte(b byte) bool {
    33  	return (b >= 0x20 && b <= 0x7f)
    34  }
    35  
    36  func validateBootID(data []byte) (string, error) {
    37  	// We're going to go for the permissive reading of
    38  	// https://source.datanerd.us/agents/agent-specs/blob/master/Utilization.md:
    39  	// any ASCII (excluding control characters, because I'm pretty sure that's not
    40  	// in the spirit of the spec) string will be sent up to and including 128
    41  	// bytes in length.
    42  	trunc := bytes.TrimSpace(data)
    43  	if len(trunc) > 128 {
    44  		trunc = trunc[:128]
    45  	}
    46  	for _, b := range trunc {
    47  		if !isASCIIByte(b) {
    48  			return "", invalidBootID(data)
    49  		}
    50  	}
    51  
    52  	return string(trunc), nil
    53  }