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package nvdmirror
import (
"bytes"
"crypto/sha256"
"errors"
"fmt"
"github.com/pablotron/cvez/atomictemp"
"github.com/pablotron/cvez/feed"
"github.com/rs/zerolog/log"
"io"
"io/fs"
"net/http"
"net/url"
"os"
"path/filepath"
)
// Fetch result.
type fetchResult struct {
src string // source URL
err error // fetch result
modified bool // Was the result modified?
path string // Destination file.
headers http.Header // response headers
}
// Check result.
type checkResult struct {
metaUrl string // meta full url
metaPath string // meta file path
fullPath string // full file path
err error // error
match bool // true if size and hash match
}
type syncMessage struct {
fetch fetchResult // fetch result
check checkResult // check result
}
// sync context
type syncContext struct {
config SyncConfig // sync config
client *http.Client // shared HTTP client
cache Cache // cache
dstDir string // destination directory
ch chan syncMessage // sync message channel
}
// Create sync context.
func newSyncContext(config SyncConfig, cache Cache, dstDir string) syncContext {
// create shared transport and client
tr := &http.Transport {
MaxIdleConns: config.MaxIdleConns,
IdleConnTimeout: config.IdleConnTimeout,
}
return syncContext {
config: config,
client: &http.Client{Transport: tr},
cache: cache,
dstDir: dstDir,
ch: make(chan syncMessage),
}
}
// Build request
func (me syncContext) getRequest(srcUrl string) (*http.Request, error) {
// create HTTP request
req, err := http.NewRequest("GET", srcUrl, nil)
if err != nil {
return nil, err
}
// Add user-agent, if-none-match, and if-modified-since headers.
req.Header.Add("user-agent", me.config.GetUserAgent())
if headers, ok := me.cache.Get(srcUrl); ok {
for k, v := range(headers) {
req.Header.Add(k, v)
}
}
// return success
return req, nil
}
// Fetch URL and write result to destination directory.
//
// Note: This method is called from a goroutine and writes the results
// back via the member channel.
func (me syncContext) fetch(srcUrl string) {
// parse source url
src, err := url.Parse(srcUrl)
if err != nil {
me.ch <- syncMessage {
fetch: fetchResult { src: srcUrl, err: err },
}
return
}
// build destination path
path := filepath.Join(me.dstDir, filepath.Base(src.Path))
log.Debug().Str("url", srcUrl).Str("path", path).Send()
// create request
req, err := me.getRequest(srcUrl)
if err != nil {
me.ch <- syncMessage {
fetch: fetchResult { src: srcUrl, err: err },
}
return
}
// send request
resp, err := me.client.Do(req)
if err != nil {
me.ch <- syncMessage {
fetch: fetchResult { src: srcUrl, err: err },
}
return
}
defer resp.Body.Close()
switch resp.StatusCode {
case 200: // success
// write to output file
err := atomictemp.Create(path, func(f io.Writer) error {
_, err := io.Copy(f, resp.Body)
return err
})
if err != nil {
// write failed
me.ch <- syncMessage {
fetch: fetchResult { src: srcUrl, err: err },
}
} else {
me.ch <- syncMessage {
fetch: fetchResult {
src: srcUrl,
modified: true,
path: path,
headers: resp.Header,
},
}
}
case 304: // not modified
me.ch <- syncMessage {
fetch: fetchResult { src: srcUrl },
}
default: // error
code := resp.StatusCode
err := fmt.Errorf("%d: %s", code, http.StatusText(code))
me.ch <- syncMessage {
fetch: fetchResult { src: srcUrl, err: err },
}
}
}
// read hash from given meta file.
func (me syncContext) getMeta(path string) (*feed.Meta, error) {
// open meta file
f, err := os.Open(path)
if err != nil {
return nil, err
}
defer f.Close()
// parse meta
return feed.NewMeta(f)
}
// get hash of file in destination directory.
func (me syncContext) getFileHash(path string) ([32]byte, error) {
var r [32]byte
// open file
f, err := os.Open(path)
if err != nil {
return r, err
}
defer f.Close()
// hash file
hash := sha256.New()
if _, err := io.Copy(hash, f); err != nil {
return r, err
}
// copy sum to result, return success
hash.Sum(r[:])
return r, nil
}
// Check the size and hash in the metadata file against the full file.
//
// Note: This method is called from a goroutine and returns it's value
// via the internal channel.
func (me syncContext) check(metaUrl, fullUrl string) {
// build result
r := syncMessage {
check: checkResult {
metaUrl: metaUrl,
// build paths
metaPath: filepath.Join(me.dstDir, filepath.Base(metaUrl)),
fullPath: filepath.Join(me.dstDir, filepath.Base(fullUrl)),
},
}
// get size of full file
size, err := getFileSize(r.check.fullPath)
if errors.Is(err, fs.ErrNotExist) {
r.check.match = false
me.ch <- r
return
} else if err != nil {
r.check.err = err
me.ch <- r
return
}
// get meta hash
m, err := me.getMeta(r.check.metaPath)
if err != nil {
r.check.err = err
me.ch <- r
return
}
// check for file size match
if size != m.GzSize {
r.check.match = false
me.ch <- r
return
}
// get full hash
fh, err := me.getFileHash(r.check.fullPath)
if err != nil {
r.check.err = err
me.ch <- r
return
}
// return result
r.check.match = (bytes.Compare(m.Sha256[:], fh[:]) == 0)
me.ch <- r
}
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