129 lines
3.4 KiB
Go
129 lines
3.4 KiB
Go
package module
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import (
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"encoding/xml"
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"fmt"
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"io"
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"net/http"
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"net/url"
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"strings"
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)
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// HttpGetter is a Getter implementation that will download a module from
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// an HTTP endpoint. The protocol for downloading a module from an HTTP
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// endpoing is as follows:
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//
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// An HTTP GET request is made to the URL with the additional GET parameter
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// "terraform-get=1". This lets you handle that scenario specially if you
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// wish. The response must be a 2xx.
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//
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// First, a header is looked for "X-Terraform-Get" which should contain
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// a source URL to download.
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//
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// If the header is not present, then a meta tag is searched for named
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// "terraform-get" and the content should be a source URL.
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//
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// The source URL, whether from the header or meta tag, must be a fully
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// formed URL. The shorthand syntax of "github.com/foo/bar" or relative
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// paths are not allowed.
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type HttpGetter struct{}
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func (g *HttpGetter) Get(dst string, u *url.URL) error {
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// Copy the URL so we can modify it
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var newU url.URL = *u
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u = &newU
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// Add terraform-get to the parameter.
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q := u.Query()
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q.Add("terraform-get", "1")
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u.RawQuery = q.Encode()
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// Get the URL
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resp, err := http.Get(u.String())
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if err != nil {
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return err
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}
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defer resp.Body.Close()
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if resp.StatusCode < 200 || resp.StatusCode >= 300 {
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return fmt.Errorf("bad response code: %d", resp.StatusCode)
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}
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// Extract the source URL
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var source string
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if v := resp.Header.Get("X-Terraform-Get"); v != "" {
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source = v
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} else {
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source, err = g.parseMeta(resp.Body)
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if err != nil {
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return err
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}
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}
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if source == "" {
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return fmt.Errorf("no source URL was returned")
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}
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// Get it!
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return Get(dst, source)
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}
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// parseMeta looks for the first meta tag in the given reader that
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// will give us the source URL.
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func (g *HttpGetter) parseMeta(r io.Reader) (string, error) {
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d := xml.NewDecoder(r)
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d.CharsetReader = charsetReader
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d.Strict = false
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var err error
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var t xml.Token
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for {
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t, err = d.Token()
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if err != nil {
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if err == io.EOF {
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err = nil
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}
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return "", err
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}
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if e, ok := t.(xml.StartElement); ok && strings.EqualFold(e.Name.Local, "body") {
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return "", nil
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}
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if e, ok := t.(xml.EndElement); ok && strings.EqualFold(e.Name.Local, "head") {
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return "", nil
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}
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e, ok := t.(xml.StartElement)
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if !ok || !strings.EqualFold(e.Name.Local, "meta") {
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continue
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}
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if attrValue(e.Attr, "name") != "terraform-get" {
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continue
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}
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if f := attrValue(e.Attr, "content"); f != "" {
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return f, nil
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}
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}
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}
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// attrValue returns the attribute value for the case-insensitive key
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// `name', or the empty string if nothing is found.
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func attrValue(attrs []xml.Attr, name string) string {
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for _, a := range attrs {
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if strings.EqualFold(a.Name.Local, name) {
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return a.Value
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}
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}
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return ""
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}
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// charsetReader returns a reader for the given charset. Currently
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// it only supports UTF-8 and ASCII. Otherwise, it returns a meaningful
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// error which is printed by go get, so the user can find why the package
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// wasn't downloaded if the encoding is not supported. Note that, in
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// order to reduce potential errors, ASCII is treated as UTF-8 (i.e. characters
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// greater than 0x7f are not rejected).
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func charsetReader(charset string, input io.Reader) (io.Reader, error) {
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switch strings.ToLower(charset) {
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case "ascii":
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return input, nil
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default:
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return nil, fmt.Errorf("can't decode XML document using charset %q", charset)
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}
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}
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