allow to specify checksum via url

Signed-off-by: Vasiliy Tolstov <v.tolstov@selfip.ru>

common/iso_config.go

@@ -1,8 +1,12 @@
 package common
 
 import (
+	"bufio"
 	"errors"
 	"fmt"
+	"net/http"
+	"net/url"
+	"path/filepath"
 	"strings"
 
 	"github.com/mitchellh/packer/template/interpolate"
@@ -23,6 +27,16 @@ func (c *ISOConfig) Prepare(ctx *interpolate.Context) ([]string, []error) {
 	var err error
 	var warnings []string
 
+	if c.RawSingleISOUrl == "" && len(c.ISOUrls) == 0 {
+		errs = append(
+			errs, errors.New("One of iso_url or iso_urls must be specified."))
+	} else if c.RawSingleISOUrl != "" && len(c.ISOUrls) > 0 {
+		errs = append(
+			errs, errors.New("Only one of iso_url or iso_urls may be specified."))
+	} else if c.RawSingleISOUrl != "" {
+		c.ISOUrls = []string{c.RawSingleISOUrl}
+	}
+
 	if c.ISOChecksumType == "" {
 		errs = append(
 			errs, errors.New("The iso_checksum_type must be specified."))
@@ -32,27 +46,73 @@ func (c *ISOConfig) Prepare(ctx *interpolate.Context) ([]string, []error) {
 			if c.ISOChecksum == "" {
 				errs = append(
 					errs, errors.New("Due to large file sizes, an iso_checksum is required"))
+				return warnings, errs
 			} else {
-				c.ISOChecksum = strings.ToLower(c.ISOChecksum)
-			}
+				if h := HashForType(c.ISOChecksumType); h == nil {
+					errs = append(
+						errs, fmt.Errorf("Unsupported checksum type: %s", c.ISOChecksumType))
+					return warnings, errs
+				}
 
-			if h := HashForType(c.ISOChecksumType); h == nil {
-				errs = append(
-					errs,
-					fmt.Errorf("Unsupported checksum type: %s", c.ISOChecksumType))
+				u, err := url.Parse(c.ISOChecksum)
+				if err != nil {
+					errs = append(errs,
+						fmt.Errorf("Error parsing checksum: %s", err))
+					return warnings, errs
+				}
+				switch u.Scheme {
+				case "http", "https", "ftp", "ftps":
+					res, err := http.Get(c.ISOChecksum)
+					c.ISOChecksum = ""
+					if err != nil {
+						errs = append(errs,
+							fmt.Errorf("Error getting checksum from url: %s", c.ISOChecksum))
+						return warnings, errs
+					}
+					defer res.Body.Close()
+
+					rd := bufio.NewReader(res.Body)
+					for {
+						line, err := rd.ReadString('\n')
+						if err != nil {
+							errs = append(errs,
+								fmt.Errorf("Error getting checksum from url: %s , %s", c.ISOChecksum, err.Error()))
+							return warnings, errs
+						}
+						parts := strings.Fields(line)
+						if len(parts) < 2 {
+							continue
+						}
+						if strings.ToLower(parts[0]) == c.ISOChecksumType {
+							// BSD-style checksum
+							if parts[1] == fmt.Sprintf("(%s)", filepath.Base(c.ISOUrls[0])) {
+								c.ISOChecksum = parts[3]
+								break
+							}
+						} else {
+							// Standard checksum
+							if parts[1][0] == '*' {
+								// Binary mode
+								parts[1] = parts[1][1:]
+							}
+							if parts[1] == filepath.Base(c.ISOUrls[0]) {
+								c.ISOChecksum = parts[0]
+								break
+							}
+						}
+					}
+				case "":
+					break
+				default:
+					errs = append(errs,
+						fmt.Errorf("Error parsing checksum url, scheme not supported: %s", u.Scheme))
+					return warnings, errs
+				}
 			}
 		}
 	}
 
-	if c.RawSingleISOUrl == "" && len(c.ISOUrls) == 0 {
-		errs = append(
-			errs, errors.New("One of iso_url or iso_urls must be specified."))
-	} else if c.RawSingleISOUrl != "" && len(c.ISOUrls) > 0 {
-		errs = append(
-			errs, errors.New("Only one of iso_url or iso_urls may be specified."))
-	} else if c.RawSingleISOUrl != "" {
-		c.ISOUrls = []string{c.RawSingleISOUrl}
-	}
+	c.ISOChecksum = strings.ToLower(c.ISOChecksum)
 
 	for i, url := range c.ISOUrls {
 		c.ISOUrls[i], err = DownloadableURL(url)

website/source/docs/builders/parallels-iso.html.markdown

@@ -59,7 +59,8 @@ builder.
 -   `iso_checksum` (string) - The checksum for the OS ISO file. Because ISO
     files are so large, this is required and Packer will verify it prior to
     booting a virtual machine with the ISO attached. The type of the checksum is
-    specified with `iso_checksum_type`, documented below.
+    specified with `iso_checksum_type`, documented below. Also can be url that
+    contains checksum file with `iso_checksum_type` type.
 
 -   `iso_checksum_type` (string) - The type of the checksum specified in
     `iso_checksum`. Valid values are "none", "md5", "sha1", "sha256", or

website/source/docs/builders/qemu.html.markdown

@@ -83,7 +83,8 @@ builder.
 -   `iso_checksum` (string) - The checksum for the OS ISO file. Because ISO
     files are so large, this is required and Packer will verify it prior to
     booting a virtual machine with the ISO attached. The type of the checksum is
-    specified with `iso_checksum_type`, documented below.
+    specified with `iso_checksum_type`, documented below. Also can be url that
+    contains checksum file with `iso_checksum_type` type.
 
 -   `iso_checksum_type` (string) - The type of the checksum specified in
     `iso_checksum`. Valid values are "md5", "sha1", "sha256", or

website/source/docs/builders/virtualbox-iso.html.markdown

@@ -57,7 +57,8 @@ builder.
 -   `iso_checksum` (string) - The checksum for the OS ISO file. Because ISO
     files are so large, this is required and Packer will verify it prior to
     booting a virtual machine with the ISO attached. The type of the checksum is
-    specified with `iso_checksum_type`, documented below.
+    specified with `iso_checksum_type`, documented below. Also can be url that
+    contains checksum file with `iso_checksum_type` type.
 
 -   `iso_checksum_type` (string) - The type of the checksum specified in
     `iso_checksum`. Valid values are "none", "md5", "sha1", "sha256", or

website/source/docs/builders/vmware-iso.html.markdown

@@ -60,7 +60,8 @@ builder.
 -   `iso_checksum` (string) - The checksum for the OS ISO file. Because ISO
     files are so large, this is required and Packer will verify it prior to
     booting a virtual machine with the ISO attached. The type of the checksum is
-    specified with `iso_checksum_type`, documented below.
+    specified with `iso_checksum_type`, documented below. Also can be url that
+    contains checksum file with `iso_checksum_type` type.
 
 -   `iso_checksum_type` (string) - The type of the checksum specified in
     `iso_checksum`. Valid values are "none", "md5", "sha1", "sha256", or