feat: support env variable substitution e.g. FOO=${MY_FOO_VAR}

go.mod

@@ -32,7 +32,7 @@ require (
 	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/stretchr/testify v1.8.4 // indirect
 	go.uber.org/multierr v1.11.0 // indirect
-	golang.org/x/sys v0.19.0 // indirect
-	golang.org/x/text v0.14.0 // indirect
+	golang.org/x/sys v0.20.0 // indirect
+	golang.org/x/text v0.15.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20240429193739-8cf5692501f6 // indirect
 )

go.sum

@@ -74,8 +74,12 @@ golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab/go.mod h1:oPkhp1MJrh7nUepCBc
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.19.0 h1:q5f1RH2jigJ1MoAWp2KTp3gm5zAGFUTarQZ5U386+4o=
 golang.org/x/sys v0.19.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/sys v0.20.0 h1:Od9JTbYCk261bKm4M/mw7AklTlFYIa0bIp9BgSm1S8Y=
+golang.org/x/sys v0.20.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/text v0.14.0 h1:ScX5w1eTa3QqT8oi6+ziP7dTV1S2+ALU0bI+0zXKWiQ=
 golang.org/x/text v0.14.0/go.mod h1:18ZOQIKpY8NJVqYksKHtTdi31H5itFRjB5/qKTNYzSU=
+golang.org/x/text v0.15.0 h1:h1V/4gjBv8v9cjcR6+AR5+/cIYK5N/WAgiv4xlsEtAk=
+golang.org/x/text v0.15.0/go.mod h1:18ZOQIKpY8NJVqYksKHtTdi31H5itFRjB5/qKTNYzSU=
 golang.org/x/tools v0.20.0 h1:hz/CVckiOxybQvFw6h7b/q80NTr9IUQb4s1IIzW7KNY=
 golang.org/x/tools v0.20.0/go.mod h1:WvitBU7JJf6A4jOdg4S1tviW9bhUxkgeCui/0JHctQg=
 google.golang.org/genproto/googleapis/api v0.0.0-20240429193739-8cf5692501f6 h1:DTJM0R8LECCgFeUwApvcEJHz85HLagW8uRENYxHh1ww=

internal/orchestrator/repo/env.go

@@ -0,0 +1,18 @@
+package repo
+
+import (
+	"os"
+	"regexp"
+)
+
+var (
+	envVarSubstRegex = regexp.MustCompile(`\${[^}]*}`)
+)
+
+// ExpandEnv expands environment variables of the form ${VAR} in a string.
+func ExpandEnv(s string) string {
+	return envVarSubstRegex.ReplaceAllStringFunc(s, func(match string) string {
+		e, _ := os.LookupEnv(match[2 : len(match)-1])
+		return e
+	})
+}

internal/orchestrator/repo/repo.go

@@ -59,7 +59,9 @@ func NewRepoOrchestrator(config *v1.Config, repoConfig *v1.Repo, resticPath stri
 	}
 
 	if env := repoConfig.GetEnv(); len(env) != 0 {
-		opts = append(opts, restic.WithEnv(repoConfig.GetEnv()...))
+		for _, e := range env {
+			opts = append(opts, restic.WithEnv(ExpandEnv(e)))
+		}
 	}
 
 	repo := restic.NewRepo(resticPath, repoConfig.GetUri(), opts...)

internal/orchestrator/repo/repo_test.go

@@ -2,7 +2,9 @@ package repo
 
 import (
 	"context"
+	"os"
 	"slices"
+	"strings"
 	"testing"
 
 	v1 "github.com/garethgeorge/backrest/gen/go/v1"
@@ -140,3 +142,51 @@ func TestSnapshotParenting(t *testing.T) {
 		t.Errorf("expected 8 snapshots, got %d", len(snapshots))
 	}
 }
+
+func TestEnvVarPropagation(t *testing.T) {
+	t.Parallel()
+
+	repo := t.TempDir()
+	testData := test.CreateTestData(t)
+
+	// create a new repo with cache disabled for testing
+	r := &v1.Repo{
+		Id:       "test",
+		Uri:      repo,
+		Password: "test",
+		Flags:    []string{"--no-cache"},
+		Env:      []string{"RESTIC_PASSWORD=${MY_FOO}"},
+	}
+
+	plan := &v1.Plan{
+		Id:    "test",
+		Repo:  "test",
+		Paths: []string{testData},
+	}
+
+	orchestrator, err := NewRepoOrchestrator(configForTest, r, helpers.ResticBinary(t))
+	if err != nil {
+		t.Fatalf("failed to create repo orchestrator: %v", err)
+	}
+
+	_, err = orchestrator.Backup(context.Background(), plan, nil)
+	if err == nil || !strings.Contains(err.Error(), "an empty password is not a password") {
+		t.Fatalf("expected error about RESTIC_PASSWORD, got: %v", err)
+	}
+
+	// set the env var
+	os.Setenv("MY_FOO", "bar")
+	orchestrator, err = NewRepoOrchestrator(configForTest, r, helpers.ResticBinary(t))
+	if err != nil {
+		t.Fatalf("failed to create repo orchestrator: %v", err)
+	}
+
+	summary, err := orchestrator.Backup(context.Background(), plan, nil)
+	if err != nil {
+		t.Fatalf("backup error: %v", err)
+	}
+
+	if summary.SnapshotId == "" {
+		t.Fatal("expected snapshot id")
+	}
+}

webui/src/views/AddRepoModal.tsx

@@ -282,63 +282,65 @@ export const AddRepoModal = ({
           </Tooltip>
 
           {/* Repo.env */}
-          <Form.Item label="Env Vars">
-            <Form.List
-              name="env"
-              rules={[
-                {
-                  validator: async (_, envVars) => {
-                    return await envVarSetValidator(form, envVars);
+          <Tooltip title={"Environment variables that are passed to restic (e.g. to provide S3 or B2 credentials). References to parent-process env variables are supported as FOO=${MY_FOO_VAR}."}>
+            <Form.Item label="Env Vars">
+              <Form.List
+                name="env"
+                rules={[
+                  {
+                    validator: async (_, envVars) => {
+                      return await envVarSetValidator(form, envVars);
+                    },
                   },
-                },
-              ]}
-            >
-              {(fields, { add, remove }, { errors }) => (
-                <>
-                  {fields.map((field, index) => (
-                    <Form.Item key={field.key}>
-                      <Form.Item
-                        {...field}
-                        validateTrigger={["onChange", "onBlur"]}
-                        rules={[
-                          {
-                            required: true,
-                            whitespace: true,
-                            pattern: /^[\w-]+=.*$/,
-                            message:
-                              "Environment variable must be in format KEY=VALUE",
-                          },
-                        ]}
-                        noStyle
-                      >
-                        <Input
-                          placeholder="KEY=VALUE"
-                          onBlur={() => form.validateFields()}
-                          style={{ width: "90%" }}
+                ]}
+              >
+                {(fields, { add, remove }, { errors }) => (
+                  <>
+                    {fields.map((field, index) => (
+                      <Form.Item key={field.key}>
+                        <Form.Item
+                          {...field}
+                          validateTrigger={["onChange", "onBlur"]}
+                          rules={[
+                            {
+                              required: true,
+                              whitespace: true,
+                              pattern: /^[\w-]+=.*$/,
+                              message:
+                                "Environment variable must be in format KEY=VALUE",
+                            },
+                          ]}
+                          noStyle
+                        >
+                          <Input
+                            placeholder="KEY=VALUE"
+                            onBlur={() => form.validateFields()}
+                            style={{ width: "90%" }}
+                          />
+                        </Form.Item>
+                        <MinusCircleOutlined
+                          className="dynamic-delete-button"
+                          onClick={() => remove(index)}
+                          style={{ paddingLeft: "5px" }}
                         />
                       </Form.Item>
-                      <MinusCircleOutlined
-                        className="dynamic-delete-button"
-                        onClick={() => remove(index)}
-                        style={{ paddingLeft: "5px" }}
-                      />
+                    ))}
+                    <Form.Item>
+                      <Button
+                        type="dashed"
+                        onClick={() => add("")}
+                        style={{ width: "90%" }}
+                        icon={<PlusOutlined />}
+                      >
+                        Set Environment Variable
+                      </Button>
+                      <Form.ErrorList errors={errors} />
                     </Form.Item>
-                  ))}
-                  <Form.Item>
-                    <Button
-                      type="dashed"
-                      onClick={() => add("")}
-                      style={{ width: "90%" }}
-                      icon={<PlusOutlined />}
-                    >
-                      Set Environment Variable
-                    </Button>
-                    <Form.ErrorList errors={errors} />
-                  </Form.Item>
-                </>
-              )}
-            </Form.List>
-          </Form.Item>
+                  </>
+                )}
+              </Form.List>
+            </Form.Item>
+          </Tooltip>
 
           {/* Repo.flags */}
           <Form.Item label="Flags">