Add --value-stdin option to sops set

README.rst

@@ -1560,6 +1560,17 @@ The value must be formatted as json.
 
     $ sops set ~/git/svc/sops/example.yaml '["an_array"][1]' '{"uid1":null,"uid2":1000,"uid3":["bob"]}'
 
+You can also provide the value from a file or stdin:
+
+.. code:: sh
+
+    # Provide the value from a file
+    $ echo '{"uid1":null,"uid2":1000,"uid3":["bob"]}' > /tmp/example-value
+    $ sops set ~/git/svc/sops/example.yaml --value-file '["an_array"][1]' /tmp/example-value
+
+    # Provide the value from stdin
+    $ echo '{"uid1":null,"uid2":1000,"uid3":["bob"]}' | sops set ~/git/svc/sops/example.yaml --value-stdin '["an_array"][1]'
+
 Unset a sub-part in a document tree
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

cmd/sops/main.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	encodingjson "encoding/json"
 	"fmt"
+	"io"
 	"net"
 	"net/url"
 	"os"
@@ -1374,8 +1375,8 @@ func main() {
 		},
 		{
 			Name:      "set",
-			Usage:     `set a specific key or branch in the input document. value must be a json encoded string. eg. '/path/to/file ["somekey"][0] {"somevalue":true}'`,
-			ArgsUsage: `file index value`,
+			Usage:     `set a specific key or branch in the input document. value must be a JSON encoded string, for example '/path/to/file ["somekey"][0] {"somevalue":true}', or a path if --value-file is used, or omitted if --value-stdin is used`,
+			ArgsUsage: `file index [ value ]`,
 			Flags: append([]cli.Flag{
 				cli.StringFlag{
 					Name:  "input-type",
@@ -1387,7 +1388,11 @@ func main() {
 				},
 				cli.BoolFlag{
 					Name:  "value-file",
-					Usage: "treat 'value' as a file to read the actual value from (avoids leaking secrets in process listings)",
+					Usage: "treat 'value' as a file to read the actual value from (avoids leaking secrets in process listings). Mutually exclusive with --value-stdin",
+				},
+				cli.BoolFlag{
+					Name:  "value-stdin",
+					Usage: "treat 'value' as a file to read the actual value from (avoids leaking secrets in process listings). Mutually exclusive with --value-file",
 				},
 				cli.IntFlag{
 					Name:  "shamir-secret-sharing-threshold",
@@ -1411,8 +1416,17 @@ func main() {
 				if c.Bool("verbose") {
 					logging.SetLevel(logrus.DebugLevel)
 				}
-				if c.NArg() != 3 {
-					return common.NewExitError("Error: no file specified, or index and value are missing", codes.NoFileSpecified)
+				if c.Bool("value-file") && c.Bool("value-stdin") {
+					return common.NewExitError("Error: cannot use both --value-file and --value-stdin", codes.ErrorGeneric)
+				}
+				if c.Bool("value-stdin") {
+					if c.NArg() != 2 {
+						return common.NewExitError("Error: file specified, or index and value are missing. Need precisely 2 positional arguments since --value-stdin is used.", codes.NoFileSpecified)
+					}
+				} else {
+					if c.NArg() != 3 {
+						return common.NewExitError("Error: no file specified, or index and value are missing. Need precisely 3 positional arguments.", codes.NoFileSpecified)
+					}
 				}
 				fileName, err := filepath.Abs(c.Args()[0])
 				if err != nil {
@@ -1435,7 +1449,13 @@ func main() {
 				}
 
 				var data string
-				if c.Bool("value-file") {
+				if c.Bool("value-stdin") {
+					content, err := io.ReadAll(os.Stdin)
+					if err != nil {
+						return toExitError(err)
+					}
+					data = string(content)
+				} else if c.Bool("value-file") {
 					filename := c.Args()[2]
 					content, err := os.ReadFile(filename)
 					if err != nil {

functional-tests/src/lib.rs

@@ -538,6 +538,57 @@ bar: baz",
         panic!("Output JSON does not have the expected structure");
     }
 
+    #[test]
+    fn set_json_file_insert_with_value_stdin() {
+        let file_path = prepare_temp_file(
+            "test_set_json_file_insert_with_value_stdin.json",
+            r#"{"a": 2, "b": "ba"}"#.as_bytes(),
+        );
+        assert!(
+            Command::new(SOPS_BINARY_PATH)
+                .arg("encrypt")
+                .arg("-i")
+                .arg(file_path.clone())
+                .output()
+                .expect("Error running sops")
+                .status
+                .success(),
+            "sops didn't exit successfully"
+        );
+        // let value_file = prepare_temp_file("insert_value_file.json", r#"{"cc": "ccc"}"#.as_bytes());
+        let process = Command::new(SOPS_BINARY_PATH)
+            .arg("set")
+            .arg("--value-stdin")
+            .arg(file_path.clone())
+            .arg(r#"["c"]"#)
+            .stdin(Stdio::piped())
+            .stdout(Stdio::piped())
+            .spawn()
+            .expect("Error running sops");
+        write_to_stdin(&process, b"{\"cc\": \"ccc\"}");
+        let output = process.wait_with_output().expect("Failed to wait on sops");
+        println!(
+            "stdout: {}, stderr: {}",
+            String::from_utf8_lossy(&output.stdout),
+            String::from_utf8_lossy(&output.stderr)
+        );
+        assert!(output.status.success(), "sops didn't exit successfully");
+        let mut s = String::new();
+        File::open(file_path)
+            .unwrap()
+            .read_to_string(&mut s)
+            .unwrap();
+        let data: Value = serde_json::from_str(&s).expect("Error parsing sops's JSON output");
+        if let Value::Mapping(data) = data {
+            let a = data.get(&Value::String("c".to_owned())).unwrap();
+            if let &Value::Mapping(ref a) = a {
+                assert_encrypted!(&a, Value::String("cc".to_owned()));
+                return;
+            }
+        }
+        panic!("Output JSON does not have the expected structure");
+    }
+
     #[test]
     fn set_yaml_file_update() {
         let file_path = prepare_temp_file(