os/exec: fix escaped quote inside the same quote

Shell quote is a hell of complex.  For example, one can write
shell that execute command that contains quote,

  sh -c "psql -c 'CREATE ... IDENTIFIED BY PASSWORD '\''pass'\'''"

or to simplify,

  sh -c "psql -c \"CREATE ... IDENTIFIED BY PASSWORD 'pass'\""

2 files changed, 43 insertions, 13 deletions

diff --git a/lib/os/exec/exec.go b/lib/os/exec/exec.go
index 0fed245c..1f6f52cf 100644
--- a/lib/os/exec/exec.go
+++ b/lib/os/exec/exec.go
@@ -32,17 +32,31 @@ func ParseCommandArgs(in string) (cmd string, args []string) {
 	for _, r := range in {
 		if quote > 0 {
 			if r == quote {
-				arg := sb.String()
-				if len(arg) > 0 {
-					cmdArgs = append(cmdArgs, sb.String())
+				if prev == '\\' {
+					sb.WriteRune(r)
+					prev = r
+				} else {
+					arg := sb.String()
+					if len(arg) > 0 {
+						cmdArgs = append(cmdArgs, sb.String())
+					}
+					sb.Reset()
+					quote = 0
+				}
+			} else if r == '\\' {
+				if prev == '\\' {
+					sb.WriteRune(r)
+					prev = 0
+				} else {
+					prev = r
 				}
-
-				sb.Reset()
-				quote = 0
 			} else {
+				if prev == '\\' {
+					sb.WriteRune('\\')
+				}
 				sb.WriteRune(r)
+				prev = r
 			}
-			prev = r
 			continue
 		}
 		if r == '\'' || r == '"' || r == '`' {
diff --git a/lib/os/exec/exec_test.go b/lib/os/exec/exec_test.go
index 38e089d0..d0da6e48 100644
--- a/lib/os/exec/exec_test.go
+++ b/lib/os/exec/exec_test.go
@@ -42,17 +42,33 @@ func TestParseCommandArg(t *testing.T) {
 		expCmd:  `a`,
 		expArgs: []string{`b'c`},
 	}, {
-		in: `a\ b c\ d`,
-		expCmd: "a b",
+		in:      `a\ b c\ d`,
+		expCmd:  "a b",
 		expArgs: []string{"c d"},
 	}, {
-		in: `a\\ b c\\ d`,
-		expCmd: `a\`,
+		in:      `a\\ b c\\ d`,
+		expCmd:  `a\`,
 		expArgs: []string{"b", `c\`, "d"},
 	}, {
-		in: `a\\\ b c\\\ d`,
-		expCmd: `a\ b`,
+		in:      `a\\\ b c\\\ d`,
+		expCmd:  `a\ b`,
 		expArgs: []string{`c\ d`},
+	}, {
+		in:      `sh -c "echo \"a\""`,
+		expCmd:  "sh",
+		expArgs: []string{`-c`, `echo "a"`},
+	}, {
+		in:      `sh -c "sh -c \"echo 'a\x'\""`,
+		expCmd:  "sh",
+		expArgs: []string{`-c`, `sh -c "echo 'a\x'"`},
+	}, {
+		in:      `sh -c "sh -c \"echo 'a'\'''\""`,
+		expCmd:  "sh",
+		expArgs: []string{`-c`, `sh -c "echo 'a'\'''"`},
+	}, {
+		in:      `sh -c "sh -c \"echo 'a\\\"'\""`,
+		expCmd:  "sh",
+		expArgs: []string{`-c`, `sh -c "echo 'a\"'"`},
 	}}
 
 	for _, c := range cases {