Merge pull request #6113 from keszybz/shell-quoting

Use "dollar-single-quotes" to escape shell-sensitive strings

src/basic/escape.c

@@ -441,10 +441,16 @@ char *octescape(const char *s, size_t len) {
 
 }
 
-static char *strcpy_backslash_escaped(char *t, const char *s, const char *bad) {
+static char *strcpy_backslash_escaped(char *t, const char *s, const char *bad, bool escape_tab_nl) {
         assert(bad);
 
         for (; *s; s++) {
+                if (escape_tab_nl && IN_SET(*s, '\n', '\t')) {
+                        *(t++) = '\\';
+                        *(t++) = *s == '\n' ? 'n' : 't';
+                        continue;
+                }
+
                 if (*s == '\\' || strchr(bad, *s))
                         *(t++) = '\\';
 
@@ -461,20 +467,21 @@ char *shell_escape(const char *s, const char *bad) {
         if (!r)
                 return NULL;
 
-        t = strcpy_backslash_escaped(r, s, bad);
+        t = strcpy_backslash_escaped(r, s, bad, false);
         *t = 0;
 
         return r;
 }
 
-char *shell_maybe_quote(const char *s) {
+char* shell_maybe_quote(const char *s, EscapeStyle style) {
         const char *p;
         char *r, *t;
 
         assert(s);
 
-        /* Encloses a string in double quotes if necessary to make it
-         * OK as shell string. */
+        /* Encloses a string in quotes if necessary to make it OK as a shell
+         * string. Note that we treat benign UTF-8 characters as needing
+         * escaping too, but that should be OK. */
 
         for (p = s; *p; p++)
                 if (*p <= ' ' ||
@@ -485,17 +492,30 @@ char *shell_maybe_quote(const char *s) {
         if (!*p)
                 return strdup(s);
 
-        r = new(char, 1+strlen(s)*2+1+1);
+        r = new(char, (style == ESCAPE_POSIX) + 1 + strlen(s)*2 + 1 + 1);
         if (!r)
                 return NULL;
 
         t = r;
-        *(t++) = '"';
+        if (style == ESCAPE_BACKSLASH)
+                *(t++) = '"';
+        else if (style == ESCAPE_POSIX) {
+                *(t++) = '$';
+                *(t++) = '\'';
+        } else
+                assert_not_reached("Bad EscapeStyle");
+
         t = mempcpy(t, s, p - s);
 
-        t = strcpy_backslash_escaped(t, p, SHELL_NEED_ESCAPE);
+        if (style == ESCAPE_BACKSLASH)
+                t = strcpy_backslash_escaped(t, p, SHELL_NEED_ESCAPE, false);
+        else
+                t = strcpy_backslash_escaped(t, p, SHELL_NEED_ESCAPE_POSIX, true);
 
-        *(t++)= '"';
+        if (style == ESCAPE_BACKSLASH)
+                *(t++) = '"';
+        else
+                *(t++) = '\'';
         *t = 0;
 
         return r;

src/basic/escape.h

@@ -31,13 +31,30 @@
 /* What characters are special in the shell? */
 /* must be escaped outside and inside double-quotes */
 #define SHELL_NEED_ESCAPE "\"\\`$"
-/* can be escaped or double-quoted */
-#define SHELL_NEED_QUOTES SHELL_NEED_ESCAPE GLOB_CHARS "'()<>|&;"
+
+/* Those that can be escaped or double-quoted.
+ *
+ * Stricly speaking, ! does not need to be escaped, except in interactive
+ * mode, but let's be extra nice to the user and quote ! in case this
+ * output is ever used in interactive mode. */
+#define SHELL_NEED_QUOTES SHELL_NEED_ESCAPE GLOB_CHARS "'()<>|&;!"
+
+/* Note that we assume control characters would need to be escaped too in
+ * addition to the "special" characters listed here, if they appear in the
+ * string. Current users disallow control characters. Also '"' shall not
+ * be escaped.
+ */
+#define SHELL_NEED_ESCAPE_POSIX "\\\'"
 
 typedef enum UnescapeFlags {
         UNESCAPE_RELAX = 1,
 } UnescapeFlags;
 
+typedef enum EscapeStyle {
+        ESCAPE_BACKSLASH = 1,
+        ESCAPE_POSIX = 2,
+} EscapeStyle;
+
 char *cescape(const char *s);
 char *cescape_length(const char *s, size_t n);
 size_t cescape_char(char c, char *buf);
@@ -51,4 +68,4 @@ char *xescape(const char *s, const char *bad);
 char *octescape(const char *s, size_t len);
 
 char *shell_escape(const char *s, const char *bad);
-char *shell_maybe_quote(const char *s);
+char* shell_maybe_quote(const char *s, EscapeStyle style);