1 files changed, 138 insertions, 0 deletions
diff --git a/src/lib/encoding/cstring.c b/src/lib/encoding/cstring.c
new file mode 100644
index 0000000000..29d3714126
--- /dev/null
+++ b/src/lib/encoding/cstring.c
@@ -0,0 +1,138 @@
+/* Copyright (c) 2001 Matej Pfajfar.
+ * Copyright (c) 2001-2004, Roger Dingledine.
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2019, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file cstring.c
+ *
+ * \brief Decode data that has been written as a C literal.
+ **/
+
+#include "lib/encoding/cstring.h"
+#include "lib/log/log.h"
+#include "lib/log/util_bug.h"
+#include "lib/malloc/malloc.h"
+#include "lib/string/compat_ctype.h"
+
+#include <string.h>
+
+#define TOR_ISODIGIT(c) ('0' <= (c) && (c) <= '7')
+
+/** Given a c-style double-quoted escaped string in <b>s</b>, extract and
+ * decode its contents into a newly allocated string.  On success, assign this
+ * string to *<b>result</b>, assign its length to <b>size_out</b> (if
+ * provided), and return a pointer to the position in <b>s</b> immediately
+ * after the string.  On failure, return NULL.
+ */
+const char *
+unescape_string(const char *s, char **result, size_t *size_out)
+{
+  const char *cp;
+  char *out;
+  if (s[0] != '\"')
+    return NULL;
+  cp = s+1;
+  while (1) {
+    switch (*cp) {
+      case '\0':
+      case '\n':
+        return NULL;
+      case '\"':
+        goto end_of_loop;
+      case '\\':
+        if (cp[1] == 'x' || cp[1] == 'X') {
+          if (!(TOR_ISXDIGIT(cp[2]) && TOR_ISXDIGIT(cp[3])))
+            return NULL;
+          cp += 4;
+        } else if (TOR_ISODIGIT(cp[1])) {
+          cp += 2;
+          if (TOR_ISODIGIT(*cp)) ++cp;
+          if (TOR_ISODIGIT(*cp)) ++cp;
+        } else if (cp[1] == 'n' || cp[1] == 'r' || cp[1] == 't' || cp[1] == '"'
+                   || cp[1] == '\\' || cp[1] == '\'') {
+          cp += 2;
+        } else {
+          return NULL;
+        }
+        break;
+      default:
+        ++cp;
+        break;
+    }
+  }
+ end_of_loop:
+  out = *result = tor_malloc(cp-s + 1);
+  cp = s+1;
+  while (1) {
+    switch (*cp)
+      {
+      case '\"':
+        *out = '\0';
+        if (size_out) *size_out = out - *result;
+        return cp+1;
+
+        /* LCOV_EXCL_START -- we caught this in parse_config_from_line. */
+      case '\0':
+        tor_fragile_assert();
+        tor_free(*result);
+        return NULL;
+        /* LCOV_EXCL_STOP */
+      case '\\':
+        switch (cp[1])
+          {
+          case 'n': *out++ = '\n'; cp += 2; break;
+          case 'r': *out++ = '\r'; cp += 2; break;
+          case 't': *out++ = '\t'; cp += 2; break;
+          case 'x': case 'X':
+            {
+              int x1, x2;
+
+              x1 = hex_decode_digit(cp[2]);
+              x2 = hex_decode_digit(cp[3]);
+              if (x1 == -1 || x2 == -1) {
+                /* LCOV_EXCL_START */
+                /* we caught this above in the initial loop. */
+                tor_assert_nonfatal_unreached();
+                tor_free(*result);
+                return NULL;
+                /* LCOV_EXCL_STOP */
+              }
+
+              *out++ = ((x1<<4) + x2);
+              cp += 4;
+            }
+            break;
+          case '0': case '1': case '2': case '3': case '4': case '5':
+          case '6': case '7':
+            {
+              int n = cp[1]-'0';
+              cp += 2;
+              if (TOR_ISODIGIT(*cp)) { n = n*8 + *cp-'0'; cp++; }
+              if (TOR_ISODIGIT(*cp)) { n = n*8 + *cp-'0'; cp++; }
+              if (n > 255) { tor_free(*result); return NULL; }
+              *out++ = (char)n;
+            }
+            break;
+          case '\'':
+          case '\"':
+          case '\\':
+          case '\?':
+            *out++ = cp[1];
+            cp += 2;
+            break;
+
+            /* LCOV_EXCL_START */
+          default:
+            /* we caught this above in the initial loop. */
+            tor_assert_nonfatal_unreached();
+            tor_free(*result); return NULL;
+            /* LCOV_EXCL_STOP */
+          }
+        break;
+      default:
+        *out++ = *cp++;
+      }
+  }
+}