Add DecodeBase32 to redbean

jart · Oct 11, 2023 · 82e6a4e · 82e6a4e
1 parent 9abacaa
commit 82e6a4e
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Showing 7 changed files with 129 additions and 15 deletions.
diff --git a/net/http/base32.c b/net/http/base32.c
@@ -33,32 +33,40 @@ int tobits(int b) {
   return bits;
 }
 
-// the next function is based on
+// these functions are based on
 // https://github.com/google/google-authenticator-libpam/blob/master/src/base32.c
 // Copyright 2010 Google Inc.; Author: Markus Gutschke
 // licensed under Apache License, Version 2.0
+
+/**
+ * Encodes binary to base32 ascii representation.
+ *
+ * @param s is input value
+ * @param sl if -1 implies strlen
+ * @param a is alphabet string (with power of 2 length)
+ * @param al is alphabet length (if 0 then Crockford's encoding is used)
+ * @param ol if non-NULL receives output length
+ * @return allocated NUL-terminated buffer, or NULL w/ errno
+ */
 char* EncodeBase32(const char *s, size_t sl,
                    const char *a, size_t al,
                    size_t *ol) {
   size_t count = 0;
-  char *r;
+  char *r = NULL;
+  if (sl == -1) sl = s ? strlen(s) : 0;
   if (al == 0) {
     a = base32def;
     al = sizeof(base32def)/sizeof(a[0]);
   }
   unassert(2 <= al && al <= 128);
   int bl = tobits(al);
   int mask = (1 << bl) - 1;
-  *ol = (sl * 8 + bl - 1) / bl; // calculate exact output length
-  if (!(r = malloc(*ol + 1))) {
-    *ol = 0;
-    return r;
-  }
-  if (sl > 0) {
+  size_t n = (sl * 8 + bl - 1) / bl; // calculate output length
+  if ((r = malloc(n + 1))) {
     int buffer = s[0];
     size_t next = 1;
     int bitsLeft = 8;
-    while (count < *ol && (bitsLeft > 0 || next < sl)) {
+    while (count < n && (bitsLeft > 0 || next < sl)) {
       if (bitsLeft < bl) {
         if (next < sl) {
           buffer <<= 8;
@@ -73,7 +81,85 @@ char* EncodeBase32(const char *s, size_t sl,
       bitsLeft -= bl;
       r[count++] = a[mask & (buffer >> bitsLeft)];
     }
+    r[count] = '\0';
+  }
+  if (ol) *ol = r ? count : 0;
+  return r;
+}
+
+static signed char kBase32cust[256];
+static signed char kBase32[256] = {
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -1, -1, -2, -1, -1,  // 0x00
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  // 0x10
+    -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -1, -1,  // 0x20
+     0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1,  // 0x30
+    -1, 10, 11, 12, 13, 14, 15, 16, 17,  1, 18, 19,  1, 20, 21, -1,  // 0x40
+    22, 23, 24, 25, 26,  0, 27, 28, 29, 30, 31, -1, -1, -1, -1, -1,  // 0x50
+    -1, 10, 11, 12, 13, 14, 15, 16, 17,  1, 18, 19,  1, 20, 21, -1,  // 0x60
+    22, 23, 24, 25, 26,  0, 27, 28, 29, 30, 31, -1, -1, -1, -1, -1,  // 0x70
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  // 0x80
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  // 0x90
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  // 0xa0
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  // 0xb0
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  // 0xc0
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  // 0xd0
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  // 0xe0
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  // 0xf0
+};
+
+/**
+ * Decodes base32 ascii representation to binary.
+ *
+ * This uses Crockford's encoding and skips whitespaces.
+ * The decoding stops at the first character not in the alphabet.
+ *
+ * @param s is input value
+ * @param sl if -1 implies strlen
+ * @param a is alphabet string (with power of 2 length)
+ * @param al is alphabet length (if 0 then Crockford's encoding is used)
+ * @param ol if non-NULL receives output length
+ * @return allocated NUL-terminated buffer, or NULL w/ errno
+ */
+char* DecodeBase32(const char *s, size_t sl,
+                   const char *a, size_t al,
+                   size_t *ol) {
+  size_t count = 0;
+  char *r = NULL;
+  if (sl == -1) sl = s ? strlen(s) : 0;
+  if (al == 0) {
+    a = base32def;
+    al = sizeof(base32def)/sizeof(a[0]);
+  }
+  unassert(2 <= al && al <= 128);
+  int bl = tobits(al);
+  size_t n = (sl * bl + 1) / 8 + 1; // calculate output length
+  // process input
+  if ((r = malloc(n + 1))) {
+    unsigned int buffer = 0;
+    signed char *map = kBase32;
+    int bitsLeft = 0;
+
+    if (a != base32def) {
+      // if the provided alphabet doesn't match the default
+      map = kBase32cust;
+      memset(map, -1, 256);
+      // populate the map based on alphabet
+      for (int i = 0; i < al; i++) map[a[i] & 0xff] = i;
+    }
+    while (count < n && *s) {
+      signed char m = map[*s++ & 0xff];
+      if (m == -2) continue;
+      if (m == -1) break;
+      buffer <<= bl;
+      buffer |= m;
+      bitsLeft += bl;
+      if (bitsLeft >= 8) {
+        r[count++] = buffer >> (bitsLeft - 8);
+        bitsLeft -= 8;
+      }
+    }
+    r[count] = '\0';
   }
-  if (count < *ol) r[count] = '\000';
+  if (ol) *ol = r ? count : 0;
   return r;
 }
diff --git a/net/http/escape.h b/net/http/escape.h
@@ -35,6 +35,7 @@ char *EncodeHttpHeaderValue(const char *, size_t, size_t *);
 char *VisualizeControlCodes(const char *, size_t, size_t *);
 char *IndentLines(const char *, size_t, size_t *, size_t);
 char *EncodeBase32(const char *, size_t, const char *, size_t, size_t *);
+char *DecodeBase32(const char *, size_t, const char *, size_t, size_t *);
 char *EncodeBase64(const char *, size_t, size_t *);
 char *DecodeBase64(const char *, size_t, size_t *);
 

diff --git a/test/tool/net/lfuncs_test.lua b/test/tool/net/lfuncs_test.lua
@@ -55,6 +55,14 @@ assert(EncodeBase32("12") == "64s0")
 assert(EncodeBase32("\33", "01") == "00100001")
 assert(EncodeBase32("\33", "0123456789abcdef") == "21")
 
+assert(DecodeBase32("64s36d1n6r") == "123456")
+assert(DecodeBase32("64s0") == "12")
+assert(DecodeBase32("64 \t\r\ns0") == "12")
+assert(DecodeBase32("64s0!64s0") == "12")
+
+assert(EncodeBase32("\1\2\3\4\255", "0123456789abcdef") == "01020304ff")
+assert(DecodeBase32("01020304ff", "0123456789abcdef") == "\1\2\3\4\255")
+
 assert(EscapeHtml(nil) == nil)
 assert(EscapeHtml("?hello&there<>") == "?hello&amp;there&lt;&gt;")
 

diff --git a/tool/net/help.txt b/tool/net/help.txt
@@ -737,12 +737,20 @@ FUNCTIONS
           Turns ASCII base-16 hexadecimal byte string into binary string,
           case-insensitively. Non-hex characters may not appear in string.
 
+  DecodeBase32(ascii:str[, alphabet:str]) → binary:str
+          Turns ASCII into binary using provided alphabet. The default
+          decoding uses Crockford's base32 alphabet in a permissive way
+          that ignores whitespaces and dash ('-') and stops at the first
+          character outside of the alphabet.
+
   EncodeBase32(binary:str[, alphabet:str]) → ascii:str
           Turns binary into ASCII using provided alphabet (using Crockford's
-          base32 encoding by default).
+          base32 encoding by default). Any alphabet that has a power of 2
+          length (up to 128) may be supplied for encoding and decoding,
+          which allows to provide alternative base32 encodings.
 
   DecodeBase64(ascii:str) → binary:str
-          Turns ASCII into binary, in a permissive way that ignores
+          Turns ASCII into binary in a permissive way that ignores
           characters outside the base64 alphabet, such as whitespace. See
           decodebase64.c.
 

diff --git a/tool/net/lfuncs.c b/tool/net/lfuncs.c
@@ -605,21 +605,30 @@ int LuaEncodeLatin1(lua_State *L) {
   }
 }
 
-int LuaEncodeBase32(lua_State *L) {
+dontinline int LuaBase32Impl(lua_State *L,
+    char *B32(const char *, size_t, const char *, size_t, size_t *)) {
   char *p;
   size_t sl, al; // source/output and alphabet lengths
   const char *s = luaL_checklstring(L, 1, &sl);
   // use an empty string, as EncodeBase32 provides a default value
   const char *a = luaL_optlstring(L, 2, "", &al);
-  if (al & (al - 1) || al > 128 || al == 1)
+  if (!IS2POW(al) || al > 128 || al == 1)
     return luaL_error(L, "alphabet length is not a power of 2 in range 2..128");
-  if (!(p = EncodeBase32(s, sl, a, al, &sl)))
+  if (!(p = B32(s, sl, a, al, &sl)))
     return luaL_error(L, "out of memory");
   lua_pushlstring(L, p, sl);
   free(p);
   return 1;
 }
 
+int LuaEncodeBase32(lua_State *L) {
+  return LuaBase32Impl(L, EncodeBase32);
+}
+
+int LuaDecodeBase32(lua_State *L) {
+  return LuaBase32Impl(L, DecodeBase32);
+}
+
 int LuaEncodeHex(lua_State *L) {
   char *p;
   size_t n;

diff --git a/tool/net/lfuncs.h b/tool/net/lfuncs.h
@@ -20,6 +20,7 @@ int LuaCompress(lua_State *);
 int LuaCrc32(lua_State *);
 int LuaCrc32c(lua_State *);
 int LuaDecimate(lua_State *);
+int LuaDecodeBase32(lua_State *);
 int LuaDecodeBase64(lua_State *);
 int LuaDecodeHex(lua_State *);
 int LuaDecodeLatin1(lua_State *);

diff --git a/tool/net/redbean.c b/tool/net/redbean.c
@@ -5127,6 +5127,7 @@ static const luaL_Reg kLuaFuncs[] = {
     {"Crc32", LuaCrc32},                                        //
     {"Crc32c", LuaCrc32c},                                      //
     {"Decimate", LuaDecimate},                                  //
+    {"DecodeBase32", LuaDecodeBase32},                          //
     {"DecodeBase64", LuaDecodeBase64},                          //
     {"DecodeHex", LuaDecodeHex},                                //
     {"DecodeJson", LuaDecodeJson},                              //