encode.c

/*
** Copyright (c) 2006 D. Richard Hipp
**
** This program is free software; you can redistribute it and/or
** modify it under the terms of the Simplified BSD License (also
** known as the "2-Clause License" or "FreeBSD License".)

** This program is distributed in the hope that it will be useful,
** but without any warranty; without even the implied warranty of
** merchantability or fitness for a particular purpose.
**
** Author contact information:
**   drh@hwaci.com
**   http://www.hwaci.com/drh/
**
*******************************************************************************
**
** Routines for encoding and decoding text.
*/
#include "config.h"
#include "encode.h"

/*
** Make the given string safe for HTML by converting every "<" into "&lt;",
** every ">" into "&gt;" and every "&" into "&amp;".  Return a pointer
** to a new string obtained from malloc().
**
** We also encode " as &quot; so that it can appear as an argument
** to markup.
*/
char *htmlize(const char *zIn, int n){
  int c;
  int i = 0;
  int count = 0;
  char *zOut;

  if( n<0 ) n = strlen(zIn);
  while( i<n && (c = zIn[i])!=0 ){
    switch( c ){
      case '<':   count += 4;       break;
      case '>':   count += 4;       break;
      case '&':   count += 5;       break;
      case '"':   count += 6;       break;
      default:    count++;          break;
    }
    i++;
  }
  i = 0;
  zOut = fossil_malloc( count+1 );
  while( n-->0 && (c = *zIn)!=0 ){
    switch( c ){
      case '<':   
        zOut[i++] = '&';
        zOut[i++] = 'l';
        zOut[i++] = 't';
        zOut[i++] = ';';
        break;
      case '>':   
        zOut[i++] = '&';
        zOut[i++] = 'g';
        zOut[i++] = 't';
        zOut[i++] = ';';
        break;
      case '&':   
        zOut[i++] = '&';
        zOut[i++] = 'a';
        zOut[i++] = 'm';
        zOut[i++] = 'p';
        zOut[i++] = ';';
        break;
      case '"':   
        zOut[i++] = '&';
        zOut[i++] = 'q';
        zOut[i++] = 'u';
        zOut[i++] = 'o';
        zOut[i++] = 't';
        zOut[i++] = ';';
        break;
      default:
        zOut[i++] = c;
        break;
    }
    zIn++;
  }
  zOut[i] = 0;
  return zOut;
}


/*
** Encode a string for HTTP.  This means converting lots of
** characters into the "%HH" where H is a hex digit.  It also
** means converting spaces to "+".
**
** This is the opposite of DeHttpizeString below.
*/
static char *EncodeHttp(const char *zIn, int n, int encodeSlash){
  int c;
  int i = 0;
  int count = 0;
  char *zOut;
  int other;
# define IsSafeChar(X)  \
     (fossil_isalnum(X) || (X)=='.' || (X)=='$' \
      || (X)=='~' || (X)=='-' || (X)=='_' || (X)==other)

  if( zIn==0 ) return 0;
  if( n<0 ) n = strlen(zIn);
  other = encodeSlash ? 'a' : '/';
  while( i<n && (c = zIn[i])!=0 ){
    if( IsSafeChar(c) || c==' ' ){
      count++;
    }else{
      count += 3;
    }
    i++;
  }
  i = 0;
  zOut = fossil_malloc( count+1 );
  while( n-->0 && (c = *zIn)!=0 ){
    if( IsSafeChar(c) ){
      zOut[i++] = c;
    }else if( c==' ' ){
      zOut[i++] = '+';
    }else{
      zOut[i++] = '%';
      zOut[i++] = "0123456789ABCDEF"[(c>>4)&0xf];
      zOut[i++] = "0123456789ABCDEF"[c&0xf];
    }
    zIn++;
  }
  zOut[i] = 0;
  return zOut;
}

/*
** Convert the input string into a form that is suitable for use as
** a token in the HTTP protocol.  Spaces are encoded as '+' and special
** characters are encoded as "%HH" where HH is a two-digit hexidecimal
** representation of the character.  The "/" character is encoded
** as "%2F".
*/
char *httpize(const char *z, int n){
  return EncodeHttp(z, n, 1);
}

/*
** Convert the input string into a form that is suitable for use as
** a token in the HTTP protocol.  Spaces are encoded as '+' and special
** characters are encoded as "%HH" where HH is a two-digit hexidecimal
** representation of the character.  The "/" character is not encoded
** by this routine. 
*/
char *urlize(const char *z, int n){
  return EncodeHttp(z, n, 0);
}

/*
** Convert a single HEX digit to an integer
*/
static int AsciiToHex(int c){
  if( c>='a' && c<='f' ){
    c += 10 - 'a';
  }else if( c>='A' && c<='F' ){
    c += 10 - 'A';
  }else if( c>='0' && c<='9' ){
    c -= '0';
  }else{
    c = 0;
  }
  return c;
}

/*
** Remove the HTTP encodings from a string.  The conversion is done
** in-place.  Return the length of the string after conversion.
*/
int dehttpize(char *z){
  int i, j;

  /* Treat a null pointer as a zero-length string. */
  if( !z ) return 0;

  i = j = 0;
  while( z[i] ){
    switch( z[i] ){
      case '%':
        if( z[i+1] && z[i+2] ){
          z[j] = AsciiToHex(z[i+1]) << 4;
          z[j] |= AsciiToHex(z[i+2]);
          i += 2;
        }
        break;
      case '+':
        z[j] = ' ';
        break;
      default:
        z[j] = z[i];
        break;
    }
    i++;
    j++;
  }
  z[j] = 0;
  return j;
}

/*
** The "fossilize" encoding is used in the headers of records
** (aka "content files") to escape special characters.  The
** fossilize encoding passes most characters through unchanged.
** The changes are these:
**
**        space    ->   \s
**        tab      ->   \t
**        newline  ->   \n
**        cr       ->   \r
**        formfeed ->   \f
**        vtab     ->   \v
**        nul      ->   \0
**        \        ->   \\
**
** The fossilize() routine does an encoding of its input and
** returns a pointer to the encoding in space obtained from
** malloc.
*/
char *fossilize(const char *zIn, int nIn){
  int n, i, j, c;
  char *zOut;
  if( nIn<0 ) nIn = strlen(zIn);
  for(i=n=0; i<nIn; i++){
    c = zIn[i];
    if( c==0 || c==' ' || c=='\n' || c=='\t' || c=='\r' || c=='\f' || c=='\v'
             || c=='\\' ) n++;
  }
  n += nIn;
  zOut = fossil_malloc( n+1 );
  if( zOut ){
    for(i=j=0; i<nIn; i++){
      int c = zIn[i];
      if( c==0 ){
        zOut[j++] = '\\';
        zOut[j++] = '0';
      }else if( c=='\\' ){
        zOut[j++] = '\\';
        zOut[j++] = '\\';
      }else if( fossil_isspace(c) ){
        zOut[j++] = '\\';
        switch( c ){
          case '\n':  c = 'n'; break;
          case ' ':   c = 's'; break;
          case '\t':  c = 't'; break;
          case '\r':  c = 'r'; break;
          case '\v':  c = 'v'; break;
          case '\f':  c = 'f'; break;
        }
        zOut[j++] = c;
      }else{
        zOut[j++] = c;
      }
    }
    zOut[j] = 0;
  }
  return zOut;
}

/*
** Decode a fossilized string in-place.
*/
void defossilize(char *z){
  int i, j, c;
  for(i=0; (c=z[i])!=0 && c!='\\'; i++){}
  if( c==0 ) return;
  for(j=i; (c=z[i])!=0; i++){
    if( c=='\\' && z[i+1] ){
      i++;
      switch( z[i] ){
        case 'n':  c = '\n';  break;
        case 's':  c = ' ';   break;
        case 't':  c = '\t';  break;
        case 'r':  c = '\r';  break;
        case 'v':  c = '\v';  break;
        case 'f':  c = '\f';  break;
        case '0':  c = 0;     break;
        case '\\': c = '\\';  break;
        default:   c = z[i];  break;
      }
    }
    z[j++] = c;
  }
  if( z[j] ) z[j] = 0;
}


/*
** The characters used for HTTP base64 encoding.
*/
static unsigned char zBase[] = 
  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

/*
** Encode a string using a base-64 encoding.
** The encoding can be reversed using the <b>decode64</b> function.
**
** Space to hold the result comes from malloc().
*/
char *encode64(const char *zData, int nData){
  char *z64;
  int i, n;

  if( nData<=0 ){
    nData = strlen(zData);
  }
  z64 = fossil_malloc( (nData*4)/3 + 8 );
  for(i=n=0; i+2<nData; i+=3){
    z64[n++] = zBase[ (zData[i]>>2) & 0x3f ];
    z64[n++] = zBase[ ((zData[i]<<4) & 0x30) | ((zData[i+1]>>4) & 0x0f) ];
    z64[n++] = zBase[ ((zData[i+1]<<2) & 0x3c) | ((zData[i+2]>>6) & 0x03) ];
    z64[n++] = zBase[ zData[i+2] & 0x3f ];
  }
  if( i+1<nData ){
    z64[n++] = zBase[ (zData[i]>>2) & 0x3f ];
    z64[n++] = zBase[ ((zData[i]<<4) & 0x30) | ((zData[i+1]>>4) & 0x0f) ];
    z64[n++] = zBase[ ((zData[i+1]<<2) & 0x3c) ];
    z64[n++] = '=';
  }else if( i<nData ){
    z64[n++] = zBase[ (zData[i]>>2) & 0x3f ];
    z64[n++] = zBase[ ((zData[i]<<4) & 0x30) ];
    z64[n++] = '=';
    z64[n++] = '=';
  }
  z64[n] = 0;
  return z64;
}

/*
** COMMAND: test-encode64 
** Usage: %fossil test-encode64 STRING
*/
void test_encode64_cmd(void){
  char *z;
  int i;
  for(i=2; i<g.argc; i++){
    z = encode64(g.argv[i], -1);
    fossil_print("%s\n", z);
    free(z);
  }
}


/*
** This function treats its input as a base-64 string and returns the
** decoded value of that string.  Characters of input that are not
** valid base-64 characters (such as spaces and newlines) are ignored.
**
** Space to hold the decoded string is obtained from malloc().
**
** The number of bytes decoded is returned in *pnByte
*/
char *decode64(const char *z64, int *pnByte){
  char *zData;
  int n64;
  int i, j;
  int a, b, c, d;
  static int isInit = 0;
  static int trans[128];

  if( !isInit ){
    for(i=0; i<128; i++){ trans[i] = 0; }
    for(i=0; zBase[i]; i++){ trans[zBase[i] & 0x7f] = i; }
    isInit = 1;
  }
  n64 = strlen(z64);
  while( n64>0 && z64[n64-1]=='=' ) n64--;
  zData = fossil_malloc( (n64*3)/4 + 4 );
  for(i=j=0; i+3<n64; i+=4){
    a = trans[z64[i] & 0x7f];
    b = trans[z64[i+1] & 0x7f];
    c = trans[z64[i+2] & 0x7f];
    d = trans[z64[i+3] & 0x7f];
    zData[j++] = ((a<<2) & 0xfc) | ((b>>4) & 0x03);
    zData[j++] = ((b<<4) & 0xf0) | ((c>>2) & 0x0f);
    zData[j++] = ((c<<6) & 0xc0) | (d & 0x3f);
  }
  if( i+2<n64 ){
    a = trans[z64[i] & 0x7f];
    b = trans[z64[i+1] & 0x7f];
    c = trans[z64[i+2] & 0x7f];
    zData[j++] = ((a<<2) & 0xfc) | ((b>>4) & 0x03);
    zData[j++] = ((b<<4) & 0xf0) | ((c>>2) & 0x0f);
  }else if( i+1<n64 ){
    a = trans[z64[i] & 0x7f];
    b = trans[z64[i+1] & 0x7f];
    zData[j++] = ((a<<2) & 0xfc) | ((b>>4) & 0x03);
  }
  zData[j] = 0;
  *pnByte = j;
  return zData;
}

/*
** COMMAND: test-decode64 
** Usage: %fossil test-decode64 STRING
*/
void test_decode64_cmd(void){
  char *z;
  int i, n;
  for(i=2; i<g.argc; i++){
    z = decode64(g.argv[i], &n);
    fossil_print("%d: %s\n", n, z);
    free(z);
  }
}

/*
** The base-16 encoding using the following characters:
**
**         0123456789abcdef
**
*/

/*
** The array used for encoding
*/                           /* 123456789 12345  */
static const char zEncode[] = "0123456789abcdef"; 

/*
** Encode a N-digit base-256 in base-16.  Return zero on success
** and non-zero if there is an error.
*/
int encode16(const unsigned char *pIn, unsigned char *zOut, int N){
  int i;
  for(i=0; i<N; i++){
    *(zOut++) = zEncode[pIn[i]>>4];
    *(zOut++) = zEncode[pIn[i]&0xf];
  }
  *zOut = 0;
  return 0;
}

/*
** An array for translating single base-16 characters into a value.
** Disallowed input characters have a value of 64.  Upper and lower
** case is the same. 
*/
static const char zDecode[] = {
  64, 64, 64, 64, 64, 64, 64, 64,  64, 64, 64, 64, 64, 64, 64, 64, 
  64, 64, 64, 64, 64, 64, 64, 64,  64, 64, 64, 64, 64, 64, 64, 64, 
  64, 64, 64, 64, 64, 64, 64, 64,  64, 64, 64, 64, 64, 64, 64, 64, 
   0,  1,  2,  3,  4,  5,  6,  7,   8,  9, 64, 64, 64, 64, 64, 64, 
  64, 10, 11, 12, 13, 14, 15, 64,  64, 64, 64, 64, 64, 64, 64, 64,
  64, 64, 64, 64, 64, 64, 64, 64,  64, 64, 64, 64, 64, 64, 64, 64,
  64, 10, 11, 12, 13, 14, 15, 64,  64, 64, 64, 64, 64, 64, 64, 64,
  64, 64, 64, 64, 64, 64, 64, 64,  64, 64, 64, 64, 64, 64, 64, 64,
  64, 64, 64, 64, 64, 64, 64, 64,  64, 64, 64, 64, 64, 64, 64, 64, 
  64, 64, 64, 64, 64, 64, 64, 64,  64, 64, 64, 64, 64, 64, 64, 64, 
  64, 64, 64, 64, 64, 64, 64, 64,  64, 64, 64, 64, 64, 64, 64, 64, 
  64, 64, 64, 64, 64, 64, 64, 64,  64, 64, 64, 64, 64, 64, 64, 64, 
  64, 64, 64, 64, 64, 64, 64, 64,  64, 64, 64, 64, 64, 64, 64, 64, 
  64, 64, 64, 64, 64, 64, 64, 64,  64, 64, 64, 64, 64, 64, 64, 64, 
  64, 64, 64, 64, 64, 64, 64, 64,  64, 64, 64, 64, 64, 64, 64, 64, 
  64, 64, 64, 64, 64, 64, 64, 64,  64, 64, 64, 64, 64, 64, 64, 64, 
};

/*
** Decode a N-character base-16 number into base-256.  N must be a 
** multiple of 2.  The output buffer must be at least N/2 characters
** in length
*/
int decode16(const unsigned char *zIn, unsigned char *pOut, int N){
  int i, j;
  if( (N&1)!=0 ) return 1;
  for(i=j=0; i<N; i += 2, j++){
    int v1, v2, a;
    a = zIn[i];
    if( (a & 0x80)!=0 || (v1 = zDecode[a])==64 ) return 1;
    a = zIn[i+1];
    if( (a & 0x80)!=0 || (v2 = zDecode[a])==64 ) return 1;
    pOut[j] = (v1<<4) + v2;
  }
  return 0;
}


/*
** Return true if the input string contains only valid base-16 digits.
** If any invalid characters appear in the string, return false.
*/
int validate16(const char *zIn, int nIn){
  int i;
  for(i=0; i<nIn; i++, zIn++){
    if( zDecode[zIn[0]&0xff]>63 ){
      return zIn[0]==0;
    }
  }
  return 1;
}

/*
** The input string is a base16 value.  Convert it into its canonical
** form.  This means that digits are all lower case and that conversions
** like "l"->"1" and "O"->"0" occur.
*/
void canonical16(char *z, int n){
  while( *z && n-- ){
    *z = zEncode[zDecode[(*z)&0x7f]&0x1f];
    z++;
  }
}

/* Randomness used for XOR-ing by the obscure() and unobscure() routines */
static const unsigned char aObscurer[16] = {
    0xa7, 0x21, 0x31, 0xe3, 0x2a, 0x50, 0x2c, 0x86,
    0x4c, 0xa4, 0x52, 0x25, 0xff, 0x49, 0x35, 0x85
};
 

/*
** Obscure plain text so that it is not easily readable.
**
** This is used for storing sensitive information (such as passwords) in a
** way that prevents their exposure through idle browsing.  This is not
** encryption.  Anybody who really wants the password can still get it.
**
** The text is XOR-ed with a repeating pattern then converted to hex.
** Space to hold the returned string is obtained from malloc and should
** be freed by the caller.
*/
char *obscure(const char *zIn){
  int n, i;
  unsigned char salt;
  char *zOut;
  
  if( zIn==0 ) return 0;
  n = strlen(zIn);
  zOut = fossil_malloc( n*2+3 );
  sqlite3_randomness(1, &salt);
  zOut[n+1] = (char)salt;
  for(i=0; i<n; i++) zOut[i+n+2] = zIn[i]^aObscurer[i&0x0f]^salt;
  encode16((unsigned char*)&zOut[n+1], (unsigned char*)zOut, n+1);
  return zOut;
}

/*
** Undo the obscuring of text performed by obscure().  Or, if the input is
** not hexadecimal (meaning the input is not the output of obscure()) then
** do the equivalent of strdup().
**
** The result is memory obtained from malloc that should be freed by the caller. 
*/
char *unobscure(const char *zIn){
  int n, i;
  unsigned char salt;
  char *zOut;
  
  if( zIn==0 ) return 0;
  n = strlen(zIn);
  zOut = fossil_malloc( n + 1 );
  if( n<2
    || decode16((unsigned char*)zIn, &salt, 2)
    || decode16((unsigned char*)&zIn[2], (unsigned char*)zOut, n-2)
  ){
    memcpy(zOut, zIn, n+1);
  }else{
    n = n/2 - 1;
    for(i=0; i<n; i++) zOut[i] = zOut[i]^aObscurer[i&0x0f]^salt;
    zOut[n] = 0;
  }
  return zOut;
}

/*
** Command to test obscure() and unobscure().  These commands are also useful
** utilities for decoding passwords found in the database.
**
** COMMAND: test-obscure
*/
void test_obscure_cmd(void){
  int i;
  char *z, *z2;
  for(i=2; i<g.argc; i++){
    z = obscure(g.argv[i]);
    z2 = unobscure(z);
    fossil_print("OBSCURE:    %s -> %s (%s)\n", g.argv[i], z, z2);
    free(z);
    free(z2);
    z = unobscure(g.argv[i]);
    fossil_print("UNOBSCURE:  %s -> %s\n", g.argv[i], z);
    free(z);
  }
}