libc: constant time implementation for encode(2) routines, fix base32
the string encoding functions touch secret key material in a bunch of places (devtls, devcap), so make sure we do not leak information by cache timing side channels, making the encoding and decoding routines constant time. we also expose the alphabets through encXchr()/decXchr() functions so caller can find the end of a encoded string before calling decode function (for libmp). the base32 encoding was broken in several ways. inputs lengths of len%5 == [2,3,4] had output truncated and it was using non-standard alphabet. documenting the alphabet change in the manpage.
This commit is contained in:
cinap_lenrek
parent
ee89c82dd3
commit
c039b52fc3
6 changed files with 186 additions and 90 deletions
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@ -369,6 +369,12 @@ extern int dec32(uchar*, int, char*, int);
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extern int enc32(char*, int, uchar*, int);
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extern int dec16(uchar*, int, char*, int);
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extern int enc16(char*, int, uchar*, int);
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extern int dec64chr(int);
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extern int enc64chr(int);
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extern int dec32chr(int);
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extern int enc32chr(int);
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extern int dec16chr(int);
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extern int enc16chr(int);
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extern int encodefmt(Fmt*);
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extern void exits(char*);
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extern double frexp(double, int*);
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@ -1,6 +1,8 @@
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.TH ENCODE 2
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.SH NAME
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dec64, enc64, dec32, enc32, dec16, enc16, encodefmt \- encoding byte arrays as strings
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dec64, enc64, dec32, enc32, dec16, enc16, \
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dec64chr, enc64chr, dec32chr, enc32chr, dec16chr, enc16chr, \
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encodefmt \- encoding byte arrays as strings
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.SH SYNOPSIS
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.B #include <u.h>
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.br
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@ -25,8 +27,28 @@ int dec16(uchar *out, int lim, char *in, int n)
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int enc16(char *out, int lim, uchar *in, int n)
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.PP
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.B
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int dec64chr(int c)
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.PP
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.B
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int enc64chr(int o)
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.PP
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.B
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int dec32chr(int c)
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.PP
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.B
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int enc32chr(int o)
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.PP
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.B
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int dec16chr(int c)
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.PP
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.B
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int enc16chr(int o)
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.PP
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.B
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int encodefmt(Fmt*)
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.SH DESCRIPTION
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The functions described here handle encoding and decoding of
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bytes to printable ASCII strings as specified by RFC4648.
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.PP
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.IR Enc16 ,
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.I enc32
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@ -47,6 +69,20 @@ The decoding fails if the output buffer is not large enough or,
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for base 32, if the input buffer length is not a multiple
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of 8.
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.PP
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.IR Dec16chr ,
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.I dec32chr
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and
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.I dec64chr
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return the value for a symbol of the alphabet or -1 when the
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symbol is not in the alphabet.
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.PP
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.IR Enc16chr ,
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.I enc32chr
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and
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.I enc64chr
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encode a symbol of the alphabet given a value.
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if the value is out of range then zero is returned.
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.PP
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.I Encodefmt
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can be used with
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.IR fmtinstall (2)
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@ -62,7 +98,8 @@ in upper case. The
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flag forces lower case.
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.TP
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.B <
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base 32
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base 32. The default is upper case, same as
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.BR H .
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.TP
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.B [
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base 64 (same as MIME)
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@ -80,8 +117,19 @@ For example, to display a 15 byte array as hex:
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.EE
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.SH SOURCE
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.B /sys/src/libc/port/u16.c
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.br
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.B /sys/src/libc/port/u32.c
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.br
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.B /sys/src/libc/port/u64.c
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.br
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.B /sys/src/libc/port/encodefmt.c
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.SH HISTORY
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In Jan 2018, base 32 encoding was changed from non-standard
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to standard RFC4648 alphabet.
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.TP
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old:
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.B "23456789abcdefghijkmnpqrstuvwxyz"
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.TP
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new:
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.B "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567"
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@ -48,17 +48,14 @@ encodefmt(Fmt *f)
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// convert
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out = buf;
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switch(f->r){
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case '<':
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rv = enc32(out, len, b, ilen);
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break;
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case '[':
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rv = enc64(out, len, b, ilen);
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break;
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case '<':
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rv = enc32(out, len, b, ilen);
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break;
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case 'H':
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rv = enc16(out, len, b, ilen);
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if(rv >= 0 && (f->flags & FmtLong))
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for(p = buf; *p; p++)
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*p = tolower(*p);
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break;
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default:
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rv = -1;
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@ -67,6 +64,10 @@ encodefmt(Fmt *f)
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if(rv < 0)
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goto error;
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if((f->flags & FmtLong) != 0 && f->r != '[')
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for(p = buf; *p; p++)
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*p = tolower(*p);
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fmtstrcpy(f, buf);
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if(buf != obuf)
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free(buf);
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@ -1,6 +1,28 @@
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#include <u.h>
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#include <libc.h>
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static char t16e[] = "0123456789ABCDEF";
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#define between(x,min,max) (((min-1-x) & (x-max-1))>>8)
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int
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enc16chr(int o)
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{
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int c;
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c = between(o, 0, 9) & ('0'+o);
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c |= between(o, 10, 15) & ('A'+(o-10));
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return c;
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}
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int
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dec16chr(int c)
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{
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int o;
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o = between(c, '0', '9') & (1+(c-'0'));
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o |= between(c, 'A', 'F') & (1+10+(c-'A'));
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o |= between(c, 'a', 'f') & (1+10+(c-'a'));
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return o-1;
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}
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int
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dec16(uchar *out, int lim, char *in, int n)
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@ -10,14 +32,8 @@ dec16(uchar *out, int lim, char *in, int n)
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uchar *eout = out + lim;
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while(n-- > 0){
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c = *in++;
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if('0' <= c && c <= '9')
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c = c - '0';
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else if('a' <= c && c <= 'z')
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c = c - 'a' + 10;
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else if('A' <= c && c <= 'Z')
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c = c - 'A' + 10;
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else
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c = dec16chr(*in++);
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if(c < 0)
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continue;
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w = (w<<4) + c;
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i++;
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@ -44,8 +60,8 @@ enc16(char *out, int lim, uchar *in, int n)
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c = *in++;
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if(out + 2 >= eout)
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goto exhausted;
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*out++ = t16e[c>>4];
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*out++ = t16e[c&0xf];
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*out++ = enc16chr(c>>4);
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*out++ = enc16chr(c&15);
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}
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exhausted:
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*out = 0;
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@ -1,21 +1,44 @@
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#include <u.h>
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#include <libc.h>
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#define between(x,min,max) (((min-1-x) & (x-max-1))>>8)
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int
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enc32chr(int o)
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{
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int c;
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c = between(o, 0, 25) & ('A'+o);
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c |= between(o, 26, 31) & ('2'+(o-26));
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return c;
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}
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int
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dec32chr(int c)
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{
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int o;
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o = between(c, 'A', 'Z') & (1+(c-'A'));
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o |= between(c, 'a', 'z') & (1+(c-'a'));
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o |= between(c, '2', '7') & (1+26+(c-'2'));
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return o-1;
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}
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int
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dec32(uchar *dest, int ndest, char *src, int nsrc)
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{
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char *s, *tab;
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uchar *start;
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int i, u[8];
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int i, j, u[8];
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if(ndest+1 < (5*nsrc+7)/8)
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return -1;
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start = dest;
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tab = "23456789abcdefghijkmnpqrstuvwxyz";
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while(nsrc>=8){
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for(i=0; i<8; i++){
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s = strchr(tab,(int)src[i]);
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u[i] = s ? s-tab : 0;
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j = dec32chr(src[i]);
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if(j < 0)
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j = 0;
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u[i] = j;
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}
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*dest++ = (u[0]<<3) | (0x7 & (u[1]>>2));
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*dest++ = ((0x3 & u[1])<<6) | (u[2]<<1) | (0x1 & (u[3]>>4));
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@ -29,8 +52,10 @@ dec32(uchar *dest, int ndest, char *src, int nsrc)
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if(nsrc == 1 || nsrc == 3 || nsrc == 6)
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return -1;
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for(i=0; i<nsrc; i++){
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s = strchr(tab,(int)src[i]);
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u[i] = s ? s-tab : 0;
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j = dec32chr(src[i]);
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if(j < 0)
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j = 0;
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u[i] = j;
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}
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*dest++ = (u[0]<<3) | (0x7 & (u[1]>>2));
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if(nsrc == 2)
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@ -50,60 +75,57 @@ out:
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int
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enc32(char *dest, int ndest, uchar *src, int nsrc)
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{
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char *tab, *start;
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char *start;
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int j;
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if(ndest <= (8*nsrc+4)/5 )
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if(ndest <= (8*nsrc+4)/5)
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return -1;
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start = dest;
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tab = "23456789abcdefghijkmnpqrstuvwxyz";
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while(nsrc>=5){
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j = (0x1f & (src[0]>>3));
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*dest++ = tab[j];
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*dest++ = enc32chr(j);
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j = (0x1c & (src[0]<<2)) | (0x03 & (src[1]>>6));
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*dest++ = tab[j];
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*dest++ = enc32chr(j);
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j = (0x1f & (src[1]>>1));
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*dest++ = tab[j];
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*dest++ = enc32chr(j);
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j = (0x10 & (src[1]<<4)) | (0x0f & (src[2]>>4));
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*dest++ = tab[j];
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*dest++ = enc32chr(j);
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j = (0x1e & (src[2]<<1)) | (0x01 & (src[3]>>7));
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*dest++ = tab[j];
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*dest++ = enc32chr(j);
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j = (0x1f & (src[3]>>2));
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*dest++ = tab[j];
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*dest++ = enc32chr(j);
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j = (0x18 & (src[3]<<3)) | (0x07 & (src[4]>>5));
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*dest++ = tab[j];
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*dest++ = enc32chr(j);
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j = (0x1f & (src[4]));
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*dest++ = tab[j];
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*dest++ = enc32chr(j);
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src += 5;
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nsrc -= 5;
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}
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if(nsrc){
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j = (0x1f & (src[0]>>3));
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*dest++ = tab[j];
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*dest++ = enc32chr(j);
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j = (0x1c & (src[0]<<2));
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if(nsrc == 1)
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goto out;
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j |= (0x03 & (src[1]>>6));
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*dest++ = tab[j];
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*dest++ = enc32chr(j);
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j = (0x1f & (src[1]>>1));
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*dest++ = enc32chr(j);
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j = (0x10 & (src[1]<<4));
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if(nsrc == 2)
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goto out;
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*dest++ = tab[j];
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j = (0x10 & (src[1]<<4));
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j |= (0x0f & (src[2]>>4));
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*dest++ = enc32chr(j);
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j = (0x1e & (src[2]<<1));
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if(nsrc == 3)
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goto out;
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j |= (0x0f & (src[2]>>4));
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*dest++ = tab[j];
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j = (0x1e & (src[2]<<1));
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if(nsrc == 4)
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goto out;
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j |= (0x01 & (src[3]>>7));
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*dest++ = tab[j];
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*dest++ = enc32chr(j);
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j = (0x1f & (src[3]>>2));
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*dest++ = tab[j];
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*dest++ = enc32chr(j);
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j = (0x18 & (src[3]<<3));
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out:
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*dest++ = tab[j];
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*dest++ = enc32chr(j);
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}
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*dest = 0;
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return dest-start;
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@ -1,29 +1,33 @@
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#include <u.h>
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#include <libc.h>
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enum {
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INVAL= 255
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};
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#define between(x,min,max) (((min-1-x) & (x-max-1))>>8)
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static uchar t64d[256] = {
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INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,
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INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,
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INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL, 62,INVAL,INVAL,INVAL, 63,
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52, 53, 54, 55, 56, 57, 58, 59, 60, 61,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,
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INVAL, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
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15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,INVAL,INVAL,INVAL,INVAL,INVAL,
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INVAL, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
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41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,INVAL,INVAL,INVAL,INVAL,INVAL,
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INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,
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INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,
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INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,
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INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,
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INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,
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INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,
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INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,
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INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL
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};
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static char t64e[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
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int
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enc64chr(int o)
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{
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int c;
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c = between(o, 0, 25) & ('A'+o);
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c |= between(o, 26, 51) & ('a'+(o-26));
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c |= between(o, 52, 61) & ('0'+(o-52));
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c |= between(o, 62, 62) & ('+');
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c |= between(o, 63, 63) & ('/');
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return c;
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}
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int
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dec64chr(int c)
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{
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int o;
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o = between(c, 'A', 'Z') & (1+(c-'A'));
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o |= between(c, 'a', 'z') & (1+26+(c-'a'));
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o |= between(c, '0', '9') & (1+52+(c-'0'));
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o |= between(c, '+', '+') & (1+62);
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o |= between(c, '/', '/') & (1+63);
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return o-1;
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}
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int
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dec64(uchar *out, int lim, char *in, int n)
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@ -36,9 +40,8 @@ dec64(uchar *out, int lim, char *in, int n)
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b24 = 0;
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i = 0;
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while(n-- > 0){
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c = t64d[*(uchar*)in++];
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if(c == INVAL)
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c = dec64chr(*in++);
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if(c < 0)
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continue;
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switch(i){
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case 0:
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@ -58,8 +61,8 @@ dec64(uchar *out, int lim, char *in, int n)
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*out++ = b24>>16;
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*out++ = b24>>8;
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*out++ = b24;
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i = -1;
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break;
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i = 0;
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continue;
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}
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i++;
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}
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@ -89,34 +92,34 @@ enc64(char *out, int lim, uchar *in, int n)
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char *e = out + lim;
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for(i = n/3; i > 0; i--){
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b24 = (*in++)<<16;
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b24 |= (*in++)<<8;
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b24 = *in++<<16;
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b24 |= *in++<<8;
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b24 |= *in++;
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if(out + 4 >= e)
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goto exhausted;
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*out++ = t64e[(b24>>18)];
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||||
*out++ = t64e[(b24>>12)&0x3f];
|
||||
*out++ = t64e[(b24>>6)&0x3f];
|
||||
*out++ = t64e[(b24)&0x3f];
|
||||
*out++ = enc64chr(b24>>18);
|
||||
*out++ = enc64chr((b24>>12)&0x3f);
|
||||
*out++ = enc64chr((b24>>6)&0x3f);
|
||||
*out++ = enc64chr(b24&0x3f);
|
||||
}
|
||||
|
||||
switch(n%3){
|
||||
case 2:
|
||||
b24 = (*in++)<<16;
|
||||
b24 |= (*in)<<8;
|
||||
b24 = *in++<<16;
|
||||
b24 |= *in<<8;
|
||||
if(out + 4 >= e)
|
||||
goto exhausted;
|
||||
*out++ = t64e[(b24>>18)];
|
||||
*out++ = t64e[(b24>>12)&0x3f];
|
||||
*out++ = t64e[(b24>>6)&0x3f];
|
||||
*out++ = enc64chr(b24>>18);
|
||||
*out++ = enc64chr((b24>>12)&0x3f);
|
||||
*out++ = enc64chr((b24>>6)&0x3f);
|
||||
*out++ = '=';
|
||||
break;
|
||||
case 1:
|
||||
b24 = (*in)<<16;
|
||||
b24 = *in<<16;
|
||||
if(out + 4 >= e)
|
||||
goto exhausted;
|
||||
*out++ = t64e[(b24>>18)];
|
||||
*out++ = t64e[(b24>>12)&0x3f];
|
||||
*out++ = enc64chr(b24>>18);
|
||||
*out++ = enc64chr((b24>>12)&0x3f);
|
||||
*out++ = '=';
|
||||
*out++ = '=';
|
||||
break;
|
||||
|
|
|
|||
Loading…
Reference in a new issue