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#include "commonKludge.h"
/* System */
#include <assert.h>
#include <errno.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define BUF_CAP (1<<15)
typedef struct PemCodec PemCodec;
typedef unsigned long long ulong;
enum Mode {
MODE_NONE = 0,
MODE_ENCODE,
MODE_DECODE,
};
struct PemCodec {
int isHelp; /* TODO flg */
enum Mode mode; /* one of "ENCODE" or "DECODE" */
int buf_len;
unsigned char buf[BUF_CAP];
};
static void printHelp(){
printf("%s%s%s", " \n"
" ", strrchr(__FILE__,'/')+1, " @ " STRQUOT(PROJECT_VERSION) "\n"
" \n"
" encode/decode PEM (PrivacyEnhancedMail) from stdin to stdout.\n"
" \n"
" HINT: Encode is not yet implemented.\n"
" \n"
" Options:\n"
" \n"
" -d decode\n"
" \n");
}
static int parseArgs( int argc, char**argv, PemCodec*app ){
app->isHelp = 0;
app->mode = MODE_ENCODE;
if( argc == 1 ){ fprintf(stderr, "EINVAL: Args missing\n"); return -1; }
for( int iArg=1 ; iArg<argc ; ++iArg ){
const char *arg = argv[iArg];
if(0){
}else if( !strcmp(arg,"--help") ){
app->isHelp = !0; return 0;
}else if( !strcmp(arg,"-d") ){
app->mode = MODE_DECODE;
}else{
fprintf(stderr, "EINVAL: '%s'\n", arg); return -1;
}
}
return 0;
}
static int decodeB64UpToDash( PemCodec*app ){
int err;
size_t sz;
int iByte;
int sextets[4];
readFourInputOctets:
iByte = 0;
readNextInputOctet:
sz = fread(app->buf, 1, 1, stdin);
if( sz != 1 ){ assert(!"TODO_20230825155237"); }
/* TODO may use switch-case instead */
if(0){
}else if( app->buf[0] >= 'A' && app->buf[0] <= 'Z' ){
sextets[iByte] = app->buf[0] - 65;
}else if( app->buf[0] >= 'a' && app->buf[0] <= 'z' ){
sextets[iByte] = app->buf[0] - 71;
}else if( app->buf[0] >= '0' && app->buf[0] <= '9' ){
sextets[iByte] = app->buf[0] + 4;
}else if( app->buf[0] == '+' ){
sextets[iByte] = 63;
}else if( app->buf[0] == '/' ){
sextets[iByte] = 64;
}else if( app->buf[0] == '=' ){
sextets[iByte] = 0;
}else if( app->buf[0] == '\n' ){ /* ignore newlines */
goto readNextInputOctet;
}else if( app->buf[0] == '-' ){ /* EndOf b64 data */
goto endFn;
}else{
fprintf(stderr, "Unexpected octet 0x%02X in b64 stream\n", app->buf[0]);
err = -1; goto endFn;
}
if( ++iByte < 4 ) goto readNextInputOctet; /* aka loop */
/* output as the three original binary octets */
err = printf("%c%c%c",
( sextets[0] << 2) | (sextets[1] >> 4) ,
((sextets[1] & 0xF) << 4) | (sextets[2] >> 2) ,
((sextets[2] & 0x3) << 6) | sextets[3]
);
if( err < 0 ){
err = errno;
fprintf(stderr, "printf: %s\n", strerror(errno));
err = -errno; goto endFn;
}
goto readFourInputOctets; /* aka loop */
err = 0;
endFn:
return err;
}
static int decodePem( PemCodec*app ){
int err;
size_t sz;
sz = fread(app->buf, 11, 1, stdin);
if( sz != 1 ){
const char *fmt = feof(stdin)
? "Unexpected EOF while reading PEM header: %s\n"
: "Cannot read PEM header: %s\n";
fprintf(stderr, fmt, strerror(errno));
err = -1; goto endFn;
}
if( memcmp(app->buf, "-----BEGIN ", 11) ){
fprintf(stderr, "EINVAL: No valid PEM header found\n");
err = -1; goto endFn;
}
/* read until EOL */
int numDashesInSequence = 0;
for(;;){
sz = fread(app->buf, 1, 1, stdin);
if( sz != 1 ){
const char *fmt = feof(stdin)
? "Unexpected EOF while reading PEM header: %s\n"
: "Cannot read PEM header: %s\n";
fprintf(stderr, fmt, strerror(errno));
err = -1; goto endFn;
}
if( app->buf[0] == '\n' ){
if( numDashesInSequence != 5 ){
fprintf(stderr, "EINVAL: No valid PEM header found\n");
err = -1; goto endFn;
}
break;
}
if( app->buf[0] == '-' ){
numDashesInSequence += 1;
}else{
numDashesInSequence = 0;
}
}
if( (err=decodeB64UpToDash(app)) < 0 ){ goto endFn; }
/* readEndOfPemLine. 1st dash got already consumed in func above */
sz = fread(app->buf, 8, 1, stdin);
if( sz != 1 || memcmp(app->buf, "----END ", 8)){
assert(fprintf(stderr, "sz=%llu\n", (ulong)sz));
goto warnAndDrain;
}
/* assume rest of trailer is ok */
goto drain;
warnAndDrain:
fprintf(stderr, "WARN: PEM trailer broken\n");
drain:
sz = fread(app->buf, BUF_CAP, 1, stdin);
if( sz > 0 ) goto drain;
if( ferror(stdin) ){
fprintf(stderr, "fread: %s\n", strerror(errno));
err = -1; goto endFn;
}
err = 0;
endFn:
return err;
}
int main( int argc, char**argv ){
int err;
PemCodec app;
#define app (&app)
if( (err=parseArgs(argc, argv, app)) != 0 ){ goto endFn; }
if( app->isHelp ){ printHelp(app); err = 0; goto endFn; }
if( app->mode == MODE_ENCODE ){
fprintf(stderr, "ENOTSUP: PEM Encode not implented yet\n");
err = -1; goto endFn;
}else{
assert(app->mode == MODE_DECODE);
err = decodePem(app);
goto endFn;
}
endFn:
return !!err;
#undef app
}
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