diff options
Diffstat (limited to 'tools/decode-email.c')
| -rw-r--r-- | tools/decode-email.c | 163 |
1 files changed, 163 insertions, 0 deletions
diff --git a/tools/decode-email.c b/tools/decode-email.c new file mode 100644 index 0000000..8945394 --- /dev/null +++ b/tools/decode-email.c @@ -0,0 +1,163 @@ +/* +** This program reads a raw email file and attempts to decode it into +** a more human-readable format. The following decodings are done: +** +** (1) Header values are prefixed by "| " at the left margin. +** +** (2) Content-Transfer-Encoding is recognized and the content is +** decoded for display. +*/ +#define _GNU_SOURCE +#include <stdio.h> +#include <string.h> +#include <ctype.h> + +#define BINARY 0 +#define BASE64 1 +#define QUOTED 2 + +static int decode_hex(char c){ + if( c>='0' && c<='9' ) return c - '0'; + if( c>='A' && c<='F' ) return c - 'A' + 10; + if( c>='a' && c<='f' ) return c - 'a' + 10; + return -1; +} + +static void convert_file(const char *zFilename, FILE *in){ + int inHdr = 1; + int n; + int nBoundary; + int decodeType = 0; + int textMimetype = 1; + char *zB; + char zBoundary[200]; + char zLine[5000]; + char zOut[5000]; + while( fgets(zLine, sizeof(zLine), in) ){ + if( !inHdr + && zLine[0]=='-' + && zLine[1]=='-' + && strncmp(zLine+2,zBoundary,nBoundary)==0 + ){ + printf("|----------------- end of body section ---------|\n"); + inHdr = 1; + } + if( !inHdr ){ + if( textMimetype && decodeType==BASE64 ){ + int ii, jj, c, x, y; + int bits = 0; + for(ii=jj=0; (c = zLine[ii])!=0; ii++){ + if( c>='A' && c<='Z' ){ + x = c - 'A'; + }else if( c>='a' && c<='z' ){ + x = c - 'a' + 26; + }else if( c>='0' && c<='9' ){ + x = c - '0' + 52; + }else if( c=='+' ){ + x = 62; + }else if( c=='/' ){ + x = 63; + }else if( c=='=' ){ + x = 0; + }else{ + continue; + } + if( bits==0 ){ + y = x; + bits = 6; + }else if( bits==6 ){ + zOut[jj++] = ((y<<2) & 0xfc) | ((x>>4) & 0x03); + y = x & 0xf; + bits = 4; + }else if( bits==4 ){ + zOut[jj++] = ((y<<4) & 0xf0) | ((x>>2) & 0x0f); + y = x & 0x3; + bits = 2; + }else if( bits==2 ){ + zOut[jj++] = ((y<<6) & 0xc0) | (x & 0x3f); + bits = 0; + } + } + zOut[jj] = 0; + printf("%s", zOut); + }else if( textMimetype && decodeType==QUOTED ){ + int ii, jj, c; + for(ii=jj=0; (c = zLine[ii])!=0; ii++){ + if( c=='=' ){ + int x1 = decode_hex(zLine[ii+1]); + int x2 = decode_hex(zLine[ii+2]); + if( x1>=0 && x2>=0 ){ + zOut[jj++] = (x1<<4) | x2; + ii += 2; + }else if( zLine[ii+1]=='\r' && zLine[ii+2]=='\n' ){ + ii += 2; + } + }else{ + zOut[jj++] = c; + } + } + zOut[jj] = 0; + printf("%s", zOut); + }else{ + printf("%s", zLine); + } + continue; + } + n = (int)strlen(zLine); + while( n>0 && isspace(zLine[n-1]) ){ n--; } + zLine[n] = 0; + if( n==0 ){ + inHdr = 0; + printf("|----------------- end of header ---------------|\n"); + continue; + } + printf("| %s\n", zLine); + if( strncasecmp(zLine,"Content-Type:", 13)==0 ){ + textMimetype = strstr(zLine, "text/")!=0; + printf("|** %s content type **|\n", + textMimetype ? "Text" : "Non-text"); + } + if( strncasecmp(zLine,"Content-Transfer-Encoding:", 26)==0 ){ + if( strcasestr(zLine, "base64") ){ + decodeType = BASE64; + }else if( strcasestr(zLine, "quoted-printable") ){ + decodeType = QUOTED; + }else{ + decodeType = BINARY; + } + printf("|** Content encoding %s **|\n", + decodeType==BASE64 ? "BASE64" : + decodeType==QUOTED ? "QUOTED" : "BINARY"); + } + zB = strstr(zLine, "boundary=\""); + if( zB ){ + int kk; + zB += 10; + for(kk=0; zB[kk] && zB[kk]!='"' && kk<sizeof(zBoundary)-1; kk++){ + zBoundary[kk] = zB[kk]; + } + zBoundary[kk] = 0; + nBoundary = kk; + printf("|** boundary [%s] **|\n", zBoundary); + } + } +} + +int main(int argc, char **argv){ + if( argc==1 ){ + convert_file("<stdin>", stdin); + return 0; + }else{ + int i; + for(i=1; i<argc; i++){ + FILE *in = fopen(argv[i], "rb"); + if( in==0 ){ + fprintf(stderr, "cannot open \"%s\"", argv[i]); + }else{ + convert_file(argv[i], in); + fclose(in); + } + } + } + return 0; +} |