1 /*
2  * For decoding the files that get passed to validateattachment.
3  * NOT a general mime decoder.
4  */
5 #include <u.h>
6 #include <libc.h>
7 #include <bio.h>
8 
9 enum { None, Base64, Quoted };
10 static int decquoted(char *out, char *in, char *e);
11 
12 void
13 main(void)
14 {
15 	Biobuf b, b1;
16 	char *p, *encoding;
17 	int e, len;
18 	
19 	Binit(&b, 0, OREAD);
20 	Binit(&b1, 1, OWRITE);
21 	
22 	/* header */
23 	encoding = nil;
24 	while((p = Brdstr(&b, '\n', 1)) != nil){
25 		if(p[0] == 0)
26 			break;
27 		if(cistrncmp(p, "Content-Transfer-Encoding: ", 27) == 0)
28 			encoding = strdup(p+27);
29 		free(p);
30 	}
31 
32 	e = None;
33 	if(encoding == nil)
34 		e = None;
35 	else if(strcmp(encoding, "base64") == 0)
36 		e = Base64;
37 	else if(strcmp(encoding, "quoted-printable") == 0)
38 		e = Quoted;
39 
40 	while((p = Brdstr(&b, '\n', 0)) != nil){
41 		if(strncmp(p, "--", 2) == 0 && e != None)
42 			break;
43 		len = strlen(p);
44 		switch(e){
45 		case None:
46 			break;
47 		case Base64:
48 			len = dec64((uchar*)p, len, p, len);
49 			break;
50 		case Quoted:
51 			len = decquoted(p, p, p+len);
52 			break;
53 		}
54 		Bwrite(&b1, p, len);
55 		free(p);
56 	}
57 	exits(0);
58 }
59 
60 /*
61  *  decode quoted 
62  */
63 enum
64 {
65 	Self=	1,
66 	Hex=	2
67 };
68 uchar	tableqp[256];
69 
70 static void
71 initquoted(void)
72 {
73 	int c;
74 
75 	memset(tableqp, 0, 256);
76 	for(c = ' '; c <= '<'; c++)
77 		tableqp[c] = Self;
78 	for(c = '>'; c <= '~'; c++)
79 		tableqp[c] = Self;
80 	tableqp['\t'] = Self;
81 	tableqp['='] = Hex;
82 }
83 
84 static int
85 hex2int(int x)
86 {
87 	if(x >= '0' && x <= '9')
88 		return x - '0';
89 	if(x >= 'A' && x <= 'F')
90 		return (x - 'A') + 10;
91 	if(x >= 'a' && x <= 'f')
92 		return (x - 'a') + 10;
93 	return 0;
94 }
95 
96 static char*
97 decquotedline(char *out, char *in, char *e)
98 {
99 	int c, soft;
100 
101 	/* dump trailing white space */
102 	while(e >= in && (*e == ' ' || *e == '\t' || *e == '\r' || *e == '\n'))
103 		e--;
104 
105 	/* trailing '=' means no newline */
106 	if(*e == '='){
107 		soft = 1;
108 		e--;
109 	} else
110 		soft = 0;
111 
112 	while(in <= e){
113 		c = (*in++) & 0xff;
114 		switch(tableqp[c]){
115 		case Self:
116 			*out++ = c;
117 			break;
118 		case Hex:
119 			c = hex2int(*in++)<<4;
120 			c |= hex2int(*in++);
121 			*out++ = c;
122 			break;
123 		}
124 	}
125 	if(!soft)
126 		*out++ = '\n';
127 	*out = 0;
128 
129 	return out;
130 }
131 
132 static int
133 decquoted(char *out, char *in, char *e)
134 {
135 	char *p, *nl;
136 
137 	if(tableqp[' '] == 0)
138 		initquoted();
139 
140 	p = out;
141 	while((nl = strchr(in, '\n')) != nil && nl < e){
142 		p = decquotedline(p, in, nl);
143 		in = nl + 1;
144 	}
145 	if(in < e)
146 		p = decquotedline(p, in, e-1);
147 
148 	/* make sure we end with a new line */
149 	if(*(p-1) != '\n'){
150 		*p++ = '\n';
151 		*p = 0;
152 	}
153 
154 	return p - out;
155 }
156