1 /* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
2 /* include/k5-der.h - Distinguished Encoding Rules (DER) declarations */
34  * Most ASN.1 encoding and decoding is done using the table-driven framework in
44 #include "k5-buf.h"
45 #include "k5-input.h"
47 /* Return the number of bytes needed to encode len as a DER encoding length. */
49 k5_der_len_len(size_t len)  in k5_der_len_len()  argument
53     if (len < 128)  in k5_der_len_len()
56     while (len > 0) {  in k5_der_len_len()
57         len >>= 8;  in k5_der_len_len()
64  * byte and length) for a given contents length. */
71 /* Add a DER identifier byte (composed by the caller, including the ASN.1
74 k5_der_add_taglen(struct k5buf *buf, uint8_t idbyte, size_t len)  in k5_der_add_taglen()  argument
77     size_t llen = k5_der_len_len(len);  in k5_der_add_taglen()
83     if (len < 128) {  in k5_der_add_taglen()
84         *p = len;  in k5_der_add_taglen()
86         *p = 0x80 | (llen - 1);  in k5_der_add_taglen()
87         /* Encode the length bytes backwards so the most significant byte is  in k5_der_add_taglen()
90         while (len > 0) {  in k5_der_add_taglen()
91             *--p = len & 0xFF;  in k5_der_add_taglen()
92             len >>= 8;  in k5_der_add_taglen()
97 /* Add a DER value (identifier byte, length, and contents). */
100                  size_t len)  in k5_der_add_value()  argument
102     k5_der_add_taglen(buf, idbyte, len);  in k5_der_add_value()
103     k5_buf_add_len(buf, contents, len);  in k5_der_add_value()
107  * If the next byte in in matches idbyte and the subsequent DER length is
119     size_t len;  in k5_der_get_value()  local
122     /* Do nothing if in is empty or the next byte doesn't match idbyte. */  in k5_der_get_value()
123     if (in->status || in->len == 0 || *in->ptr != idbyte)  in k5_der_get_value()
126     /* Advance past the identifier byte and decode the length. */  in k5_der_get_value()
130         len = lenbyte;  in k5_der_get_value()
132         len = 0;  in k5_der_get_value()
134             if (len > (SIZE_MAX >> 8)) {  in k5_der_get_value()
138             len = (len << 8) | k5_input_get_byte(in);  in k5_der_get_value()
142     bytes = k5_input_get_bytes(in, len);  in k5_der_get_value()
145     k5_input_init(contents_out, bytes, len);  in k5_der_get_value()