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Diffstat (limited to 'doc/examples/asn1.cpp')
| -rw-r--r-- | doc/examples/asn1.cpp | 312 |
1 files changed, 312 insertions, 0 deletions
diff --git a/doc/examples/asn1.cpp b/doc/examples/asn1.cpp new file mode 100644 index 000000000..b0a6aa104 --- /dev/null +++ b/doc/examples/asn1.cpp @@ -0,0 +1,312 @@ +/* +* (C) 2009 Jack Lloyd +* +* Distributed under the terms of the Botan license +*/ + +/* + A simple ASN.1 parser, similiar to 'dumpasn1' or 'openssl asn1parse', though + without some of the bells and whistles of those. Primarily used for testing + the BER decoder. The output format is modeled loosely on 'asn1parse -i' + + The output is actually less precise than the other decoders named, because + the underlying BER_Decoder hides quite a bit from userspace, such as the use + of indefinite length encodings (and the EOC markers). At some point it will + also hide the constructed string types from the user, but right now you'll + seem them as-is. + + Written by Jack Lloyd, November 9-10, 2003 + - Nov 22: Updated to new BER_Object format (tag -> class_tag/type_tag) + - Nov 25: Much improved BIT STRING output + Can deal with non-constructed taggings + Can produce UTF-8 output +*/ + +// Set this if your terminal understands UTF-8; otherwise output is in Latin-1 +#define UTF8_TERMINAL 1 + +/* + What level the outermost layer of stuff is at. Probably 0 or 1; asn1parse + uses 0 as the outermost, while 1 makes more sense to me. 2+ doesn't make + much sense at all. +*/ +#define INITIAL_LEVEL 0 + +#include <botan/botan.h> +#include <botan/bigint.h> +#include <botan/der_enc.h> +#include <botan/ber_dec.h> +#include <botan/asn1_obj.h> +#include <botan/oids.h> +#include <botan/pem.h> +#include <botan/charset.h> +using namespace Botan; + +#include <stdio.h> +#include <ctype.h> + +void decode(BER_Decoder&, u32bit); +void emit(const std::string&, u32bit, u32bit, const std::string& = ""); +std::string type_name(ASN1_Tag); + +int main(int argc, char* argv[]) + { + if(argc != 2) + { + printf("Usage: %s <file>\n", argv[0]); + return 1; + } + + Botan::LibraryInitializer init; + + try { + DataSource_Stream in(argv[1]); + + if(!PEM_Code::matches(in)) + { + BER_Decoder decoder(in); + decode(decoder, INITIAL_LEVEL); + } + else + { + std::string label; // ignored + BER_Decoder decoder(PEM_Code::decode(in, label)); + decode(decoder, INITIAL_LEVEL); + } + + } + catch(std::exception& e) + { + printf("%s\n", e.what()); + return 1; + } + return 0; + } + +void decode(BER_Decoder& decoder, u32bit level) + { + BER_Object obj = decoder.get_next_object(); + + while(obj.type_tag != NO_OBJECT) + { + const ASN1_Tag type_tag = obj.type_tag; + const ASN1_Tag class_tag = obj.class_tag; + const u32bit length = obj.value.size(); + + /* hack to insert the tag+length back in front of the stuff now + that we've gotten the type info */ + DER_Encoder encoder; + encoder.add_object(type_tag, class_tag, obj.value, obj.value.size()); + SecureVector<byte> bits = encoder.get_contents(); + + BER_Decoder data(bits); + + if(class_tag & CONSTRUCTED) + { + BER_Decoder cons_info(obj.value); + if(type_tag == SEQUENCE) + { + emit("SEQUENCE", level, length); + decode(cons_info, level+1); + } + else if(type_tag == SET) + { + emit("SET", level, length); + decode(cons_info, level+1); + } + else + { + std::string name; + + if((class_tag & APPLICATION) || (class_tag & CONTEXT_SPECIFIC) || + (class_tag & PRIVATE)) + { + name = "cons [" + to_string(type_tag) + "]"; + + if(class_tag & APPLICATION) + name += " appl"; + if(class_tag & CONTEXT_SPECIFIC) + name += " context"; + if(class_tag & PRIVATE) + name += " private"; + } + else + name = type_name(type_tag) + " (cons)"; + + emit(name, level, length); + decode(cons_info, level+1); + } + } + else if(class_tag == APPLICATION || class_tag == CONTEXT_SPECIFIC || + class_tag == PRIVATE) + { + bool not_text = false; + + for(u32bit j = 0; j != bits.size(); j++) + if(!isgraph(bits[j]) && !isspace(bits[j])) + not_text = true; + + Pipe pipe(((not_text) ? new Hex_Encoder : 0)); + pipe.process_msg(bits); + emit("[" + to_string(type_tag) + "]", level, length, + pipe.read_all_as_string()); + } + else if(type_tag == OBJECT_ID) + { + OID oid; + data.decode(oid); + + std::string out = OIDS::lookup(oid); + if(out != oid.as_string()) + out += " [" + oid.as_string() + "]"; + + emit(type_name(type_tag), level, length, out); + } + else if(type_tag == INTEGER) + { + BigInt number; + data.decode(number); + + SecureVector<byte> rep; + + /* If it's small, it's probably a number, not a hash */ + if(number.bits() <= 16) + rep = BigInt::encode(number, BigInt::Decimal); + else + rep = BigInt::encode(number, BigInt::Hexadecimal); + + std::string str; + for(u32bit j = 0; j != rep.size(); j++) + str += (char)rep[j]; + + emit(type_name(type_tag), level, length, str); + } + else if(type_tag == BOOLEAN) + { + bool boolean; + data.decode(boolean); + emit(type_name(type_tag), + level, length, (boolean ? "true" : "false")); + } + else if(type_tag == NULL_TAG) + { + emit(type_name(type_tag), level, length); + } + else if(type_tag == OCTET_STRING) + { + SecureVector<byte> bits; + data.decode(bits, type_tag); + bool not_text = false; + + for(u32bit j = 0; j != bits.size(); j++) + if(!isgraph(bits[j]) && !isspace(bits[j])) + not_text = true; + + Pipe pipe(((not_text) ? new Hex_Encoder : 0)); + pipe.process_msg(bits); + emit(type_name(type_tag), level, length, pipe.read_all_as_string()); + } + else if(type_tag == BIT_STRING) + { + SecureVector<byte> bits; + data.decode(bits, type_tag); + + std::vector<bool> bit_set; + + for(u32bit j = 0; j != bits.size(); j++) + for(u32bit k = 0; k != 8; k++) + bit_set.push_back((bool)((bits[bits.size()-j-1] >> (7-k)) & 1)); + + std::string bit_str; + for(u32bit j = 0; j != bit_set.size(); j++) + { + bool the_bit = bit_set[bit_set.size()-j-1]; + + if(!the_bit && bit_str.size() == 0) + continue; + bit_str += (the_bit ? "1" : "0"); + } + + emit(type_name(type_tag), level, length, bit_str); + } + else if(type_tag == PRINTABLE_STRING || + type_tag == NUMERIC_STRING || + type_tag == IA5_STRING || + type_tag == T61_STRING || + type_tag == VISIBLE_STRING || + type_tag == UTF8_STRING || + type_tag == BMP_STRING) + { + ASN1_String str; + data.decode(str); + if(UTF8_TERMINAL) + emit(type_name(type_tag), level, length, + Charset::transcode(str.iso_8859(), + LATIN1_CHARSET, UTF8_CHARSET)); + else + emit(type_name(type_tag), level, length, str.iso_8859()); + } + else if(type_tag == UTC_TIME || type_tag == GENERALIZED_TIME) + { + X509_Time time; + data.decode(time); + emit(type_name(type_tag), level, length, time.readable_string()); + } + else + fprintf(stderr, "Unknown tag: class=%02X, type=%02X\n", + class_tag, type_tag); + + obj = decoder.get_next_object(); + } + } + +void emit(const std::string& type, u32bit level, u32bit length, + const std::string& value) + { + const u32bit LIMIT = 128; + const u32bit BIN_LIMIT = 64; + + int written = 0; + written += printf(" d=%2d, l=%4d: ", level, length); + for(u32bit j = INITIAL_LEVEL; j != level; j++) + written += printf(" "); + written += printf("%s ", type.c_str()); + + bool should_skip = false; + if(value.length() > LIMIT) should_skip = true; + if((type == "OCTET STRING" || type == "BIT STRING") && + value.length() > BIN_LIMIT) + should_skip = true; + + if(value != "" && !should_skip) + { + if(written % 2 == 0) printf(" "); + while(written < 50) written += printf(" "); + printf(":%s\n", value.c_str()); + } + else + printf("\n"); + } + +std::string type_name(ASN1_Tag type) + { + if(type == PRINTABLE_STRING) return "PRINTABLE STRING"; + if(type == NUMERIC_STRING) return "NUMERIC STRING"; + if(type == IA5_STRING) return "IA5 STRING"; + if(type == T61_STRING) return "T61 STRING"; + if(type == UTF8_STRING) return "UTF8 STRING"; + if(type == VISIBLE_STRING) return "VISIBLE STRING"; + if(type == BMP_STRING) return "BMP STRING"; + + if(type == UTC_TIME) return "UTC TIME"; + if(type == GENERALIZED_TIME) return "GENERALIZED TIME"; + + if(type == OCTET_STRING) return "OCTET STRING"; + if(type == BIT_STRING) return "BIT STRING"; + + if(type == INTEGER) return "INTEGER"; + if(type == NULL_TAG) return "NULL"; + if(type == OBJECT_ID) return "OBJECT"; + if(type == BOOLEAN) return "BOOLEAN"; + return "(UNKNOWN)"; + } |