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README.EN.md

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ASN1DUMP

NOTE: I use Baidu Translator to translate this file

中文 README 文件

The asn1 printing tool supports parsing data in PEM or DER format and outputting it in ASN1 format. For the basic knowledge of ASN1, refer to Microsoft's Related Documents

1. Quick start

│ asn1.h        external interface header file
│ appmain.c     APP application (console)
│ demo.c        Sample code
│ main.c        Main function
│
└─lib           code directory
    asn1_der.c      ASN1 and DER/PEM conversion
    asn1_dump.c     Print ASN1 data
    asn1_inner.c    ASN1 function
    asn1_inner.h    ASN1 function
    mString.c       String processing function
    mString.h       String processing function

Compilation Example

gcc -o asn1dump.exe *.c lib/*.c

Command line parameters

asn1dump -in <input file> -from <PEM|DER>

2. Operation test

Note: The files used in this section have been placed in the test directory.

Use OPENSSL to generate PEM and DER format files

#Generate 1024 bit RSA key in PEM format
$ openssl genrsa -out rsa_skey.pem 1024

#Convert the key to traditional format
$ openssl rsa -in rsa_skey.pem -out rsa_skey_t.pem -outform pem -traditional

#Convert PEM format key to DER format
$ openssl rsa -in rsa_skey.pem -out rsa_skey.der -outform der

#Create a certificate request
$ openssl req -new -key rsa_skey.der -out rsa.csr

Test and parse PEM and DER files

  • Print key information using OPENSSL
# openssl rsa -in rsa_skey_t.pem -noout -text
# openssl rsa -in rsa_skey.der -noout -text
$ openssl rsa -in rsa_skey.pem -noout -text
Private-Key: (1024 bit, 2 primes)
modulus:
    00:a1:5b:8b:ae:38:e7:c8:cd:77:68:00:3c:dc:90:
    c8:69:e8:b9:a3:82:0d:3c:99:33:d8:94:92:c8:8d:
    67:9f:c6:30:f7:61:a4:26:a9:da:27:fa:e6:05:09:
    8f:1e:75:58:5d:c8:be:ab:da:26:a4:8c:04:5f:dd:
    88:78:69:73:89:d5:cd:57:0a:2c:2e:5d:de:21:cc:
    27:0f:08:a5:a1:5c:85:d2:e1:15:15:3e:c6:6a:14:
    b4:a2:ec:ca:58:7b:05:5b:dc:47:b7:17:44:ab:84:
    b0:3b:f2:50:93:54:42:ba:a8:f1:24:6f:13:48:f4:
    89:80:a0:5f:86:c2:ab:f6:5d
publicExponent: 65537 (0x10001)
privateExponent:
  • Use asn1 dump to print key information
# asn1dump.exe -in rsa_skey.pem -from PEM
$ asn1dump.exe -in rsa_skey.der -from DER
30 82 02 77                       ; SEQUENCE (631 Bytes)
   02 01                             ; INTEGER (1 Bytes)
   |  00
   30 0d                             ; SEQUENCE (13 Bytes)
      06 09                             ; OBJECT_IDENTIFIER (9 Bytes)
      |  2a 86 48 86 f7 0d 01 01 01     ;    *.H......
      05 00                             ; NULL (0 Bytes)
   04 82 02 61                       ; OCTET_STRING (609 Bytes)
   |  30 82 02 5d 02 01 00 02 81 81  ;    0..]......
   |  00 a1 5b 8b ae 38 e7 c8 cd 77  ;    ..[..8...w

$ asn1dump.exe -in rsa_skey_t.pem -from PEM
30 82 02 5d                       ; SEQUENCE (605 Bytes)
   02 01                             ; INTEGER (1 Bytes)
   |  00
   02 81 81                          ; INTEGER (129 Bytes)
   |  00 a1 5b 8b ae 38 e7 c8 cd 77

Test resolution certificate request CSR

  • Print CSR using OPENSSL
$ openssl req -in rsa.csr -noout -text
Certificate Request:
    Data:
        Version: 1 (0x0)
        Subject: C = CN, ST = Some-State, O = Internet Widgits Pty Ltd, CN = oldprincess
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                Public-Key: (1024 bit)
                Modulus:
                    00:a1:5b:8b:ae:38:e7:c8:cd:77:68:00:3c:dc:90:
                    c8:69:e8:b9:a3:82:0d:3c:99:33:d8:94:92:c8:8d:
  • Print CSR using asn1 dump
$ asn1dump.exe -in rsa.csr -from PEM
30 82 01 9b                       ; SEQUENCE (411 Bytes)
   30 82 01 04                       ; SEQUENCE (260 Bytes)
      02 01                             ; INTEGER (1 Bytes)
      |  00
      30 5b                             ; SEQUENCE (91 Bytes)
         31 0b                             ; SET (11 Bytes)

3. Program with asn1.h

ASN1 Each node is a (tag, length, value) triplet, and ASN1 is defined in the ASN1_NODE type. In addition to the above contents, it also includes the raw_data (raw of the Data) and length total_length. In addition, in the relationship between ASN1 nodes, in addition to the parallel relationship at the same level, nodes such as SEQUENCE and SET also have child nodes, that is, parent-child relationships. The nxt pointer is the node of the same layer, and the child pointer is the internal node (child node) of SEQUENCE/SET.

typedef struct ASN1_NODE {
    // <tag> <length> <value>
    const ASN1_TAG* tag;
    uint32_t length;
    uint8_t* value;

    uint8_t* raw_data;
    size_t total_length;

    struct ASN1_NODE* nxt;    // next Node(in the same depth)
    struct ASN1_NODE* child;  // for SEQUENCE/SET
} ASN1_NODE;

For the rest, refer to the asn1.h file and demo.c