3 ASN.1 is a specification for how to encode structured 'data' in binary form.
4 The approach I have take to the manipulation of structures and their encoding
5 into ASN.1 is as follows.
7 For each distinct structure there are 4 function of the following form
9 void TYPE_free(TYPE *);
10 TYPE *d2i_TYPE(TYPE **a,unsigned char **pp,long length);
11 long i2d_TYPE(TYPE *a,unsigned char **pp); /* CHECK RETURN VALUE */
13 where TYPE is the type of the 'object'. The TYPE that have these functions
14 can be in one of 2 forms, either the internal C malloc()ed data structure
15 or in the DER (a variant of ASN.1 encoding) binary encoding which is just
16 an array of unsigned bytes. The 'i2d' functions converts from the internal
17 form to the DER form and the 'd2i' functions convert from the DER form to
20 The 'new' function returns a malloc()ed version of the structure with all
21 substructures either created or left as NULL pointers. For 'optional'
22 fields, they are normally left as NULL to indicate no value. For variable
23 size sub structures (often 'SET OF' or 'SEQUENCE OF' in ASN.1 syntax) the
24 STACK data type is used to hold the values. Have a read of stack.doc
25 and have a look at the relevant header files to see what I mean. If there
26 is an error while malloc()ing the structure, NULL is returned.
28 The 'free' function will free() all the sub components of a particular
29 structure. If any of those sub components have been 'removed', replace
30 them with NULL pointers, the 'free' functions are tolerant of NULL fields.
32 The 'd2i' function copies a binary representation into a C structure. It
33 operates as follows. 'a' is a pointer to a pointer to
34 the structure to populate, 'pp' is a pointer to a pointer to where the DER
35 byte string is located and 'length' is the length of the '*pp' data.
36 If there are no errors, a pointer to the populated structure is returned.
37 If there is an error, NULL is returned. Errors can occur because of
38 malloc() failures but normally they will be due to syntax errors in the DER
39 encoded data being parsed. It is also an error if there was an
40 attempt to read more that 'length' bytes from '*p'. If
41 everything works correctly, the value in '*p' is updated
42 to point at the location just beyond where the DER
43 structure was read from. In this way, chained calls to 'd2i' type
44 functions can be made, with the pointer into the 'data' array being
45 'walked' along the input byte array.
46 Depending on the value passed for 'a', different things will be done. If
47 'a' is NULL, a new structure will be malloc()ed and returned. If '*a' is
48 NULL, a new structure will be malloc()ed and put into '*a' and returned.
49 If '*a' is not NULL, the structure in '*a' will be populated, or in the
50 case of an error, free()ed and then returned.
51 Having these semantics means that a structure
52 can call a 'd2i' function to populate a field and if the field is currently
53 NULL, the structure will be created.
55 The 'i2d' function type is used to copy a C structure to a byte array.
56 The parameter 'a' is the structure to convert and '*p' is where to put it.
57 As for the 'd2i' type structure, 'p' is updated to point after the last
58 byte written. If p is NULL, no data is written. The function also returns
59 the number of bytes written. Where this becomes useful is that if the
60 function is called with a NULL 'p' value, the length is returned. This can
61 then be used to malloc() an array of bytes and then the same function can
62 be recalled passing the malloced array to be written to. e.g.
65 unsigned char *bytes,*p;
66 len=i2d_X509(x,NULL); /* get the size of the ASN1 encoding of 'x' */
67 if ((bytes=(unsigned char *)malloc(len)) == NULL)
72 Please note that a new variable, 'p' was passed to i2d_X509. After the
73 call to i2d_X509 p has been incremented by len bytes.
75 Now the reason for this functional organisation is that it allows nested
76 structures to be built up by calling these functions as required. There
77 are various macros used to help write the general 'i2d', 'd2i', 'new' and
78 'free' functions. They are discussed in another file and would only be
79 used by some-one wanting to add new structures to the library. As you
80 might be able to guess, the process of writing ASN.1 files can be a bit CPU
81 expensive for complex structures. I'm willing to live with this since the
82 simpler library code make my life easier and hopefully most programs using
83 these routines will have their execution profiles dominated by cipher or
84 message digest routines.
85 What follows is a list of 'TYPE' values and the corresponding ASN.1
86 structure and where it is used.
90 ASN1_BIT_STRING BIT STRING
91 ASN1_OCTET_STRING OCTET STRING
92 ASN1_OBJECT OBJECT IDENTIFIER
93 ASN1_PRINTABLESTRING PrintableString
94 ASN1_T61STRING T61String
95 ASN1_IA5STRING IA5String
97 ASN1_TYPE Any of the above mentioned types plus SEQUENCE and SET
99 Most of the above mentioned types are actualled stored in the
100 ASN1_BIT_STRING type and macros are used to differentiate between them.
103 typedef struct asn1_object_st
105 /* both null if a dynamic ASN1_OBJECT, one is
106 * defined if a 'static' ASN1_OBJECT */
112 This is used to store ASN1 OBJECTS. Read 'objects.doc' for details ono
113 routines to manipulate this structure. 'sn' and 'ln' are used to hold text
114 strings that represent the object (short name and long or lower case name).
115 These are used by the 'OBJ' library. 'nid' is a number used by the OBJ
116 library to uniquely identify objects. The ASN1 routines will populate the
117 'length' and 'data' fields which will contain the bit string representing
120 typedef struct asn1_bit_string_st
126 This structure is used to hold all the other base ASN1 types except for
127 ASN1_UTCTIME (which is really just a 'char *'). Length is the number of
128 bytes held in data and type is the ASN1 type of the object (there is a list
131 typedef struct asn1_type_st
136 ASN1_INTEGER * integer;
137 ASN1_BIT_STRING * bit_string;
138 ASN1_OCTET_STRING * octet_string;
139 ASN1_OBJECT * object;
140 ASN1_PRINTABLESTRING * printablestring;
141 ASN1_T61STRING * t61string;
142 ASN1_IA5STRING * ia5string;
143 ASN1_UTCTIME * utctime;
144 ASN1_BIT_STRING * set;
145 ASN1_BIT_STRING * sequence;
148 This structure is used in a few places when 'any' type of object can be
152 X509_CINF CertificateInfo
153 X509_ALGOR AlgorithmIdentifier
155 X509_NAME_ENTRY A single sub component of the name.
157 X509_PUBKEY SubjectPublicKeyInfo
158 The above mentioned types are declared in x509.h. They are all quite
159 straight forward except for the X509_NAME/X509_NAME_ENTRY pair.
160 A X509_NAME is a STACK (see stack.doc) of X509_NAME_ENTRY's.
161 typedef struct X509_name_entry_st
164 ASN1_BIT_STRING *value;
166 int size; /* temp variable */
168 The size is a temporary variable used by i2d_NAME and set is the set number
169 for the particular NAME_ENTRY. A X509_NAME is encoded as a sequence of
170 sequence of sets. Normally each set contains only a single item.
171 Sometimes it contains more. Normally throughout this library there will be
172 only one item per set. The set field contains the 'set' that this entry is
173 a member of. So if you have just created a X509_NAME structure and
174 populated it with X509_NAME_ENTRYs, you should then traverse the X509_NAME
175 (which is just a STACK) and set the 'set/' field to incrementing numbers.
176 For more details on why this is done, read the ASN.1 spec for Distinguished
179 X509_REQ CertificateRequest
180 X509_REQ_INFO CertificateRequestInfo
181 These are used to hold certificate requests.
183 X509_CRL CertificateRevocationList
184 These are used to hold a certificate revocation list
186 RSAPrivateKey PrivateKeyInfo
187 RSAPublicKey PublicKeyInfo
188 Both these 'function groups' operate on 'RSA' structures (see rsa.doc).
189 The difference is that the RSAPublicKey operations only manipulate the m
190 and e fields in the RSA structure.
192 DSAPrivateKey DSS private key
193 DSAPublicKey DSS public key
194 Both these 'function groups' operate on 'DSS' structures (see dsa.doc).
195 The difference is that the RSAPublicKey operations only manipulate the
196 XXX fields in the DSA structure.
199 This is used to hold the p and g value for The Diffie-Hellman operation.
200 The function deal with the 'DH' strucure (see dh.doc).
202 Now all of these function types can be used with several other functions to give
203 quite useful set of general manipulation routines. Normally one would
204 not uses these functions directly but use them via macros.
206 char *ASN1_dup(int (*i2d)(),char *(*d2i)(),char *x);
207 'x' is the input structure case to a 'char *', 'i2d' is the 'i2d_TYPE'
208 function for the type that 'x' is and d2i is the 'd2i_TYPE' function for the
209 type that 'x' is. As is obvious from the parameters, this function
210 duplicates the strucutre by transforming it into the DER form and then
211 re-loading it into a new strucutre and returning the new strucutre. This
212 is obviously a bit cpu intensive but when faced with a complex dynamic
213 structure this is the simplest programming approach. There are macros for
214 duplicating the major data types but is simple to add extras.
216 char *ASN1_d2i_fp(char *(*new)(),char *(*d2i)(),FILE *fp,unsigned char **x);
217 'x' is a pointer to a pointer of the 'desired type'. new and d2i are the
218 corresponding 'TYPE_new' and 'd2i_TYPE' functions for the type and 'fp' is
219 an open file pointer to read from. This function reads from 'fp' as much
220 data as it can and then uses 'd2i' to parse the bytes to load and return
221 the parsed strucutre in 'x' (if it was non-NULL) and to actually return the
222 strucutre. The behavior of 'x' is as per all the other d2i functions.
224 char *ASN1_d2i_bio(char *(*new)(),char *(*d2i)(),BIO *fp,unsigned char **x);
225 The 'BIO' is the new IO type being used in SSLeay (see bio.doc). This
226 function is the same as ASN1_d2i_fp() except for the BIO argument.
227 ASN1_d2i_fp() actually calls this function.
229 int ASN1_i2d_fp(int (*i2d)(),FILE *out,unsigned char *x);
230 'x' is converted to bytes by 'i2d' and then written to 'out'. ASN1_i2d_fp
231 and ASN1_d2i_fp are not really symetric since ASN1_i2d_fp will read all
232 available data from the file pointer before parsing a single item while
233 ASN1_i2d_fp can be used to write a sequence of data objects. To read a
234 series of objects from a file I would sugest loading the file into a buffer
235 and calling the relevent 'd2i' functions.
237 char *ASN1_d2i_bio(char *(*new)(),char *(*d2i)(),BIO *fp,unsigned char **x);
238 This function is the same as ASN1_i2d_fp() except for the BIO argument.
239 ASN1_i2d_fp() actually calls this function.
241 char * PEM_ASN1_read(char *(*d2i)(),char *name,FILE *fp,char **x,int (*cb)());
242 This function will read the next PEM encoded (base64) object of the same
243 type as 'x' (loaded by the d2i function). 'name' is the name that is in
244 the '-----BEGIN name-----' that designates the start of that object type.
245 If the data is encrypted, 'cb' will be called to prompt for a password. If
246 it is NULL a default function will be used to prompt from the password.
247 'x' is delt with as per the standard 'd2i' function interface. This
248 function can be used to read a series of objects from a file. While any
249 data type can be encrypted (see PEM_ASN1_write) only RSA private keys tend
252 char * PEM_ASN1_read_bio(char *(*d2i)(),char *name,BIO *fp,
253 char **x,int (*cb)());
254 Same as PEM_ASN1_read() except using a BIO. This is called by
257 int PEM_ASN1_write(int (*i2d)(),char *name,FILE *fp,char *x,EVP_CIPHER *enc,
258 unsigned char *kstr,int klen,int (*callback)());
260 int PEM_ASN1_write_bio(int (*i2d)(),char *name,BIO *fp,
261 char *x,EVP_CIPHER *enc,unsigned char *kstr,int klen,
264 int ASN1_sign(int (*i2d)(), X509_ALGOR *algor1, X509_ALGOR *algor2,
265 ASN1_BIT_STRING *signature, char *data, RSA *rsa, EVP_MD *type);
266 int ASN1_verify(int (*i2d)(), X509_ALGOR *algor1,
267 ASN1_BIT_STRING *signature,char *data, RSA *rsa);
269 int ASN1_BIT_STRING_cmp(ASN1_BIT_STRING *a, ASN1_BIT_STRING *b);
270 ASN1_BIT_STRING *ASN1_BIT_STRING_type_new(int type );
272 int ASN1_UTCTIME_check(ASN1_UTCTIME *a);
273 void ASN1_UTCTIME_print(BIO *fp,ASN1_UTCTIME *a);
274 ASN1_UTCTIME *ASN1_UTCTIME_dup(ASN1_UTCTIME *a);
276 ASN1_BIT_STRING *d2i_asn1_print_type(ASN1_BIT_STRING **a,unsigned char **pp,
277 long length,int type);
279 int i2d_ASN1_SET(STACK *a, unsigned char **pp,
280 int (*func)(), int ex_tag, int ex_class);
281 STACK * d2i_ASN1_SET(STACK **a, unsigned char **pp, long length,
282 char *(*func)(), int ex_tag, int ex_class);
284 int i2a_ASN1_OBJECT(BIO *bp,ASN1_OBJECT *object);
285 int i2a_ASN1_INTEGER(BIO *bp, ASN1_INTEGER *a);
286 int a2i_ASN1_INTEGER(BIO *bp,ASN1_INTEGER *bs,char *buf,int size);
288 int ASN1_INTEGER_set(ASN1_INTEGER *a, long v);
289 long ASN1_INTEGER_get(ASN1_INTEGER *a);
290 ASN1_INTEGER *BN_to_ASN1_INTEGER(BIGNUM *bn, ASN1_INTEGER *ai);
291 BIGNUM *ASN1_INTEGER_to_BN(ASN1_INTEGER *ai,BIGNUM *bn);
293 /* given a string, return the correct type. Max is the maximum number
294 * of bytes to parse. It stops parsing when 'max' bytes have been
295 * processed or a '\0' is hit */
296 int ASN1_PRINTABLE_type(unsigned char *s,int max);
298 void ASN1_parse(BIO *fp,unsigned char *pp,long len);
300 int i2d_ASN1_bytes(ASN1_BIT_STRING *a, unsigned char **pp, int tag, int class);
301 ASN1_BIT_STRING *d2i_ASN1_bytes(ASN1_OCTET_STRING **a, unsigned char **pp,
302 long length, int Ptag, int Pclass);
305 int asn1_Finish(ASN1_CTX *c);
308 int ASN1_get_object(unsigned char **pp, long *plength, int *ptag,
309 int *pclass, long omax);
310 int ASN1_check_infinite_end(unsigned char **p,long len);
311 void ASN1_put_object(unsigned char **pp, int constructed, int length,
313 int ASN1_object_size(int constructed, int length, int tag);
315 X509 * X509_get_cert(CERTIFICATE_CTX *ctx,X509_NAME * name,X509 *tmp_x509);
316 int X509_add_cert(CERTIFICATE_CTX *ctx,X509 *);
318 char * X509_cert_verify_error_string(int n);
319 int X509_add_cert_file(CERTIFICATE_CTX *c,char *file, int type);
320 char * X509_gmtime (char *s, long adj);
321 int X509_add_cert_dir (CERTIFICATE_CTX *c,char *dir, int type);
322 int X509_load_verify_locations (CERTIFICATE_CTX *ctx,
323 char *file_env, char *dir_env);
324 int X509_set_default_verify_paths(CERTIFICATE_CTX *cts);
325 X509 * X509_new_D2i_X509(int len, unsigned char *p);
326 char * X509_get_default_cert_area(void );
327 char * X509_get_default_cert_dir(void );
328 char * X509_get_default_cert_file(void );
329 char * X509_get_default_cert_dir_env(void );
330 char * X509_get_default_cert_file_env(void );
331 char * X509_get_default_private_dir(void );
332 X509_REQ *X509_X509_TO_req(X509 *x, RSA *rsa);
333 int X509_cert_verify(CERTIFICATE_CTX *ctx,X509 *xs, int (*cb)());
335 CERTIFICATE_CTX *CERTIFICATE_CTX_new();
336 void CERTIFICATE_CTX_free(CERTIFICATE_CTX *c);
338 void X509_NAME_print(BIO *fp, X509_NAME *name, int obase);
339 int X509_print_fp(FILE *fp,X509 *x);
340 int X509_print(BIO *fp,X509 *x);
342 X509_INFO * X509_INFO_new(void);
343 void X509_INFO_free(X509_INFO *a);
345 char * X509_NAME_oneline(X509_NAME *a);
347 #define X509_verify(x,rsa)
348 #define X509_REQ_verify(x,rsa)
349 #define X509_CRL_verify(x,rsa)
351 #define X509_sign(x,rsa,md)
352 #define X509_REQ_sign(x,rsa,md)
353 #define X509_CRL_sign(x,rsa,md)
355 #define X509_dup(x509)
356 #define d2i_X509_fp(fp,x509)
357 #define i2d_X509_fp(fp,x509)
358 #define d2i_X509_bio(bp,x509)
359 #define i2d_X509_bio(bp,x509)
361 #define X509_CRL_dup(crl)
362 #define d2i_X509_CRL_fp(fp,crl)
363 #define i2d_X509_CRL_fp(fp,crl)
364 #define d2i_X509_CRL_bio(bp,crl)
365 #define i2d_X509_CRL_bio(bp,crl)
367 #define X509_REQ_dup(req)
368 #define d2i_X509_REQ_fp(fp,req)
369 #define i2d_X509_REQ_fp(fp,req)
370 #define d2i_X509_REQ_bio(bp,req)
371 #define i2d_X509_REQ_bio(bp,req)
373 #define RSAPrivateKey_dup(rsa)
374 #define d2i_RSAPrivateKey_fp(fp,rsa)
375 #define i2d_RSAPrivateKey_fp(fp,rsa)
376 #define d2i_RSAPrivateKey_bio(bp,rsa)
377 #define i2d_RSAPrivateKey_bio(bp,rsa)
379 #define X509_NAME_dup(xn)
380 #define X509_NAME_ENTRY_dup(ne)
382 void X509_REQ_print_fp(FILE *fp,X509_REQ *req);
383 void X509_REQ_print(BIO *fp,X509_REQ *req);
385 RSA *X509_REQ_extract_key(X509_REQ *req);
386 RSA *X509_extract_key(X509 *x509);
388 int X509_issuer_and_serial_cmp(X509 *a, X509 *b);
389 unsigned long X509_issuer_and_serial_hash(X509 *a);
391 X509_NAME * X509_get_issuer_name(X509 *a);
392 int X509_issuer_name_cmp(X509 *a, X509 *b);
393 unsigned long X509_issuer_name_hash(X509 *a);
395 X509_NAME * X509_get_subject_name(X509 *a);
396 int X509_subject_name_cmp(X509 *a,X509 *b);
397 unsigned long X509_subject_name_hash(X509 *x);
399 int X509_NAME_cmp (X509_NAME *a, X509_NAME *b);
400 unsigned long X509_NAME_hash(X509_NAME *x);