ssleay.txt

This last flag is mostly used when reading a password for encryption.

For all of these functions, a NULL callback will call the above mentioned
default callback.  This default function does not work under Windows 3.1.
For other machines, it will use an application defined prompt string
(EVP_set_pw_prompt(), which defines a library wide prompt string)
if defined, otherwise it will use it's own PEM password prompt.
It will then call EVP_read_pw_string() to get a password from the console.
If your application wishes to use nice fancy windows to retrieve passwords,
replace this function.  The callback should return the number of bytes read
into 'buf'.  If the number of bytes <= 0, it is considered an error.

Functions that take this callback are listed below.  For the 'read' type
functions, the callback will only be required if the PEM data is encrypted.

For the Write functions, normally a password can be passed in 'kstr', of
'klen' bytes which will be used if the 'enc' cipher is not NULL.  If
'kstr' is NULL, the callback will be used to retrieve a password.

int PEM_do_header (EVP_CIPHER_INFO *cipher, unsigned char *data,long *len,
	int (*callback)());
char *PEM_ASN1_read_bio(char *(*d2i)(),char *name,BIO *bp,char **x,int (*cb)());
char *PEM_ASN1_read(char *(*d2i)(),char *name,FILE *fp,char **x,int (*cb)());
int PEM_ASN1_write_bio(int (*i2d)(),char *name,BIO *bp,char *x,
	EVP_CIPHER *enc,unsigned char *kstr,int klen,int (*callback)());
int PEM_ASN1_write(int (*i2d)(),char *name,FILE *fp,char *x,
	EVP_CIPHER *enc,unsigned char *kstr,int klen,int (*callback)());
STACK *PEM_X509_INFO_read(FILE *fp, STACK *sk, int (*cb)());
STACK *PEM_X509_INFO_read_bio(BIO *fp, STACK *sk, int (*cb)());

#define	PEM_write_RSAPrivateKey(fp,x,enc,kstr,klen,cb)
#define	PEM_write_DSAPrivateKey(fp,x,enc,kstr,klen,cb)
#define	PEM_write_bio_RSAPrivateKey(bp,x,enc,kstr,klen,cb)
#define	PEM_write_bio_DSAPrivateKey(bp,x,enc,kstr,klen,cb)
#define	PEM_read_SSL_SESSION(fp,x,cb)
#define	PEM_read_X509(fp,x,cb)
#define	PEM_read_X509_REQ(fp,x,cb)
#define	PEM_read_X509_CRL(fp,x,cb)
#define	PEM_read_RSAPrivateKey(fp,x,cb)
#define	PEM_read_DSAPrivateKey(fp,x,cb)
#define	PEM_read_PrivateKey(fp,x,cb)
#define	PEM_read_PKCS7(fp,x,cb)
#define	PEM_read_DHparams(fp,x,cb)
#define	PEM_read_bio_SSL_SESSION(bp,x,cb)
#define	PEM_read_bio_X509(bp,x,cb)
#define	PEM_read_bio_X509_REQ(bp,x,cb)
#define	PEM_read_bio_X509_CRL(bp,x,cb)
#define	PEM_read_bio_RSAPrivateKey(bp,x,cb)
#define	PEM_read_bio_DSAPrivateKey(bp,x,cb)
#define	PEM_read_bio_PrivateKey(bp,x,cb)
#define	PEM_read_bio_PKCS7(bp,x,cb)
#define	PEM_read_bio_DHparams(bp,x,cb)
int i2d_Netscape_RSA(RSA *a, unsigned char **pp, int (*cb)());
RSA *d2i_Netscape_RSA(RSA **a, unsigned char **pp, long length, int (*cb)());

Now you will notice that macros like
#define PEM_write_X509(fp,x) \
                PEM_ASN1_write((int (*)())i2d_X509,PEM_STRING_X509,fp, \
		                        (char *)x, NULL,NULL,0,NULL)
Don't do encryption normally.  If you want to PEM encrypt your X509 structure,
either just call PEM_ASN1_write directly or just define your own
macro variant.  As you can see, this macro just sets all encryption related
parameters to NULL.


--------------------------
The SSL library.

#define SSL_set_info_callback(ssl,cb)
#define SSL_CTX_set_info_callback(ctx,cb)
void callback(SSL *ssl,int location,int ret)
This callback is called each time around the SSL_connect()/SSL_accept() 
state machine.  So it will be called each time the SSL protocol progresses.
It is mostly present for use when debugging.  When SSL_connect() or
SSL_accept() return, the location flag is SSL_CB_ACCEPT_EXIT or
SSL_CB_CONNECT_EXIT and 'ret' is the value about to be returned.
Have a look at the SSL_CB_* defines in ssl.h.  If an info callback is defined
against the SSL_CTX, it is called unless there is one set against the SSL.
Have a look at
void client_info_callback() in apps/s_client() for an example.

Certificate verification.
void SSL_set_verify(SSL *s, int mode, int (*callback) ());
void SSL_CTX_set_verify(SSL_CTX *ctx,int mode,int (*callback)());
This callback is used to help verify client and server X509 certificates.
It is actually passed to X509_cert_verify(), along with the SSL structure
so you have to read about X509_cert_verify() :-).  The SSL_CTX version is used
if the SSL version is not defined.  X509_cert_verify() is the function used
by the SSL part of the library to verify certificates.  This function is
nearly always defined by the application.

void SSL_CTX_set_cert_verify_cb(SSL_CTX *ctx, int (*cb)(),char *arg);
int callback(char *arg,SSL *s,X509 *xs,STACK *cert_chain);
This call is used to replace the SSLeay certificate verification code.
The 'arg' is kept in the SSL_CTX and is passed to the callback.
If the callback returns 0, the certificate is rejected, otherwise it
is accepted.  The callback is replacing the X509_cert_verify() call.
This feature is not often used, but if you wished to implement
some totally different certificate authentication system, this 'hook' is
vital.

SSLeay keeps a cache of session-ids against each SSL_CTX.  These callbacks can
be used to notify the application when a SSL_SESSION is added to the cache
or to retrieve a SSL_SESSION that is not in the cache from the application.
#define SSL_CTX_sess_set_get_cb(ctx,cb)
SSL_SESSION *callback(SSL *s,char *session_id,int session_id_len,int *copy);
If defined, this callback is called to return the SESSION_ID for the
session-id in 'session_id', of 'session_id_len' bytes.  'copy' is set to 1
if the server is to 'take a copy' of the SSL_SESSION structure.  It is 0
if the SSL_SESSION is being 'passed in' so the SSLeay library is now
responsible for 'free()ing' the structure.  Basically it is used to indicate
if the reference count on the SSL_SESSION structure needs to be incremented.

#define SSL_CTX_sess_set_new_cb(ctx,cb)
int callback(SSL *s, SSL_SESSION *sess);
When a new connection is established, if the SSL_SESSION is going to be added
to the cache, this callback is called.  Return 1 if a 'copy' is required,
otherwise, return 0.  This return value just causes the reference count
to be incremented (on return of a 1), this means the application does
not need to worry about incrementing the refernece count (and the
locking that implies in a multi-threaded application).

void SSL_CTX_set_default_passwd_cb(SSL_CTX *ctx,int (*cb)());
This sets the SSL password reading function.
It is mostly used for windowing applications
and used by PEM_read_bio_X509() and PEM_read_bio_RSAPrivateKey()
calls inside the SSL library.   The only reason this is present is because the
calls to PEM_* functions is hidden in the SSLeay library so you have to
pass in the callback some how.

#define SSL_CTX_set_client_cert_cb(ctx,cb)
int callback(SSL *s,X509 **x509, EVP_PKEY **pkey);
Called when a client certificate is requested but there is not one set
against the SSL_CTX or the SSL.  If the callback returns 1, x509 and
pkey need to point to valid data.  The library will free these when
required so if the application wants to keep these around, increment
their reference counts.  If 0 is returned, no client cert is
available.  If -1 is returned, it is assumed that the callback needs
to be called again at a later point in time.  SSL_connect will return
-1 and SSL_want_x509_lookup(ssl) returns true.  Remember that
application data can be attached to an SSL structure via the
SSL_set_app_data(SSL *ssl,char *data) call.

--------------------------
The X509 library.

int X509_cert_verify(CERTIFICATE_CTX *ctx,X509 *xs, int (*cb)(),
	int *error,char *arg,STACK *cert_chain);
int verify_callback(int ok,X509 *xs,X509 *xi,int depth,int error,char *arg,
	STACK *cert_chain);

X509_cert_verify() is used to authenticate X509 certificates.  The 'ctx' holds
the details of the various caches and files used to locate certificates.
'xs' is the certificate to verify and 'cb' is the application callback (more
detail later).  'error' will be set to the error code and 'arg' is passed
to the 'cb' callback.  Look at the VERIFY_* defines in crypto/x509/x509.h

When ever X509_cert_verify() makes a 'negative' decision about a
certitificate, the callback is called.  If everything checks out, the
callback is called with 'VERIFY_OK' or 'VERIFY_ROOT_OK' (for a self
signed cert that is not the passed certificate).

The callback is passed the X509_cert_verify opinion of the certificate 
in 'ok', the certificate in 'xs', the issuer certificate in 'xi',
the 'depth' of the certificate in the verification 'chain', the
VERIFY_* code in 'error' and the argument passed to X509_cert_verify()
in 'arg'. cert_chain is a list of extra certs to use if they are not
in the cache.

The callback can be used to look at the error reason, and then return 0
for an 'error' or '1' for ok.  This will override the X509_cert_verify()
opinion of the certificates validity.  Processing will continue depending on
the return value.  If one just wishes to use the callback for informational
reason, just return the 'ok' parameter.

--------------------------
The BN and DH library.

BIGNUM *BN_generate_prime(int bits,int strong,BIGNUM *add,
	BIGNUM *rem,void (*callback)(int,int));
int BN_is_prime(BIGNUM *p,int nchecks,void (*callback)(int,int),

Read doc/bn.doc for the description of these 2.

DH *DH_generate_parameters(int prime_len,int generator,
	void (*callback)(int,int));
Read doc/bn.doc for the description of the callback, since it is just passed
to BN_generate_prime(), except that it is also called as
callback(3,0) by this function.

--------------------------
The CRYPTO library.

void CRYPTO_set_locking_callback(void (*func)(int mode,int type,char *file,
	int line));
void CRYPTO_set_add_lock_callback(int (*func)(int *num,int mount,
	int type,char *file, int line));
void CRYPTO_set_id_callback(unsigned long (*func)(void));

Read threads.doc for info on these ones.


==== cipher.doc ========================================================

The Cipher subroutines.

These routines require "evp.h" to be included.

These functions are a higher level interface to the various cipher
routines found in this library.  As such, they allow the same code to be
used to encrypt and decrypt via different ciphers with only a change
in an initial parameter.  These routines also provide buffering for block
ciphers.

These routines all take a pointer to the following structure to specify
which cipher to use.  If you wish to use a new cipher with these routines,
you would probably be best off looking an how an existing cipher is
implemented and copying it.  At this point in time, I'm not going to go
into many details.  This structure should be considered opaque

typedef struct pem_cipher_st
	{
	int type;
	int block_size;
	int key_len;
	int iv_len;
	void (*enc_init)();	/* init for encryption */
	void (*dec_init)();	/* init for decryption */
	void (*do_cipher)();	/* encrypt data */
	} EVP_CIPHER;
	
The type field is the object NID of the cipher type
(read the section on Objects for an explanation of what a NID is).
The cipher block_size is how many bytes need to be passed
to the cipher at a time.  Key_len is the
length of the key the cipher requires and iv_len is the length of the
initialisation vector required.  enc_init is the function
called to initialise the ciphers context for encryption and dec_init is the
function to initialise for decryption (they need to be different, especially
for the IDEA cipher).

One reason for specifying the Cipher via a pointer to a structure
is that if you only use des-cbc, only the des-cbc routines will
be included when you link the program.  If you passed an integer
that specified which cipher to use, the routine that mapped that
integer to a set of cipher functions would cause all the ciphers
to be link into the code.  This setup also allows new ciphers
to be added by the application (with some restrictions).

The thirteen ciphers currently defined in this library are

EVP_CIPHER *EVP_des_ecb();     /* DES in ecb mode,     iv=0, block=8, key= 8 */
EVP_CIPHER *EVP_des_ede();     /* DES in ecb ede mode, iv=0, block=8, key=16 */
EVP_CIPHER *EVP_des_ede3();    /* DES in ecb ede mode, iv=0, block=8, key=24 */
EVP_CIPHER *EVP_des_cfb();     /* DES in cfb mode,     iv=8, block=1, key= 8 */
EVP_CIPHER *EVP_des_ede_cfb(); /* DES in ede cfb mode, iv=8, block=1, key=16 */
EVP_CIPHER *EVP_des_ede3_cfb();/* DES in ede cfb mode, iv=8, block=1, key=24 */
EVP_CIPHER *EVP_des_ofb();     /* DES in ofb mode,     iv=8, block=1, key= 8 */
EVP_CIPHER *EVP_des_ede_ofb(); /* DES in ede ofb mode, iv=8, block=1, key=16 */
EVP_CIPHER *EVP_des_ede3_ofb();/* DES in ede ofb mode, iv=8, block=1, key=24 */
EVP_CIPHER *EVP_des_cbc();     /* DES in cbc mode,     iv=8, block=8, key= 8 */
EVP_CIPHER *EVP_des_ede_cbc(); /* DES in cbc ede mode, iv=8, block=8, key=16 */
EVP_CIPHER *EVP_des_ede3_cbc();/* DES in cbc ede mode, iv=8, block=8, key=24 */
EVP_CIPHER *EVP_desx_cbc();    /* DES in desx cbc mode,iv=8, block=8, key=24 */
EVP_CIPHER *EVP_rc4();         /* RC4,                 iv=0, block=1, key=16 */
EVP_CIPHER *EVP_idea_ecb();    /* IDEA in ecb mode,    iv=0, block=8, key=16 */
EVP_CIPHER *EVP_idea_cfb();    /* IDEA in cfb mode,    iv=8, block=1, key=16 */
EVP_CIPHER *EVP_idea_ofb();    /* IDEA in ofb mode,    iv=8, block=1, key=16 */
EVP_CIPHER *EVP_idea_cbc();    /* IDEA in cbc mode,    iv=8, block=8, key=16 */
EVP_CIPHER *EVP_rc2_ecb();     /* RC2 in ecb mode,     iv=0, block=8, key=16 */
EVP_CIPHER *EVP_rc2_cfb();     /* RC2 in cfb mode,     iv=8, block=1, key=16 */
EVP_CIPHER *EVP_rc2_ofb();     /* RC2 in ofb mode,     iv=8, block=1, key=16 */
EVP_CIPHER *EVP_rc2_cbc();     /* RC2 in cbc mode,     iv=8, block=8, key=16 */
EVP_CIPHER *EVP_bf_ecb();      /* Blowfish in ecb mode,iv=0, block=8, key=16 */
EVP_CIPHER *EVP_bf_cfb();      /* Blowfish in cfb mode,iv=8, block=1, key=16 */
EVP_CIPHER *EVP_bf_ofb();      /* Blowfish in ofb mode,iv=8, block=1, key=16 */
EVP_CIPHER *EVP_bf_cbc();      /* Blowfish in cbc mode,iv=8, block=8, key=16 */

The meaning of the compound names is as follows.
des	The base cipher is DES.
idea	The base cipher is IDEA
rc4	The base cipher is RC4-128
rc2	The base cipher is RC2-128
ecb	Electronic Code Book form of the cipher.
cbc	Cipher Block Chaining form of the cipher.
cfb	64 bit Cipher Feedback form of the cipher.
ofb	64 bit Output Feedback form of the cipher.
ede	The cipher is used in Encrypt, Decrypt, Encrypt mode.  The first
	and last keys are the same.
ede3	The cipher is used in Encrypt, Decrypt, Encrypt mode.

All the Cipher routines take a EVP_CIPHER_CTX pointer as an argument.
The state of the cipher is kept in this structure.

typedef struct EVP_CIPHER_Ctx_st
	{
	EVP_CIPHER *cipher;
	int encrypt;		/* encrypt or decrypt */
	int buf_len;		/* number we have left */
	unsigned char buf[8];
	union	{
		.... /* cipher specific stuff */
		} c;
	} EVP_CIPHER_CTX;

Cipher is a pointer the the EVP_CIPHER for the current context.  The encrypt
flag indicates encryption or decryption.  buf_len is the number of bytes
currently being held in buf.
The 'c' union holds the cipher specify context.

The following functions are to be used.

int EVP_read_pw_string(
char *buf,
int len,
char *prompt,
int verify,
	This function is the same as des_read_pw_string() (des.doc).

void EVP_set_pw_prompt(char *prompt);
	This function sets the 'default' prompt to use to use in
	EVP_read_pw_string when the prompt parameter is NULL.  If the
	prompt parameter is NULL, this 'default prompt' feature is turned
	off.  Be warned, this is a global variable so weird things
	will happen if it is used under Win16 and care must be taken
	with a multi-threaded version of the library.

char *EVP_get_pw_prompt();
	This returns a pointer to the default prompt string.  NULL
	if it is not set.

int EVP_BytesToKey(
EVP_CIPHER *type,
EVP_MD *md,
unsigned char *salt,
unsigned char *data,
int datal,
int count,
unsigned char *key,
unsigned char *iv);
	This function is used to generate a key and an initialisation vector
	for a specified cipher from a key string and a salt.  Type
	specifies the cipher the 'key' is being generated for.  Md is the
	message digest algorithm to use to generate the key and iv.  The salt
	is an optional 8 byte object that is used to help seed the key
	generator.
	If the salt value is NULL, it is just not used.  Datal is the
	number of bytes to use from 'data' in the key generation.  
	This function returns the key size for the specified cipher, if
	data is NULL, this value is returns and no other
	computation is performed.  Count is
	the number of times to loop around the key generator.  I would
	suggest leaving it's value as 1.  Key and iv are the structures to
	place the returning iv and key in.  If they are NULL, no value is
	generated for that particular value.
	The algorithm used is as follows
	
	/* M[] is an array of message digests
	 * MD() is the message digest function */
	M[0]=MD(data . salt);
	for (i=1; i<count; i++) M[0]=MD(M[0]);

	i=1
	while (data still needed for key and iv)
		{
		M[i]=MD(M[i-1] . data . salt);
		for (i=1; i<count; i++) M[i]=MD(M[i]);
		i++;
		}

	If the salt is NULL, it is not used.
	The digests are concatenated together.
	M = M[0] . M[1] . M[2] .......

	For key= 8, iv=8 => key=M[0.. 8], iv=M[ 9 .. 16].
	For key=16, iv=0 => key=M[0..16].
	For key=16, iv=8 => key=M[0..16], iv=M[17 .. 24].
	For key=24, iv=8 => key=M[0..24], iv=M[25 .. 32].

	This routine will produce DES-CBC keys and iv that are compatible
	with the PKCS-5 standard when md2 or md5 are used.  If md5 is
	used, the salt is NULL and count is 1, this routine will produce
	the password to key mapping normally used with RC4.
	I have attempted to logically extend the PKCS-5 standard to
	generate keys and iv for ciphers that require more than 16 bytes,
	if anyone knows what the correct standard is, please inform me.
	When using sha or sha1, things are a bit different under this scheme,
	since sha produces a 20 byte digest.  So for ciphers requiring
	24 bits of data, 20 will come from the first MD and 4 will
	come from the second.

	I have considered having a separate function so this 'routine'
	can be used without the requirement of passing a EVP_CIPHER *,
	but I have decided to not bother.  If you wish to use the
	function without official EVP_CIPHER structures, just declare
	a local one and set the key_len and iv_len fields to the
	length you desire.

The following routines perform encryption and decryption 'by parts'.  By
this I mean that there are groups of 3 routines.  An Init function that is
used to specify a cipher and initialise data structures.  An Update routine
that does encryption/decryption, one 'chunk' at a time.  And finally a
'Final' function that finishes the encryption/decryption process.
All these functions take a EVP_CIPHER pointer to specify which cipher to
encrypt/decrypt with.  They also take a EVP_CIPHER_CTX object as an
argument.  This structure is used to hold the state information associated
with the operation in progress.

void EVP_EncryptInit(
EVP_CIPHER_CTX *ctx,
EVP_CIPHER *type,
unsigned char *key,
unsigned char *iv);
	This function initialise a EVP_CIPHER_CTX for encryption using the
	cipher passed in the 'type' field.  The cipher is initialised to use
	'key' as the key and 'iv' for the initialisation vector (if one is
	required).  If the type, key or iv is NULL, the value currently in the
	EVP_CIPHER_CTX is reused.  So to perform several decrypt
	using the same cipher, key and iv, initialise with the cipher,
	key and iv the first time and then for subsequent calls,
	reuse 'ctx' but pass NULL for type, key and iv.  You must make sure
	to pass a key that is large enough for a particular cipher.  I
	would suggest using the EVP_BytesToKey() function.

void EVP_EncryptUpdate(
EVP_CIPHER_CTX *ctx,
unsigned char *out,
int *outl,
unsigned char *in,
int inl);
	This function takes 'inl' bytes from 'in' and outputs bytes
	encrypted by the cipher 'ctx' was initialised with into 'out'.  The
	number of bytes written to 'out' is put into outl.  If a particular
	cipher encrypts in blocks, less or more bytes than input may be
	output.  Currently the largest block size used by supported ciphers
	is 8 bytes, so 'out' should have room for 'inl+7' bytes.  Normally
	EVP_EncryptInit() is called once, followed by lots and lots of
	calls to EVP_EncryptUpdate, followed by a single EVP_EncryptFinal
	call.

void EVP_EncryptFinal(
EVP_CIPHER_CTX *ctx,
unsigned char *out,
int *outl);
	Because quite a large number of ciphers are block ciphers, there is
	often an incomplete block to write out at the end of the
	encryption.  EVP_EncryptFinal() performs processing on this last
	block.  The last block in encoded in such a way that it is possible
	to determine how many bytes in the last block are valid.  For 8 byte
	block size ciphers, if only 5 bytes in the last block are valid, the
	last three bytes will be filled with the value 3.  If only 2 were
	valid, the other 6 would be filled with sixes.  If all 8 bytes are
	valid, a extra 8 bytes are appended to the cipher stream containing
	nothing but 8 eights.  These last bytes are output into 'out' and
	the number of bytes written is put into 'outl'  These last bytes
	are output into 'out' and the number of bytes written is put into
	'outl'.  This form of block cipher finalisation is compatible with
	PKCS-5.  Please remember that even if you are using ciphers like
	RC4 that has no blocking and so the function will not write
	anything into 'out', it would still be a good idea to pass a
	variable for 'out' that can hold 8 bytes just in case the cipher is
	changed some time in the future.  It should also be remembered
	that the EVP_CIPHER_CTX contains the password and so when one has
	finished encryption with a particular EVP_CIPHER_CTX, it is good
	practice to zero the structure 
	(ie. memset(ctx,0,sizeof(EVP_CIPHER_CTX)).
	
void EVP_DecryptInit(
EVP_CIPHER_CTX *ctx,
EVP_CIPHER *type,
unsigned char *key,
unsigned char *iv);
	This function is basically the same as EVP_EncryptInit() accept that
	is prepares the EVP_CIPHER_CTX for decryption.

void EVP_DecryptUpdate(
EVP_CIPHER_CTX *ctx,
unsigned char *out,
int *outl,
unsigned char *in,
int inl);
	This function is basically the same as EVP_EncryptUpdate()
	except that it performs decryption.  There is one
	fundamental difference though.  'out' can not be the same as
	'in' for any ciphers with a block size greater than 1 if more
	than one call to EVP_DecryptUpdate() will be made.  This
	is because this routine can hold a 'partial' block between
	calls.  When a partial block is decrypted (due to more bytes
	being passed via this function, they will be written to 'out'
	overwriting the input bytes in 'in' that have not been read
	yet.  From this it should also be noted that 'out' should
	be at least one 'block size' larger than 'inl'.  This problem
	only occurs on the second and subsequent call to
	EVP_DecryptUpdate() when using a block cipher.

int EVP_DecryptFinal(
EVP_CIPHER_CTX *ctx,
unsigned char *out,
int *outl);
	This function is different to EVP_EncryptFinal in that it 'removes'
	any padding bytes appended when the data was encrypted.  Due to the
	way in which 1 to 8 bytes may have been appended when encryption
	using a block cipher, 'out' can end up with 0 to 7 bytes being put
	into it.  When decoding the padding bytes, it is possible to detect
	an incorrect decryption.  If the decryption appears to be wrong, 0
	is returned.  If everything seems ok, 1 is returned.  For ciphers
	with a block size of 1 (RC4), this function would normally not
	return any bytes and would always return 1.  Just because this
	function returns 1 does not mean the decryption was correct. It
	would normally be wrong due to either the wrong key/iv or
	corruption of the cipher data fed to EVP_DecryptUpdate().
	As for EVP_EncryptFinal, it is a good idea to zero the
	EVP_CIPHER_CTX after use since the structure contains the key used
	to decrypt the data.
	
The following Cipher routines are convenience routines that call either
EVP_EncryptXxx or EVP_DecryptXxx depending on weather the EVP_CIPHER_CTX
was setup to encrypt or decrypt.  

void EVP_CipherInit(
EVP_CIPHER_CTX *ctx,
EVP_CIPHER *type,
unsigned char *key,
unsigned char *iv,
int enc);
	This function take arguments that are the same as EVP_EncryptInit()
	and EVP_DecryptInit() except for the extra 'enc' flag.  If 1, the
	EVP_CIPHER_CTX is setup for encryption, if 0, decryption.

void EVP_CipherUpdate(
EVP_CIPHER_CTX *ctx,
unsigned char *out,
int *outl,
unsigned char *in,
int inl);
	Again this function calls either EVP_EncryptUpdate() or
	EVP_DecryptUpdate() depending on state in the 'ctx' structure.
	As noted for EVP_DecryptUpdate(), when this routine is used
	for decryption with block ciphers, 'out' should not be the
	same as 'in'.

int EVP_CipherFinal(
EVP_CIPHER_CTX *ctx,
unsigned char *outm,
int *outl);
	This routine call EVP_EncryptFinal() or EVP_DecryptFinal()
	depending on the state information in 'ctx'.  1 is always returned
	if the mode is encryption, otherwise the return value is the return
	value of EVP_DecryptFinal().

==== cipher.m ========================================================

Date: Tue, 15 Oct 1996 08:16:14 +1000 (EST)
From: Eric Young <eay@mincom.com>
X-Sender: eay@orb
To: Roland Haring <rharing@tandem.cl>
Cc: ssl-users@mincom.com
Subject: Re: Symmetric encryption with ssleay
In-Reply-To: <m0vBpyq-00001aC@tandemnet.tandem.cl>
Message-Id: <Pine.SOL.3.91.961015075623.11394A-100000@orb>
Mime-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: ssl-lists-owner@mincom.com
Precedence: bulk
Status: RO
X-Status: 

On Fri, 11 Oct 1996, Roland Haring wrote:
> THE_POINT:
> 	Would somebody be so kind to give me the minimum basic 
> 	calls I need to do to libcrypto.a to get some text encrypted
> 	and decrypted again? ...hopefully with code included to do
> 	base64 encryption and decryption ... e.g. that sign-it.c code
> 	posted some while ago was a big help :-) (please, do not point
> 	me to apps/enc.c where I suspect my Heissenbug to be hidden :-)

Ok, the base64 encoding stuff in 'enc.c' does the wrong thing sometimes 
when the data is less than a line long (this is for decoding).  I'll dig 
up the exact fix today and post it.  I am taking longer on 0.6.5 than I 
intended so I'll just post this patch.

The documentation to read is in
doc/cipher.doc,
doc/encode.doc (very sparse :-).
and perhaps
doc/digest.doc,

The basic calls to encrypt with say triple DES are

Given
char key[EVP_MAX_KEY_LENGTH];
char iv[EVP_MAX_IV_LENGTH];
EVP_CIPHER_CTX ctx;
unsigned char out[512+8];
int outl;

/* optional generation of key/iv data from text password using md5
 * via an upward compatable verson of PKCS#5. */
EVP_BytesToKey(EVP_des_ede3_cbc,EVP_md5,NULL,passwd,strlen(passwd),
	key,iv);

/* Initalise the EVP_CIPHER_CTX */
EVP_EncryptInit(ctx,EVP_des_ede3_cbc,key,iv);

while (....)
	{
	/* This is processing 512 bytes at a time, the bytes are being
	 * copied into 'out', outl bytes are output.  'out' should not be the
	 * same as 'in' for reasons mentioned in the documentation. */
	EVP_EncryptUpdate(ctx,out,&outl,in,512);
	}

/* Output the last 'block'.  If the cipher is a block cipher, the last
 * block is encoded in such a way so that a wrong decryption will normally be
 * detected - again, one of the PKCS standards. */

EVP_EncryptFinal(ctx,out,&outl);

To decrypt, use the EVP_DecryptXXXXX functions except that EVP_DecryptFinal()
will return 0 if the decryption fails (only detectable on block ciphers).

You can also use
EVP_CipherInit()
EVP_CipherUpdate()
EVP_CipherFinal()
which does either encryption or decryption depending on an extra 
parameter to EVP_CipherInit().


To do the base64 encoding,
EVP_EncodeInit()
EVP_EncodeUpdate()
EVP_EncodeFinal()

EVP_DecodeInit()
EVP_DecodeUpdate()
EVP_DecodeFinal()

where the encoding is quite simple, but the decoding can be a bit more 
fun (due to dud input).

EVP_DecodeUpdate() returns -1 for an error on an input line, 0 if the 
'last line' was just processed, and 1 if more lines should be submitted.

EVP_DecodeFinal() returns -1 for an error or 1 if things are ok.

So the loop becomes
EVP_DecodeInit(....)
for (;;)
	{
	i=EVP_DecodeUpdate(....);
	if (i < 0) goto err;

	/* process the data */

	if (i == 0) break;
	}
EVP_DecodeFinal(....);
/* process the data */

The problem in 'enc.c' is that I was stuff the processing up after the 
EVP_DecodeFinal(...) when the for(..) loop was not being run (one line of 
base64 data) and this was because 'enc.c' tries to scan over a file until
it hits the first valid base64 encoded line.

hope this helps a bit.
eric
--
Eric Young                  | BOOL is tri-state according to Bill Gates.
AARNet: eay@mincom.oz.au    | RTFM Win32 GetMessage().

==== conf.doc ========================================================

The CONF library.

The CONF library is a simple set of routines that can be used to configure
programs.  It is a superset of the genenv() function with some extra
structure.

The library consists of 5 functions.

LHASH *CONF_load(LHASH *config,char *file);
This function is called to load in a configuration file.  Multiple
configuration files can be loaded, with each subsequent 'load' overwriting
any already defined 'variables'.  If there is an error, NULL is returned.
If config is NULL, a new LHASH structure is created and returned, otherwise
the new data in the 'file' is loaded into the 'config' structure.

void CONF_free(LHASH *config);
This function free()s the data in config.

char *CONF_get_string(LHASH *config,char *section,char *name);
This function returns the string found in 'config' that corresponds to the
'section' and 'name' specified.  Classes and the naming system used will be
discussed later in this document.  If the variable is not defined, an NULL
is returned.

long CONF_get_long(LHASH *config,char *section, char *name);
This function is the same as CONF_get_string() except that it converts the
string to an long and returns it.  If variable is not a number or the
variable does not exist, 0 is returned.  This is a little problematic but I
don't know of a simple way around it.

STACK *CONF_get_section(LHASH *config, char *section);
This function returns a 'stack' of CONF_VALUE items that are all the
items defined in a particular section.  DO NOT free() any of the
variable returned.  They will disappear when CONF_free() is called.

The 'lookup' model.
The configuration file is divided into 'sections'.  Each section is started by
a line of the form '[ section ]'.  All subsequent variable definitions are
of this section.  A variable definition is a simple alpha-numeric name
followed by an '=' and then the data.  A section or variable name can be
described by a regular expression of the following form '[A-Za-z0-9_]+'.
The value of the variable is the text after the '=' until the end of the
line, stripped of leading and trailing white space.
At this point I should mention that a '#' is a comment character, \ is the
escape character, and all three types of quote can be used to stop any
special interpretation of the data.
Now when the data is being loaded, variable expansion can occur.  This is
done by expanding any $NAME sequences into the value represented by the
variable NAME.  If the variable is not in the current section, the different
section can be specified by using the $SECTION::NAME form.  The ${NAME} form
also works and is very useful for expanding variables inside strings.

When a variable is looked up, there are 2 special section. 'default', which
is the initial section, and 'ENV' which is the processes environment
variables (accessed via getenv()).  When a variable is looked up, it is
first 'matched' with it's section (if one was specified), if this fails, the
'default' section is matched.
If the 'lhash' variable passed was NULL, the environment is searched.

Now why do we bother with sections?  So we can have multiple programs using
the same configuration file, or multiple instances of the same program
using different variables.  It also provides a nice mechanism to override
the processes environment variables (eg ENV::HOME=/tmp).  If there is a
program specific variable missing, we can have default values.
Multiple configuration files can be loaded, with each new value clearing
any predefined values.  A system config file can provide 'default' values,
and application/usr specific files can provide overriding values.

Examples

# This is a simple example
SSLEAY_HOME	= /usr/local/ssl
ENV::PATH	= $SSLEAY_HOME/bin:$PATH	# override my path

[X509]
cert_dir	= $SSLEAY_HOME/certs	# /usr/local/ssl/certs

[SSL]
CIPHER		= DES-EDE-MD5:RC4-MD5
USER_CERT	= $HOME/${USER}di'r 5'	# /home/eay/eaydir 5
USER_CERT	= $HOME/\${USER}di\'r	# /home/eay/${USER}di'r
USER_CERT	= "$HOME/${US"ER}di\'r	# $HOME/${USER}di'r

TEST		= 1234\
5678\
9ab					# TEST=123456789ab
TTT		= 1234\n\n		# TTT=1234<nl><nl>



==== des.doc ========================================================

The DES library.

Please note that this library was originally written to operate with
eBones, a version of Kerberos that had had encryption removed when it left
the USA and then put back in.  As such there are some routines that I will
advise not using but they are still in the library for historical reasons.
For all calls that have an 'input' and 'output' variables, they can be the
same.

This library requires the inclusion of 'des.h'.

All of the encryption functions take what is called a des_key_schedule as an 
argument.  A des_key_schedule is an expanded form of the des key.
A des_key is 8 bytes of odd parity, the type used to hold the key is a
des_cblock.  A des_cblock is an array of 8 bytes, often in this library
description I will refer to input bytes when the function specifies
des_cblock's as input or output, this just means that the variable should
be a multiple of 8 bytes.

The define DES_ENCRYPT is passed to specify encryption, DES_DECRYPT to
specify decryption.  The functions and global variable are as follows:

int des_check_key;
	DES keys are supposed to be odd parity.  If this variable is set to
	a non-zero value, des_set_key() will check that the key has odd
	parity and is not one of the known weak DES keys.  By default this
	variable is turned off;
	
void des_set_odd_parity(
des_cblock *key );
	This function takes a DES key (8 bytes) and sets the parity to odd.
	
int des_is_weak_key(
des_cblock *key );
	This function returns a non-zero value if the DES key passed is a
	weak, DES key.  If it is a weak key, don't use it, try a different
	one.  If you are using 'random' keys, the chances of hitting a weak
	key are 1/2^52 so it is probably not worth checking for them.
	
int des_set_key(
des_cblock *key,
des_key_schedule schedule);
	Des_set_key converts an 8 byte DES key into a des_key_schedule.
	A des_key_schedule is an expanded form of the key which is used to
	perform actual encryption.  It can be regenerated from the DES key
	so it only needs to be kept when encryption or decryption is about
	to occur.  Don't save or pass around des_key_schedule's since they
	are CPU architecture dependent, DES keys are not.  If des_check_key
	is non zero, zero is returned if the key has the wrong parity or
	the key is a weak key, else 1 is returned.
	
int des_key_sched(
des_cblock *key,
des_key_schedule schedule);
	An alternative name for des_set_key().

int des_rw_mode;		/* defaults to DES_PCBC_MODE */
	This flag holds either DES_CBC_MODE or DES_PCBC_MODE (default).
	This specifies the function to use in the enc_read() and enc_write()
	functions.

void des_encrypt(
unsigned long *data,
des_key_schedule ks,
int enc);
	This is the DES encryption function that gets called by just about
	every other DES routine in the library.  You should not use this
	function except to implement 'modes' of DES.  I say this because the
	functions that call this routine do the conversion from 'char *' to
	long, and this needs to be done to make sure 'non-aligned' memory
	access do not occur.  The characters are loaded 'little endian',
	have a look at my source code for more details on how I use this
	function.
	Data is a pointer to 2 unsigned long's and ks is the
	des_key_schedule to use.  enc, is non zero specifies encryption,
	zero if decryption.

void des_encrypt2(
unsigned long *data,
des_key_schedule ks,
int enc);
	This functions is the same as des_encrypt() except that the DES
	initial permutation (IP) and final permutation (FP) have been left
	out.  As for des_encrypt(), you should not use this function.
	It is used by the routines in my library that implement triple DES.
	IP() des_encrypt2() des_encrypt2() des_encrypt2() FP() is the same
	as des_encrypt() des_encrypt() des_encrypt() except faster :-).

void des_ecb_encrypt(
des_cblock *input,
des_cblock *output,
des_key_schedule ks,
int enc);
	This is the basic Electronic Code Book form of DES, the most basic
	form.  Input is encrypted into output using the key represented by
	ks.  If enc is non zero (DES_ENCRYPT), encryption occurs, otherwise
	decryption occurs.  Input is 8 bytes long and output is 8 bytes.
	(the des_cblock structure is 8 chars).
	
void des_ecb3_encrypt(
des_cblock *input,
des_cblock *output,
des_key_schedule ks1,
des_key_schedule ks2,
des_key_schedule ks3,
int enc);
	This is the 3 key EDE mode of ECB DES.  What this means is that 
	the 8 bytes of input is encrypted with ks1, decrypted with ks2 and
	then encrypted again with ks3, before being put into output;
	C=E(ks3,D(ks2,E(ks1,M))).  There is a macro, des_ecb2_encrypt()
	that only takes 2 des_key_schedules that implements,
	C=E(ks1,D(ks2,E(ks1,M))) in that the final encrypt is done with ks1.
	
void des_cbc_encrypt(
des_cblock *input,
des_cblock *output,
long length,
des_key_schedule ks,
des_cblock *ivec,
int enc);
	This routine implements DES in Cipher Block Chaining mode.
	Input, which should be a multiple of 8 bytes is encrypted
	(or decrypted) to output which will also be a multiple of 8 bytes.
	The number of bytes is in length (and from what I've said above,
	should be a multiple of 8).  If length is not a multiple of 8, I'm
	not being held responsible :-).  ivec is the initialisation vector.
	This function does not modify this variable.  To correctly implement
	cbc mode, you need to do one of 2 things; copy the last 8 bytes of
	cipher text for use as the next ivec in your application,
	or use des_ncbc_encrypt(). 
	Only this routine has this problem with updating the ivec, all
	other routines that are implementing cbc mode update ivec.
	
void des_ncbc_encrypt(
des_cblock *input,
des_cblock *output,
long length,
des_key_schedule sk,
des_cblock *ivec,
int enc);
	For historical reasons, des_cbc_encrypt() did not update the
	ivec with the value requires so that subsequent calls to
	des_cbc_encrypt() would 'chain'.  This was needed so that the same
	'length' values would not need to be used when decrypting.
	des_ncbc_encrypt() does the right thing.  It is the same as
	des_cbc_encrypt accept that ivec is updates with the correct value
	to pass in subsequent calls to des_ncbc_encrypt().  I advise using
	des_ncbc_encrypt() instead of des_cbc_encrypt();

void des_xcbc_encrypt(
des_cblock *input,
des_cblock *output,
long length,
des_key_schedule sk,
des_cblock *ivec,
des_cblock *inw,
des_cblock *outw,
int enc);
	This is RSA's DESX mode of DES.  It uses inw and outw to
	'whiten' the encryption.  inw and outw are secret (unlike the iv)
	and are as such, part of the key.  So the key is sort of 24 bytes.
	This is much better than cbc des.
	
void des_3cbc_encrypt(
des_cblock *input,
des_cblock *output,
long length,
des_key_schedule sk1,
des_key_schedule sk2,
des_cblock *ivec1,
des_cblock *ivec2,
int enc);
	This function is flawed, do not use it.  I have left it in the
	library because it is used in my des(1) program and will function
	correctly when used by des(1).  If I removed the function, people
	could end up unable to decrypt files.
	This routine implements outer triple cbc encryption using 2 ks and
	2 ivec's.  Use des_ede2_cbc_encrypt() instead.
	
void des_ede3_cbc_encrypt(
des_cblock *input,
des_cblock *output, 
long length,
des_key_schedule ks1,
des_key_schedule ks2, 
des_key_schedule ks3, 
des_cblock *ivec,
int enc);
	This function implements outer triple CBC DES encryption with 3
	keys.  What this means is that each 'DES' operation
	inside the cbc mode is really an C=E(ks3,D(ks2,E(ks1,M))).
	Again, this is cbc mode so an ivec is requires.
	This mode is used by SSL.
	There is also a des_ede2_cbc_encrypt() that only uses 2
	des_key_schedule's, the first being reused for the final
	encryption.  C=E(ks1,D(ks2,E(ks1,M))).  This form of triple DES
	is used by the RSAref library.
	
void des_pcbc_encrypt(
des_cblock *input,
des_cblock *output,
long length,
des_key_schedule ks,
des_cblock *ivec,
int enc);
	This is Propagating Cipher Block Chaining mode of DES.  It is used
	by Kerberos v4.  It's parameters are the same as des_ncbc_encrypt().
	
void des_cfb_encrypt(
unsigned char *in,
unsigned char *out,
int numbits,
long length,
des_key_schedule ks,
des_cblock *ivec,
int enc);
	Cipher Feedback Back mode of DES.  This implementation 'feeds back'
	in numbit blocks.  The input (and output) is in multiples of numbits
	bits.  numbits should to be a multiple of 8 bits.  Length is the
	number of bytes input.  If numbits is not a multiple of 8 bits,
	the extra bits in the bytes will be considered padding.  So if
	numbits is 12, for each 2 input bytes, the 4 high bits of the
	second byte will be ignored.  So to encode 72 bits when using
	a numbits of 12 take 12 bytes.  To encode 72 bits when using
	numbits of 9 will take 16 bytes.  To encode 80 bits when using
	numbits of 16 will take 10 bytes. etc, etc.  This padding will
	apply to both input and output.

	
void des_cfb64_encrypt(
unsigned char *in,
unsigned char *out,
long length,
des_key_schedule ks,
des_cblock *ivec,