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[系统教程]Linux安全体系学习笔记之四：OpenSSL源代码分析(3)
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发布于：2011-12-29 21:25
 | |  |  | BIO是对IO操作的封装，OpenSSL的BIO抽象接口不仅可以对SSL连接的I/O使用，也可以对非加密的网络连接和文件的I/O使用。BIO的相关源代码在crypto/bio文件夹下。
BIO的相关数据结构列出如下。
BIO结构：
struct bio_st
{
BIO_METHOD *method;
/* bio, mode, argp, argi, argl, ret */
long (*callback)(struct bio_st *,int,const char *,int, long,long);
char *cb_arg; /* first argument for the callback */
int init;
int shutdown;
int flags; /* extra storage */
int retry_reason;
int num;
void *ptr;
struct bio_st *next_bio; /* used by filter Bios */
struct bio_st *prev_bio; /* used by filter BIOs */
int references;
unsigned long num_read;
unsigned long num_write;
CRYPTO_EX_DATA ex_data;
};
BIO操作的结构：
typedef struct bio_method_st
{
int type;
const char *name;
int (*bwrite)(BIO *, const char *, int);
int (*bread)(BIO *, char *, int);
int (*bputs)(BIO *, const char *);
int (*bgets)(BIO *, char *, int);
long (*ctrl)(BIO *, int, long, void *);
int (*create)(BIO *);
int (*destroy)(BIO *);
long (*callback_ctrl)(BIO *, int, bio_info_cb *);
} BIO_METHOD;
BIO接口类型分为源/接收类型和过滤类型两种。
#define BIO_TYPE_DESCRIPTOR0x0100 /* socket, fd, connect or accept */
#define BIO_TYPE_FILTER 0x0200
#define BIO_TYPE_SOURCE_SINK 0x0400
1、源/接收类型
#define BIO_TYPE_MEM(1|0x0400)
#define BIO_TYPE_FILE (2|0x0400)
#define BIO_TYPE_FD (4|0x0400|0x0100)
#define BIO_TYPE_SOCKET (5|0x0400|0x0100)
#define BIO_TYPE_NULL (6|0x0400)
#define BIO_TYPE_CONNECT(12|0x0400|0x0100)/* socket - connect */
#define BIO_TYPE_ACCEPT(13|0x0400|0x0100)/* socket for accept */
#define BIO_TYPE_BIO(19|0x0400)/* (half a) BIO pair */
#define BIO_TYPE_DGRAM(21|0x0400|0x0100)
2、过滤类型
#define BIO_TYPE_SSL(7|0x0200)
#define BIO_TYPE_MD(8|0x0200) /* passive filter */
#define BIO_TYPE_BUFFER (9|0x0200)/* filter */
#define BIO_TYPE_CIPHER (10|0x0200)/* filter */
#define BIO_TYPE_BASE64 (11|0x0200)/* filter */
#define BIO_TYPE_PROXY_CLIENT (14|0x0200)/* client proxy BIO */
#define BIO_TYPE_PROXY_SERVER (15|0x0200)/* server proxy BIO */
#define BIO_TYPE_NBIO_TEST (16|0x0200)/* server proxy BIO */
#define BIO_TYPE_NULL_FILTER (17|0x0200)
#define BIO_TYPE_BER (18|0x0200)/* BER -> bin filter */
#define BIO_TYPE_LINEBUFFER (20|0x0200)/* filter */
#define BIO_TYPE_ASN1 (22|0x0200)/* filter */
#define BIO_TYPE_COMP (23|0x0200)/* filter */
BIO过滤缓冲结构：
typedef struct bio_f_buffer_ctx_struct
{
/* BIO *bio; */ /* this is now in the BIO struct */
int ibuf_size; /* how big is the input buffer */
int obuf_size; /* how big is the output buffer */
char *ibuf; /* the char array */
int ibuf_len; /* how many bytes are in it */
int ibuf_off; /* write/read offset */
char *obuf; /* the char array */
int obuf_len; /* how many bytes are in it */
int obuf_off; /* write/read offset */
} BIO_F_BUFFER_CTX;
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