#include#include
BIO_METHOD * BIO_f_md(void); int BIO_set_md(BIO *b,EVP_MD *md); int BIO_get_md(BIO *b,EVP_MD **mdp); int BIO_get_md_ctx(BIO *b,EVP_MD_CTX **mdcp);
Any data written or read through a digest BIO using _B_I_O___r_e_a_d_(_) and _B_I_O___w_r_i_t_e_(_) is digested.
_B_I_O___g_e_t_s_(_), if its ssiizzee parameter is large enough finishes the digest calculation and returns the digest value. _B_I_O___p_u_t_s_(_) is not supported.
_B_I_O___r_e_s_e_t_(_) reinitialises a digest BIO.
_B_I_O___s_e_t___m_d_(_) sets the message digest of BIO bb to mmdd: this must be called to initialize a digest BIO before any data is passed through it. It is a _B_I_O___c_t_r_l_(_) macro.
_B_I_O___g_e_t___m_d_(_) places the a pointer to the digest BIOs digest method in mmddpp, it is a _B_I_O___c_t_r_l_(_) macro.
_B_I_O___g_e_t___m_d___c_t_x_(_) returns the digest BIOs context into mmddccpp.
The context returned by _B_I_O___g_e_t___m_d___c_t_x_(_) is an internal context structure. Changes made to this context will affect the digest BIO itself and the context pointer will become invalid when the digest BIO is freed.
After the digest has been retrieved from a digest BIO it must be reinitialized by calling _B_I_O___r_e_s_e_t_(_), or _B_I_O___s_e_t___m_d_(_) before any more data is passed through it.
If an application needs to call _B_I_O___g_e_t_s_(_) or _B_I_O___p_u_t_s_(_) through a chain containing digest BIOs then this can be done by prepending a buffering BIO.
Before OpenSSL 0.9.9 the call to _B_I_O___g_e_t___m_d___c_t_x_(_) would only work if the BIO had been initialized for example by calling _B_I_O___s_e_t___m_d_(_) ). In OpenSSL 0.9.9 and later the context is always returned and the BIO is state is set to initialized. This allows applications to initialize the context externally if the standard calls such as _B_I_O___s_e_t___m_d_(_) are not sufficiently flexible.
_B_I_O___s_e_t___m_d_(_), _B_I_O___g_e_t___m_d_(_) and _B_I_O___m_d___c_t_x_(_) return 1 for success and 0 for failure.
BIO *bio, *mdtmp; char message[] = "Hello World"; bio = BIO_new(BIO_s_null()); mdtmp = BIO_new(BIO_f_md()); BIO_set_md(mdtmp, EVP_sha1()); /* For BIO_push() we want to append the sink BIO and keep a note of * the start of the chain. */ bio = BIO_push(mdtmp, bio); mdtmp = BIO_new(BIO_f_md()); BIO_set_md(mdtmp, EVP_md5()); bio = BIO_push(mdtmp, bio); /* Note: mdtmp can now be discarded */ BIO_write(bio, message, strlen(message));
The next example digests data by reading through a chain instead:
BIO *bio, *mdtmp; char buf[1024]; int rdlen; bio = BIO_new_file(file, "rb"); mdtmp = BIO_new(BIO_f_md()); BIO_set_md(mdtmp, EVP_sha1()); bio = BIO_push(mdtmp, bio); mdtmp = BIO_new(BIO_f_md()); BIO_set_md(mdtmp, EVP_md5()); bio = BIO_push(mdtmp, bio); do { rdlen = BIO_read(bio, buf, sizeof(buf)); /* Might want to do something with the data here */ } while(rdlen > 0);
This next example retrieves the message digests from a BIO chain and outputs them. This could be used with the examples above.
BIO *mdtmp; unsigned char mdbuf[EVP_MAX_MD_SIZE]; int mdlen; int i; mdtmp = bio; /* Assume bio has previously been set up */ do { EVP_MD *md; mdtmp = BIO_find_type(mdtmp, BIO_TYPE_MD); if(!mdtmp) break; BIO_get_md(mdtmp, &md); printf("%s digest", OBJ_nid2sn(EVP_MD_type(md))); mdlen = BIO_gets(mdtmp, mdbuf, EVP_MAX_MD_SIZE); for(i = 0; i < mdlen; i++) printf(":%02X", mdbuf[i]); printf("\n"); mdtmp = BIO_next(mdtmp); } while(mdtmp);
BIO_free_all(bio);