cryptography - Reading PEM-formatted RSA keyfile with the OpenSSL C API -

i trying read in aes-128-cbc encrypted pem key file generated using ruby openssl api. code generated pem key following:

openssl::pkey::rsa.new(2048).to_pem(openssl::cipher::aes.new('128-cbc'), "password") 

here's code reads pem file:

rsa *rsa;  bio *pem = bio_new(bio_s_mem()); bio_puts(pem, "-----begin rsa private key-----\n"   "proc-type: 4,encrypted\n"   "dek-info: aes-128-cbc,bb13d39833dd6ed1ff9843644e7981ee\n\n   "eugt8jznkqkersabwkwfm3wqhu/tmp9t0qap5hm8viwpzwkldmrlsudptadu6rpd\n"   "5vtg3dpiexcf+6deyarimid9sbbmq9mk2omknrctmemqtohauakbu78tmt9g4ysf\n"   "rjoxwsqu3jmwrlcgkpn7bium8wimitrz3p28oszk9adunbriu/2si8dm4ryiz/fk\n"   "uvvgdok9dgcd0sjvucivx2hageg/iuz23q1jg9indpimzvfjd1fjfgeuwdgyfjfa\n"   "m8jixtkbwopeopondkt7u4dc5vcsjk29mvbfd7ickfpmh5un+c96rpxtng/owyw5\n"   "0tvzhyyyvag9p0hx5lr4pdbv21ghyu43sa6wbs9jwyqo3ab7caoeeqhumwflsdjj\n"   "ygrx6bwthpyv/xnbdmmvlthlkffe01ncybivob4kwbnvi45x21pbqazckdtfdekl\n"   "iwdmtig2itxsuvpfly30vfoze+pgymcgduyzdvqjsaqi/mrj8khnn5nyubxc27g3\n"   "8kbsnlix2sw2m0vdxqiy9dyjcxxrkfrsnofyvs1pflgjfvtg4mwh6czxkw8mfvbi\n"   "emlvuywzodz1ve4vxspp/vrkeh33juhhm0vjopqi6wqw0qr0i2o6etm1zrjclpcw\n"   "vicgcvweneglokohdqor0izqatywvauqq822wkt258hc6z8+alqf5imroqk7add4\n"   "flrlz4xtwqlg7ppttde/emi1dt8dqwzq++qi0lr0cs/n1gxjkqtqdvauxliii3qy\n"   "kffyfpv9jyyfrftjntisi/edptp98auk0mb9o/ws/hrufi9behgv63iw1iwaoxcw\n"   "zlkwgobuh13gs864rl+acraxreo2j4ddqouterajueg0hoytp65zun/vsci2asoh\n"   "jwsnnmhz9oxvcgy80wjdn3kqocbrijodkbv6jcoxgvcsvk+wsdgz7cfb8lwp7aa8\n"   "8nd1bwl9fykwkeisoakj91iinqv4o3+3pupgcu5oe68wyvafjuu+criyf+ehmxjv\n"   "jq1vffzprgzgntjz19uxxh1h2iwqpggroujm2rozywvv1nz4eq40y3et1f9uoyju\n"   "ckehoti2nplevoayqo8g9wo2oc+cqvhzhdybe5o7pm7akfnylvrg9s1uswdcvt0g\n"   "ipfmejlsrj/f954aqmhtuc6vbojzh/vnc5qt+ulfxl634sr9wqqk2qlqsjya04tr\n"   "1ixbcnox71esvpfimsrlso5ota22t3h2gyjpum10xhqgtdxtstnal6smlna9u9b3\n"   "gtvxfwwukqof5lm8zfqipo2lohwjkoztbc4repyp44soxjxstv7k4pt1ck7x6/2h\n"   "elspxzjveqmhcrvewv1kaa2ogd+hgfuinscoidapjjlz1bd/+oiq/zwqeo0nrowe\n"   "r/hlbbed3v+fridjpgydfeaw6gk5e9syjcgf7uf/n2nabfxxezl3g6mjq64dtusg\n"   "deh/mpviydsx4navh1gtwctoeg1czw3diyaqbzk+uzcblfu7j27yvvpsd6f2+wud\n"   "wnaqu3s5bcpqk5od3wqzv+secqjggpgy1gv0tl8arjomdkaru03ksrn2eiwqr5/c\n"   "-----end rsa private key-----\n");  // retrieve rsa key pem file. rsa = pem_read_bio_rsaprivatekey(pem, null, pem_password_callback, "password"); 

and here's dummy password callback (not sure function's purpose, think may return length of password):

int pem_password_callback(char *buf, int max_len, int flag, void *pwd) {   return 8; } 

currently, rsa = ... part not throw error, doesn't return well-formed result either.

and here's dummy password callback (not sure function's purpose, think may return length of password):

 int pem_password_callback(char *buf, int max_len, int flag, void *pwd)  {      return 8;  } 

no, not dummy. in example, returned buffer 8 junk characters (whatever happened in buf).

the password callback programmatically plug in password. supplied buff of max_len, , need copy password buffer , return number of bytes copied.

int pem_password_callback(char *buf, int max_len, int flag, void *ctx) {     const char* passwd = "password";     int len = strlen(passwd);      if(len > max_len)         return 0;      memcpy(buf, passwd, len);     return len; } 

the flag read/write flag denote if reading key or writing key. in practice, have never used it.

you use similar to:

file* file = ...; evp_pkey* pkey = pem_read_privatekey(file, null, pem_password_callback, null); 

unlike write routine (which needs evp_* cipher), read routine knows used encrypt key because encoded in private key.

in systems, use context label ensure same passwords arrive @ different derived keys:

evp_pkey* pkey = pem_read_privatekey(file, null, pem_password_callback, "some context"); 

then, in password callback:

int pem_password_callback(char *buf, int max_len, int flag, void *ctx) {     // "some context" in example above     char* label = (char*)ctx;      // hash password , label     // ...      // copy hash buffer, return length     ... }