/* rsa.c -- RSA key handling Copyright (C) 2007 Guus Sliepen This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. */ #include "system.h" #include #include "logger.h" #include "rsa.h" // Base64 decoding table static const uint8_t b64d[128] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x3e, 0xff, 0xff, 0xff, 0x3f, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0xff, 0xff, 0xff, 0xff, 0xff }; // PEM encoding/decoding functions static bool pem_decode(FILE *fp, const char *header, uint8_t *buf, size_t size, size_t *outsize) { bool decode = false; char line[1024]; uint16_t word = 0; int shift = 10; size_t i, j = 0; while(!feof(fp)) { if(!fgets(line, sizeof line, fp)) return false; if(!decode && !strncmp(line, "-----BEGIN ", 11)) { if(!strncmp(line + 11, header, strlen(header))) decode = true; continue; } if(decode && !strncmp(line, "-----END", 8)) { break; } if(!decode) continue; for(i = 0; line[i] >= ' '; i++) { if((signed char)line[i] < 0 || b64d[(int)line[i]] == 0xff) break; word |= b64d[(int)line[i]] << shift; shift -= 6; if(shift <= 2) { if(j > size) { errno = ENOMEM; return false; } buf[j++] = word >> 8; word <<= 8; shift += 8; } } } if(outsize) *outsize = j; return true; } // BER decoding functions static int ber_read_id(unsigned char **p, size_t *buflen) { if(*buflen <= 0) return -1; if((**p & 0x1f) == 0x1f) { int id = 0; bool more; while(*buflen > 0) { id <<= 7; id |= **p & 0x7f; more = *(*p)++ & 0x80; (*buflen)--; if(!more) break; } return id; } else { (*buflen)--; return *(*p)++ & 0x1f; } } static size_t ber_read_len(unsigned char **p, size_t *buflen) { if(*buflen <= 0) return -1; if(**p & 0x80) { size_t result = 0; int len = *(*p)++ & 0x7f; (*buflen)--; if(len > *buflen) return 0; while(len--) { result <<= 8; result |= *(*p)++; (*buflen)--; } return result; } else { (*buflen)--; return *(*p)++; } } static bool ber_read_sequence(unsigned char **p, size_t *buflen, size_t *result) { int tag = ber_read_id(p, buflen); size_t len = ber_read_len(p, buflen); if(tag == 0x10) { if(result) *result = len; return true; } else { return false; } } static bool ber_read_mpi(unsigned char **p, size_t *buflen, gcry_mpi_t *mpi) { int tag = ber_read_id(p, buflen); size_t len = ber_read_len(p, buflen); gcry_error_t err = 0; if(tag != 0x02 || len > *buflen) return false; if(mpi) err = gcry_mpi_scan(mpi, GCRYMPI_FMT_USG, *p, len, NULL); *p += len; *buflen -= len; return mpi ? !err : true; } bool rsa_set_hex_public_key(rsa_t *rsa, char *n, char *e) { gcry_error_t err = 0; err = gcry_mpi_scan(&rsa->n, GCRYMPI_FMT_HEX, n, 0, NULL) ?: gcry_mpi_scan(&rsa->e, GCRYMPI_FMT_HEX, e, 0, NULL); if(err) { logger(LOG_ERR, "Error while reading RSA public key: %s", gcry_strerror(errno)); return false; } return true; } bool rsa_set_hex_private_key(rsa_t *rsa, char *n, char *e, char *d) { gcry_error_t err = 0; err = gcry_mpi_scan(&rsa->n, GCRYMPI_FMT_HEX, n, 0, NULL) ?: gcry_mpi_scan(&rsa->e, GCRYMPI_FMT_HEX, e, 0, NULL) ?: gcry_mpi_scan(&rsa->d, GCRYMPI_FMT_HEX, d, 0, NULL); if(err) { logger(LOG_ERR, "Error while reading RSA public key: %s", gcry_strerror(errno)); return false; } return true; } // Read PEM RSA keys bool rsa_read_pem_public_key(rsa_t *rsa, FILE *fp) { uint8_t derbuf[8096], *derp = derbuf; size_t derlen; if(!pem_decode(fp, "RSA PUBLIC KEY", derbuf, sizeof derbuf, &derlen)) { logger(LOG_ERR, "Unable to read RSA public key: %s", strerror(errno)); return NULL; } if(!ber_read_sequence(&derp, &derlen, NULL) || !ber_read_mpi(&derp, &derlen, &rsa->n) || !ber_read_mpi(&derp, &derlen, &rsa->e) || derlen) { logger(LOG_ERR, "Error while decoding RSA public key"); return NULL; } return true; } bool rsa_read_pem_private_key(rsa_t *rsa, FILE *fp) { uint8_t derbuf[8096], *derp = derbuf; size_t derlen; if(!pem_decode(fp, "RSA PRIVATE KEY", derbuf, sizeof derbuf, &derlen)) { logger(LOG_ERR, "Unable to read RSA private key: %s", strerror(errno)); return NULL; } if(!ber_read_sequence(&derp, &derlen, NULL) || !ber_read_mpi(&derp, &derlen, NULL) || !ber_read_mpi(&derp, &derlen, &rsa->n) || !ber_read_mpi(&derp, &derlen, &rsa->e) || !ber_read_mpi(&derp, &derlen, &rsa->d) || !ber_read_mpi(&derp, &derlen, NULL) // p || !ber_read_mpi(&derp, &derlen, NULL) // q || !ber_read_mpi(&derp, &derlen, NULL) || !ber_read_mpi(&derp, &derlen, NULL) || !ber_read_mpi(&derp, &derlen, NULL) // u || derlen) { logger(LOG_ERR, "Error while decoding RSA private key"); return NULL; } return true; } size_t rsa_size(rsa_t *rsa) { return (gcry_mpi_get_nbits(rsa->n) + 7) / 8; } /* Well, libgcrypt has functions to handle RSA keys, but they suck. * So we just use libgcrypt's mpi functions, and do the math ourselves. */ // TODO: get rid of this macro, properly clean up gcry_ structures after use #define check(foo) { gcry_error_t err = (foo); if(err) {logger(LOG_ERR, "gcrypt error %s/%s at %s:%d\n", gcry_strsource(err), gcry_strerror(err), __FILE__, __LINE__); return false; }} bool rsa_public_encrypt(rsa_t *rsa, void *in, size_t len, void *out) { gcry_mpi_t inmpi; check(gcry_mpi_scan(&inmpi, GCRYMPI_FMT_USG, in, len, NULL)); gcry_mpi_t outmpi = gcry_mpi_new(len * 8); gcry_mpi_powm(outmpi, inmpi, rsa->e, rsa->n); int pad = len - (gcry_mpi_get_nbits(outmpi) + 7) / 8; while(pad--) *(char *)out++ = 0; check(gcry_mpi_print(GCRYMPI_FMT_USG, out,len, NULL, outmpi)); return true; } bool rsa_private_decrypt(rsa_t *rsa, void *in, size_t len, void *out) { gcry_mpi_t inmpi; check(gcry_mpi_scan(&inmpi, GCRYMPI_FMT_USG, in, len, NULL)); gcry_mpi_t outmpi = gcry_mpi_new(len * 8); gcry_mpi_powm(outmpi, inmpi, rsa->d, rsa->n); int pad = len - (gcry_mpi_get_nbits(outmpi) + 7) / 8; while(pad--) *(char *)out++ = 0; check(gcry_mpi_print(GCRYMPI_FMT_USG, out,len, NULL, outmpi)); return true; }