f542ef8f9e
If the result of an RSA encryption or decryption operation can be represented in less bytes than given, gcry_mpi_print() will not add leading zero bytes. Fix this by adding those ourself.
302 lines
7.3 KiB
C
302 lines
7.3 KiB
C
/*
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rsa.c -- RSA key handling
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Copyright (C) 2007 Guus Sliepen <guus@tinc-vpn.org>
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along
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with this program; if not, write to the Free Software Foundation, Inc.,
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51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include "system.h"
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#include <gcrypt.h>
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#include "logger.h"
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#include "rsa.h"
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// Base64 decoding table
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static const uint8_t b64d[128] = {
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0x3e, 0xff, 0xff, 0xff, 0x3f,
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0x34, 0x35, 0x36, 0x37, 0x38, 0x39,
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0x3a, 0x3b, 0x3c, 0x3d, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0x00,
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0x01, 0x02, 0x03, 0x04, 0x05, 0x06,
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0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c,
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0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12,
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0x13, 0x14, 0x15, 0x16, 0x17, 0x18,
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0x19, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e,
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0x1f, 0x20, 0x21, 0x22, 0x23, 0x24,
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0x25, 0x26, 0x27, 0x28, 0x29, 0x2a,
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0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30,
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0x31, 0x32, 0x33, 0xff, 0xff, 0xff,
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0xff, 0xff
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};
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// PEM encoding/decoding functions
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static bool pem_decode(FILE *fp, const char *header, uint8_t *buf, size_t size, size_t *outsize) {
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bool decode = false;
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char line[1024];
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uint16_t word = 0;
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int shift = 10;
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size_t i, j = 0;
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while(!feof(fp)) {
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if(!fgets(line, sizeof line, fp))
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return false;
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if(!decode && !strncmp(line, "-----BEGIN ", 11)) {
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if(!strncmp(line + 11, header, strlen(header)))
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decode = true;
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continue;
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}
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if(decode && !strncmp(line, "-----END", 8)) {
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break;
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}
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if(!decode)
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continue;
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for(i = 0; line[i] >= ' '; i++) {
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if((signed char)line[i] < 0 || b64d[(int)line[i]] == 0xff)
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break;
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word |= b64d[(int)line[i]] << shift;
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shift -= 6;
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if(shift <= 2) {
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if(j > size) {
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errno = ENOMEM;
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return false;
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}
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buf[j++] = word >> 8;
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word <<= 8;
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shift += 8;
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}
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}
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}
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if(outsize)
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*outsize = j;
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return true;
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}
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// BER decoding functions
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static int ber_read_id(unsigned char **p, size_t *buflen) {
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if(*buflen <= 0)
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return -1;
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if((**p & 0x1f) == 0x1f) {
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int id = 0;
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bool more;
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while(*buflen > 0) {
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id <<= 7;
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id |= **p & 0x7f;
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more = *(*p)++ & 0x80;
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(*buflen)--;
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if(!more)
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break;
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}
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return id;
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} else {
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(*buflen)--;
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return *(*p)++ & 0x1f;
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}
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}
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static size_t ber_read_len(unsigned char **p, size_t *buflen) {
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if(*buflen <= 0)
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return -1;
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if(**p & 0x80) {
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size_t result = 0;
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int len = *(*p)++ & 0x7f;
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(*buflen)--;
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if(len > *buflen)
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return 0;
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while(len--) {
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result <<= 8;
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result |= *(*p)++;
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(*buflen)--;
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}
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return result;
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} else {
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(*buflen)--;
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return *(*p)++;
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}
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}
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static bool ber_read_sequence(unsigned char **p, size_t *buflen, size_t *result) {
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int tag = ber_read_id(p, buflen);
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size_t len = ber_read_len(p, buflen);
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if(tag == 0x10) {
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if(result)
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*result = len;
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return true;
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} else {
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return false;
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}
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}
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static bool ber_read_mpi(unsigned char **p, size_t *buflen, gcry_mpi_t *mpi) {
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int tag = ber_read_id(p, buflen);
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size_t len = ber_read_len(p, buflen);
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gcry_error_t err = 0;
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if(tag != 0x02 || len > *buflen)
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return false;
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if(mpi)
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err = gcry_mpi_scan(mpi, GCRYMPI_FMT_USG, *p, len, NULL);
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*p += len;
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*buflen -= len;
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return mpi ? !err : true;
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}
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bool rsa_set_hex_public_key(rsa_t *rsa, char *n, char *e) {
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gcry_error_t err = 0;
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err = gcry_mpi_scan(&rsa->n, GCRYMPI_FMT_HEX, n, 0, NULL)
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?: gcry_mpi_scan(&rsa->e, GCRYMPI_FMT_HEX, e, 0, NULL);
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if(err) {
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logger(LOG_ERR, "Error while reading RSA public key: %s", gcry_strerror(errno));
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return false;
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}
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return true;
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}
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bool rsa_set_hex_private_key(rsa_t *rsa, char *n, char *e, char *d) {
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gcry_error_t err = 0;
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err = gcry_mpi_scan(&rsa->n, GCRYMPI_FMT_HEX, n, 0, NULL)
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?: gcry_mpi_scan(&rsa->e, GCRYMPI_FMT_HEX, e, 0, NULL)
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?: gcry_mpi_scan(&rsa->d, GCRYMPI_FMT_HEX, d, 0, NULL);
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if(err) {
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logger(LOG_ERR, "Error while reading RSA public key: %s", gcry_strerror(errno));
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return false;
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}
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return true;
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}
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// Read PEM RSA keys
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bool rsa_read_pem_public_key(rsa_t *rsa, FILE *fp) {
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uint8_t derbuf[8096], *derp = derbuf;
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size_t derlen;
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if(!pem_decode(fp, "RSA PUBLIC KEY", derbuf, sizeof derbuf, &derlen)) {
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logger(LOG_ERR, "Unable to read RSA public key: %s", strerror(errno));
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return NULL;
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}
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if(!ber_read_sequence(&derp, &derlen, NULL)
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|| !ber_read_mpi(&derp, &derlen, &rsa->n)
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|| !ber_read_mpi(&derp, &derlen, &rsa->e)
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|| derlen) {
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logger(LOG_ERR, "Error while decoding RSA public key");
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return NULL;
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}
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return true;
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}
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bool rsa_read_pem_private_key(rsa_t *rsa, FILE *fp) {
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uint8_t derbuf[8096], *derp = derbuf;
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size_t derlen;
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if(!pem_decode(fp, "RSA PRIVATE KEY", derbuf, sizeof derbuf, &derlen)) {
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logger(LOG_ERR, "Unable to read RSA private key: %s", strerror(errno));
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return NULL;
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}
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if(!ber_read_sequence(&derp, &derlen, NULL)
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|| !ber_read_mpi(&derp, &derlen, NULL)
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|| !ber_read_mpi(&derp, &derlen, &rsa->n)
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|| !ber_read_mpi(&derp, &derlen, &rsa->e)
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|| !ber_read_mpi(&derp, &derlen, &rsa->d)
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|| !ber_read_mpi(&derp, &derlen, NULL) // p
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|| !ber_read_mpi(&derp, &derlen, NULL) // q
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|| !ber_read_mpi(&derp, &derlen, NULL)
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|| !ber_read_mpi(&derp, &derlen, NULL)
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|| !ber_read_mpi(&derp, &derlen, NULL) // u
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|| derlen) {
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logger(LOG_ERR, "Error while decoding RSA private key");
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return NULL;
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}
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return true;
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}
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size_t rsa_size(rsa_t *rsa) {
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return (gcry_mpi_get_nbits(rsa->n) + 7) / 8;
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}
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/* Well, libgcrypt has functions to handle RSA keys, but they suck.
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* So we just use libgcrypt's mpi functions, and do the math ourselves.
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*/
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// TODO: get rid of this macro, properly clean up gcry_ structures after use
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#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; }}
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bool rsa_public_encrypt(rsa_t *rsa, void *in, size_t len, void *out) {
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gcry_mpi_t inmpi;
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check(gcry_mpi_scan(&inmpi, GCRYMPI_FMT_USG, in, len, NULL));
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gcry_mpi_t outmpi = gcry_mpi_new(len * 8);
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gcry_mpi_powm(outmpi, inmpi, rsa->e, rsa->n);
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int pad = len - (gcry_mpi_get_nbits(outmpi) + 7) / 8;
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while(pad--)
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*(char *)out++ = 0;
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check(gcry_mpi_print(GCRYMPI_FMT_USG, out,len, NULL, outmpi));
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return true;
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}
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bool rsa_private_decrypt(rsa_t *rsa, void *in, size_t len, void *out) {
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gcry_mpi_t inmpi;
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check(gcry_mpi_scan(&inmpi, GCRYMPI_FMT_USG, in, len, NULL));
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gcry_mpi_t outmpi = gcry_mpi_new(len * 8);
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gcry_mpi_powm(outmpi, inmpi, rsa->d, rsa->n);
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int pad = len - (gcry_mpi_get_nbits(outmpi) + 7) / 8;
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while(pad--)
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*(char *)out++ = 0;
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check(gcry_mpi_print(GCRYMPI_FMT_USG, out,len, NULL, outmpi));
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return true;
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}
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