1 /*
2  *  X.509 Certificate Signing Request writing
3  *
4  *  Copyright The Mbed TLS Contributors
5  *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
6  */
7 /*
8  * References:
9  * - CSRs: PKCS#10 v1.7 aka RFC 2986
10  * - attributes: PKCS#9 v2.0 aka RFC 2985
11  */
12 
13 #include "common.h"
14 
15 #if defined(MBEDTLS_X509_CSR_WRITE_C)
16 
17 #include "mbedtls/x509.h"
18 #include "mbedtls/x509_csr.h"
19 #include "mbedtls/asn1write.h"
20 #include "mbedtls/error.h"
21 #include "mbedtls/oid.h"
22 #include "mbedtls/platform_util.h"
23 
24 #if defined(MBEDTLS_USE_PSA_CRYPTO)
25 #include "psa/crypto.h"
26 #include "psa_util_internal.h"
27 #include "md_psa.h"
28 #endif /* MBEDTLS_USE_PSA_CRYPTO */
29 
30 #include <string.h>
31 #include <stdlib.h>
32 
33 #if defined(MBEDTLS_PEM_WRITE_C)
34 #include "mbedtls/pem.h"
35 #endif
36 
37 #include "mbedtls/platform.h"
38 
mbedtls_x509write_csr_init(mbedtls_x509write_csr * ctx)39 void mbedtls_x509write_csr_init(mbedtls_x509write_csr *ctx)
40 {
41     memset(ctx, 0, sizeof(mbedtls_x509write_csr));
42 }
43 
mbedtls_x509write_csr_free(mbedtls_x509write_csr * ctx)44 void mbedtls_x509write_csr_free(mbedtls_x509write_csr *ctx)
45 {
46     mbedtls_asn1_free_named_data_list(&ctx->subject);
47     mbedtls_asn1_free_named_data_list(&ctx->extensions);
48 
49     mbedtls_platform_zeroize(ctx, sizeof(mbedtls_x509write_csr));
50 }
51 
mbedtls_x509write_csr_set_md_alg(mbedtls_x509write_csr * ctx,mbedtls_md_type_t md_alg)52 void mbedtls_x509write_csr_set_md_alg(mbedtls_x509write_csr *ctx, mbedtls_md_type_t md_alg)
53 {
54     ctx->md_alg = md_alg;
55 }
56 
mbedtls_x509write_csr_set_key(mbedtls_x509write_csr * ctx,mbedtls_pk_context * key)57 void mbedtls_x509write_csr_set_key(mbedtls_x509write_csr *ctx, mbedtls_pk_context *key)
58 {
59     ctx->key = key;
60 }
61 
mbedtls_x509write_csr_set_subject_name(mbedtls_x509write_csr * ctx,const char * subject_name)62 int mbedtls_x509write_csr_set_subject_name(mbedtls_x509write_csr *ctx,
63                                            const char *subject_name)
64 {
65     return mbedtls_x509_string_to_names(&ctx->subject, subject_name);
66 }
67 
mbedtls_x509write_csr_set_extension(mbedtls_x509write_csr * ctx,const char * oid,size_t oid_len,int critical,const unsigned char * val,size_t val_len)68 int mbedtls_x509write_csr_set_extension(mbedtls_x509write_csr *ctx,
69                                         const char *oid, size_t oid_len,
70                                         int critical,
71                                         const unsigned char *val, size_t val_len)
72 {
73     return mbedtls_x509_set_extension(&ctx->extensions, oid, oid_len,
74                                       critical, val, val_len);
75 }
76 
mbedtls_x509write_csr_set_subject_alternative_name(mbedtls_x509write_csr * ctx,const mbedtls_x509_san_list * san_list)77 int mbedtls_x509write_csr_set_subject_alternative_name(mbedtls_x509write_csr *ctx,
78                                                        const mbedtls_x509_san_list *san_list)
79 {
80     return mbedtls_x509_write_set_san_common(&ctx->extensions, san_list);
81 }
82 
mbedtls_x509write_csr_set_key_usage(mbedtls_x509write_csr * ctx,unsigned char key_usage)83 int mbedtls_x509write_csr_set_key_usage(mbedtls_x509write_csr *ctx, unsigned char key_usage)
84 {
85     unsigned char buf[4] = { 0 };
86     unsigned char *c;
87     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
88 
89     c = buf + 4;
90 
91     ret = mbedtls_asn1_write_named_bitstring(&c, buf, &key_usage, 8);
92     if (ret < 3 || ret > 4) {
93         return ret;
94     }
95 
96     ret = mbedtls_x509write_csr_set_extension(ctx, MBEDTLS_OID_KEY_USAGE,
97                                               MBEDTLS_OID_SIZE(MBEDTLS_OID_KEY_USAGE),
98                                               0, c, (size_t) ret);
99     if (ret != 0) {
100         return ret;
101     }
102 
103     return 0;
104 }
105 
mbedtls_x509write_csr_set_ns_cert_type(mbedtls_x509write_csr * ctx,unsigned char ns_cert_type)106 int mbedtls_x509write_csr_set_ns_cert_type(mbedtls_x509write_csr *ctx,
107                                            unsigned char ns_cert_type)
108 {
109     unsigned char buf[4] = { 0 };
110     unsigned char *c;
111     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
112 
113     c = buf + 4;
114 
115     ret = mbedtls_asn1_write_named_bitstring(&c, buf, &ns_cert_type, 8);
116     if (ret < 3 || ret > 4) {
117         return ret;
118     }
119 
120     ret = mbedtls_x509write_csr_set_extension(ctx, MBEDTLS_OID_NS_CERT_TYPE,
121                                               MBEDTLS_OID_SIZE(MBEDTLS_OID_NS_CERT_TYPE),
122                                               0, c, (size_t) ret);
123     if (ret != 0) {
124         return ret;
125     }
126 
127     return 0;
128 }
129 
x509write_csr_der_internal(mbedtls_x509write_csr * ctx,unsigned char * buf,size_t size,unsigned char * sig,size_t sig_size,int (* f_rng)(void *,unsigned char *,size_t),void * p_rng)130 static int x509write_csr_der_internal(mbedtls_x509write_csr *ctx,
131                                       unsigned char *buf,
132                                       size_t size,
133                                       unsigned char *sig, size_t sig_size,
134                                       int (*f_rng)(void *, unsigned char *, size_t),
135                                       void *p_rng)
136 {
137     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
138     const char *sig_oid;
139     size_t sig_oid_len = 0;
140     unsigned char *c, *c2;
141     unsigned char hash[MBEDTLS_MD_MAX_SIZE];
142     size_t pub_len = 0, sig_and_oid_len = 0, sig_len;
143     size_t len = 0;
144     mbedtls_pk_type_t pk_alg;
145 #if defined(MBEDTLS_USE_PSA_CRYPTO)
146     size_t hash_len;
147     psa_algorithm_t hash_alg = mbedtls_md_psa_alg_from_type(ctx->md_alg);
148 #endif /* MBEDTLS_USE_PSA_CRYPTO */
149 
150     /* Write the CSR backwards starting from the end of buf */
151     c = buf + size;
152 
153     MBEDTLS_ASN1_CHK_ADD(len, mbedtls_x509_write_extensions(&c, buf,
154                                                             ctx->extensions));
155 
156     if (len) {
157         MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
158         MBEDTLS_ASN1_CHK_ADD(len,
159                              mbedtls_asn1_write_tag(
160                                  &c, buf,
161                                  MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE));
162 
163         MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
164         MBEDTLS_ASN1_CHK_ADD(len,
165                              mbedtls_asn1_write_tag(
166                                  &c, buf,
167                                  MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SET));
168 
169         MBEDTLS_ASN1_CHK_ADD(len,
170                              mbedtls_asn1_write_oid(
171                                  &c, buf, MBEDTLS_OID_PKCS9_CSR_EXT_REQ,
172                                  MBEDTLS_OID_SIZE(MBEDTLS_OID_PKCS9_CSR_EXT_REQ)));
173 
174         MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
175         MBEDTLS_ASN1_CHK_ADD(len,
176                              mbedtls_asn1_write_tag(
177                                  &c, buf,
178                                  MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE));
179     }
180 
181     MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
182     MBEDTLS_ASN1_CHK_ADD(len,
183                          mbedtls_asn1_write_tag(
184                              &c, buf,
185                              MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_CONTEXT_SPECIFIC));
186 
187     MBEDTLS_ASN1_CHK_ADD(pub_len, mbedtls_pk_write_pubkey_der(ctx->key,
188                                                               buf, c - buf));
189     c -= pub_len;
190     len += pub_len;
191 
192     /*
193      *  Subject  ::=  Name
194      */
195     MBEDTLS_ASN1_CHK_ADD(len, mbedtls_x509_write_names(&c, buf,
196                                                        ctx->subject));
197 
198     /*
199      *  Version  ::=  INTEGER  {  v1(0), v2(1), v3(2)  }
200      */
201     MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_int(&c, buf, 0));
202 
203     MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
204     MBEDTLS_ASN1_CHK_ADD(len,
205                          mbedtls_asn1_write_tag(
206                              &c, buf,
207                              MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE));
208 
209     /*
210      * Sign the written CSR data into the sig buffer
211      * Note: hash errors can happen only after an internal error
212      */
213 #if defined(MBEDTLS_USE_PSA_CRYPTO)
214     if (psa_hash_compute(hash_alg,
215                          c,
216                          len,
217                          hash,
218                          sizeof(hash),
219                          &hash_len) != PSA_SUCCESS) {
220         return MBEDTLS_ERR_PLATFORM_HW_ACCEL_FAILED;
221     }
222 #else /* MBEDTLS_USE_PSA_CRYPTO */
223     ret = mbedtls_md(mbedtls_md_info_from_type(ctx->md_alg), c, len, hash);
224     if (ret != 0) {
225         return ret;
226     }
227 #endif
228     if ((ret = mbedtls_pk_sign(ctx->key, ctx->md_alg, hash, 0,
229                                sig, sig_size, &sig_len,
230                                f_rng, p_rng)) != 0) {
231         return ret;
232     }
233 
234     if (mbedtls_pk_can_do(ctx->key, MBEDTLS_PK_RSA)) {
235         pk_alg = MBEDTLS_PK_RSA;
236     } else if (mbedtls_pk_can_do(ctx->key, MBEDTLS_PK_ECDSA)) {
237         pk_alg = MBEDTLS_PK_ECDSA;
238     } else {
239         return MBEDTLS_ERR_X509_INVALID_ALG;
240     }
241 
242     if ((ret = mbedtls_oid_get_oid_by_sig_alg(pk_alg, ctx->md_alg,
243                                               &sig_oid, &sig_oid_len)) != 0) {
244         return ret;
245     }
246 
247     /*
248      * Move the written CSR data to the start of buf to create space for
249      * writing the signature into buf.
250      */
251     memmove(buf, c, len);
252 
253     /*
254      * Write sig and its OID into buf backwards from the end of buf.
255      * Note: mbedtls_x509_write_sig will check for c2 - ( buf + len ) < sig_len
256      * and return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL if needed.
257      */
258     c2 = buf + size;
259     MBEDTLS_ASN1_CHK_ADD(sig_and_oid_len,
260                          mbedtls_x509_write_sig(&c2, buf + len, sig_oid, sig_oid_len,
261                                                 sig, sig_len, pk_alg));
262 
263     /*
264      * Compact the space between the CSR data and signature by moving the
265      * CSR data to the start of the signature.
266      */
267     c2 -= len;
268     memmove(c2, buf, len);
269 
270     /* ASN encode the total size and tag the CSR data with it. */
271     len += sig_and_oid_len;
272     MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c2, buf, len));
273     MBEDTLS_ASN1_CHK_ADD(len,
274                          mbedtls_asn1_write_tag(
275                              &c2, buf,
276                              MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE));
277 
278     /* Zero the unused bytes at the start of buf */
279     memset(buf, 0, c2 - buf);
280 
281     return (int) len;
282 }
283 
mbedtls_x509write_csr_der(mbedtls_x509write_csr * ctx,unsigned char * buf,size_t size,int (* f_rng)(void *,unsigned char *,size_t),void * p_rng)284 int mbedtls_x509write_csr_der(mbedtls_x509write_csr *ctx, unsigned char *buf,
285                               size_t size,
286                               int (*f_rng)(void *, unsigned char *, size_t),
287                               void *p_rng)
288 {
289     int ret;
290     unsigned char *sig;
291 
292     if ((sig = mbedtls_calloc(1, MBEDTLS_PK_SIGNATURE_MAX_SIZE)) == NULL) {
293         return MBEDTLS_ERR_X509_ALLOC_FAILED;
294     }
295 
296     ret = x509write_csr_der_internal(ctx, buf, size,
297                                      sig, MBEDTLS_PK_SIGNATURE_MAX_SIZE,
298                                      f_rng, p_rng);
299 
300     mbedtls_free(sig);
301 
302     return ret;
303 }
304 
305 #define PEM_BEGIN_CSR           "-----BEGIN CERTIFICATE REQUEST-----\n"
306 #define PEM_END_CSR             "-----END CERTIFICATE REQUEST-----\n"
307 
308 #if defined(MBEDTLS_PEM_WRITE_C)
mbedtls_x509write_csr_pem(mbedtls_x509write_csr * ctx,unsigned char * buf,size_t size,int (* f_rng)(void *,unsigned char *,size_t),void * p_rng)309 int mbedtls_x509write_csr_pem(mbedtls_x509write_csr *ctx, unsigned char *buf, size_t size,
310                               int (*f_rng)(void *, unsigned char *, size_t),
311                               void *p_rng)
312 {
313     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
314     size_t olen = 0;
315 
316     if ((ret = mbedtls_x509write_csr_der(ctx, buf, size,
317                                          f_rng, p_rng)) < 0) {
318         return ret;
319     }
320 
321     if ((ret = mbedtls_pem_write_buffer(PEM_BEGIN_CSR, PEM_END_CSR,
322                                         buf + size - ret,
323                                         ret, buf, size, &olen)) != 0) {
324         return ret;
325     }
326 
327     return 0;
328 }
329 #endif /* MBEDTLS_PEM_WRITE_C */
330 
331 #endif /* MBEDTLS_X509_CSR_WRITE_C */
332