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Merge pull request #3489 from CodeMonkeyLeet/mbedtls-2.16_backport_3464

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Backport 2.16: PR #3464 Dynamically allocate requested CSR write buffer size
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Gilles Peskine 2020-08-12 18:22:22 +02:00 committed by GitHub
commit de7e03688d
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 103 additions and 41 deletions
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4
ChangeLog.d/x509write_csr_heap_alloc.txt Normal file
View File

@ -0,0 +1,4 @@
Bugfix
* Reduce the stack consumption of mbedtls_x509write_csr_der() which
previously could lead to stack overflow on constrained devices.
Contributed by Doru Gucea and Simon Leet in #3464.

132
library/x509write_csr.c
View File

@ -81,6 +81,14 @@
#define SIGNATURE_MAX_SIZE MBEDTLS_MPI_MAX_SIZE
#endif
#if defined(MBEDTLS_PLATFORM_C)
#include "mbedtls/platform.h"
#else
#include <stdlib.h>
#define mbedtls_calloc calloc
#define mbedtls_free free
#endif
void mbedtls_x509write_csr_init( mbedtls_x509write_csr *ctx )
{
memset( ctx, 0, sizeof( mbedtls_x509write_csr ) );
@ -187,7 +195,10 @@ int mbedtls_x509write_csr_set_ns_cert_type( mbedtls_x509write_csr *ctx,
return( 0 );
}
int mbedtls_x509write_csr_der( mbedtls_x509write_csr *ctx, unsigned char *buf, size_t size,
static int x509write_csr_der_internal( mbedtls_x509write_csr *ctx,
unsigned char *buf,
size_t size,
unsigned char *sig,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng )
{
@ -196,62 +207,73 @@ int mbedtls_x509write_csr_der( mbedtls_x509write_csr *ctx, unsigned char *buf, s
size_t sig_oid_len = 0;
unsigned char *c, *c2;
unsigned char hash[64];
unsigned char sig[SIGNATURE_MAX_SIZE];
unsigned char tmp_buf[2048];
size_t pub_len = 0, sig_and_oid_len = 0, sig_len;
size_t len = 0;
mbedtls_pk_type_t pk_alg;
/*
* Prepare data to be signed in tmp_buf
*/
c = tmp_buf + sizeof( tmp_buf );
/* Write the CSR backwards starting from the end of buf */
c = buf + size;
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_x509_write_extensions( &c, tmp_buf, ctx->extensions ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_x509_write_extensions( &c, buf,
ctx->extensions ) );
if( len )
{
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, tmp_buf, len ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, tmp_buf, MBEDTLS_ASN1_CONSTRUCTED |
MBEDTLS_ASN1_SEQUENCE ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
MBEDTLS_ASN1_CHK_ADD( len,
mbedtls_asn1_write_tag(
&c, buf,
MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, tmp_buf, len ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, tmp_buf, MBEDTLS_ASN1_CONSTRUCTED |
MBEDTLS_ASN1_SET ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
MBEDTLS_ASN1_CHK_ADD( len,
mbedtls_asn1_write_tag(
&c, buf,
MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SET ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_oid( &c, tmp_buf, MBEDTLS_OID_PKCS9_CSR_EXT_REQ,
MBEDTLS_ASN1_CHK_ADD( len,
mbedtls_asn1_write_oid(
&c, buf, MBEDTLS_OID_PKCS9_CSR_EXT_REQ,
MBEDTLS_OID_SIZE( MBEDTLS_OID_PKCS9_CSR_EXT_REQ ) ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, tmp_buf, len ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, tmp_buf, MBEDTLS_ASN1_CONSTRUCTED |
MBEDTLS_ASN1_SEQUENCE ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
MBEDTLS_ASN1_CHK_ADD( len,
mbedtls_asn1_write_tag(
&c, buf,
MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) );
}
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, tmp_buf, len ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, tmp_buf, MBEDTLS_ASN1_CONSTRUCTED |
MBEDTLS_ASN1_CONTEXT_SPECIFIC ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
MBEDTLS_ASN1_CHK_ADD( len,
mbedtls_asn1_write_tag(
&c, buf,
MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_CONTEXT_SPECIFIC ) );
MBEDTLS_ASN1_CHK_ADD( pub_len, mbedtls_pk_write_pubkey_der( ctx->key,
tmp_buf, c - tmp_buf ) );
buf, c - buf ) );
c -= pub_len;
len += pub_len;
/*
* Subject ::= Name
*/
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_x509_write_names( &c, tmp_buf, ctx->subject ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_x509_write_names( &c, buf,
ctx->subject ) );
/*
* Version ::= INTEGER { v1(0), v2(1), v3(2) }
*/
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_int( &c, tmp_buf, 0 ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_int( &c, buf, 0 ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, tmp_buf, len ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, tmp_buf, MBEDTLS_ASN1_CONSTRUCTED |
MBEDTLS_ASN1_SEQUENCE ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
MBEDTLS_ASN1_CHK_ADD( len,
mbedtls_asn1_write_tag(
&c, buf,
MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) );
/*
* Prepare signature
* Sign the written CSR data into the sig buffer
* Note: hash errors can happen only after an internal error
*/
ret = mbedtls_md( mbedtls_md_info_from_type( ctx->md_alg ), c, len, hash );
if( ret != 0 )
@ -277,26 +299,62 @@ int mbedtls_x509write_csr_der( mbedtls_x509write_csr *ctx, unsigned char *buf, s
}
/*
* Write data to output buffer
* Move the written CSR data to the start of buf to create space for
* writing the signature into buf.
*/
memmove( buf, c, len );
/*
* Write sig and its OID into buf backwards from the end of buf.
* Note: mbedtls_x509_write_sig will check for c2 - ( buf + len ) < sig_len
* and return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL if needed.
*/
c2 = buf + size;
MBEDTLS_ASN1_CHK_ADD( sig_and_oid_len, mbedtls_x509_write_sig( &c2, buf,
sig_oid, sig_oid_len, sig, sig_len ) );
if( len > (size_t)( c2 - buf ) )
return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
MBEDTLS_ASN1_CHK_ADD( sig_and_oid_len,
mbedtls_x509_write_sig( &c2, buf + len, sig_oid, sig_oid_len,
sig, sig_len ) );
/*
* Compact the space between the CSR data and signature by moving the
* CSR data to the start of the signature.
*/
c2 -= len;
memcpy( c2, c, len );
memmove( c2, buf, len );
/* ASN encode the total size and tag the CSR data with it. */
len += sig_and_oid_len;
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c2, buf, len ) );
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c2, buf, MBEDTLS_ASN1_CONSTRUCTED |
MBEDTLS_ASN1_SEQUENCE ) );
MBEDTLS_ASN1_CHK_ADD( len,
mbedtls_asn1_write_tag(
&c2, buf,
MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) );
/* Zero the unused bytes at the start of buf */
memset( buf, 0, c2 - buf);
return( (int) len );
}
int 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 )
{
int ret;
unsigned char *sig;
if( ( sig = mbedtls_calloc( 1, SIGNATURE_MAX_SIZE ) ) == NULL )
{
return( MBEDTLS_ERR_X509_ALLOC_FAILED );
}
ret = x509write_csr_der_internal( ctx, buf, size, sig, f_rng, p_rng );
mbedtls_free( sig );
return( ret );
}
#define PEM_BEGIN_CSR "-----BEGIN CERTIFICATE REQUEST-----\n"
#define PEM_END_CSR "-----END CERTIFICATE REQUEST-----\n"