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PK parse/write: support keylen=0 correctly

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A 0-length buffer for the key is a legitimate edge case. Ensure that
it works, even with buf=NULL. Document the key and keylen parameters.

There are already test cases for parsing an empty buffer. A subsequent
commit will add tests for writing to an empty buffer.
This commit is contained in:
Gilles Peskine
2018-12-19 17:03:28 +01:00
parent 1f19fa6f62
commit 159171b72a
3 changed files with 39 additions and 25 deletions
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22
library/pkparse.c
View File

@ -1170,15 +1170,16 @@ int mbedtls_pk_parse_key( mbedtls_pk_context *pk,
#endif
PK_VALIDATE_RET( pk != NULL );
PK_VALIDATE_RET( key != NULL || keylen == 0 );
PK_VALIDATE_RET( pwd != NULL || pwdlen == 0 );
if( keylen == 0 )
return( MBEDTLS_ERR_PK_KEY_INVALID_FORMAT );
PK_VALIDATE_RET( key != NULL );
#if defined(MBEDTLS_PEM_PARSE_C)
mbedtls_pem_init( &pem );
#if defined(MBEDTLS_RSA_C)
/* Avoid calling mbedtls_pem_read_buffer() on non-null-terminated string */
if( keylen == 0 || key[keylen - 1] != '\0' )
if( key[keylen - 1] != '\0' )
ret = MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
else
ret = mbedtls_pem_read_buffer( &pem,
@ -1209,7 +1210,7 @@ int mbedtls_pk_parse_key( mbedtls_pk_context *pk,
#if defined(MBEDTLS_ECP_C)
/* Avoid calling mbedtls_pem_read_buffer() on non-null-terminated string */
if( keylen == 0 || key[keylen - 1] != '\0' )
if( key[keylen - 1] != '\0' )
ret = MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
else
ret = mbedtls_pem_read_buffer( &pem,
@ -1239,7 +1240,7 @@ int mbedtls_pk_parse_key( mbedtls_pk_context *pk,
#endif /* MBEDTLS_ECP_C */
/* Avoid calling mbedtls_pem_read_buffer() on non-null-terminated string */
if( keylen == 0 || key[keylen - 1] != '\0' )
if( key[keylen - 1] != '\0' )
ret = MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
else
ret = mbedtls_pem_read_buffer( &pem,
@ -1262,7 +1263,7 @@ int mbedtls_pk_parse_key( mbedtls_pk_context *pk,
#if defined(MBEDTLS_PKCS12_C) || defined(MBEDTLS_PKCS5_C)
/* Avoid calling mbedtls_pem_read_buffer() on non-null-terminated string */
if( keylen == 0 || key[keylen - 1] != '\0' )
if( key[keylen - 1] != '\0' )
ret = MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
else
ret = mbedtls_pem_read_buffer( &pem,
@ -1300,9 +1301,6 @@ int mbedtls_pk_parse_key( mbedtls_pk_context *pk,
{
unsigned char *key_copy;
if( keylen == 0 )
return( MBEDTLS_ERR_PK_KEY_INVALID_FORMAT );
if( ( key_copy = mbedtls_calloc( 1, keylen ) ) == NULL )
return( MBEDTLS_ERR_PK_ALLOC_FAILED );
@ -1387,13 +1385,15 @@ int mbedtls_pk_parse_public_key( mbedtls_pk_context *ctx,
#endif
PK_VALIDATE_RET( ctx != NULL );
if( keylen == 0 )
return( MBEDTLS_ERR_PK_KEY_INVALID_FORMAT );
PK_VALIDATE_RET( key != NULL || keylen == 0 );
#if defined(MBEDTLS_PEM_PARSE_C)
mbedtls_pem_init( &pem );
#if defined(MBEDTLS_RSA_C)
/* Avoid calling mbedtls_pem_read_buffer() on non-null-terminated string */
if( keylen == 0 || key[keylen - 1] != '\0' )
if( key[keylen - 1] != '\0' )
ret = MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
else
ret = mbedtls_pem_read_buffer( &pem,
@ -1424,7 +1424,7 @@ int mbedtls_pk_parse_public_key( mbedtls_pk_context *ctx,
#endif /* MBEDTLS_RSA_C */
/* Avoid calling mbedtls_pem_read_buffer() on non-null-terminated string */
if( keylen == 0 || key[keylen - 1] != '\0' )
if( key[keylen - 1] != '\0' )
ret = MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
else
ret = mbedtls_pem_read_buffer( &pem,

8
library/pkwrite.c
View File

@ -186,7 +186,9 @@ int mbedtls_pk_write_pubkey_der( mbedtls_pk_context *key, unsigned char *buf, si
const char *oid;
PK_VALIDATE_RET( key != NULL );
PK_VALIDATE_RET( buf != NULL || size == 0 );
if( size == 0 )
return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
PK_VALIDATE_RET( buf != NULL );
c = buf + size;
@ -236,7 +238,9 @@ int mbedtls_pk_write_key_der( mbedtls_pk_context *key, unsigned char *buf, size_
size_t len = 0;
PK_VALIDATE_RET( key != NULL );
PK_VALIDATE_RET( buf != NULL || size == 0 );
if( size == 0 )
return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
PK_VALIDATE_RET( buf != NULL );
c = buf + size;