From cb37aa5912d9d172dd4f252bed37b7f7447816a8 Mon Sep 17 00:00:00 2001 From: Paul Bakker Date: Wed, 30 Nov 2011 16:00:20 +0000 Subject: [PATCH] - Better buffer handling in mpi_read_file() --- include/polarssl/bignum.h | 22 +++++++++++++++++----- library/bignum.c | 8 ++++++-- tests/data_files/mpi_too_big | 1 + tests/suites/test_suite_mpi.data | 4 ++++ 4 files changed, 28 insertions(+), 7 deletions(-) create mode 100644 tests/data_files/mpi_too_big diff --git a/include/polarssl/bignum.h b/include/polarssl/bignum.h index 12435f728..b4496b847 100644 --- a/include/polarssl/bignum.h +++ b/include/polarssl/bignum.h @@ -33,7 +33,7 @@ #define POLARSSL_ERR_MPI_FILE_IO_ERROR -0x0002 /**< An error occurred while reading from or writing to a file. */ #define POLARSSL_ERR_MPI_BAD_INPUT_DATA -0x0004 /**< Bad input parameters to function. */ #define POLARSSL_ERR_MPI_INVALID_CHARACTER -0x0006 /**< There is an invalid character in the digit string. */ -#define POLARSSL_ERR_MPI_BUFFER_TOO_SMALL -0x0008 /**< The output buffer is too small to write too. */ +#define POLARSSL_ERR_MPI_BUFFER_TOO_SMALL -0x0008 /**< The buffer is too small to write too. */ #define POLARSSL_ERR_MPI_NEGATIVE_VALUE -0x000A /**< The input arguments are negative or result in illegal output. */ #define POLARSSL_ERR_MPI_DIVISION_BY_ZERO -0x000C /**< The input argument for division is zero, which is not allowed. */ #define POLARSSL_ERR_MPI_NOT_ACCEPTABLE -0x000E /**< The input arguments are not acceptable. */ @@ -66,6 +66,16 @@ #define POLARSSL_MPI_MAX_SIZE 512 /**< Maximum number of bytes for usable MPIs. */ #define POLARSSL_MPI_MAX_BITS ( 8 * POLARSSL_MPI_MAX_SIZE ) /**< Maximum number of bits for usable MPIs. */ +/* + * When reading from files with mpi_read_file() the buffer should have space + * for a (short) label, the MPI (in the provided radix), the newline + * characters and the '\0'. + * + * By default we assume at least a 10 char label, a minimum radix of 10 + * (decimal) and a maximum of 4096 bit numbers (1234 decimal chars). + */ +#define POLARSSL_MPI_READ_BUFFER_SIZE 1250 + /* * Define the base integer type, architecture-wise */ @@ -223,7 +233,7 @@ size_t mpi_size( const mpi *X ); * \param radix Input numeric base * \param s Null-terminated string buffer * - * \return 0 if successful, or an POLARSSL_ERR_MPI_XXX error code + * \return 0 if successful, or a POLARSSL_ERR_MPI_XXX error code */ int mpi_read_string( mpi *X, int radix, const char *s ); @@ -235,7 +245,7 @@ int mpi_read_string( mpi *X, int radix, const char *s ); * \param s String buffer * \param slen String buffer size * - * \return 0 if successful, or an POLARSSL_ERR_MPI_XXX error code. + * \return 0 if successful, or a POLARSSL_ERR_MPI_XXX error code. * *slen is always updated to reflect the amount * of data that has (or would have) been written. * @@ -251,7 +261,9 @@ int mpi_write_string( const mpi *X, int radix, char *s, size_t *slen ); * \param radix Input numeric base * \param fin Input file handle * - * \return 0 if successful, or an POLARSSL_ERR_MPI_XXX error code + * \return 0 if successful, POLARSSL_ERR_MPI_BUFFER_TOO_SMALL if + * the file read buffer is too small or a + * POLARSSL_ERR_MPI_XXX error code */ int mpi_read_file( mpi *X, int radix, FILE *fin ); @@ -263,7 +275,7 @@ int mpi_read_file( mpi *X, int radix, FILE *fin ); * \param radix Output numeric base * \param fout Output file handle (can be NULL) * - * \return 0 if successful, or an POLARSSL_ERR_MPI_XXX error code + * \return 0 if successful, or a POLARSSL_ERR_MPI_XXX error code * * \note Set fout == NULL to print X on the console. */ diff --git a/library/bignum.c b/library/bignum.c index 6591b5b67..59209563c 100644 --- a/library/bignum.c +++ b/library/bignum.c @@ -441,15 +441,19 @@ int mpi_read_file( mpi *X, int radix, FILE *fin ) size_t slen; char *p; /* - * Buffer should have space for (short) label and hexified MPI and '\0' + * Buffer should have space for (short) label and decimal formatted MPI, + * newline characters and '\0' */ - char s[ 2 * POLARSSL_MPI_MAX_SIZE + 10 ]; + char s[ POLARSSL_MPI_READ_BUFFER_SIZE ]; memset( s, 0, sizeof( s ) ); if( fgets( s, sizeof( s ) - 1, fin ) == NULL ) return( POLARSSL_ERR_MPI_FILE_IO_ERROR ); slen = strlen( s ); + if( slen == sizeof( s ) - 2 ) + return( POLARSSL_ERR_MPI_BUFFER_TOO_SMALL ); + if( s[slen - 1] == '\n' ) { slen--; s[slen] = '\0'; } if( s[slen - 1] == '\r' ) { slen--; s[slen] = '\0'; } diff --git a/tests/data_files/mpi_too_big b/tests/data_files/mpi_too_big new file mode 100644 index 000000000..2d98757fb --- /dev/null +++ b/tests/data_files/mpi_too_big @@ -0,0 +1 @@ +64380800680355443923012985496149269915138610753401343291807343952413826484237063006136971539473913409092293733259038472039713333596954925632262097903668663321390395296617510709676918001764616185157314759639015364380800680355443923012985496149269915138610753401343291807343952413826484237063006136971539473913409092293733259038472039713333596954925632262097903668663321390395296617510709676918001764616185157314759639015364380800680355443923012985496149269915138610753401343291807343952413826484237063006136971539473913409092293733259038472039713333596954925632262097903668663321390395296617510709676918001764616185157314759639015364380800680355443923012985496149269915138610753401343291807343952413826484237063006136971539473913409092293733259038472039713333596954925632262097903668663321390395296617510709676918001764616185157314759639015364380800680355443923012985496149269915138610753401343291807343952413826484237063006136971539473913409092293733259038472039713333596954925632262097903668663321390395296617510709676918001764616185157314759639015364380800680355443923012985496149269915138610753401343291807343952413826484237063006136971539473913409092293733259038472039713333596954925632262097903668663321390395296617510709676918001764616185157 diff --git a/tests/suites/test_suite_mpi.data b/tests/suites/test_suite_mpi.data index ca98f0ce8..0a8c10332 100644 --- a/tests/suites/test_suite_mpi.data +++ b/tests/suites/test_suite_mpi.data @@ -61,6 +61,10 @@ Test mpi_read_file #2 (Illegal input) depends_on:POLARSSL_FS_IO mpi_read_file:10:"data_files/hash_file_3":"":0 +Test mpi_read_file #3 (Input too big) +depends_on:POLARSSL_FS_IO +mpi_read_file:10:"data_files/mpi_too_big":"":POLARSSL_ERR_MPI_BUFFER_TOO_SMALL + Base test mpi_write_file #1 depends_on:POLARSSL_FS_IO mpi_write_file:10:"56125680981752282334141896320372489490613963693556392520816017892111350604111697682705498319512049040516698827829292076808006940873974979584527073481012636016353913462376755556720019831187364993587901952757307830896531678727717924":16:"data_files/mpi_write":0