From 556e27b14f652fa39daa1148035e22b62525df15 Mon Sep 17 00:00:00 2001 From: "Dr. Stephen Henson" Date: Thu, 19 Apr 2012 11:36:09 +0000 Subject: [PATCH] Check for potentially exploitable overflows in asn1_d2i_read_bio BUF_mem_grow and BUF_mem_grow_clean. Refuse attempts to shrink buffer in CRYPTO_realloc_clean. Thanks to Tavis Ormandy, Google Security Team, for discovering this issue and to Adam Langley for fixing it. (CVE-2012-2110) --- CHANGES | 9 ++++++- crypto/asn1/a_d2i_fp.c | 54 +++++++++++++++++++++++++++++++----------- crypto/buffer/buffer.c | 17 +++++++++++++ crypto/mem.c | 4 ++++ 4 files changed, 69 insertions(+), 15 deletions(-) diff --git a/CHANGES b/CHANGES index b3424e898e..a2275713fb 100644 --- a/CHANGES +++ b/CHANGES @@ -4,7 +4,14 @@ Changes between 0.9.8u and 0.9.8v [xx XXX xxxx] - *) + *) Check for potentially exploitable overflows in asn1_d2i_read_bio + BUF_mem_grow and BUF_mem_grow_clean. Refuse attempts to shrink buffer + in CRYPTO_realloc_clean. + + Thanks to Tavis Ormandy, Google Security Team, for discovering this + issue and to Adam Langley for fixing it. + (CVE-2012-2110) + [Adam Langley (Google), Tavis Ormandy, Google Security Team] Changes between 0.9.8t and 0.9.8u [12 Mar 2012] diff --git a/crypto/asn1/a_d2i_fp.c b/crypto/asn1/a_d2i_fp.c index ece40bc4c0..52b2ebdb63 100644 --- a/crypto/asn1/a_d2i_fp.c +++ b/crypto/asn1/a_d2i_fp.c @@ -57,6 +57,7 @@ */ #include +#include #include "cryptlib.h" #include #include @@ -143,17 +144,11 @@ static int asn1_d2i_read_bio(BIO *in, BUF_MEM **pb) BUF_MEM *b; unsigned char *p; int i; - int ret=-1; ASN1_const_CTX c; - int want=HEADER_SIZE; + size_t want=HEADER_SIZE; int eos=0; -#if defined(__GNUC__) && defined(__ia64) - /* pathetic compiler bug in all known versions as of Nov. 2002 */ - long off=0; -#else - int off=0; -#endif - int len=0; + size_t off=0; + size_t len=0; b=BUF_MEM_new(); if (b == NULL) @@ -169,7 +164,7 @@ static int asn1_d2i_read_bio(BIO *in, BUF_MEM **pb) { want-=(len-off); - if (!BUF_MEM_grow_clean(b,len+want)) + if (len + want < len || !BUF_MEM_grow_clean(b,len+want)) { ASN1err(ASN1_F_ASN1_D2I_READ_BIO,ERR_R_MALLOC_FAILURE); goto err; @@ -181,7 +176,14 @@ static int asn1_d2i_read_bio(BIO *in, BUF_MEM **pb) goto err; } if (i > 0) + { + if (len+i < len) + { + ASN1err(ASN1_F_ASN1_D2I_READ_BIO,ASN1_R_TOO_LONG); + goto err; + } len+=i; + } } /* else data already loaded */ @@ -206,6 +208,11 @@ static int asn1_d2i_read_bio(BIO *in, BUF_MEM **pb) { /* no data body so go round again */ eos++; + if (eos < 0) + { + ASN1err(ASN1_F_ASN1_D2I_READ_BIO,ASN1_R_HEADER_TOO_LONG); + goto err; + } want=HEADER_SIZE; } else if (eos && (c.slen == 0) && (c.tag == V_ASN1_EOC)) @@ -220,10 +227,16 @@ static int asn1_d2i_read_bio(BIO *in, BUF_MEM **pb) else { /* suck in c.slen bytes of data */ - want=(int)c.slen; + want=c.slen; if (want > (len-off)) { want-=(len-off); + if (want > INT_MAX /* BIO_read takes an int length */ || + len+want < len) + { + ASN1err(ASN1_F_ASN1_D2I_READ_BIO,ASN1_R_TOO_LONG); + goto err; + } if (!BUF_MEM_grow_clean(b,len+want)) { ASN1err(ASN1_F_ASN1_D2I_READ_BIO,ERR_R_MALLOC_FAILURE); @@ -238,11 +251,18 @@ static int asn1_d2i_read_bio(BIO *in, BUF_MEM **pb) ASN1_R_NOT_ENOUGH_DATA); goto err; } + /* This can't overflow because + * |len+want| didn't overflow. */ len+=i; - want -= i; + want-=i; } } - off+=(int)c.slen; + if (off + c.slen < off) + { + ASN1err(ASN1_F_ASN1_D2I_READ_BIO,ASN1_R_TOO_LONG); + goto err; + } + off+=c.slen; if (eos <= 0) { break; @@ -252,9 +272,15 @@ static int asn1_d2i_read_bio(BIO *in, BUF_MEM **pb) } } + if (off > INT_MAX) + { + ASN1err(ASN1_F_ASN1_D2I_READ_BIO,ASN1_R_TOO_LONG); + goto err; + } + *pb = b; return off; err: if (b != NULL) BUF_MEM_free(b); - return(ret); + return -1; } diff --git a/crypto/buffer/buffer.c b/crypto/buffer/buffer.c index b3e947771d..3fa7229977 100644 --- a/crypto/buffer/buffer.c +++ b/crypto/buffer/buffer.c @@ -60,6 +60,11 @@ #include "cryptlib.h" #include +/* LIMIT_BEFORE_EXPANSION is the maximum n such that (n+3)/3*4 < 2**31. That + * function is applied in several functions in this file and this limit ensures + * that the result fits in an int. */ +#define LIMIT_BEFORE_EXPANSION 0x5ffffffc + BUF_MEM *BUF_MEM_new(void) { BUF_MEM *ret; @@ -105,6 +110,12 @@ int BUF_MEM_grow(BUF_MEM *str, int len) str->length=len; return(len); } + /* This limit is sufficient to ensure (len+3)/3*4 < 2**31 */ + if (len > LIMIT_BEFORE_EXPANSION) + { + BUFerr(BUF_F_BUF_MEM_GROW,ERR_R_MALLOC_FAILURE); + return 0; + } n=(len+3)/3*4; if (str->data == NULL) ret=OPENSSL_malloc(n); @@ -142,6 +153,12 @@ int BUF_MEM_grow_clean(BUF_MEM *str, int len) str->length=len; return(len); } + /* This limit is sufficient to ensure (len+3)/3*4 < 2**31 */ + if (len > LIMIT_BEFORE_EXPANSION) + { + BUFerr(BUF_F_BUF_MEM_GROW,ERR_R_MALLOC_FAILURE); + return 0; + } n=(len+3)/3*4; if (str->data == NULL) ret=OPENSSL_malloc(n); diff --git a/crypto/mem.c b/crypto/mem.c index 00ebaf0b9b..05d7b9cd3d 100644 --- a/crypto/mem.c +++ b/crypto/mem.c @@ -372,6 +372,10 @@ void *CRYPTO_realloc_clean(void *str, int old_len, int num, const char *file, if (num <= 0) return NULL; + /* We don't support shrinking the buffer. Note the memcpy that copies + * |old_len| bytes to the new buffer, below. */ + if (num < old_len) return NULL; + if (realloc_debug_func != NULL) realloc_debug_func(str, NULL, num, file, line, 0); ret=malloc_ex_func(num,file,line); -- 2.25.1