diff --git a/doc/crypt.tex b/doc/crypt.tex index fbe9098cc..9285fa1d9 100644 --- a/doc/crypt.tex +++ b/doc/crypt.tex @@ -2556,6 +2556,7 @@ \subsection{Encryption / Decryption} \begin{verbatim} int siv_encrypt_memory( int cipher, const unsigned char *key, unsigned long keylen, + unsigned long adnum, const unsigned char *ad[], unsigned long adlen[], const unsigned char *pt, unsigned long ptlen, unsigned char *ct, unsigned long *ctlen); @@ -2571,13 +2572,13 @@ \subsection{Encryption / Decryption} The AAD is passed as array of pointers in \textit{ad}. The length of each AAD is passed as array of \textit{unsigned long} in \textit{adlen}. -As soon as an array element of \textit{ad} is hit which equals \texttt{NULL} or an array element of \textit{adlen} -is hit which equals \texttt{0}, processing of the AAD is stopped. +The number of AAD elements is passed in \textit{adnum}, when it equals \texttt{0} both \textit{ad} and \textit{adlen} may be \texttt{NULL}. \index{siv\_decrypt\_memory()} \begin{verbatim} int siv_decrypt_memory( int cipher, const unsigned char *key, unsigned long keylen, + unsigned long adnum, const unsigned char *ad[], unsigned long adlen[], const unsigned char *ct, unsigned long ctlen, unsigned char *pt, unsigned long *ptlen); @@ -2609,9 +2610,10 @@ \subsection{Encryption / Decryption} * but a string is on most platforms defined as a "signed" `char*`. */ if ((err = siv_encrypt_memory(find_cipher("aes"), ((unsigned char[32]) {0x0}), 32, + 3, ((const unsigned char*[]) {(void*)"aad0", (void*)"aad1", - (void*)"NONCE", NULL}), - ((unsigned long[]) {4, 4, 5, 0}), + (void*)"NONCE"}), + ((unsigned long[]) {4, 4, 5}), plain, plainlen, ct, &ctlen)) != CRYPT_OK) { whine_and_pout(err); @@ -2619,9 +2621,10 @@ \subsection{Encryption / Decryption} if ((err = siv_decrypt_memory(find_cipher("aes"), ((unsigned char[32]) {0x0}), 32, + 3, ((const unsigned char*[]) {(void*)"aad0", (void*)"aad1", - (void*)"NONCE", NULL}), - ((unsigned long[]) {4, 4, 5, 0}), + (void*)"NONCE"}), + ((unsigned long[]) {4, 4, 5}), ct, ctlen, plain, &plainlen)) != CRYPT_OK) { whine_and_pout(err); @@ -2641,6 +2644,7 @@ \subsection{One--Shot Packet} const unsigned char *key, unsigned long keylen, const unsigned char *in, unsigned long inlen, unsigned char *out, unsigned long *outlen, + unsigned long adnum, ...); \end{verbatim} @@ -2648,6 +2652,7 @@ \subsection{One--Shot Packet} using the \textit{cipher} with the \textit{key} of len \textit{keylen}. The AAD is optionally passed as varargs of the form \textit{(const unsigned char*, unsigned long)}, which musst be NULL terminated. +Exactly \textit{adnum} such pairs are read; the terminating \texttt{NULL} does not delimit the list; see \ref{SIV_zero_vs_empty_ad}. The input is passed via the \textit{in} argument of length \textit{inlen}. The output is stored in the buffer pointer to by the \textit{out} argument where the length is passed as \textit{outlen}. \textit{outlen} shall contain the initial size of the buffer behind \textit{out} when calling the function and on @@ -2677,7 +2682,7 @@ \subsection{One--Shot Packet} ((unsigned char[32]) {0x0}), 32, plain, plainlen, ct, &ctlen, - "aad0", 4uL, "aad1", 4uL, "NONCE", 5uL, NULL)) != CRYPT_OK) { + 3, "aad0", 4uL, "aad1", 4uL, "NONCE", 5uL, NULL)) != CRYPT_OK) { whine_and_pout(err); } @@ -2685,7 +2690,7 @@ \subsection{One--Shot Packet} ((unsigned char[32]) {0x0}), 32, ct, ctlen, plain, &plainlen, - "aad0", 4uL, "aad1", 4uL, "NONCE", 5uL, NULL)) != CRYPT_OK) { + 3, "aad0", 4uL, "aad1", 4uL, "NONCE", 5uL, NULL)) != CRYPT_OK) { whine_and_pout(err); } @@ -2694,6 +2699,29 @@ \subsection{One--Shot Packet} \end{verbatim} \end{small} +\subsection{No Associated Data vs. Empty Associated Data} +\label{SIV_zero_vs_empty_ad} + +RFC 5297 computes the synthetic IV as $S2V(K_1, AD_1, \ldots, AD_m, P)$ i.e. S2V is fed a \textit{list} of strings +and the result depends on the number of components not only on their contents. + +Passing \textbf{no} associated data ($m = 0$) is therefore \textbf{not} the same as passing \textbf{one empty} +associated data string ($m = 1$). For the same key and plaintext the two produce a different ciphertext and one +will not decrypt as the other. This is also why \textit{adnum} has to be passed explicitly: neither a \texttt{NULL} +pointer nor a length of \texttt{0} can terminate the list as both are valid contents of a component. + +\begin{small} +\begin{verbatim} +/* no associated data, m = 0 */ +siv_encrypt_memory(cipher, key, keylen, 0, NULL, NULL, pt, ptlen, ct, &ctlen); +siv_memory(cipher, LTC_ENCRYPT, key, keylen, pt, ptlen, ct, &ctlen, 0, NULL); + +/* one empty associated data string, m = 1 */ +siv_encrypt_memory(cipher, key, keylen, 1, ((const unsigned char*[]) {NULL}), ((unsigned long[]) {0}), pt, ptlen, ct, &ctlen); +siv_memory(cipher, LTC_ENCRYPT, key, keylen, pt, ptlen, ct, &ctlen, 1, NULL, 0, NULL); +\end{verbatim} +\end{small} + \mysection{GCM-SIV} \label{GCM-SIV} diff --git a/src/encauth/siv/siv.c b/src/encauth/siv/siv.c index bd6d5b45b..3106deee7 100644 --- a/src/encauth/siv/siv.c +++ b/src/encauth/siv/siv.c @@ -191,7 +191,8 @@ static int s_siv_S2V(int cipher, return err; } - do { + /* With zero AD components the loop runs zero times. */ + while (n < adnum) { if (n >= s_siv_max_aad_components) { return CRYPT_INPUT_TOO_LONG; } @@ -199,7 +200,7 @@ static int s_siv_S2V(int cipher, return err; } n++; - } while(n < adnum); + } return s_siv_S2V_T(&ctx, in, inlen, &D, V); } @@ -470,23 +471,19 @@ int siv_memory( int cipher, int direction, goto err_out; } va_start(args, adnum); - do { - if (adnum) { - aad = va_arg(args, const unsigned char*); - aadlen = va_arg(args, unsigned long); - } else { - aad = NULL; - aadlen = 0; - } + /* With zero AD components the loop runs zero times. */ + while (n < adnum) { if (n >= s_siv_max_aad_components) { err = CRYPT_INPUT_TOO_LONG; goto err_out2; } + aad = va_arg(args, const unsigned char*); + aadlen = va_arg(args, unsigned long); if ((err = s_siv_S2V_dbl_xor_cmac(&ctx, aad, aadlen, &D)) != CRYPT_OK) { goto err_out2; } n++; - } while (n < adnum); + } if ((err = s_siv_S2V_T(&ctx, in_work, in_work_len, &D, &siv.V)) != CRYPT_OK) { goto err_out2; @@ -614,6 +611,19 @@ int siv_test(void) 0x3d, 0x58, 0x8e, 0x85, 0x64, 0xa5, 0xfe }; + /* Zero AD components vs. a single *empty* AD component (vectors were cross-checked against OpenSSL 3.5.6) */ + const unsigned char output_A1_zeroad[] = + { 0xf1, 0xc5, 0xfd, 0xea, 0xc1, 0xf1, 0x5a, 0x26, + 0x77, 0x9c, 0x15, 0x01, 0xf9, 0xfb, 0x75, 0x88, + 0x27, 0xe9, 0x46, 0xc6, 0x69, 0x08, 0x8a, 0xb0, + 0x6d, 0xa5, 0x8c, 0x5c, 0x83, 0x1c }; + const unsigned char output_A1_emptyad[] = + { 0xd1, 0x02, 0x2f, 0x5b, 0x36, 0x64, 0xe5, 0xa4, + 0xdf, 0xaf, 0x90, 0xf8, 0x5b, 0xe6, 0xf2, 0x8a, + 0xb6, 0x6c, 0xff, 0x6b, 0x8e, 0xca, 0x0b, 0x79, + 0xf0, 0x83, 0xb3, 0x9a, 0x09, 0x01 }; + const unsigned char *ad_emptyad[] = { NULL, NULL }; + unsigned long adlen_emptyad[] = { 0, 0 }; #define PL_PAIR(n) n, sizeof(n) struct { @@ -632,6 +642,8 @@ int siv_test(void) { PL_PAIR(Key_A2), PL_PAIR(Plaintext_A2), 3, &ad_A2, &adlen_A2, PL_PAIR(output_A2), "RFC5297 - A.2. Nonce-Based Authenticated Encryption Example" }, { PL_PAIR(Key_A2), PL_PAIR(Plaintext_A2), 3, &ad_ossl0, &adlen_ossl0, PL_PAIR(output_ossl0), "OpenSSL based example 0" }, { PL_PAIR(Key_A2), PL_PAIR(Plaintext_A2), 3, &ad_ossl1, &adlen_ossl1, PL_PAIR(output_ossl1), "OpenSSL based example 1" }, + { PL_PAIR(Key_A1), PL_PAIR(Plaintext_A1), 0, NULL, NULL, PL_PAIR(output_A1_zeroad), "Zero AD components (ad = adlen = NULL)" }, + { PL_PAIR(Key_A1), PL_PAIR(Plaintext_A1), 1, &ad_emptyad, &adlen_emptyad, PL_PAIR(output_A1_emptyad), "One empty AD component" }, }; #undef PL_PAIR @@ -736,6 +748,44 @@ int siv_test(void) return CRYPT_FAIL_TESTVECTOR; } + n++; + + /* Testcase 0x4 - siv_memory() - zero AD components - encrypt */ + buflen = sizeof(buf); + if ((err = siv_memory(cipher, LTC_ENCRYPT, Key_A1, sizeof(Key_A1), Plaintext_A1, sizeof(Plaintext_A1), buf, &buflen, 0, NULL)) != CRYPT_OK) { + return err; + } + if (ltc_compare_testvector(buf, buflen, output_A1_zeroad, sizeof(output_A1_zeroad), "siv_memory() - zero AD components", n) != 0) { + return CRYPT_FAIL_TESTVECTOR; + } + /* Testcase 0x1004 - siv_memory() - zero AD components - decrypt */ + buflen = sizeof(buf); + if ((err = siv_memory(cipher, LTC_DECRYPT, Key_A1, sizeof(Key_A1), output_A1_zeroad, sizeof(output_A1_zeroad), buf, &buflen, 0, NULL)) != CRYPT_OK) { + return err; + } + if (ltc_compare_testvector(buf, buflen, Plaintext_A1, sizeof(Plaintext_A1), "siv_memory() - zero AD components", n + 0x1000) != 0) { + return CRYPT_FAIL_TESTVECTOR; + } + + n++; + + /* Testcase 0x5 - siv_memory() - one empty AD component - encrypt */ + buflen = sizeof(buf); + if ((err = siv_memory(cipher, LTC_ENCRYPT, Key_A1, sizeof(Key_A1), Plaintext_A1, sizeof(Plaintext_A1), buf, &buflen, 1, NULL, 0UL, NULL)) != CRYPT_OK) { + return err; + } + if (ltc_compare_testvector(buf, buflen, output_A1_emptyad, sizeof(output_A1_emptyad), "siv_memory() - one empty AD component", n) != 0) { + return CRYPT_FAIL_TESTVECTOR; + } + /* Testcase 0x1005 - siv_memory() - one empty AD component - decrypt */ + buflen = sizeof(buf); + if ((err = siv_memory(cipher, LTC_DECRYPT, Key_A1, sizeof(Key_A1), output_A1_emptyad, sizeof(output_A1_emptyad), buf, &buflen, 1, NULL, 0UL, NULL)) != CRYPT_OK) { + return err; + } + if (ltc_compare_testvector(buf, buflen, Plaintext_A1, sizeof(Plaintext_A1), "siv_memory() - one empty AD component", n + 0x1000) != 0) { + return CRYPT_FAIL_TESTVECTOR; + } + for (n = 0; n < LTC_ARRAY_SIZE(tmp); ++n) { tmp[n] = XCALLOC(1, tmpmax); if (tmp[n] == NULL) {