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pdf-crypt.c
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pdf-crypt.c
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// Copyright (C) 2004-2021 Artifex Software, Inc.
//
// This file is part of MuPDF.
//
// MuPDF is free software: you can redistribute it and/or modify it under the
// terms of the GNU Affero General Public License as published by the Free
// Software Foundation, either version 3 of the License, or (at your option)
// any later version.
//
// MuPDF is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
// FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
// details.
//
// You should have received a copy of the GNU Affero General Public License
// along with MuPDF. If not, see <https://www.gnu.org/licenses/agpl-3.0.en.html>
//
// Alternative licensing terms are available from the licensor.
// For commercial licensing, see <https://www.artifex.com/> or contact
// Artifex Software, Inc., 39 Mesa Street, Suite 108A, San Francisco,
// CA 94129, USA, for further information.
#include "mupdf/fitz.h"
#include "mupdf/pdf.h"
#include <string.h>
enum
{
PDF_CRYPT_NONE,
PDF_CRYPT_RC4,
PDF_CRYPT_AESV2,
PDF_CRYPT_AESV3,
PDF_CRYPT_UNKNOWN,
};
typedef struct
{
int method;
int length;
} pdf_crypt_filter;
struct pdf_crypt
{
pdf_obj *id;
int v;
int length;
pdf_obj *cf;
pdf_crypt_filter stmf;
pdf_crypt_filter strf;
int r;
unsigned char o[48];
unsigned char u[48];
unsigned char oe[32];
unsigned char ue[32];
unsigned char perms[16];
int p;
int encrypt_metadata;
unsigned char key[32]; /* decryption key generated from password */
};
static void pdf_parse_crypt_filter(fz_context *ctx, pdf_crypt_filter *cf, pdf_crypt *crypt, pdf_obj *name);
pdf_crypt *
pdf_new_crypt(fz_context *ctx, pdf_obj *dict, pdf_obj *id)
{
pdf_crypt *crypt;
pdf_obj *obj;
crypt = fz_malloc_struct(ctx, pdf_crypt);
/* Common to all security handlers (PDF 1.7 table 3.18) */
obj = pdf_dict_get(ctx, dict, PDF_NAME(Filter));
if (!pdf_is_name(ctx, obj))
{
pdf_drop_crypt(ctx, crypt);
fz_throw(ctx, FZ_ERROR_FORMAT, "unspecified encryption handler");
}
if (!pdf_name_eq(ctx, PDF_NAME(Standard), obj))
{
pdf_drop_crypt(ctx, crypt);
fz_throw(ctx, FZ_ERROR_FORMAT, "unknown encryption handler: '%s'", pdf_to_name(ctx, obj));
}
crypt->v = pdf_dict_get_int_default(ctx, dict, PDF_NAME(V), 0);
if (crypt->v != 0 && crypt->v != 1 && crypt->v != 2 && crypt->v != 4 && crypt->v != 5)
{
pdf_drop_crypt(ctx, crypt);
fz_throw(ctx, FZ_ERROR_FORMAT, "unknown encryption version");
}
/* Standard security handler (PDF 1.7 table 3.19) */
obj = pdf_dict_get(ctx, dict, PDF_NAME(R));
if (pdf_is_int(ctx, obj))
crypt->r = pdf_to_int(ctx, obj);
else if (crypt->v <= 4)
{
fz_warn(ctx, "encryption dictionary missing revision value, guessing...");
if (crypt->v < 2)
crypt->r = 2;
else if (crypt->v == 2)
crypt->r = 3;
else if (crypt->v == 4)
crypt->r = 4;
}
else
{
pdf_drop_crypt(ctx, crypt);
fz_throw(ctx, FZ_ERROR_FORMAT, "encryption dictionary missing version and revision value");
}
if (crypt->r < 1 || crypt->r > 6)
{
int r = crypt->r;
pdf_drop_crypt(ctx, crypt);
fz_throw(ctx, FZ_ERROR_FORMAT, "unknown crypt revision %d", r);
}
obj = pdf_dict_get(ctx, dict, PDF_NAME(O));
if (pdf_is_string(ctx, obj) && pdf_to_str_len(ctx, obj) == 32)
memcpy(crypt->o, pdf_to_str_buf(ctx, obj), 32);
/* /O and /U are supposed to be 48 bytes long for revision 5 and 6, they're often longer, though */
else if (crypt->r >= 5 && pdf_is_string(ctx, obj) && pdf_to_str_len(ctx, obj) >= 48)
memcpy(crypt->o, pdf_to_str_buf(ctx, obj), 48);
else
{
pdf_drop_crypt(ctx, crypt);
fz_throw(ctx, FZ_ERROR_FORMAT, "encryption dictionary missing owner password");
}
obj = pdf_dict_get(ctx, dict, PDF_NAME(U));
if (pdf_is_string(ctx, obj) && pdf_to_str_len(ctx, obj) == 32)
memcpy(crypt->u, pdf_to_str_buf(ctx, obj), 32);
/* /O and /U are supposed to be 48 bytes long for revision 5 and 6, they're often longer, though */
else if (crypt->r >= 5 && pdf_is_string(ctx, obj) && pdf_to_str_len(ctx, obj) >= 48)
memcpy(crypt->u, pdf_to_str_buf(ctx, obj), 48);
else if (pdf_is_string(ctx, obj) && pdf_to_str_len(ctx, obj) < 32)
{
fz_warn(ctx, "encryption password key too short (%zu)", pdf_to_str_len(ctx, obj));
memcpy(crypt->u, pdf_to_str_buf(ctx, obj), pdf_to_str_len(ctx, obj));
}
else
{
pdf_drop_crypt(ctx, crypt);
fz_throw(ctx, FZ_ERROR_FORMAT, "encryption dictionary missing user password");
}
obj = pdf_dict_get(ctx, dict, PDF_NAME(P));
if (pdf_is_int(ctx, obj))
crypt->p = pdf_to_int(ctx, obj);
else
{
fz_warn(ctx, "encryption dictionary missing permissions");
crypt->p = 0xfffffffc;
}
if (crypt->r == 5 || crypt->r == 6)
{
obj = pdf_dict_get(ctx, dict, PDF_NAME(OE));
if (!pdf_is_string(ctx, obj) || pdf_to_str_len(ctx, obj) != 32)
{
pdf_drop_crypt(ctx, crypt);
fz_throw(ctx, FZ_ERROR_FORMAT, "encryption dictionary missing owner encryption key");
}
memcpy(crypt->oe, pdf_to_str_buf(ctx, obj), 32);
obj = pdf_dict_get(ctx, dict, PDF_NAME(UE));
if (!pdf_is_string(ctx, obj) || pdf_to_str_len(ctx, obj) != 32)
{
pdf_drop_crypt(ctx, crypt);
fz_throw(ctx, FZ_ERROR_FORMAT, "encryption dictionary missing user encryption key");
}
memcpy(crypt->ue, pdf_to_str_buf(ctx, obj), 32);
}
crypt->encrypt_metadata = pdf_dict_get_bool_default(ctx, dict, PDF_NAME(EncryptMetadata), 1);
/* Extract file identifier string */
if (pdf_is_array(ctx, id) && pdf_array_len(ctx, id) == 2)
{
obj = pdf_array_get(ctx, id, 0);
if (pdf_is_string(ctx, obj))
crypt->id = pdf_keep_obj(ctx, obj);
}
else
fz_warn(ctx, "missing file identifier, may not be able to do decryption");
/* Determine encryption key length */
crypt->length = 40;
if (crypt->v == 2 || crypt->v == 4)
{
crypt->length = pdf_dict_get_int_default(ctx, dict, PDF_NAME(Length), crypt->length);
/* work-around for pdf generators that assume length is in bytes */
if (crypt->length < 40)
crypt->length = crypt->length * 8;
if (crypt->length % 8 != 0)
{
pdf_drop_crypt(ctx, crypt);
fz_throw(ctx, FZ_ERROR_FORMAT, "invalid encryption key length");
}
if (crypt->length < 40 || crypt->length > 128)
{
pdf_drop_crypt(ctx, crypt);
fz_throw(ctx, FZ_ERROR_FORMAT, "invalid encryption key length");
}
}
if (crypt->v == 5)
crypt->length = 256;
if (crypt->v == 0 || crypt->v == 1 || crypt->v == 2)
{
crypt->stmf.method = PDF_CRYPT_RC4;
crypt->stmf.length = crypt->length;
crypt->strf.method = PDF_CRYPT_RC4;
crypt->strf.length = crypt->length;
}
if (crypt->v == 4 || crypt->v == 5)
{
crypt->stmf.method = PDF_CRYPT_NONE;
crypt->stmf.length = crypt->length;
crypt->strf.method = PDF_CRYPT_NONE;
crypt->strf.length = crypt->length;
obj = pdf_dict_get(ctx, dict, PDF_NAME(CF));
if (pdf_is_dict(ctx, obj))
{
crypt->cf = pdf_keep_obj(ctx, obj);
}
else
{
crypt->cf = NULL;
}
fz_try(ctx)
{
obj = pdf_dict_get(ctx, dict, PDF_NAME(StmF));
if (pdf_is_name(ctx, obj))
pdf_parse_crypt_filter(ctx, &crypt->stmf, crypt, obj);
obj = pdf_dict_get(ctx, dict, PDF_NAME(StrF));
if (pdf_is_name(ctx, obj))
pdf_parse_crypt_filter(ctx, &crypt->strf, crypt, obj);
}
fz_catch(ctx)
{
pdf_drop_crypt(ctx, crypt);
fz_rethrow(ctx);
}
/* in crypt revision 4, the crypt filter determines the key length */
if (crypt->strf.method != PDF_CRYPT_NONE)
crypt->length = crypt->stmf.length;
}
return crypt;
}
void
pdf_drop_crypt(fz_context *ctx, pdf_crypt *crypt)
{
if (!crypt)
return;
pdf_drop_obj(ctx, crypt->id);
pdf_drop_obj(ctx, crypt->cf);
fz_free(ctx, crypt);
}
/*
* Parse a CF dictionary entry (PDF 1.7 table 3.22)
*/
static void
pdf_parse_crypt_filter(fz_context *ctx, pdf_crypt_filter *cf, pdf_crypt *crypt, pdf_obj *name)
{
pdf_obj *obj;
pdf_obj *dict;
int is_identity = (pdf_name_eq(ctx, name, PDF_NAME(Identity)));
int is_stdcf = (!is_identity && pdf_name_eq(ctx, name, PDF_NAME(StdCF)));
if (!is_identity && !is_stdcf)
fz_throw(ctx, FZ_ERROR_FORMAT, "Crypt Filter not Identity or StdCF (%d 0 R)", pdf_to_num(ctx, crypt->cf));
cf->method = PDF_CRYPT_NONE;
cf->length = crypt->length;
if (!crypt->cf)
{
cf->method = (is_identity ? PDF_CRYPT_NONE : PDF_CRYPT_RC4);
return;
}
dict = pdf_dict_get(ctx, crypt->cf, name);
if (pdf_is_dict(ctx, dict))
{
obj = pdf_dict_get(ctx, dict, PDF_NAME(CFM));
if (pdf_is_name(ctx, obj))
{
if (pdf_name_eq(ctx, PDF_NAME(None), obj))
cf->method = PDF_CRYPT_NONE;
else if (pdf_name_eq(ctx, PDF_NAME(V2), obj))
cf->method = PDF_CRYPT_RC4;
else if (pdf_name_eq(ctx, PDF_NAME(AESV2), obj))
cf->method = PDF_CRYPT_AESV2;
else if (pdf_name_eq(ctx, PDF_NAME(AESV3), obj))
cf->method = PDF_CRYPT_AESV3;
else
fz_warn(ctx, "unknown encryption method: %s", pdf_to_name(ctx, obj));
}
cf->length = pdf_dict_get_int_default(ctx, dict, PDF_NAME(Length), cf->length);
}
else if (!is_identity)
fz_throw(ctx, FZ_ERROR_FORMAT, "cannot parse crypt filter (%d 0 R)", pdf_to_num(ctx, crypt->cf));
if (cf->method != PDF_CRYPT_NONE)
{
if (crypt->r == 4 && cf->method != PDF_CRYPT_RC4 && cf->method != PDF_CRYPT_AESV2)
fz_warn(ctx, "unexpected encryption method for revision 4 crypto: %s", pdf_crypt_method(ctx, crypt));
else if (crypt->r >= 5 && cf->method != PDF_CRYPT_AESV3)
{
fz_warn(ctx, "illegal encryption method for revision 5/6, assuming AESV3");
cf->method = PDF_CRYPT_AESV3;
}
}
/* the length for crypt filters is supposed to be in bytes not bits */
if (cf->length < 40)
cf->length = cf->length * 8;
if ((cf->length % 8) != 0)
fz_throw(ctx, FZ_ERROR_FORMAT, "invalid key length: %d", cf->length);
if ((crypt->r == 1 || crypt->r == 2 || crypt->r == 3 || crypt->r == 4) &&
(cf->length < 40 || cf->length > 128))
fz_throw(ctx, FZ_ERROR_FORMAT, "invalid key length: %d", cf->length);
if ((crypt->r == 5 || crypt->r == 6) && cf->length != 256)
{
fz_warn(ctx, "illegal key length for revision 5/6, assuming 256 bits");
cf->length = 256;
}
}
/*
* Compute an encryption key (PDF 1.7 algorithm 3.2)
*/
static const unsigned char padding[32] =
{
0x28, 0xbf, 0x4e, 0x5e, 0x4e, 0x75, 0x8a, 0x41,
0x64, 0x00, 0x4e, 0x56, 0xff, 0xfa, 0x01, 0x08,
0x2e, 0x2e, 0x00, 0xb6, 0xd0, 0x68, 0x3e, 0x80,
0x2f, 0x0c, 0xa9, 0xfe, 0x64, 0x53, 0x69, 0x7a
};
static void
pdf_compute_encryption_key(fz_context *ctx, pdf_crypt *crypt, unsigned char *password, size_t pwlen, unsigned char *key)
{
unsigned char buf[32];
unsigned int p;
int i, n;
fz_md5 md5;
n = fz_clampi(crypt->length / 8, 0, 16);
/* Step 1 - copy and pad password string */
if (pwlen > 32)
pwlen = 32;
memcpy(buf, password, pwlen);
if (pwlen < 32)
memcpy(buf + pwlen, padding, 32 - pwlen);
/* Step 2 - init md5 and pass value of step 1 */
fz_md5_init(&md5);
fz_md5_update(&md5, buf, 32);
/* Step 3 - pass O value */
fz_md5_update(&md5, crypt->o, 32);
/* Step 4 - pass P value as unsigned int, low-order byte first */
p = (unsigned int) crypt->p;
buf[0] = (p) & 0xFF;
buf[1] = (p >> 8) & 0xFF;
buf[2] = (p >> 16) & 0xFF;
buf[3] = (p >> 24) & 0xFF;
fz_md5_update(&md5, buf, 4);
/* Step 5 - pass first element of ID array */
fz_md5_update(&md5, (unsigned char *)pdf_to_str_buf(ctx, crypt->id), pdf_to_str_len(ctx, crypt->id));
/* Step 6 (revision 4 or greater) - if metadata is not encrypted pass 0xFFFFFFFF */
if (crypt->r >= 4)
{
if (!crypt->encrypt_metadata)
{
buf[0] = 0xFF;
buf[1] = 0xFF;
buf[2] = 0xFF;
buf[3] = 0xFF;
fz_md5_update(&md5, buf, 4);
}
}
/* Step 7 - finish the hash */
fz_md5_final(&md5, buf);
/* Step 8 (revision 3 or greater) - do some voodoo 50 times */
if (crypt->r >= 3)
{
for (i = 0; i < 50; i++)
{
fz_md5_init(&md5);
fz_md5_update(&md5, buf, n);
fz_md5_final(&md5, buf);
}
}
/* Step 9 - the key is the first 'n' bytes of the result */
memcpy(key, buf, n);
}
/*
* Compute an encryption key (PDF 1.7 ExtensionLevel 3 algorithm 3.2a)
*/
static void
pdf_compute_encryption_key_r5(fz_context *ctx, pdf_crypt *crypt, unsigned char *password, size_t pwlen, int ownerkey, unsigned char *validationkey)
{
unsigned char buffer[128 + 8 + 48];
fz_sha256 sha256;
fz_aes aes;
/* Step 2 - truncate UTF-8 password to 127 characters */
if (pwlen > 127)
pwlen = 127;
/* Step 3/4 - test password against owner/user key and compute encryption key */
memcpy(buffer, password, pwlen);
if (ownerkey)
{
memcpy(buffer + pwlen, crypt->o + 32, 8);
memcpy(buffer + pwlen + 8, crypt->u, 48);
}
else
memcpy(buffer + pwlen, crypt->u + 32, 8);
fz_sha256_init(&sha256);
fz_sha256_update(&sha256, buffer, pwlen + 8 + (ownerkey ? 48 : 0));
fz_sha256_final(&sha256, validationkey);
/* Step 3.5/4.5 - compute file encryption key from OE/UE */
if (ownerkey)
{
memcpy(buffer + pwlen, crypt->o + 40, 8);
memcpy(buffer + pwlen + 8, crypt->u, 48);
}
else
memcpy(buffer + pwlen, crypt->u + 40, 8);
fz_sha256_init(&sha256);
fz_sha256_update(&sha256, buffer, pwlen + 8 + (ownerkey ? 48 : 0));
fz_sha256_final(&sha256, buffer);
/* clear password buffer and use it as iv */
memset(buffer + 32, 0, sizeof(buffer) - 32);
if (fz_aes_setkey_dec(&aes, buffer, crypt->length))
fz_throw(ctx, FZ_ERROR_FORMAT, "aes invalid key size (%d)", crypt->length);
fz_aes_crypt_cbc(&aes, FZ_AES_DECRYPT, 32, buffer + 32, ownerkey ? crypt->oe : crypt->ue, crypt->key);
}
/*
* Compute an encryption key (PDF 1.7 ExtensionLevel 8 algorithm)
*
* Adobe has not yet released the details, so the algorithm reference is:
* http://esec-lab.sogeti.com/post/The-undocumented-password-validation-algorithm-of-Adobe-Reader-X
*/
static void
pdf_compute_hardened_hash_r6(fz_context *ctx, unsigned char *password, size_t pwlen, unsigned char salt[8], unsigned char *ownerkey, unsigned char hash[32])
{
unsigned char data[(128 + 64 + 48) * 64];
unsigned char block[64];
int block_size = 32;
size_t data_len = 0;
int i, j, sum;
fz_sha256 sha256;
fz_sha384 sha384;
fz_sha512 sha512;
fz_aes aes;
/* Step 1: calculate initial data block */
fz_sha256_init(&sha256);
fz_sha256_update(&sha256, password, pwlen);
fz_sha256_update(&sha256, salt, 8);
if (ownerkey)
fz_sha256_update(&sha256, ownerkey, 48);
fz_sha256_final(&sha256, block);
for (i = 0; i < 64 || i < data[data_len * 64 - 1] + 32; i++)
{
/* Step 2: repeat password and data block 64 times */
memcpy(data, password, pwlen);
memcpy(data + pwlen, block, block_size);
if (ownerkey)
memcpy(data + pwlen + block_size, ownerkey, 48);
data_len = pwlen + block_size + (ownerkey ? 48 : 0);
for (j = 1; j < 64; j++)
memcpy(data + j * data_len, data, data_len);
/* Step 3: encrypt data using data block as key and iv */
(void)fz_aes_setkey_enc(&aes, block, 128);
fz_aes_crypt_cbc(&aes, FZ_AES_ENCRYPT, data_len * 64, block + 16, data, data);
/* Step 4: determine SHA-2 hash size for this round */
for (j = 0, sum = 0; j < 16; j++)
sum += data[j];
/* Step 5: calculate data block for next round */
block_size = 32 + (sum % 3) * 16;
switch (block_size)
{
case 32:
fz_sha256_init(&sha256);
fz_sha256_update(&sha256, data, data_len * 64);
fz_sha256_final(&sha256, block);
break;
case 48:
fz_sha384_init(&sha384);
fz_sha384_update(&sha384, data, data_len * 64);
fz_sha384_final(&sha384, block);
break;
case 64:
fz_sha512_init(&sha512);
fz_sha512_update(&sha512, data, data_len * 64);
fz_sha512_final(&sha512, block);
break;
}
}
memset(data, 0, sizeof(data));
memcpy(hash, block, 32);
}
static void
pdf_compute_encryption_key_r6(fz_context *ctx, pdf_crypt *crypt, unsigned char *password, size_t pwlen, int ownerkey, unsigned char *validationkey)
{
unsigned char hash[32];
unsigned char iv[16];
fz_aes aes;
if (pwlen > 127)
pwlen = 127;
pdf_compute_hardened_hash_r6(ctx, password, pwlen,
(ownerkey ? crypt->o : crypt->u) + 32,
ownerkey ? crypt->u : NULL, validationkey);
pdf_compute_hardened_hash_r6(ctx, password, pwlen,
(ownerkey ? crypt->o : crypt->u) + 40,
(ownerkey ? crypt->u : NULL),
hash);
memset(iv, 0, sizeof(iv));
(void)fz_aes_setkey_dec(&aes, hash, 256);
fz_aes_crypt_cbc(&aes, FZ_AES_DECRYPT, 32, iv, ownerkey ? crypt->oe : crypt->ue, crypt->key);
}
/*
* Computing the user password (PDF 1.7 algorithm 3.4 and 3.5)
* Also save the generated key for decrypting objects and streams in crypt->key.
*/
static void
pdf_compute_user_password(fz_context *ctx, pdf_crypt *crypt, unsigned char *password, size_t pwlen, unsigned char *output)
{
int n = fz_clampi(crypt->length / 8, 0, 16);
if (crypt->r == 2)
{
fz_arc4 arc4;
pdf_compute_encryption_key(ctx, crypt, password, pwlen, crypt->key);
fz_arc4_init(&arc4, crypt->key, n);
fz_arc4_encrypt(&arc4, output, padding, 32);
}
if (crypt->r == 3 || crypt->r == 4)
{
unsigned char xor[32];
unsigned char digest[16];
fz_md5 md5;
fz_arc4 arc4;
int i, x;
pdf_compute_encryption_key(ctx, crypt, password, pwlen, crypt->key);
fz_md5_init(&md5);
fz_md5_update(&md5, padding, 32);
fz_md5_update(&md5, (unsigned char*)pdf_to_str_buf(ctx, crypt->id), pdf_to_str_len(ctx, crypt->id));
fz_md5_final(&md5, digest);
fz_arc4_init(&arc4, crypt->key, n);
fz_arc4_encrypt(&arc4, output, digest, 16);
for (x = 1; x <= 19; x++)
{
for (i = 0; i < n; i++)
xor[i] = crypt->key[i] ^ x;
fz_arc4_init(&arc4, xor, n);
fz_arc4_encrypt(&arc4, output, output, 16);
}
memcpy(output + 16, padding, 16);
}
if (crypt->r == 5)
{
pdf_compute_encryption_key_r5(ctx, crypt, password, pwlen, 0, output);
}
if (crypt->r == 6)
{
pdf_compute_encryption_key_r6(ctx, crypt, password, pwlen, 0, output);
}
}
/*
* Authenticating the user password (PDF 1.7 algorithm 3.6
* and ExtensionLevel 3 algorithm 3.11)
* This also has the side effect of saving a key generated
* from the password for decrypting objects and streams.
*/
static int
pdf_authenticate_user_password(fz_context *ctx, pdf_crypt *crypt, unsigned char *password, size_t pwlen)
{
unsigned char output[32];
pdf_compute_user_password(ctx, crypt, password, pwlen, output);
if (crypt->r == 2 || crypt->r == 5 || crypt->r == 6)
return memcmp(output, crypt->u, 32) == 0;
if (crypt->r == 3 || crypt->r == 4)
return memcmp(output, crypt->u, 16) == 0;
return 0;
}
/*
* Authenticating the owner password (PDF 1.7 algorithm 3.7,
* ExtensionLevel 3 algorithm 3.12, ExtensionLevel 8 algorithm)
* Generates the user password from the owner password
* and calls pdf_authenticate_user_password.
*/
static int
pdf_authenticate_owner_password(fz_context *ctx, pdf_crypt *crypt, unsigned char *ownerpass, size_t pwlen)
{
int n = fz_clampi(crypt->length / 8, 0, 16);
if (crypt->r == 2)
{
unsigned char pwbuf[32];
unsigned char key[16];
unsigned char userpass[32];
fz_md5 md5;
fz_arc4 arc4;
if (pwlen > 32)
pwlen = 32;
memcpy(pwbuf, ownerpass, pwlen);
if (pwlen < 32)
memcpy(pwbuf + pwlen, padding, 32 - pwlen);
fz_md5_init(&md5);
fz_md5_update(&md5, pwbuf, 32);
fz_md5_final(&md5, key);
fz_arc4_init(&arc4, key, n);
fz_arc4_encrypt(&arc4, userpass, crypt->o, 32);
return pdf_authenticate_user_password(ctx, crypt, userpass, 32);
}
if (crypt->r == 3 || crypt->r == 4)
{
unsigned char pwbuf[32];
unsigned char key[16];
unsigned char xor[32];
unsigned char userpass[32];
int i, x;
fz_md5 md5;
fz_arc4 arc4;
if (pwlen > 32)
pwlen = 32;
memcpy(pwbuf, ownerpass, pwlen);
if (pwlen < 32)
memcpy(pwbuf + pwlen, padding, 32 - pwlen);
fz_md5_init(&md5);
fz_md5_update(&md5, pwbuf, 32);
fz_md5_final(&md5, key);
for (i = 0; i < 50; i++)
{
fz_md5_init(&md5);
fz_md5_update(&md5, key, n);
fz_md5_final(&md5, key);
}
memcpy(userpass, crypt->o, 32);
for (x = 0; x < 20; x++)
{
for (i = 0; i < n; i++)
xor[i] = key[i] ^ (19 - x);
fz_arc4_init(&arc4, xor, n);
fz_arc4_encrypt(&arc4, userpass, userpass, 32);
}
return pdf_authenticate_user_password(ctx, crypt, userpass, 32);
}
if (crypt->r == 5)
{
unsigned char key[32];
pdf_compute_encryption_key_r5(ctx, crypt, ownerpass, pwlen, 1, key);
return !memcmp(key, crypt->o, 32);
}
if (crypt->r == 6)
{
unsigned char key[32];
pdf_compute_encryption_key_r6(ctx, crypt, ownerpass, pwlen, 1, key);
return !memcmp(key, crypt->o, 32);
}
return 0;
}
static void pdf_docenc_from_utf8(char *password, const char *utf8, int n)
{
int i = 0, k, c;
while (*utf8 && i + 1 < n)
{
utf8 += fz_chartorune(&c, utf8);
for (k = 0; k < 256; k++)
{
if (c == fz_unicode_from_pdf_doc_encoding[k])
{
password[i++] = k;
break;
}
}
/* FIXME: drop characters that can't be encoded or return an error? */
}
password[i] = 0;
}
static void pdf_saslprep_from_utf8(char *password, const char *utf8, int n)
{
/* TODO: stringprep with SALSprep profile */
fz_strlcpy(password, utf8, n);
}
int
pdf_authenticate_password(fz_context *ctx, pdf_document *doc, const char *pwd_utf8)
{
char password[2048];
int auth;
if (!doc->crypt)
return 1; /* No password required */
password[0] = 0;
if (pwd_utf8)
{
if (doc->crypt->r <= 4)
pdf_docenc_from_utf8(password, pwd_utf8, sizeof password);
else
pdf_saslprep_from_utf8(password, pwd_utf8, sizeof password);
}
auth = 0;
if (pdf_authenticate_user_password(ctx, doc->crypt, (unsigned char *)password, strlen(password)))
auth = 2;
if (pdf_authenticate_owner_password(ctx, doc->crypt, (unsigned char *)password, strlen(password)))
auth |= 4;
else if (auth & 2)
{
/* We need to reauthenticate the user password,
* because the failed attempt to authenticate
* the owner password will have invalidated the
* stored keys. */
(void)pdf_authenticate_user_password(ctx, doc->crypt, (unsigned char *)password, strlen(password));
}
/* To match Acrobat, we choose not to allow an empty owner
* password, unless the user password is also the empty one. */
if (*password == 0 && auth == 4)
return 0;
return auth;
}
int
pdf_needs_password(fz_context *ctx, pdf_document *doc)
{
if (!doc->crypt)
return 0;
if (pdf_authenticate_password(ctx, doc, ""))
return 0;
return 1;
}
int
pdf_has_permission(fz_context *ctx, pdf_document *doc, fz_permission p)
{
if (!doc->crypt)
return 1;
switch (p)
{
case FZ_PERMISSION_PRINT: return doc->crypt->p & PDF_PERM_PRINT;
case FZ_PERMISSION_EDIT: return doc->crypt->p & PDF_PERM_MODIFY;
case FZ_PERMISSION_COPY: return doc->crypt->p & PDF_PERM_COPY;
case FZ_PERMISSION_ANNOTATE: return doc->crypt->p & PDF_PERM_ANNOTATE;
case FZ_PERMISSION_FORM: return doc->crypt->p & PDF_PERM_FORM;
case FZ_PERMISSION_ACCESSIBILITY: return doc->crypt->p & PDF_PERM_ACCESSIBILITY;
case FZ_PERMISSION_ASSEMBLE: return doc->crypt->p & PDF_PERM_ASSEMBLE;
case FZ_PERMISSION_PRINT_HQ: return doc->crypt->p & PDF_PERM_PRINT_HQ;
}
return 1;
}
int
pdf_document_permissions(fz_context *ctx, pdf_document *doc)
{
if (doc->crypt)
return doc->crypt->p;
/* all permissions granted, reserved bits set appropriately */
return (int)0xFFFFFFFC;
}
/*
* Compute the owner password (PDF 1.7 algorithm 3.3)
*/
static void
pdf_compute_owner_password(fz_context *ctx, pdf_crypt *crypt, unsigned char *opassword, size_t opwlen, unsigned char *upassword, size_t upwlen, unsigned char *output)
{
unsigned char obuf[32];
unsigned char ubuf[32];
unsigned char digest[32];
int i, n;
fz_md5 md5;
fz_arc4 arc4;
n = fz_clampi(crypt->length / 8, 0, 16);
/* Step 1 - copy and pad owner password string */
if (opwlen > 32)
opwlen = 32;
memcpy(obuf, opassword, opwlen);
if (opwlen < 32)
memcpy(obuf + opwlen, padding, 32 - opwlen);
/* Step 2 - init md5 and pass value of step 1 */
fz_md5_init(&md5);
fz_md5_update(&md5, obuf, 32);
fz_md5_final(&md5, obuf);
/* Step 3 (revision 3 or greater) - do some voodoo 50 times */
if (crypt->r >= 3)
{
for (i = 0; i < 50; i++)
{
fz_md5_init(&md5);
fz_md5_update(&md5, obuf, n);
fz_md5_final(&md5, obuf);
}
}
/* Step 4 - encrypt owner password md5 hash */
fz_arc4_init(&arc4, obuf, n);
/* Step 5 - copy and pad user password string */
if (upwlen > 32)
upwlen = 32;
memcpy(ubuf, upassword, upwlen);
if (upwlen < 32)
memcpy(ubuf + upwlen, padding, 32 - upwlen);
/* Step 6 - encrypt user password md5 hash */
fz_arc4_encrypt(&arc4, digest, ubuf, 32);
/* Step 7 - */
if (crypt->r >= 3)
{
unsigned char xor[32];
int x;
for (x = 1; x <= 19; x++)
{
for (i = 0; i < n; i++)
xor[i] = obuf[i] ^ x;
fz_arc4_init(&arc4, xor, n);
fz_arc4_encrypt(&arc4, digest, digest, 32);
}
}
/* Step 8 - the owner password is the first 16 bytes of the result */
memcpy(output, digest, 32);
}
unsigned char *
pdf_crypt_key(fz_context *ctx, pdf_crypt *crypt)
{
if (crypt)
return crypt->key;
return NULL;
}
int
pdf_crypt_version(fz_context *ctx, pdf_crypt *crypt)
{
if (crypt)
return crypt->v;
return 0;
}
int pdf_crypt_revision(fz_context *ctx, pdf_crypt *crypt)
{
if (crypt)
return crypt->r;
return 0;
}
static char *
crypt_method(fz_context *ctx, int method)
{
switch (method)
{
default:
case PDF_CRYPT_UNKNOWN: return "Unknown";
case PDF_CRYPT_NONE: return "None";
case PDF_CRYPT_RC4: return "RC4";
case PDF_CRYPT_AESV2: return "AES";
case PDF_CRYPT_AESV3: return "AES";
}
}
const char *
pdf_crypt_string_method(fz_context *ctx, pdf_crypt *crypt)
{
if (crypt)
return crypt_method(ctx, crypt->strf.method);
return "None";
}
const char *
pdf_crypt_stream_method(fz_context *ctx, pdf_crypt *crypt)
{
if (crypt)
return crypt_method(ctx, crypt->stmf.method);
return "None";
}
const char *
pdf_crypt_method(fz_context *ctx, pdf_crypt *crypt)
{
return pdf_crypt_string_method(ctx, crypt);
}
int
pdf_crypt_length(fz_context *ctx, pdf_crypt *crypt)
{
if (crypt)
return crypt->length;
return 0;
}
int
pdf_crypt_permissions(fz_context *ctx, pdf_crypt *crypt)
{
if (crypt)
return crypt->p;
return 0;
}