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RAND_bytes( ), 604 RAND_load_file( ), 604 random( ), 570 random identifiers, usage in email confirmations, 447 random nonces vs. sequential, 134 random number generation for shared secret, 435 random numbers, 568–646 data with entropy, compressing into a fixed-size seed, 613 determining what kind to use, 568–573 entropy harvesters and PRNGs, 569 entropy gathering (see entropy, gathering) generating on Unix without /dev/random and urandom devices, 594–599 generic API for, 573 OpenSSL random number API, 603–605 pseudo-random number generators (see PRNGs) random floating-point values, getting nonuniform distribution, 609 uniform distribution, 608 random integer in a range, getting, 606–608 random integers, getting, 605 random printable ASCII strings converting to, 611 generating, security and string length, 611 shuffling fairly, 612 statistically testing, 615–621 continuous output test, 619–620 power-up and on-demand tests, 617–619 Unix, generating in, 575–579 Windows, generating in, 580 RAND_pseudo_bytes( ), insecurity of, 605 RAND_seed( ), 604 RAND_write_file( ), 604 RAs (registration authorities), 506 raw data, hexadecimal representation, 120 RC2 algorithm, effective key bits function, OpenSSL, 228 RC4 algorithm, 158, 159 limits as random number source, 588 LION, 215 setting up and using, 233–236 stream cipher as PRNG, 587 supported key sizes, 226 using in self-modifying code, 694–699 754 | Index RC5 algorithm number of rounds, configuration in OpenSSL, 228 supported key sizes, 226 RDTSC instruction, 151 vs. gettimeofday( ), 153 read( ), 576 read_data( ), 61 readpassphrase( ), 393 readpassphrase.h header file, 394 real vs. effective user and group IDs, 17 realpath( ), 97 thread-safety, lack of, 97 REBUILD_VAR macro, 669 recipes, xxii for Unix, xxii for Windows, xxii OS compatibility, xxii registration authorities (RAs), 506 relative paths, 4 remove_private_key( ), 330 replay attacks, sequential nonces, prevention using, 134 representing binary keys as hexadecimal, 120 representing keys and certificates in plaintext (PEM encoding), 355–361 representing keys for use in cryptographic algorithms, 117 representing keys (or other binary data) as English text, 128 representing public keys and certificates in binary (DER encoding), 352–355 resource starvation attacks preventing, 727–734 on Unix, 727–730 on Windows, 730–734 restricted tokens, 8 restricting access permissions for new files (Unix), 55 restricting filesystem access on Unix, 68 restricting filesystem and network access on BSD, 69 restricting privileges, 7–16 RetrieveWebData( ), 560 RFC 822, email syntax, 101 Rijndael, 228 ring0 debuggers, 685 RIPEMD-160 algorithm, 257 Rivest, Ron, 257, 314 RMAC, 261, 281 rollback attacks, 161, 492 This is the Title of the Book, eMatter Edition Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.
oot certificates, 519–522 CAs, list, 520–522 obtaining and checking, 519 validating, 520 Root Report, 519 RSA algorithm, 142, 312 authenticated key exchange, 429–431 MACs, usage, 431 complexity of implementation, 333 converting binary strings to integers for use with, 330 converting integers to binary strings, 331 DER-encoding of public keys, 353 dictionary attacks and, 335 EME-OAEP padding, 333–336 generating key pairs, 327–329 and man-in-the-middle attacks, 333 padding and, 333 private keys, decryption using, 336–337 private keys, signing with, 338–340 public keys, encryption using, 332–336 raw decryption using a private key, 336–337 raw encryption with a public key, 332–336 recommended key lengths, 313 secure signing and encryption, 343 signature verification with public keys, 340–343 symmetric encryption, usage in implementations, 333 RSA_blinding_on( ), 341 RSA_generate_key( ), 327 RSA_private_decrypt( ), 337 RSA_public_encrypt( ), 332, 334, 335 RSA_sign( ), 339 RSA_size( ), 333 RSASSA-PKCS1v1.5 signing standard, 338 RSASSA-PSS digital signing standard, 338 RtlSecureMemory( ), 707 S SACL (system access control list), 41 safe primes, 318, 323 SafeStr library, 82, 85–88 functions and C equivalents, 86 SAFESTR_ALLOC( ), 86 SAFESTR_CREATE( ), 86 safestr_free( ), 87 safestr_istrusted( ), 88 safestr_reference( ), 87 safestr_release( ), 87 safestr_t type, 85 SAFESTR_TEMP( ), 86 SAFESTR_TEMP_TRUSTED( ), 88 salt, 133 dictionary attacks, prevention with, 141 hardening hash functions against birthday attacks, 270 sanitizing the environment, 1–7 SASL (Simple Authentication and Security Layer), 364 saved user and group IDs, 17 SAX (Symmetric Authenticated eXchange), 369, 422–429 client side, 427–429 server-side, 423–427 Schneier, Bruce, 116 secure programming, 71 web sites, xviii secure server certificates, 517 securely creating child processes, 26–28 securely signing and encrypting with RSA, 343 SecureZeroMemory( ), 707 security authentication mechanisms, requirements, 365 bit size of algorithms, 313 function errors and, 700 initialization and, 1 weak vs. strong passwords, 391 security identifiers (see SIDs) Security Support Provider Interface (SSPI), 454 seeds, random numbers, 568 select( ) preventing file descriptor overflows, 112–115 typical usage, 112 selecting a cipher mode, 162–171 selecting a public key algorithm, 311 selecting public key sizes, 312–314 self-signed certificates, 511 sequential nonces vs. random nonces, 134 Serpent, 158, 159 home page, 160 servers authentication without third-party, 438–444 for network logging, 734 SSL servers, creating, 457–460 SSL servers, improving efficiency with caching, 460–463 This is the Title of the Book, eMatter Edition Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved. Index | 755
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Secure Programming Cookbook ΤΜ fo
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Secure Programming CookbookΤΜ for
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Table of Contents Foreword . . . .
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5.8 Using a Generic OFB Mode Implem
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8.10 Performing Password-Based Auth
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12.10 Restructuring Arrays 672 12.1
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they are in the top 50% of safe dri
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think you are in, you will probably
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the C programming language, with so
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igger risks than anticipated. You s
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Recipe Compatibility Most of the re
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The O’Reilly web site for the boo
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Chapter 1 CHAPTER 1 Safe Initializa
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using the code in this recipe on Wi
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variables you preserve, be sure to
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ptr = (char *)new_environ + (arr_si
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an impersonation token for a thread
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Creating a new process with a restr
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array that is the Privileges field.
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eturn 0; } if (!LookupAccountName(0
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privileges. We strongly advise agai
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#include #include #include #incl
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sockets provide a means by which fi
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The privman library provides a numb
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The potential for security vulnerab
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It’s important to remember that t
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Discussion execve( ) is the system
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should call pclose( ) to clean up t
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dup2(stdout_pipe[1], 1); close(stdo
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lpCommandLine Any command-line argu
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#include #include #include void
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and a saved user ID. * The effectiv
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See Also Recipes 1.3, 1.4, 2.8 2.2
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of the object, regardless of what t
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There are many other situations whe
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if (!(fd = opendir("."))) break; if
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spc_file_wipe( ) A wrapper around t
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if (pattern_pass(fd, buf, sizeof(bu
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CryptReleaseContext(hProvider, 0);
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2.7 Restricting Access Permissions
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eset the umask between your adjustm
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Locking files on Windows Where Unix
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NFS older than Version 3 in particu
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a loop until all the data is read.
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if (!(hResourceLock = CreateMutex(0
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generator. The code presented here
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access to the filesystem, the poten
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Chapter 3 CHAPTER 3 Input Validatio
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components of the system are truste
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try to use them. For example, what
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To combat malicious uses of “%n
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Discussion Buffer overflows get a l
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Unfortunately, strlcpy( ) and strlc
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The second problem area occurs when
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(see Recipe 3.2). The format-string
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safestr_release( ) or safestr_free(
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Solution Unfortunately, integer coe
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which the records begin. Generally,
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pointer or a different value altoge
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if (!(new_environ = (char **)malloc
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if (spc_environ) free(environ); env
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GetFullPathName( ) requires the len
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if (*c != '%' || !isxdigit(c[1]) ||
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3.10 Preventing Cross-Site Scriptin
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* These are HTML tags that do not t
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*ptr++ = *c; } while (*++c != ’>
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Finally, if you are using the LIKE
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Table 3-2. UTF-8 encoding byte sequ
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the connections to the server. The
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SPC_FD_SET read_mask; for (;;) { sp
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To ensure that you choose the right
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See Also Recipe 13.2 4.2 Generating
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This function takes the following a
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} break; default: if (isspace(p[0])
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*p = 0; return output; } } } The pu
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} return result; case -1: if (stric
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#define MAX_WORDLEN 4 /* len parame
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Discussion This function spc_words2
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4.9 Using Salts, Nonces, and Initia
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the lifetime of the key; the counte
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#include #include #include #incl
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#include #include /* This value n
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} CryptReleaseContext(hProvider, hK
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cryptographic one-way hash from a t
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HMAC_CTX c; unsigned long ctr = 0,
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database does not support binary st
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Remember to use a MAC anytime you e
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For many different reasons, it can
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A more portable but less accurate w
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Chapter 5 CHAPTER 5 Symmetric Encry
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Discussion Be sure to read this dis
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Pentium III, which should give a go
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locations where 40-bit keys or 56-b
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can arise. For general-purpose use,
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or similar mechanism is used. As wi
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shares many properties with CTR mod
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case, the faster of the two algorit
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parison to standard modes. As of th
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work, which severely limits portabi
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Table 5-4. Implementations for the
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Plaintext block 1 Plaintext block 2
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typedef struct { SPC_KEY_SCHED ks;
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If you are using padding and you kn
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This function has the following arg
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if (ol) *ol = out - start; return 1
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that the state function is always r
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Note that this code depends on the
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if (!il--) return 1; ctx->nonce[ctx
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one block at a time, by encrypting
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spc_memset(key,0, kl); memcpy(ctx->
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5.9 Using a Generic CTR Mode Implem
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These two functions also erase the
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we ignore that because it will alwa
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Once those bindings are made, the Z
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output Buffer into which the plaint
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eturn the number of valid bytes in
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In CBC, CFB, and OFB modes, encrypt
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void spc_pctr_do_odd(SPC_CTR2_CTX *
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5.15 Performing File or Disk Encryp
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Therefore, we’ll show you LION, b
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} RC4_set_key(&k, HASH_SZ, (char *)
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techniques from Chapter 8), the key
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communicate asynchronously (that is
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key Pointer to the encryption key t
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Table 5-6. Cipher instantiation ref
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While RC2, RC4, and RC5 support abs
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The function EVP_CIPHER_CTX_ctrl( )
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Discussion As a reminder, use a raw
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ol = 0; if (!(ret = (char *)malloc(
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The “official” RC4 key setup fu
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Discussion One-time pads are provab
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Once a provider context has been su
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Table 5-8. Symmetric ciphers suppor
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hKey Key to use for performing the
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if (!CryptAcquireContext(&hProvider
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exportable from key objects, but th
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Chapter 6 CHAPTER 6 Hashes and Mess
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Generally, you should prefer an enc
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See Also Recipes 6.7, 6.8, 6.12 6.2
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Noncorrelation It should also be co
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Let’s look briefly at the pros an
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Solution In most cases, instead of
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MAC (which we recommend), we strong
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Libraries with cryptographic hash f
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#include int main(int argc, char *
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See Also Implementations of SHA-256
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CryptAcquireContext(&hProvider, 0,
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To ensure the best security, we str
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if (!(vfy = (unsigned char *)malloc
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you might use a library such as Ope
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Otherwise, you can use the HMAC imp
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if (klen inner[i] ^= key[i]; ctx->o
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OMAC has been explicitly specified
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unsigned char c1[SPC_BLOCK_SZ]; /*
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ing the all-zero data block. Each p
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CMAC is the message-integrity compo
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To postprocess, we encrypt the hash
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6.15 Constructing a Hash Function f
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unsigned char b[SPC_KEY_SZ]; size_t
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Figure 6-2. The Mayas-Meyer-Oseas c
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c->ix = 0; c->tl = 0; } static void
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modes such as CWC and CCM are start
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authentication in a straightforward
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SPC_HMAC_Reset(&ctx); SPC_HMAC_Upda
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divide up the data stream between t
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Chapter 7 CHAPTER 7 Public Key Cryp
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The code presented in this chapter
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Because public key encryption is so
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Solution There’s some debate on t
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7.4 Manipulating Big Numbers Proble
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There’s a similar function for as
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Additionally, you can ask for a ran
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In addition, you might wish to test
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Table 7-2. Math operations supporte
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313, 317, 331, 337, 347, 349, 353,
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for (b = 0; !BN_is_odd(x); b++) BN_
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BIGNUM *dP, *dQ, *qInv; } RSA_PRIVA
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This would map to the hexadecimal v
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compute d. Without those two primes
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The constants that may be used to s
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When using OpenSSL, decryption can
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ecommend using it, unless you are c
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ture is valid. A successful check w
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et = RSA_verify(NID_sha1, hash, 20,
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#define MIN(x,y) ((x) > (y) ? (y) :
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memcpy(signedtext, decrypt, 16); if
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h_ret Optional argument that, if no
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siglen The number of bytes written
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data ready to go into the certifica
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ut it requires you to pass in the l
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LjKQ2r1Yt9foxbHdLKZeClqZuzN7PoEmy+b
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ing in data, pass in a pointer to a
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Table 7-6 lists the FILE object-bas
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Solution The correct method depends
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Use across applications For some pe
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key agreement protocol, where both
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consider slightly more sophisticate
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Kerberos does assume that the envir
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The function used to look up user i
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The group structure that is returne
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found, NULL will be returned, and G
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ReferencedDomainName = (LPTSTR)Loca
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if (errno != EINTR && errno != EAGA
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if (!(spc_host_rulecount % 256)) {
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} else { if (inet_addr(tmp) = = INA
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8.5 Generating Random Passwords and
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for this list is not insignificant.
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file, it may allocate a sizable amo
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On Windows, you can use the standar
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Once getpass( ) or readpassphrase(
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ters typed by the user. Instead, th
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compute the future time at which th
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decrypt the encrypted data. To make
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On systems that support MCF through
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for (i = 0; i < 1000; i++) { MD5_In
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CryptHashData(hHash1, lpszKey, dwKe
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Solution Use the PBKDF2 method of c
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Verifying a password encrypted usin
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c Pointer to an integer that will r
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each of these pieces of information
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server-side part of the authenticat
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8.14 Authenticating with HTTP Cooki
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char *spc_cookie_encode(char *cooki
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• Let the salt be public, in whic
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extra Additional application-specif
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xl Pointer into which the length of
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With a valid socket descriptor in h
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11. The client and the server compu
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Some people like to use a fixed mod
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Often, you’ll want to generate a
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Discussion Remember, authentication
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• Provide the user with some way
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if (!fgets(answer, sizeof(answer),
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uffer = (char *)realloc(buffer, buf
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compromise. If our system has such
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When using RSA, if you’re doing o
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see the confirmation request and th
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Upon receipt of a response to a con
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BOOL SpcConfirmationCreate(LPCTSTR
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Additionally, over time, SSPI-speci
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if (!spc_verify_cert_hostname(SSL_g
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The next step is to call spc_accept
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Discussion Session caching is norma
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if (BIO_do_connect(conn)
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The next step is to connect to the
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DWORD dwHeadersLength = 0; LPSTR lp
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attempt to develop and debug SSL-en
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API for encryption and decryption,
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memcpy(in_data.data, inbuf, inlen);
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*outlen = out_data.length - (blksz
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so. Likewise, any process with the
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struct sockaddr_un *addr_unix; *dom
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error_exit: if (sock) spc_socket_cl
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different ways. On FreeBSD systems,
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msg.msg_iov->iov_base = (void *)&sy
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it’s unique and unpredictable! Yo
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if (mysql_real_connect(mysql, host,
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maintenance. Adding or removing ser
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ut they shouldn’t tolerate reorde
Page 523 and 524:
#define SPC_CLIENT_DISTINGUISHER 0x
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} static void spc_ssock_write( int
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while (mlen) { if ((r = read(fd, ms
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In such cases, you need to be able
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Discussion One of the big motivator
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A digital certificate contains info
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Certificate revocation What happens
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cate as long as it still has its pr
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Currently, OCSP is not nearly as wi
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ple is the permissible uses for a c
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automated email to the address you
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The type of code-signing certificat
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10.3 Using Root Certificates Proble
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Table 10-1. CA certificates, their
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ights of the entity tied to that ce
Page 553 and 554:
10.5 Performing X.509 Certificate V
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sk_X509_free(spc_store->crls); sk_X
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X509_LOOKUP *lookup; store = X509_S
Page 559 and 560:
CertGetIssuerCertificateFromStore(
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HCERTSTORE hCertStore; PCCERT_CONTE
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See Also Recipe 10.11 10.7 Verifyin
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SPC_X509STORE_SSL_VERIFY_NONE This
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verify_flags |= SSL_VERIFY_FAIL_IF_
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int spc_verify_cert_hostname(X509 *
Page 571 and 572:
for (i = 0; !bResult && i < pNameIn
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only work you really need to do is
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digest = EVP_sha1( ); fingerprint_l
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if (cert && (uri = get_distribution
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"\xb3\x9c\x25\xb1\xc3\x2e\x32\x53\x
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headerlen -= (*datalen + 2); if (*d
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In this recipe, we have used a numb
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{ "\x8d\x26\xff\x2f\x31\x6d\x59x\29
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LocalFree(pvStructInfo); return 0;
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lpFullBuffer = lpNewBuffer; lpBuffe
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of tunable variables that affect th
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SPC_OCSPRESULT_CERTIFICATE_VALID =
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* All done. Set the return code bas
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Solution There are essentially thre
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the byte is even, he reduces the nu
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See Also Recipes 11.16, 11.18, 11.1
Page 603 and 604:
11.3 Using the Standard Unix Random
Page 605 and 606:
a pointer to data. Instead, they re
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if (errno = = EINTR) continue; perr
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Here we show how to use this functi
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attacks are a realistic threat, you
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This function never fails (save for
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Using a stream cipher as a generato
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One very safe way to use a cryptogr
Page 619 and 620:
out Buffer into which the random da
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1. Figure out how big a seed you ne
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0x00 Query the amount of entropy be
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strncpy(a.sun_path, EGD_SOCKET_PATH
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} } while (nb = = -1); } } } See Al
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nbytes Number of bytes of entropy t
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See Also • EGADS by Secure Softwa
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If the generator is not seeded with
Page 635 and 636:
Discussion In all cases, you will s
Page 637 and 638:
Solution Because of the way that fl
Page 639 and 640:
double spc_rand_cunifvariate(double
Page 641 and 642:
See Also Recipe 11.11 11.16 Compres
Page 643 and 644:
It would be nice if you did not hav
Page 645 and 646:
For this reason, we think the full
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} int cur_val, i, j, runsz; unsigne
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See Also • NIST Cryptographic Mod
Page 651 and 652:
ecause even if a source does fail c
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you use a seed file, you can just c
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• If you have to accept data from
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with a high-resolution clock (i.e.,
Page 659 and 660:
Collecting entropy from the keyboar
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f[c + 2] = '>'; } else snprintf(bf,
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SpcGatherKeyboardEntropy( ) uses th
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} } if (hWndParent) EnableWindow(hW
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number of bits of entropy has been
Page 669 and 670:
} return TRUE; pDlgData->cbRequeste
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See Also Recipes 11.19, 11.20 11.22
Page 673 and 674:
Discussion We strongly recommend th
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Chapter 12 CHAPTER 12 Anti-Tamperin
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tecture-specific checks to determin
Page 679 and 680:
ure or to examine a hardware valida
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• Detecting modification to a com
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for (j = 8; j > 0; j--) { if (crc &
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#include CRC_START_BLOCK(test) int
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Solution Obfuscating compiled code
Page 689 and 690:
" movl 0f( , %%ebx ), %%eax \n\t" \
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Because library functions are loade
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encoded as a series of 32 Obcode bi
Page 695 and 696:
12.5 Performing Constant Transforms
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12.7 Splitting Variables Problem La
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12.9 Using Function Pointers Proble
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arrays. This array type will hide t
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eak; case SPC_ARRAY_FOLD: index = (
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The following example demonstrates
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Discussion The techniques for hidin
Page 709 and 710:
12.12 Detecting Debuggers Problem S
Page 711 and 712:
Discussion The spc_trap_detect( ) f
Page 713 and 714:
12.14 Detecting Windows Debuggers P
Page 715 and 716:
The int3 interface can also be used
Page 717 and 718:
To demonstrate the effect this macr
Page 719 and 720:
08048388 83 db 83h ; â 08048389 7D
Page 721 and 722:
ine the instruction making the refe
Page 723 and 724:
mprotect(buf, buf_len, PROT_READ |
Page 725 and 726:
eturn 4; } /* get entry point : her
Page 727 and 728:
need to use one of the three ring3
Page 729 and 730:
cates failure, it’s likely that n
Page 731 and 732: tion gets caught. The only ways to
Page 733 and 734: memory location will generally stil
Page 735 and 736: eturn dst; } volatile void *spc_mem
Page 737 and 738: The mlock( ) system call on Unix im
Page 739 and 740: Discussion Both C and C++ allow the
Page 741 and 742: Do not share signal handlers. Sever
Page 743 and 744: #endif } static int signal_was_caug
Page 745 and 746: paper reached the widest audience,
Page 747 and 748: The proper way to handle a program
Page 749 and 750: handles[0] = cond; handles[1] = mut
Page 751 and 752: #ifndef WIN32 pool->tids = (pthread
Page 753 and 754: #define SPC_ACQUIRE_MUTEX(mtx) pthr
Page 755 and 756: if (socketpool_limit > 0 && socketp
Page 757 and 758: Table 13-1. Resources that may be l
Page 759 and 760: ability to run. The default limits
Page 761 and 762: Note that the structures as present
Page 763 and 764: access to the machine. This makes i
Page 765: ing log entries. It is possible, ho
Page 768 and 769: attacks (continued) capture replay
Page 770 and 771: CFB (Cipher Feedback) mode, 167, 18
Page 772 and 773: deriving symmetric keys from a pass
Page 774 and 775: EVP_CIPHER_CTX_set_padding( ), 227
Page 776 and 777: integrity checking cipher modes, 16
Page 778 and 779: message digests (continued) desirab
Page 780 and 781: parallelizing MACs, 304 parent and
Page 784 and 785: session ID context, 461 session IDs
Page 786 and 787: spc_gather_keyboard_entropy( ), 631
Page 788 and 789: symmetric cryptography, 116-154 alg
Page 790 and 791: Windows (continued) Win 2000, restr
Page 792: oads. They will often travel up to
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Problem - Kevin Tafuro

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