Add tests for PKCS#1 v1.5 decoding

Functional tests for various payload sizes and output buffer sizes.

When the padding is bad or the plaintext is too large for the output
buffer, verify that function writes some outputs. This doesn't
validate that the implementation is time-constant, but it at least
validates that it doesn't just return early without outputting anything.
diff --git a/tests/suites/test_suite_pkcs1_v15.data b/tests/suites/test_suite_pkcs1_v15.data
index 0309400..a4d6eb5 100644
--- a/tests/suites/test_suite_pkcs1_v15.data
+++ b/tests/suites/test_suite_pkcs1_v15.data
@@ -33,3 +33,93 @@
 
 RSASSA-V15 Verification Test Vector Int
 pkcs1_rsassa_v15_verify:1024:16:"a2ba40ee07e3b2bd2f02ce227f36a195024486e49c19cb41bbbdfbba98b22b0e577c2eeaffa20d883a76e65e394c69d4b3c05a1e8fadda27edb2a42bc000fe888b9b32c22d15add0cd76b3e7936e19955b220dd17d4ea904b1ec102b2e4de7751222aa99151024c7cb41cc5ea21d00eeb41f7c800834d2c6e06bce3bce7ea9a5":16:"010001":MBEDTLS_MD_SHA1:MBEDTLS_MD_SHA1:"859eef2fd78aca00308bdc471193bf55bf9d78db8f8a672b484634f3c9c26e6478ae10260fe0dd8c082e53a5293af2173cd50c6d5d354febf78b26021c25c02712e78cd4694c9f469777e451e7f8e9e04cd3739c6bbfedae487fb55644e9ca74ff77a53cb729802f6ed4a5ffa8ba159890fc":"e3b5d5d002c1bce50c2b65ef88a188d83bce7e61":"2154f928615e5101fcdeb57bc08fc2f35c3d5996403861ae3efb1d0712f8bb05cc21f7f5f11f62e5b6ea9f0f2b62180e5cbe7ba535032d6ac8068fff7f362f73d2c3bf5eca6062a1723d7cfd5abb6dcf7e405f2dc560ffe6fc37d38bee4dc9e24fe2bece3e3b4a3f032701d3f0947b42930083dd4ad241b3309b514595482d42":0
+
+RSAES-V15 decoding: good, payload=max, tight output buffer
+pkcs1_v15_decode:MBEDTLS_RSA_PRIVATE:"0002505152535455565700":117:117:0
+
+RSAES-V15 decoding: good, payload=max, larger output buffer
+pkcs1_v15_decode:MBEDTLS_RSA_PRIVATE:"0002505152535455565700":117:128:0
+
+RSAES-V15 decoding: good, payload=max-1, tight output buffer
+pkcs1_v15_decode:MBEDTLS_RSA_PRIVATE:"000250515253545556575800":116:116:0
+
+RSAES-V15 decoding: good, payload=max-1, larger output buffer
+pkcs1_v15_decode:MBEDTLS_RSA_PRIVATE:"000250515253545556575800":116:117:0
+
+RSAES-V15 decoding: good, payload=1
+pkcs1_v15_decode:MBEDTLS_RSA_PRIVATE:"00025050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505000":1:1:0
+
+RSAES-V15 decoding: good, empty payload
+pkcs1_v15_decode:MBEDTLS_RSA_PRIVATE:"0002505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505000":0:0:0
+
+RSAES-V15 decoding: payload=max, output too large
+pkcs1_v15_decode:MBEDTLS_RSA_PRIVATE:"0002505152535455565700":117:116:MBEDTLS_ERR_RSA_OUTPUT_TOO_LARGE
+
+RSAES-V15 decoding: payload=max-1, output too large
+pkcs1_v15_decode:MBEDTLS_RSA_PRIVATE:"000250515253545556575800":116:115:MBEDTLS_ERR_RSA_OUTPUT_TOO_LARGE
+
+RSAES-V15 decoding: bad first byte
+pkcs1_v15_decode:MBEDTLS_RSA_PRIVATE:"0102505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050":0:42:MBEDTLS_ERR_RSA_INVALID_PADDING
+
+RSAES-V15 decoding: bad second byte (0 instead of 2)
+pkcs1_v15_decode:MBEDTLS_RSA_PRIVATE:"0000505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050":0:42:MBEDTLS_ERR_RSA_INVALID_PADDING
+
+RSAES-V15 decoding: bad second byte (1 instead of 2)
+pkcs1_v15_decode:MBEDTLS_RSA_PRIVATE:"0001505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050":0:42:MBEDTLS_ERR_RSA_INVALID_PADDING
+
+RSAES-V15 decoding: padding too short (0)
+pkcs1_v15_decode:MBEDTLS_RSA_PRIVATE:"000200":0:42:MBEDTLS_ERR_RSA_INVALID_PADDING
+
+RSAES-V15 decoding: padding too short (7)
+pkcs1_v15_decode:MBEDTLS_RSA_PRIVATE:"0002505050505050500000ffffffffffffffffff00":0:42:MBEDTLS_ERR_RSA_INVALID_PADDING
+
+RSAES-V15 decoding: unfinished padding
+pkcs1_v15_decode:MBEDTLS_RSA_PRIVATE:"0002505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050505050":0:42:MBEDTLS_ERR_RSA_INVALID_PADDING
+
+EMSA-V15 decoding: good, payload=max, tight output buffer
+pkcs1_v15_decode:MBEDTLS_RSA_PUBLIC:"0001ffffffffffffffff00":117:117:0
+
+EMSA-V15 decoding: good, payload=max, larger output buffer
+pkcs1_v15_decode:MBEDTLS_RSA_PUBLIC:"0001ffffffffffffffff00":117:128:0
+
+EMSA-V15 decoding: good, payload=max-1, tight output buffer
+pkcs1_v15_decode:MBEDTLS_RSA_PUBLIC:"0001ffffffffffffffffff00":116:116:0
+
+EMSA-V15 decoding: good, payload=max-1, larger output buffer
+pkcs1_v15_decode:MBEDTLS_RSA_PUBLIC:"0001ffffffffffffffffff00":116:117:0
+
+EMSA-V15 decoding: good, payload=1
+pkcs1_v15_decode:MBEDTLS_RSA_PUBLIC:"0001ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff00":1:1:0
+
+EMSA-V15 decoding: good, empty payload
+pkcs1_v15_decode:MBEDTLS_RSA_PUBLIC:"0001ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff00":0:0:0
+
+EMSA-V15 decoding: bad first byte
+pkcs1_v15_decode:MBEDTLS_RSA_PUBLIC:"0101ffffffffffffffff00":0:42:MBEDTLS_ERR_RSA_INVALID_PADDING
+
+EMSA-V15 decoding: bad second byte (0 instead of 1)
+pkcs1_v15_decode:MBEDTLS_RSA_PUBLIC:"0000ffffffffffffffff00":0:42:MBEDTLS_ERR_RSA_INVALID_PADDING
+
+EMSA-V15 decoding: bad second byte (2 instead of 1)
+pkcs1_v15_decode:MBEDTLS_RSA_PUBLIC:"0002ffffffffffffffff00":0:42:MBEDTLS_ERR_RSA_INVALID_PADDING
+
+EMSA-V15 decoding: padding too short (0)
+pkcs1_v15_decode:MBEDTLS_RSA_PUBLIC:"000100":0:42:MBEDTLS_ERR_RSA_INVALID_PADDING
+
+EMSA-V15 decoding: padding too short (7)
+pkcs1_v15_decode:MBEDTLS_RSA_PUBLIC:"0001ffffffffffffff0000ffffffffffffffff00":0:42:MBEDTLS_ERR_RSA_INVALID_PADDING
+
+EMSA-V15 decoding: invalid padding at first byte
+pkcs1_v15_decode:MBEDTLS_RSA_PUBLIC:"0001fffffffffffffffe00":0:42:MBEDTLS_ERR_RSA_INVALID_PADDING
+
+EMSA-V15 decoding: invalid padding at last byte
+pkcs1_v15_decode:MBEDTLS_RSA_PUBLIC:"0001feffffffffffffff00":0:42:MBEDTLS_ERR_RSA_INVALID_PADDING
+
+EMSA-V15 decoding: unfinished padding
+pkcs1_v15_decode:MBEDTLS_RSA_PUBLIC:"0001ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff":0:42:MBEDTLS_ERR_RSA_INVALID_PADDING
+
+EMSA-V15 decoding: unfinished padding with invalid first byte
+pkcs1_v15_decode:MBEDTLS_RSA_PUBLIC:"0001feffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff":0:42:MBEDTLS_ERR_RSA_INVALID_PADDING
+
+EMSA-V15 decoding: unfinished padding with invalid last byte
+pkcs1_v15_decode:MBEDTLS_RSA_PUBLIC:"0001fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffe":0:42:MBEDTLS_ERR_RSA_INVALID_PADDING